September 2008 Archives

It's getting to be the time of year when lake-effect precipitation appears on the weather
scene. Mention lake-effect precipitation and Chicagoans invariably think of snow.
However, if temperatures are sufficiently cold to generate precipitation but not quite
cold enough for snow, the atmosphere gives us lake-effect rain. That's the situation
today. Residents of northern Indiana can expect rain showers today and tonight, the
result of chilly air surging down the full length of Lake Michigan's relatively warm
waters. Steering winds, blowing north to south, may carry a few showers onto the
near-shore areas of Chicago.

CHICAGO'S OCTOBER SNOW

A trace of snow has been observed in Chicago as early as Sept. 25 (in 1942) but the
city's snow season doesn't really get under way until November. But don't count out
October: It's had its snowy moments. Eighty years (1928-2007) of Midway snowfall
data reveals that 38 Octobers (about one out of two) have delivered at least a few
snowflakes. Measurable snow (an accumulation of one-tenth inch or more) occurred in
11 Octobers (one October out of seven) and an inch or more has come down in four
Octobers (one out of 20).

--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
If a tornado is heading toward a city, why couldn't the Air Force shoot a missile into it
to mess up its circulation?
Bryan Roberts (age 11), Naperville, Ill.

Dear Bryan,

Tornado forecaster Roger Edwards at the Storm Prediction Center in Norman, Okla.,
which issues tornado watches for the United States) says, "Bad idea!"

He explains that a tornado is much larger than it looks. The "tornado" that we see
below the clouds actually extends many thousands of feet upward through the
thunderhead. Disrupting the tornado would require disrupting the entire thunderstorm.
Could an H-bomb do it? Possibly, but that would cause far more damage than the
tornado itself.

For more information, check out "Frequently Asked Questions About Tornadoes," an
excellent web site prepared by Edwards, at: http://www.spc.noaa.gov/faq/tornado/

A cooling trend that began on Sunday continues today, gathers strength Tuesday and
arrives with vigor on Wednesday and Thursday. Saturday’s 81-degree reading is a warm
memory, and before the cooldown runs its course, Chicago’s temperatures will have
declined to an expected early-morning minimum of 41 degrees on Thursday. That’s a
40-degree plunge over a five-day period.

Air of Canadian origin surges into Chicago Tuesday on the wings of 25 m.p.h. winds from
the northwest, and jackets will be the order of the day. Afternoon temperatures won’t
make it out of the 50s on Wednesday and Thursday, though winds will subside.

HIGHS IN 50s THIS TIME OF YEAR: RARE

Historically, Chicago’s highs have failed to reach 60 degrees on only 14 percent of the
days on record during Sept. 29-Oct. 3.

Dear Tom,

Weather information is used in many ways. In your experience, what is the most
unusual use that it has been put to? Can you relate an interesting story?

Lynn Schneider

Dear Lynn,

Indeed I can. One of my co-workers here in the WGN-TV weather center spent his
childhood in southwest suburban Brookfield. He remembers that a neighbor, Mrs.
Woods, specialized in growing potted cacti, and she took great pride in her collection
of about 75 varieties of those plants. Her house was full of all kinds of cacti.

Mrs. Woods claimed that the secret to growing cacti successfully was water -- not too
much and not too little. Every day, without fail, she would check the weather listing in
the Chicago Daily News (which ceased publication in 1978) for Phoenix, Arizona. If and
only if it had rained in Phoenix did Mrs. Woods water her cacti.

Our thanks to Jim Bollow from Wheaton for passing along the picture taken by his son Marine Master Sgt. Keith Bollow stationed in Iraq for this stunning shot taken during a morning dust storm in Fallujah. The thick clouds of airborne dust turned the skies an eerie orange color.

Photo by Master Sgt. Keith Bollow, USMC

Steve Kahn WGN Weather Center Meteorologist

A cooling trend that began on Sunday continues today, gathers strength Tuesday and
arrives with vigor on Wednesday and Thursday. Saturday's 81-degree reading is a warm
memory, and before the cooldown runs its course, Chicago's temperatures will have
declined to an expected early-morning minimum of 41 degrees on Thursday. That's a
40-degree plunge over a five-day period.
Air of Canadian origin surges into Chicago Tuesday on the wings of 25 m.p.h. winds from
the northwest, and jackets will be the order of the day. Afternoon temperatures won't
make it out of the 50s on Wednesday and Thursday, though winds will subside.

HIGHS IN 50s THIS TIME OF YEAR: RARE
Historically, Chicago's highs have failed to reach 60 degrees on only 14 percent of the
days on record during Sept. 29-Oct. 3.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
You often mention Chicago's daily normal high and low temperatures. How are
they arrived at?
Jim Welch
Dear Jim,
The National Weather Service calculates normals for a location (like Midway
Airport) based on temperatures observed there during a 30-year period,
currently the period from 1971 through 2000. Those normals, to be used for
10 years, will next be updated for the period 1981 through 2010.
At a specific location, average high and low temperatures for a given day,
say Aug. 10, are obtained by averaging the 30 daily highs and 30 daily lows
observed on Aug. 10 in all years from 1971 through 2000, and the same is
done for all days of the year. The daily averages, which bounce up and down
a few degrees from one day to the next, are "smoothed," and those smoothed
values are adopted as the normal daily temperatures for that location.

Upper-level "steering winds" (the winds, blowing 20,000 to 30,000 feet aloft that govern
the movement of weather systems at the surface) will shift from westerly to northerly
early this week.
That means chilly air centered over western Canada will be directed into the Great Lakes
region.
Only the southern (and mildest) portion of that Canadian air mass will affect Chicago
today and Monday, but it will be enough to lower readings 10 degrees from Saturday's
balmy 81-degree high. An additional 10-degree drop occurs Tuesday.

WARM-UP EXPECTED IN SEVEN DAYS
By next weekend, the jet stream is expected to shift to a southwesterly flow over the
central portion of the United States, bringing significant warming to Chicago and the
upper Midwest.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
We found a green fuzzy caterpillar in late July, the earliest we have ever
seen that kind before. Does this mean an early winter, or is it just a myth?
Dan Gazdziak, Chicago
Dear Dan,
It's an enduring myth. Your question is similar to many that we receive
concerning the ability of animals to predict the weather. There is no
documented evidence that robins or groundhogs (the usual suspects) -- or any
animals, including green fuzzy caterpillars -- have that ability.
Animal behavior, even when uncharacteristic or unusual, is a response to
past or current weather or the result of instinctive imperatives; it is not
based on predictive ability. That goes for plants, too. An exceptionally
great production of seeds, as with oak trees and acorns, or premature leaf
coloring in the autumn always result from past weather conditions or other
environmental factors, not from predictive ability.

Summer-weather enthusiasts will enjoy a final day of sunny, warm weather today. A
look at Chicago's climatic history tells us that a few 80-degree days at this time of year
are not at all unusual. In fact, it happens in 6 out of 10 years. The end lies just ahead,
however. The first surge of cooler air arrives Sunday, and a second and more powerful
surge -- of Canadian origin -- pushes into the area on Tuesday. Blustery, chilly
conditions will dominate conditions on Wednesday and Thursday.

WINDY, RAINY WEATHER HITS ALONG
THE ATLANTIC COAST THIS WEEKEND
Tropical Storm Kyle, predicted by the National Hurricane Center to intensify to
hurricane status, sweeps northward just off the Atlantic Coast. It's due to make landfall
late Sunday on the coast of Maine and then crash northward into Canada's Maritime
Provinces. Heavy and flooding rains, high winds and major shoreline erosion are a given
in such situations.
Hurricanes, while rare visitors to New England, are not unknown -- and that applies to
Canada's Maritime Provinces as well. The National Hurricane Center advises that a
slight eastward shift in the forecast trajectory of the storm would significantly lessen
its impact on New England.
--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,
Watching hourly weather reports, I notice the relative humidity is often not
100 percent when it is raining. Is this correct?
Simon Palmer
Dear Simon,
It's correct, and it can rain when the relative humidity is less than 100
percent. In fact, relative humidity values are in the range of 90 to 99
percent most of the time when it is raining.
Clouds form when invisible water vapor gas condenses into visible water
droplets, and rain occurs when cloud droplets grow too large to be supported
by currents of rising air within rain clouds. Condensation and raindrop
formation occur within clouds -- where the air is saturated and the relative
humidity is, indeed, 100 percent.
Most of the time, though, clouds lie above drier air at the ground, and
that's where we live. Relative humidity at the surface reflects the actual
moisture content of the air at ground level -- drier air into which rain is
falling.

Wide temperature swings expected in the next 10 to 16 days are a reminder that
Chicago's weather is marching to an autumnal drum. Summery temperatures Friday and
Saturday will yield to cooler air Sunday and then yield further to showery, windy and
much cooler weather Monday and Tuesday. Afternoon readings in the lower 80s Friday
collapse to nighttime temperatures in the lower 40s by the middle of next week. That's
a 40-degree plunge over a four-day period, from 9 degrees above normal Friday to 10
degrees below normal Wednesday. And then another temperature pattern reversal sends
temperatures upward, ultimately carrying readings into the 70s by about Oct. 5.

WINDY, RAINY WEATHER ON EASTERN SEABOARD

Two weather systems, an unnamed disturbance with semi-tropical characteristics and
Tropical Storm Kyle (destined to become Hurricane Kyle), are sending deluges of
wind-driven rain into the eastern United States from the Carolinas to Maine. Interior
areas of the Southeast, especially the Carolinas, need the rain. They've been
experiencing serious drought conditions since February.

--By Richard Koeneman, WGN Weather Center Meteorologist

Dear Tom,

Why do hurricanes cause coastal flooding?

Charles Kesman, Chicago

Dear Charles,

It's complicated. First, there is wave setup. A hurricane's huge breaking waves transport
so much water to shore so rapidly that it cannot all flow back before the next wave
arrives. Water literally piles up and the sea level rises as much as 3 feet along the coast.

Then there is the soda-straw effect. Lower air pressure at a hurricane's center causes
the sea there to rise about 1 foot for every 1-inch difference in air pressure. The rise
can be three feet. Finally, there is storm surge. A hurricane's counterclockwise winds
spiral inward toward the eye, pushing water with it. At the storm's center, the water
sinks and flows outward. But as a hurricane approaches land and shallow water, the
water cannot sink; the sea mounds up as much as 20 feet.

Additional complicating factors: storm speed and strength, coastline configuration and
near-shore water depth.

Thunderstorm downpours, the first since flooding rains with the remnants of Hurricane
Ike and Tropical Storm Lowell forced area rivers out of their banks, doused sections of
the Chicago area Wednesday afternoon. Hardest hit were the northwest suburbs where
as much as 0.83 inches fell at Hoffman Estates, 0.50 inches at Itasca and 0.40 inches at
Palatine. Though the rains bypassed a majority of the Chicago area, Doppler radar
estimates suggested a few locations may have recorded as much as 1.50 inches of rain.
The most impressive cloud tops soared to heights of 42,000 feet, according to Doppler
radar scans.

The storms followed a fifth day at or above 80 degrees at O'Hare. While O'Hare topped
out at 82 degrees, the area's warmest readings included 88 degrees at New Lenox and
87 degrees at Orland Park and Munster, Ind., according to unofficial measurements
from WeatherBug sensors.

High winds with a mammoth area of low pressure continues battering the East Coast
from Florida to New England Thursday. Tropical forecasters are monitoring two
systems in the Atlantic which may take on tropical characteristics.

BRIEF INTERRUPTION IN CHICAGO'S 5-DAY STRING of 80 DEGREE DAYS-- BUT
MORE 80s AHEAD

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,

After the Sept. 12-14 deluge across the Chicago area, I'm wondering how much snow
would have fallen had it been mid January instead. I'm guessing since the ground would
be frozen, it would greatly exceed the eight to ten inches of rain that hit most areas.
Rick, Crown Point, Ind.

Dear Rick,

"Greatly exceed" is quite an understatement. A typical snow-to-water ratio in big
snowstorms around here is 12-1 (12 inches of snow will melt down to one inch of
water). The ratio varies greatly because it is strongly affected by air temperature, wind
speed and snowflake size during the storm. The state of the ground in the winter,
frozen or unfrozen, isn't too important. The 12-1 ratio works well for temperatures in
the upper 20s with moderate wind with little drifting and a mix of snowflake sizes. That
said, 8 to 10 inches of rain would yield 96 to 120 inches of snow.

Thanks for joining us for this Wednesday edition of Before the Forecast!
A big thank you goes out to our weather intern Eric, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

Scattered downpours developed Wednesday afternoon across sections of Lake, sections of
Kenosha and northern Cook counties. A few isolated cells also traversed portions of De Kalb
and Kane counties---though rain coverage was quite limited. Anson Mount sends us this
snapshot taken at 4:15 p.m. of heavy rain he encountered traveling home. Doppler radar scans
put cloud tops up to 37,000 ft. and lightning data indicated sporadic though comparatively
infrequent cloud to ground lightning with a t-storm cell near the Wisconsin line and others
northwest of Streator, Illinois. Thanks Anson for sharing this photo with us!

Tom Skilling

Photo courtesy of Anson Mount of Algonquin, Illinois

Temperatures surged above 80 degrees a fourth consecutive day Tuesday, and
Wednesday's predicted 80-degree high may extend the streak to five. The late-season
warm spell is occurring despite the seasonal challenges of shorter days and weaker
sunlight. The warmth caps a month of volatile temperature swings that have produced
an average September 2008 temperature of 66.7 degrees -- equal the 137 year
long-term average, yet 2.5-degrees cooler than a year ago. Not only did the mercury hit
90 degrees on this date last year, Chicagoans enjoyed 10 additional 80-degree or
warmer days before the chill of fall and winter took hold.

Chicago isn't alone in enjoying the warmth. LaCrosse, Wis., recorded its eighth
consecutive 80-degree day Tuesdayaa -- the longest late-season string in 100 years
there.

SPRAWLING ATLANTIC STORM COULD INCLUDE TROPICAL STORM KYLE

With tropical forecasters fearful forma- tion of 2008's 11th tropical storm could occur
at any time, it's worth remembering two tropical storms (Jerry and Melissa) and two
hurricanes (Karen and Lorenzo) developed this week a year ago. Powerful winds and
10-12 foot waves pounded the area from Florida to New England Tuesday.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,

People always talk about the "Blizzard of January 1967".
What snowstorm did they talk about before that one?

David Jackson Wheaton

Dear David,

It ranks as the city's fourth largest snowstorm, but prior to the 23 inch Big Snow of
January 26-27, 1967, Chicago's premier snow event was a 19.2-inch blizzard that
paralyzed the city on March 25-26, 1930. Snow fell for 43 consecutive hours, and
strong northeast winds created 4-5 foot drifts that made travel nearly impossible. Parts
of the city received even more snow than the official University of Chicago station.
Fledgling Midway Airport measured 22.3 inches of snow, putting it right up there with
the 1967 storm. However, this time the snow melted however under the strengthening
late-March sun and two weeks later the mercury soared to 90 degrees on April 10 and
11, the city's earliest 90-degree days on record.

Thanks for joining us for this Tuesday edition of Before the Forecast!
A slight chance for showers and possibly a rumble of thunder late tomorrow afternoon as well as new development in the tropics. Watch today's Before the Forecast to see all the details.
A big thank you goes out to our weather interns Aaron Brackett and Ellen Lytle, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

With warm late season weather locked in place into the coming weekend a growing
string of warm inland temperatures through Saturday could tie a half-century -old
record for the greatest number of consecutive late-season 80s here. The current record
was set from Oct. 15-22, 1953 -- a period of eight consecutive days over which a
series of four new daytime record highs were established. Lake breezes and the extent
of any cloud cover in coming days will make all the difference in whether daytime highs
make it to 80 degrees or fall a few degrees shy. Clouds this time of year easily disturb
warming.

The National Weather Service's Climate Prediction Center reports the area of the U.S. in
drought has tumbled. While 30 percent of the country had drought conditions in June,
just over 20 percent was in drought in the most recent report.

FIRST TROPICAL TROUBLES BREWING SINCE HURRICANE IKE

Hurricane forecasters are watching a developing area of low pressure near Hispanola
and fear it may become a depression. Winds of more than 39 m.p.h. would qualify the
system as Tropical Storm Kyle. Early computer forecasts suggest the system could
affect the Mid-Atlantic Coast over the coming five days.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,

Do hurricanes form in the South Atlantic? It seems that we only hear about storms in
the North Atlantic. What about storms in the Indian and Pacific oceans?

Rebecca Jeffery

Dear Rebecca,

We never hear about hurricanes in the South Atlantic because, with only one
documented exception, they just do not occur there. Cool ocean currents, strong winds
aloft and a lack of trade wind convergence all combine to provide an inhospitable
environment for tropical cyclone formation. The meteorological community was truly
surprised when unprecedented hurricane dubbed "Catarina" struck coastal Brazil on
March 28, 2004.

Numerous tropical cyclones roam both the northern and southern portions of the
Pacific and Indian oceans each year. Earlier this year a devastating storm known as
Cyclone Nargis struck Myanmar in early May, with the death toll estimated as high as
150,000.

Thanks for joining us for this Thursday edition of Before the Forecast! A slight warmup is in the cards for the Chicagoland area, but how long is it expected to last? Tom Skilling has all the details on Tonight's BTF. A big thank you goes out to our weather intern Eric, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

Check out this optical phenomenon known as “sun dogs”----the product of sunlight
refraction by the ice crystals which comprise high clouds. Jay C. Dahl of Rolling
Meadows took this photograph and was good enough to pass it along to us—and what
a shot it is! Sun dogs have been described over the years as “false suns” because they
make it look like there are two additional suns---"false suns"---on either side of the
disc of the sun. Jay C. has captured the phenomenon here to a tee! MANY THANKS Jay
C.! Great shot!

Tom Skilling

Photo courtesy of Jay C. Dahl of Rolling Meadows, Illinois

Even though autumn begins Monday at 10:44 a.m., Chicagoans will enjoy at least another week of summery weather. Highs should be close to 80 degrees on most days in a week that promises to be mainly sunny and dry. Rain chances increase as cold fronts approach late Tuesday and over the weekend, but with limited moisture any precipitation should be light, continuing the dry pattern that has followed in the wake of last weekend's deluges.
Sunday opened dreary with some clouds and fog, but conditions quickly improved as clouds thinned, paving the way for a sunny 80-degree afternoon. Such was not the case in areas far south and west of Chicago where afternoon thunderstorms brought brief soaking downpours. Downstate Ottawa was doused by 1.3 inches of rain in just 30 minutes, while torrential rain near Fowler in northwest Indiana prompted a flash flood warning.

PUERTO RICAN RAINS COULD SPELL TROUBLE FOR ATLANTIC SEABOARD
Heavy rains are accompanying a tropical disturbance near Puerto Rico. Computer forecasts show this system strengthening into a tropical storm (Kyle) that could impact the East Coast later this week.
--By Steve Kahn, WGN Weather Center Meteorologist

Dear Tom,
We just broke the record for most rain in a calendar day. What is the city's
record for rainfall in any 24-hour period?
Mark Kristoff, Lincolnwood
Dear Mark,
Chicago's record 24-hour rainfall of 9.35 inches was established during the
historic deluge that swamped the O'Hare area on Aug. 13-14, 1987. The rain
began at 9:16 p.m. on Aug. 13 and finally ended 17 hours and 29 minutes
later at 2:45 p.m. on Aug. 14. The flooding was so severe the airport was
turned into an inaccessible island. As devastating as this rainfall episode
was, it was dwarfed by Illinois' 24-hour rainfall record of 16.91 inches set
at Aurora on July 17-18, 1996. The U.S. 24-hour rainfall record is 43 inches
at Alvin, Texas, on July 25-26, 1979, while the world record is an
incredible 73.62 inches measured on March 15-16, 1952 on Reunion Island at
Cilaos, about 500 miles east of Madagascar.

Autumn begins at 10:44 a.m. Monday, but the change of seasons will go largely
unnoticed as the city basks in a summery week highlighted by an abundance of sun
and warmth. Temperatures should approach 80 degrees on several days, especially
inland. Such readings are nearly 10 degrees above the steadily declining seasonal
normals (currently in the lower 70s).

The welcome dry-out after last weekend's deluge is expected to continue. This will
allow the levels of streams and rivers to continue to fall. Isolated thunderstorms could
pop up, with afternoon heating mainly west and south of Chicago on Sunday. A few
more thunderstorms could develop midweek before a cold front, but coverage should
be spotty and rainfall totals light.

AFTER LULL IN STORMINESS, TROPICS SHOWING NEW SIGNS OF LIFE

The Atlantic Basin has been quiet after a tumultuous period, where storms Gustav,
Hanna, Ike and Josephine developed in rapid succession. Now a tropical wave in the
northeast Caribbean shows potential for developing into Tropical Storm Kyle. The
system is bringing gusty rains to that region.

--By Steve Kahn, WGN Weather Center Meteorologist

Dear Tom,

The Earth's surface is always split 50-50, the part receiving direct sunlight and the part
not receiving it. That's common sense, but a friend claims there is always more daylight
than darkness (excluding twilight). Please shoot him down.

-Ken Nathanson

Dear Ken,

Reality sometimes defies common sense. Your friend is correct: There is more sun than no
sun. Here’s why: The sun is not a point in space. Triton College astronomer Dan Joyce
says direct sunlight first reaches a given spot the moment the top of the sun’s disk pokes
above the horizon at sunrise; at sunset, sunlight continues until the top of the disk sinks
below the horizon. The sunrise/sunset minutes when only a portion of the solar disk is
above the horizon add to daylight time. Also atmospheric refraction makes the sun appear
higher in the sky, lengthening daylight by a few minutes.

Come see Tom Skilling present WGN's documentary When Lightning Strikes
on SATURDAY Sept. 20, 2008 at 1 p.m. at the Museum of Science and Industry in Chicago.

This event is suitable for Grades 4-8, Grades 9-12 and Adults. After the screening Tom Skilling will lead a discussion of this fascinating topic.

Requires a FREE ticket for entry. Space is limited and reservations are recommended.
Advance tickets are recommended by calling the Museum at (773) 684-1414 and will be
available for pick-up the day of the event.

CLICK HERE FOR FURTHER DETAIL

Dry, comparatively warm weather dominates the vast majority of this final weekend of
summer. But, the atmosphere is hardly moisture free. Nearly an inch of evaporated water
hangs in the air over Chicago both Saturday and Sunday. Daytime heating is to increase
the rate at which temperatures decline with height. It’s a situation referred to as an
unstable atmosphere, and it encourages air to rise. With an inland-moving lake breeze
likely to slice into the moderately moist air, it’s not inconceivable a few isolated t-storms
may form. The same process repeats Sunday, but strengthening northeast winds may
force any isolated showers to drift inland to the west or south suburbs in the afternoon.
Rainfall coverage is to be limited.

SIX OF SEPTEMBER 2007’S FINAL 10 DAYS SURGED PAST 80 DEGREES
To date, Chicago has had only three days in the 80s this month, versus 11 a year ago.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
How do winds affect Lake Michigan water temperatures? Is the lake still warm
enough for one more family outing at the St. Joseph, Mich., beach?
Mark Tieszen
Dear Mark,
Current Lake Michigan water temperatures are available at this web address:
http://www.coastwatch.msu.edu/twomichigans.html
Right now (Sept. 19), waters at St. Joseph are in the upper 60s.
During the warmer months of the year, a layer of mild water at the surface
of Lake Michigan floats over much cooler water beneath it. Winds push the
surface waters around and stormy weather causes colder water to mix upward.
The highest surface water temperatures therefore occur during periods of
sunny, tranquil weather. Onshore winds will push the warmest surface water
to the beaches, whereas offshore winds cause cold-water upwelling at the
beaches.

Thanks for joining us for this Thursday edition of Before the Forecast! A slight warmup is in the cards for the Chicagoland area, but how long is it expected to last? Tom Skilling has all the details on Tonight's BTF. A big thank you goes out to our weather intern Eric, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

Our intrepid traveler from the U.K., Mark Vogan, shares these beautiful shots of Wales.
Mark tells us:

"These pictures were taken from the holiday resort town of Llandudno on the
north coast of Wales, some 287 miles from home, we also drove to the Isle of Anglesey,
which is in extreme northwest Wales, which sticks out into the Irish Sea. The weather
was simply stunning with warm sunshine and stunning scenery. The round trip tallied
665 miles."

Thanks, Mark, for sharing these spectacular views with us from such a beautiful place
in the world!
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Photos courtesy of Mark Vogan, Glasgow, Scotland

The final weekend of summer arrives with radically different weather than last weekend
-- though wet soils and a bit of instability may be just enough to prod isolated
thunderstorm development in a few spots Sunday afternoon. Temps are to warm above
last weekend's highs (75 degrees Saturday and 72 degrees Sunday) but without the
huge 8.45-inch rain tally at O'Hare or the 13.06 inches at Crown Point, Ind. -- the
region's heaviest reported.

Friday's high temperature hits 80 degrees for only the fourth time this month and
readings are likely to flirt with 80 degrees again on Saturday. The warmth is welcome in
a month running 2 degrees cooler than a year ago.

Signs of autumn, which arrives officially at 10.44 a.m. Monday, are becoming more
numerous. Fall colors are out and expanding in coverage across the Upper Midwest.

SEPTEMBER'S HEFTY RAINS SLASH SUN 23% FROM YEAR AGO

Though on hold this past week, the month's exorbitant rainfall has slashed Chicago's
September sunshine tally 23% over the same period a year ago. Veteran weather
observer Frank Wachowski reports just 53% of the month's possible sun has occurred
-- well below the normal of 63%.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Mr. Skilling,

Was the "record rain" this past weekend really a record? I remember more than nine
inches of rain back in mid August in 1987.

Steve Platko, Prospect Heights, Ill.

Dear Steve,

Although your memory is correct, a record was established. Chicago logged 9.35 inches
of rain Aug. 13-14, 1987 --2.86 inches the 13th and 6.49 inches the 14th -- and that
two-day event stands as the city's greatest rain event.

Sept. 12-13-14, 2008, brought less rain: 8.45 inches officially (0.37 of an inch the
12th, 6.64 inches the 13th and 1.44 inches the 14th). But the 6.64 inches on Sept. 13
established a calendar-day rainfall record by surpassing the August 14, 1987, total.

The recent rain and resultant flooding was far more widespread, affecting all of
metropolitan Chicago (including northwest Indiana), whereas the 1987 event affected
only extreme northwest Chicago and the northwest suburbs.

Thanks for joining us for this Thursday edition of Before the Forecast! A slight warmup is in the cards for the Chicagoland area, but how long is it expected to last? Tom Skilling has all the details on Tonight's BTF. A big thank you goes out to our weather intern Eric, for helping us out with tonight's video.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

The colors are already out along Highway 70 in northern Wisconsin! These photos come
to us from Dan Hanson who also reports the fire danger there is “moderate”. That area
didn’t get in on the rain which swamped the Chicago area and a large swath of the
Midwest last weekend from the remnants of Tropical Storm Lowell and Hurricane Ike.
Many thanks, Daniel, for sharing these shots with us.

Tom Skilling

Photos courtesy of Daniel Hanson

The approach of a dust storm is s sight to behold as you can see from these Arizona
photos taken last week and forwarded to us by Steve Michaelis The dust storm pictured
here bearing down on Peoria, Arizona was 25 miles across, Steve tells us. He also reports
it never produced a drop of rain. Terrific shots, Steve---THANKS for sharing them with us!

Tom Skilling

Photos courtesy of Steve Michaelis, Peoria, Arizona

Did you see our full moon this week? Thomas Nava photographed it around 9pm
Wednesday evening (September 17). Nice job, Thomas—and THANKS for sharing this with
us!

Tom Skilling


Photo courtesy of Thomas Nava, Chicago, Illinois

Until Wednesday afternoon's 82-degree high at O'Hare and 83-degree high at Midway,
September had been no bargain for the warm-weather enthusiasts among us. It was
only the third time this month the mercury has reached or exceeded 80 degrees -- the
fewest in a September here since the two recorded in 1993. In 80 years of weather
observations at Midway Airport, September's opening 18 days have hosted eight 80s.
The lack of warm days has occurred with the month averaging 2.5 degrees below the
long-term average -- cool enough to rank among the chilliest 25 percent of
Septembers on the books over the past 138 years at the city's official observation sites.

Wednesday's warmest highs included an unofficial 86 degrees at the WeatherBug
temperature sensor at Orland Park and 85 degrees at Itasca. A wind shift to the
northeast that swept into the area between 3 and 5 p.m. sent temperatures tumbling
from the 80s to the 60s. Warmer weather returns Friday and Saturday.

83 MINUTES OF DAILY SUNLIGHT DISAPPEARS OVER THE NEXT 30
DAYS

Chicago's daily dose of sun has dropped by nearly three hours since days began
shortening June 20. Another 83 minutes vanishes in the next month.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,

What tropical cyclone hold the record for longevity?

Ken Bockelmann

Dear Ken,

The tropical cyclone longevity award goes to Hurricane/Typhoon John, which roamed
the Pacific Ocean for 31 days back in 1994. John formed off southern Mexico on August
11 and gradually strengthened to a Category 5 monster with 175 m.p.h. winds By Aug.
23.

As it traveled west it eventually crossed the dateline and was reclassified as Typhoon
John. The storm then turned and headed east where it again crossed the dateline
regaining its hurricane title. John finally dissipated in the cooler waters of the North
Pacific on September 11.

In the Atlantic Basin, two storms lasted about 28 days, the San Ciriaco Hurricane, which
affected Puerto Rico, the Bahamas and North Carolina in 1899 and Hurricane Ginger that
made a North Carolina landfall in 1971.

Thanks for joining us for this Wednesday edition of Before the Forecast! A huge thank you to our amazing weather intern, Eric, for helping us out with tonight's BTF!

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

The run-off from this past weekend's record-breaking rains is impacting Lake
Michigan. Water levels have risen an inch this month alone, U. S. Army Corps of
Engineers meteorologist Keith Kompoltowicz tells us. It's an increase that has
occurred at a time of the year when lake levels typically fall an inch or two.
Kompoltowicz estimates as much as 877.5-billion additional gallons of water now
reside in Lake Michigan. With September rainfall across the lake's drainage basin 227
percent of normal to date and water from last weekend's rains still working through
tributaries that feed into the mammoth water body, the full impact of the recent
downpours may not yet be fully reflected in lake levels.

Northeast winds Sunday piled water up along the northeast Illinois shoreline
temporarily boosting water levels there 12 to 18 inches .

ERUPTION OF ALASKA'S KASATOCHI VOLCANO BEHIND COLORFUL SUNSETS

Beautiful sunsets worldwide since late August are being attributed to an eruption of
the Kasatochi Volcano on Alaska's Aleutian Islands. Stratospheric winds have
distributed volcanic ash which refracts sunlight producing the array of warm colors at
sunset.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,

The symbols for cold fronts and warm fronts on weather maps are used everywhere.
Who dreamed up those symbols?

Barry Phillips

Dear Barry,

In the 1920s, an energetic group of researchers in Bergen, Norway, was making
significant progress in theoretical and applied meteorology. At the time, the group was
advancing the concept of "fronts," the boundaries between different air masses.

On their maps, the researchers used blue lines to indicate cold fronts and red lines for
warm fronts, but color maps were expensive to print.

Tor Bergeron (1891-1977), a member of the group, proposed a solution. While on a trip,
he mailed a postcard dated Jan. 8, 1924, to Bergen. On the postcard he sketched a cold
front with sharp, triangular barbs and a warm front with rounded, semicircular pips --
and a new meteorological tradition was born.

Amanda Pickett sends us this photo in south Hobart. She tell us:

"I went to Deep River county park in south Hobart today to see where the river level was.
I am attaching a photo of a bridge that previously had water running under it with a
brick path leading up to it. As you can see, it's a bridge to nowhere right now. The
water has receded quite a bit there and it's still flooded!"

Amanda Pickett, Winfield, IN

Thanks for joining us for this Tuesday edition of Before the Forecast! A huge thank you to our amazing weather interns, Ellen and Aaron, for helping us out with tonight's BTF!

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

It took a rare one-two punch by the remnants of two separate tropical systems to
produce the weekend's one-of-a-kind Midwest deluge. Rain fell in Chicago 48 of the
72 hours between Friday and Sunday and totaled 8.54 inches. There have been heavier
rains outside the city -- among them a 17-inch drenching that hit the west and
southern suburbs in July 1996 centered on Aurora and Naperville. It established a new
24 hour statewide record. But, only once before -- in August 1987 -- has more rain
fallen in a three day period in the city. Moisture associated with landfalling Pacific

Tropical Storm Lowell hit first on Saturday and was followed by Hurricane Ike's
remnants Sunday. The downpour has pushed September's rain tally to 12.61 inches --
a level near seven times normal at this point in the month and four times the full month
norm.

In the wake of the wet weekend, Monday's 63-degree high was Chicago's coolest since
the thermometer hit 62 degrees May 28.

WINTERS FOLLOWING WET SEPTEMBERS SHOW MODEST BIAS TOWARD SNOW

Snow enthusiasts may be encouraged to learn that 7 of 12 winters since 1895 which
followed wet Septembers ended up with more than the long-term average amount of
snow.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,

Have we ever been hit by hurricane remnants twice in one season let alone one month
like we've have with Gustav and Ike?

Judy Serwatka Valparaiso and Mary King

Dear Judy and Mary,

Since 1900 there have been 17 low pressure centers that were once hurricanes that have
passed within about 100 miles of Chicago. Some, like Carla's remnants in 1961, have
brought Chicago torrential rain and strong winds, while others have passed bearing
only light showers

Before this month, the last hurricane remnant to affect Chicago was Rita's on September
25-26, 2005, when a meager 0.14 of an inch of rain fell. While Chicago has
undoubtedly received rainfall associated with moisture from a hurricane more than
once in a season, this month's close encounters with the remains of both Hurricane
Gustav and Hurricane Ike appear to be a first for the city.

Doug Pellegrino sent this photo taken in Bartlett, Ill and the devastation around Beaver Pond.

Doug tells us:

"..the water has run up the driveway of houses that sit across the street from
the pond, so you can imagine how badly the water affected those houses lying on the
same side of the street as the pond. In fact, water is already up to the ceiling in the
basements of these homes and into the 1st floor in some of them."

Photo courtesy of Doug Pellegrino

Leslie Spreitzer sends us this photo of flooding in Minooka, Il.

Photo courtesy of Leslie Spreitzer

Tom Janito from Oswego sent us this photo of the Elmhurst Stone Quarry. Tom tell us:

"Here is a picture of the east lobe of the Elmhurst Stone Quarry, they have been
pumping water into the quarry from Salt Creek. I gues the water my be 150' deep so
far"

Photo courtesy Tom Janita, Oswego, Illinois

George Hamilton from DesPlaines sent us these photos of the flooding on Oakton Street in Des Plaines

Photos courtesy of George Hamilton,  Des Plaines, Illinois

Thanks for joining us for this Monday edition of Before the Forecast! Today was the premiere of the WGN's Evening News at 5:30, which includes Tom's evening forecast! If you missed it, you can catch it on the wgntv.com website under "Evening News," and thanks for watching Before the Forecast tonight!

Some big weather news tonight: Big rains are scheduled for tonight and tomorrow in Chicagoland, but the big story is the possibly catastrophic Hurricane Ike, which is moving closer and closer to the Texas coastline. Watch tonight's BTF to find out why this weather event is turning out to be unlike anything that Gustav produced.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

Check these photos out. They come to us from Roxie and Dave who report their rain
gauge collected 7.50”. Amazing shots—MANY THANKS Roxie and Dave!

-Tom Skilling

Photos courtesy of Roxie and Dave in Streamwood

Patrick Skach, who always keeps us wonderfully up to date on the meteorological
happenings in Oak Brook, relays this photo of a chipmunk he photographed Sunday hiding
from then rain in the wheel well of a car. Looks like this is one fella who actually
succeeded in staying dry over our record rainy weekend! THANKS Patrick! Great shot!

Tom Skilling


Photo courtesy of Patrick Skach, Oak Brook, Illinois

Thanks to all who have shared photos of the past weekend's devastating Chicago area
flooding with us. Andrew Lennie sent us these shots from River Forest. There is no way to
look at these and not feel for the residents of these neighborhoods. Thanks Andrew!

Tom Skilling

Photos courtesy of Andrew Lennie, River Forest, Illinois

Flooding in Addison and Medinah

Photo by Nathan Filip

Flooding in Bensenville

Photo by Dan Giampaolo

Flooding in Carol Stream

Photos by Robert Guico

Flooding at Lake Holiday in Somanauk

Photo by Jamie Wesbrock

Steve Kahn WGN Weather Center Meteorologist

The remnant low-pressure area associated with Hurricane Ike has moved to northern
New England, but runoff from record-breaking rainfall continues to promote and
prolong flooding along rivers and creeks over northeast Illinois and northwest Indiana.
Greatest area storm totals reported by Sunday evening were 10.48 inches near Crown
Point, Ind., and 10.4 inches in Peotone.
The water has gone down in many neighborhoods, but the Des Plaines River is at record
levels at Des Plaines and Riverside and forecast to remain above flood stage until
Wednesday.
Record flooding along the Little Calumet River in South Holland and Munster, Ind., is
forecast to fall below flood stage Monday evening. Flooding is also occurring along the
Fox River at Dayton, the Illinois River at Morris and Thorn Creek in Thornton and at
many points along the Kankakee River.

AN EXTENDED DRYING-OUT PERIOD
High pressure builds into the Midwest and dominates Chicago weather the remainder of
the week. After today, mostly clear skies with occasional scattered cumulus and cirrus
clouds along with light southerly winds will hold into next weekend. Daytime highs will
be mostly in the 70s and nighttime lows in the 50s.
--By Paul Dailey, WGN Weather Center Meteorologist

Dear Tom,
The storm surge at Galveston did not reach the 20-foot level that would have
been disastrous, but the surge close to New Orleans topped some levees in
that area and was higher than observed with Katrina. How could this be, when
Ike tracked right over Galveston?
Diane, western suburbs
Dear Diane,
The top of the sea wall at Galveston stands at 17 feet above mean sea level,
and a 20-foot rise there would have inundated the city. Hurricane Ike was an
unusually large storm and it was rather slow-moving -- both factors (long
fetch for a long time) allowed it to generate excessively high waves. Buoy
data indicated 25-35 feet.
At New Orleans, Katrina's winds mainly blew offshore (the hurricane made
landfall slightly to the east on the city), whereas Ike's winds blew onshore
(Ike made landfall 285 miles west of New Orleans). Surge is always higher
where winds blow onshore.

Heavy rain totaling up to 8 inches brought widespread flooding to the Chicago area Saturday.

Flooding in Carol Stream

Photos by Jennifer Gulco

Flooding in Bensenville

Photos by Carol Perry

Flooding in Hoffman Estates

Photo by Dave Schroeder

Flooding in Evanston

Photo by Mario

Steve Kahn WGN Weather Center Meteorologist

Flooding in Franklin Park

Photos by Francine Jackson

Dear Tom,

This year Chicago’s hottest day occurred after Labor Day. Has this ever happened before?
James Cook, Chicago

Dear James,

In Chicago, the occurrence of the year’s highest temperature after Labor Day is not
without precedent, but it is rare: only two times in 80 years at Midway Airport.
(Note:Labor Day is observed on the first Monday in September and the holiday can land
on any day from Sept. 1 through Sept. 7. It fell on Sept. 1 this year and the year’s
highest temperature, 94 degrees, occurred on Sept. 2.) In 1939, the year’s highest
temperature, 102 degrees, was on Sept. 15. That reading was a record high for the date
and also the latest-occurring date for an annual high. The year 1978 stands as the only
other year whose highest temperature occurred after Labor Day: 95 degrees on Sept. 8.

Big rains sweep the area this weekend, and flood watches have been hoisted. The waves
of drenching rainfall could deposit 3- to 4-inch totals -- locally more -- which, if true,
would place the multiday rain event among the 11 heaviest in September over 138 years
of records here. This comes in the midst of a September already among the three
wettest on the books. Rain is to hit with two separate systems separated by a pause
Saturday night. The first features clusters of gusty t-storms in warm, humid air
Saturday. Wind-driven downpours follow as the remnants of Hurricane Ike roar by
Sunday.
Ike -- a huge storm more than 500 miles across -- lambasted the northwest Gulf
Coast on Friday. By late morning, 100 m.p.h.-plus wind gusts were being clocked on
offshore oil rigs. And the colossal storm's punishing onshore winds, gusting past 80
m.p.h. on Galveston Island outside Houston, had pushed a 9-foot dome of water across
parts of the coastline -- a storm surge which threatened to grow to 15 to 22 feet --
one of the highest on record in Texas.

SATURDAY'S WARM, MUGGY AIR BRINGS SEVERE THUNDERSTORM RISK
Thunderstorms may grow severe in parts of the area Saturday if any heating at all
materializes.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
News reports Friday morning said water at the shore of the Gulf of Mexico
had already risen three feet. In a video from Galveston, it was sunny, a
gentle breeze was blowing and water a couple feet deep covered roads and was
into houses -- 30 hours before Ike was due to arrive. How can this be?
John Wilkerson
Dear John,
Dr. Bob Sheets, past director of the National Hurricane Center, says it's
called "wave set-up." Abnormally large waves generated by hurricane winds
bring to the shore abnormally large amounts of water in the tops of breaking
waves -- too much water to be sent back into deeper water before the next
wave arrives. Incoming and outgoing water are not in balance. All that water
pushing into the coastal zone has no place to go but up, and the sea
literally rises along the coast. The rise at a given spot depends on the
depth of water near shore and the configuration of the shoreline.

Thanks for joining us for this Friday, weekend edition of Before the Forecast.

Some big weather news tonight: Big rains are scheduled for tonight and tomorrow in Chicagoland, but the big story is the possibly catastrophic Hurricane Ike, which is moving closer and closer to the Texas coastline. Watch tonight's BTF to find out why this weather event is turning out to be unlike anything that Gustav produced.

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

Thunderstorms drenched Downstate Illinois on Thursday and provide a guide on just
how sporadic and thundery rains may sweep the Chicago area from time to time over
the coming days -- hitting hard and fast but limited at any given time to specific
sections of the metro area. The coming rains are likely to include possible downpours
over southern sections of the metro area as Hurricane Ike's remnants sweep across the
Midwest on Sunday into Sunday night. Computer estimates of Chicago's rainfall in the
next three days range from 2 to 4 inches -- but a few areas could get hit by heavier
rains. What's important to underscore as outdoor weekend planning takes place is that
the rains here will be separated by extended dry periods. Moisture content of the
atmosphere exceeds 2 inches Friday night into Saturday, suggesting any thunderstorms
that erupt could include local downpours. Petersburg, Ill., northwest of Springfield, was
hit by 3.02 inches of rain Thursday and nearby Greenview recorded 2.99 inches
underscoring the potential of any subsequent downpours in coming days.

GALVESTON COASTAL RESIDENTS TOLD TO LEAVE OR PERISH AS HURRICANE IKE
THREATENS MONSTER STORM SURGE.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,

Who decides to sound tornado sirens in the Chicago area?

Mary Harris Russell, Chicago

Dear Mary,

The decision to sound tornado sirens is made by individual communities. The Chicago
National Weather Service (NWS), which issues tornado warnings in northeast Illinois, has
no control.

"Procedures (to sound sirens) vary from community to community." says meteorologist
Jim Allsopp of the weather service . "The sirens can be set off at the request of village
officials such as mayor, police or fire chief or emergency management coordinator." A
standard criterion for sounding sirens is the report of a tornado or funnel cloud, usually
within five to ten miles of the town. Allsopp advises that, "NOAA weather radio is the
best way to get warnings direct from the NWS," Allsopp says.

Thanks for joining us for this Thursday edition of Before the Forecast! Thanks again to Kim for helping us out with tonight's webcast!

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

With the arrival of noticeably muggier Gulf Coast level 70-degree dew points in the
next day, the atmospheric stage is being set for another rare big September rain. Only
12 times in the past 138 years -- just 9 percent of Septembers on record here since
1871 -- has the month produced three 1-inch-plus rain events. Computer models
boost the air's moisture content (precipitable water) to more than 2 inches Friday into
Saturday. Thunderstorms have the unique ability to sweep moisture from the
environment and concentrate it in especially heavy downpours. This makes projections
of local 2-inch totals from now through Monday in the hardest hit areas look
reasonable. Rain won't be continuous, arriving instead in clusters or waves -- the first
due late Thursday night and early Friday. Saturday's t-storm frequency appears the
greatest of the next three days.

IKE COULD BE REAL TROUBLE FOR HOUSTON/GALVESTON AREAS

A hurricane hasn't hit the Houston/Galveston area since Chantal came ashore in 1989.
The city's last Category 3 storm was Alicia in 1983 -- a devastating $2-billion
Category 3 storm. Ike could give the area and the Texas Coast quite a blow, piling Gulf
water onto the shoreline in powerhouse east winds.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,

I always assumed the moon came up at dark and set at dawn, just the opposite of the
sun, but now I find I was wrong. On Aug. 1, both the moon and sun rose and set within
a few minutes of each other. What's the theory of this?
Jane Kuntz, Arlington Heights

Dear Jane,

Triton College astronomer Dan Joyce explains:

The moon orbits the Earth on roughly a monthly basis in the same direction the Earth
rotates on its axis, thereby permitting the moon to appear either close to or far from the
sun. When near the sun, the moon's far side is illuminated and we cannot see it, the
phase called new moon.

Halfway to becoming full, we see a half-lit moon (1st quarter), which rises near noon
and sets near midnight. The full moon rises at sunset and sets at sunrise . The phase
halfway back to new moon from full, also half-lit (3rd quarter) it rises at midnight and
sets at noon.

Thanks for joining us for this Wednesday edition of Before the Forecast!

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

Big changes lie ahead. Summerlike warmth and humidity return in coming days.
Readings are headed to 80 degrees Thursday for the first time in 10 days and are likely
to flirt with 80 degrees Friday and Saturday. A multiday 80-degree spell isn't unusual
this time of year. Weather records put odds of back to back 80s beyond this date at 97
percent.

The higher temperatures return with surging humidities -- a set-up which threatens a
new round of heavy rains Friday night into Saturday. More rain involving the remnants
of Hurricane Ike could hit late in the weekend.

RECENT NIGHTS AMONG COOLEST IN EARLY SEPTEMBER SINCE 1997

Warmth has been a no-show of late. Until the recent chill, it's been 11 years since two
consecutive early September Chicago mornings have recorded low temps in the 40s.
Daybreak lows dipped as low as 43 degrees early Tuesday just west of Aurora and in
Rockford. But it was Ogle County's Rochelle -- west of De Kalb -- which logged the
area's chilliest reading of 37 degrees. Weather history suggests the first freezing
temperatures at O'Hare, if this proves a typical meteorological autumn, are still more
than month away.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,

How did meteorologists track hurricanes before satellites?
Mike Schaeffer

Dear Mike,
Today, meteorologists have the luxury of continuous global satellite coverage that
makes it impossible for a tropical cyclone to escape detection. Before the advent of
aircraft and satellite surveillance, forecasters had to rely on a smattering of ship reports
and weather transmissions from the islands to learn about approaching storms. In the
era before radio communication, when an island was devastated by a hurricane, there
was no way to spread the warning to areas in the storm's path.

Detailed Atlantic Basin tropical cyclone records date back to 1851, but it is almost a
certainty that these records are incomplete with some storms that never made landfall
going undetected. In many instances, hurricanes struck with little advance warning,
other than a rapid increase in wind and rain and a rapidly falling barometer.

Thanks for joining us for this Tuesday edition of Before the Forecast!

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

Rains drenched Chicago a second time in just four days Monday, dumping 1.01 inches
at Midway Airport and 1.22 inches at O'Hare International Airport. Monday's dousing
pushed the official O'Hare monthly tally to 4.15 inches, the second wettest in 138 years
and wettest since 1894. Temperatures, which had struggled to reach 67 degrees late
morning, tumbled to the mid-50s as the rain arrived -- levels more typical of
November.

ASTRONOMERS MARVELING AT QUIET STATE OF THE SUN

Only four years ago, sunspots -- the product of intense storms on the surface of our
nearest star -- were at a 1,000 year high. It's been 14 months since the last significant
solar eruption, reports astronomer Dan Joyce. Some in the astronomy community report
the past month has been the first to be free of sunspots in 95 years. Energy from the
sun declines slightly in such periods. The Maunder Minimum, an extended period void
of sunspots in the late 17th Century, may have played a role in a global temperature
decline that caused the Thames River in London to freeze and European harvests to fail.
There is no consensus on how long the current solar lull may last, but some scientists
believe it may end in the next half year.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,

Who put out the first hurricane forecast, and when?
-Kathleen Samaras

Dear Kathleen,

The answer will surprise you: July, 1502, by Christopher Columbus. In the several years
since his epic voyage to the New World in 1492, Columbus had learned to read the
signs of an approaching hurricane in the behavior of the clouds and sea. In July 1502,
he saw those signs again and requested the Spanish governor of Hispaniola permission
to harbor his ships there. Permission denied, Columbus rode out the hurricane in a less
favorable port, but 21 of 30 Spanish ships that sailed from Hispaniola against his
advice sank, with more than 500 lives lost.

The incensed Columbus wrote, "What man ever born, not excepting Job, who would not
have died of despair when in such weather, seeking safety for ... my shipmates and
myself, we were forbidden the land and the harbors that I, by God's will and sweating
blood, had won for Spain?"

Thanks for joining us for this Monday edition of Before the Forecast. Heavy rains have poured down on the Chicago area all day -- find out what Tom has to say about the rains for tonight and tomorrow in BTF!

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

It's going to be a lot more fall-like in Chicago early this week as the city braces for
another round of rain Monday afternoon and night followed by the coolest weather here
since late May.
High temperatures Monday and Tuesday are expected to hold below 70 degrees, and as
chilly north winds arrive in the wake of the rain, overnight lows are likely to drop below
the 50-degree mark for the first time in more than three months.
Heaviest rainfall could approach an inch by Monday night as a strong disturbance
moves through the region.

HANNA DEPARTS AFTER SOAKING THE NORTHEAST; IKE TAKES CENTER STAGE
Tropical Storm Hanna brought a wet and blustery weekend to the Northeast, causing
some flash flooding as up to 6 inches of rain fell in areas around New York City. Gusty
winds downed trees and power lines, but overall damage was minor. Hanna may have
spawned a tornado in Allentown, Pa., Saturday. A funnel was sighted shortly before high
winds partially ripped off roofs and damaged homes in the area.
Hurricane Ike weakened a bit Sunday as it approached Cuba, but it was still packing
120 m.p.h. top winds Sunday evening. Ike is expected to make landfall somewhere on
the Gulf Coast by the end of the week.
--By Steve Kahn, WGN Weather Center Meteorologist

Dear Tom,
Recently you talked about disturbances near the Cape Verde Islands that turn
into hurricanes. Can you elaborate?
Rich Gardner
Dear Rich,
Cape Verde hurricanes are Atlantic Basin tropical cyclones that develop from
"easterly waves" that move west across Africa into the Atlantic near the
Cape Verde Islands off the coast of Senegal and Mauritania. The
disturbances, usually clusters of thunderstorms, travel west across the
tropical Atlantic along the southern periphery of the Atlantic Subtropical
Ridge, gradually gaining strength and circulation from the warm ocean. On
average two Cape Verde storms form each season, usually in August and
September. Some notable Cape Verde hurricane include the 1900 Galveston
Hurricane, Donna (1960), Hugo (1989) and Andrew (1992). The current
Hurricane Ike is also a Cape Verde type.

Just days after a thorough soaking by the remnants of Gustav, more rain is headed for
Chicago. Some light showers may develop Sunday, but the city is in line for another
round of significant shower and thunderstorm activity Monday and Monday night as a
cold front pushes through the area. Chilly weather will follow, and low temperatures
may dip below 50 degrees both Tuesday and Wednesday mornings for the first time
since May 29, when the mercury dipped to 42 degrees.

A brief warm-up will boost readings back to around 80 by Thursday, but another cold
front will drop temperatures back to around 70 by next weekend.

HANNA EUROPE-BOUND AS DANGEROUS HURRICANE IKE MARCHES TOWARD FLORIDA AND THE GULF

Tropical Storm Hanna brushed the Eastern Seaboard with gusty winds and heavy rainfall
Saturday. After speeding through the Canadian Maritimes Sunday, it will make a beeline
for the British Isles. Meanwhile, Ike, now a Category 4 hurricane packing top winds of
135 m.p.h., appears headed on a path that will threaten Cuba and southern Florida
before entering the Gulf of Mexico by midweek.

--By Steve Kahn, WGN Weather Center Meteorologist

Dear Tom,
Please tell me a few things about the “eye” of a hurricane.
-Leecie Pearce, Delavan, Wis.

Dear Leecie,

The “eye” is a roughly circular area of rather quiet weather found at the center of a
hurricane. Eyes generally are 20 to 40 miles across, but they range in size from about 5
miles to (rarely) more than 120 miles. Winds are light or calm at the very center of an
eye, but strong winds can sometimes extend into its periphery. There is little or no rain,
and sometimes the sky is partially clear, but the eye is surrounded by a circular ring of
towering cumulonimbus clouds— the “eyewall”—that often extends upward more than
30,000 feet. A hurricane’s lowest air pressure is found in its eye, and its highest winds
occur in the eyewall. Temperatures in the eye are only slightly warmer than in the
surrounding storm.

The cool air mass responsible for Chicago's first back-to-back 60s -- on Thursday and
Friday at Midway Airport -- in nearly 11 years during September's opening five days
dominates this weekend. While both Saturday and Sunday a week ago produced highs
of 90 degrees, peak readings Saturday and Sunday will average 20 degrees cooler.
Those are levels modestly below normal by early September standards. Weak
disturbances embedded in the jet stream will produce several periods in which showers
may flare.
Final rain tallies from Gustav's blustery remnants Thursday approached 3 inches. The
National Weather Service confirms damage in Wheatfield in northwest Indiana was
produced by winds that were part of an EF1 twister that hit the community around 5:30
p.m.

DANGEROUS IKE MAY THREATEN FLORIDA AND ENTER THE GULF OF MEXICO
While Tropical Storm Hanna rapidly spins up the Eastern Seaboard, all eyes are turning
to Hurricane Ike, currently heading toward the Bahamas.
Ike, a Category 3 hurricane packing top winds of 115 m.p.h. Friday night, is expected to
grow even stronger as it steadily churns westward toward Florida and the Gulf of
Mexico.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
Why does the Atlantic Ocean get more hurricane activity than the Pacific?
Scott Okun
Dear Scott,
With all of the recent hurricane activity in the Atlantic Basin it may seem
that way, but the truth is the Pacific wins the tropical cyclone competition
hands down. The Atlantic Basin averages about 10 named storms each year
while the Eastern Pacific typically logs 16 storms. Because of the potential
threat to the United States, the Atlantic storms get a lot of publicity
while most of the eastern Pacific storms get little press as they pose a
threat only to shipping. In addition, each year the Northwest Pacific
averages 20 typhoons and the Southwest Pacific waters generate as many as 10
hurricanes. In contrast, because of colder water and strong winds aloft
there are almost no hurricanes in the South Atlantic.

Thanks for joining us for this Friday, weekend edition of Before the Forecast! And a special thanks to Kim, our intern, for working hard to bring you today's webcast!

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

Gustav's blustery remnants lived up to the advance billing Thursday, dousing the
Chicago area with its heaviest official rain in more than five years. By evening,
preliminary totals at the Whitney Young High School Weather Bug sensor had reached
4.12 inches with rain still falling. Other reports included 4.06 inches at Justice, 3.76
inches at Palatine, 3.67 inches at Wilmette, 3.62 inches at Orland Park and 3.51 inches
at Lake Zurich. A rainfall of 4.50 inches hit Downstate at London Mills -- located
between Peoria and the Mississippi River. It marked the first time in three years that the
remnants of a landfalling Gulf Coast hurricane reached Chicago. Hurricane's Rita's
remnants were the last to occur here in 2005.

POWERHOUSE HURRICANE IKE CHURNS TOWARD BAHAMAS; FLORIDIANS
UNEASY

Ragged Tropical Storm Hanna is headed for the Carolinas -- but more ominously,
powerhouse Category 4-intensity (135 m.p.h. peak winds) Hurricane Ike appears
headed for the Bahamas. Some computer models indicate Florida may later be a target
which has residents there on edge. The storm is still five days aways and much can
change. But it's a situation that warrants close observation.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,

I lived in Liberia for seven years and we experienced dust storms called harmattans. Do
these winds eventually cause the hurricanes that reach the U.S.
-Patrick McKeen Buffalo Grove

Dear Patrick,

Hurricanes that affect United States often do develop from westward-moving
disturbances the move out of Africa into the Atlantic near the Cape Verde Islands.
However, these dust storms are not associated with hurricanes. Instead, the harmattan
winds are dry, dust-carrying winds from the northeast or east that blow in West Africa
especially from late November until mid-March. In summer, an onshore flow called the
southwest monsoon brings cooler air inland to West Africa, undercutting the
harmattan. The harmattan continue to blow aloft in a layer from about 3,000-6000 feet
carrying dust out into the Atlantic.

Thanks for joining us for this Thursday edition of Before the Forecast!

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

Chicago braces for an encounter with Hurricane Gustav's rainy, blustery remnants
Thursday. The storm's impact across the central U.S. has been ongoing since landfall
early Tuesday. Rains in Arkansas on Wednesday alone approached 7 inches at Bee
Branch and 5.89 inches at Jacksonville. The system is responsible for 49 twisters from
Lousiana to Arkansas since coming ashore -- and severe storms are a possibility as far
north as central Illinois and Indiana on Thursday.

For Chicago, Gustav means rain and possibly a good deal of it. Of 26 computer
projections of rainfall here through Friday night, 23 indicated amounts exceeding 2
inches. The average of all estimates topped 3 inches with several in the 4- to 5-inch
range. A tally of 3 inches or more would make this the heaviest official rain event in the
city since 3.20 inches fell on April 30-May 1, 2003.

Since 1900, the remnants of 15 landfalling tropical storms and hurricanes have passed
within 100 miles of Chicago.

2008'S HEAT NOT DONE JUST YET DESPITE COOLER SHORT-TERM
PATTERN

Hot weather -- days with high temps of at leats 90 degrees -- may not be finished yet.
Since 1928, 49 years have produced a 90∞ or higher temp beyond Sept. 4 in Chicago.

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,

While watching the morning news on Sept. 1 regarding Hurricane Gustav as it was
making landfall, the videos showed a complete lack of lightning. Was this trick
photography?

Peter Gottstein

Dear Peter,

There were no tricks. Despite widespread belief to the contrary, hurricanes are
notoriously lacking in lightning. Hurricane Gustav, like most hurricanes, contained very
little of it. What lightning there was occurred not in the storm's warm and violent
interior but in its cooler outlying rain bands.

Dr. John Hallett, Director of the Ice Physics Laboratory at the Desert Research Institute
in Reno, Nevada, explains that electrification of clouds requires the presence of large
numbers of ice particles held aloft by violent updrafts. Hurricanes, though, are warm
systems usually lacking in the powerful localized updrafts found in "standard"
thunderstorms. As a result, lightning production in hurricanes is minimal.

Thanks for joining us for this Wednesday edition of Before the Forecast!

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

These ominous skies and the rain shaft depicted here are the opening salvo of a
significant rain event expected to douse northern Illinois and Indiana’s parched lawns and
farm fields! The photo comes to us from our friend and frequent contributor Anson
Mount and was taken in Mundelein Wednesday morning on his way to the airport.
Anson, as those of you who follow our blog know, is a pilot and is always incredibly
generous in sharing great photos with us. This one’s no exception. THANKS Anson!

Tom Skilling

Photo courtesy of Anson Mount

Jerry and Sandy Clark e-mailed to tell me they’ve just returned from a spectacular trip to
Alaska and that they plan to return to our 49th state. They shared these photos with
me and I wanted to post them for you to see. MANY THANKS Jerry and Sandy for letting
me know about your trip and for sharing these amazing scenes with all of us!

Tom Skilling

Photos courtesy of Jerry and Sandy Clark, Chicago

A million dollar rain is headed for the brown lawns and thirsty crops of the Chicago
area Thursday as a month's worth of rain -- 3.27 inches falls in a "normal" September
here -- rides gusty northeast winds into the area much of Thursday and Thursday
night. The remnants of tropical cyclones -- i.e. tropical storms and hurricanes -- are
finicky and have been known to go overboard in their rain production. Some
Downstate areas could approach or exceed the flood threshold of 5 to 6 inches of
rain in 24 hours. But for the Chicago area, the predicted 2- to 4-inch deluge couldn't
come at a better time. The region has just recorded one of its three driest late
summer spells of the past 138 years. Several storms southwest of the city late
Tuesday unleashed 1.90 inches in Kendall County near Oswego in just 90 minutes.

Subsiding air vented out Gustav's top strengthened warming here Tuesday. The
thermometer at O'Hare hit 94 degrees and Midway topped out at 95 degrees -- the
first such high there in 761 days.

2008 SEASON IN OVERDRIVE; 3 TROPICAL STORMS
WITH HURRICANE POTENTIAL CHURNING THE ATLANTIC!

--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Dear Tom,
This morning there are four named storms from Gustav to Josephine in
existence. Is this a record?
Ruth Patton

Dear Ruth,
Not quite. We checked the tropical cyclone archives and according to Dr.
Christopher Landsea of the Tropical Prediction Center this morning's four
named storms: Gustav, Hanna, Ike and Josephine fell just short of record of
five named tropical cyclones that coexisted during the period from Sept.
10-12, 1971 when Edith, Fern, Ginger, Heidi and Irene all roamed the
Atlantic Basin.

Landsea noted two other instances with four concurrent storms, the first was in August
1893 (before storms were named) and more recently from Sept. 25-27, 1998, with the
tropical quartet of Georges, Ivan, Jeanne and Karl. One of the main reasons that
meteorologists began naming tropical cyclones in 1950 was to help the public avoid
confusion when referring to multiple storms which used to be referenced only by
number.

Thunderstorms walloped sections of the Chicago area Tuesday evening. Doppler radar
scanned cloud tops—like the one pictured here and photographed and sent to us by
Brett Smith---as high as 48,000 ft. Final rainfall reached 1.40” near Wilmington in
south suburban Will County and 1.90” in just 90 minutes in sections of Kendall County.
Brett also captured the mammatus cloud on the underside of the storm’s anvil
overhang. Great job Brett—and MANY THANKS for sharing these shots with us!

Tom Skilling

Photos courtesy of Brett Smith

Another beautiful sunset courtesy of Kasatochi aerosols left over from the early August
eruption in Alaska’s Aleutian Island chain

Mike Frankowski of South Elgin never misses out on an opportunity to share beautiful
photos with us---like this sunset Tuesday evening (9/2). Aerosols produced by the
eruption of the Kasatochi Volcano in Alaska’s Aleutian Islands—an eruption which on
August 8 of this year sent a thick plume of ash 35,000 ft. into the atmosphere---are
acting on sunlight globally and producing especially vivid sunset over a large swath of
the planet. Our thanks to Mike for sharing this stunning sunset with us!

Tom Skilling

Photo courtesy of Mike Frankowski, South Elgin

High clouds are the first to arrive of many approaching systems. Northbound Gustav is no
exception. Paul Hadfield share this photo of some of Gustav’s cirrus clouds as they move
over downstate central Illinois. Thanks Paul!!

-Tom Skilling


Photo courtesy of Paul Hadfield

Thunderstorms erupt across south and west suburbs--cloud tops tower to
48,000 ft.; some local rain tallies top 1.50 inches--more coming with Gustav
remnants in days ahead!

Walt Stagner sends us this picture of thunderstorms which are sweeping
our west and southern suburbs Tuesday evening. Walt informs us--and our
lightning data confirms--that the storms, which are towering to 48,000
ft. as we file this at 5:30 pm Tuesday evening (9/2), are prolific
lightning producers.

And the following has just arrived at 5:30 pm Tuesday from our
friend John Hazzard, who farms near Wilmington in southern Will County:
John writes:

"Then the rains came! In the last hour 1.2 inches of welcome rain
has fallen here in the last hour and its still coming down. I see on the
radar screen that its not covering a large area, but guess down here we
were lucky enough to be under this storm complex. Mother nature can sure
change things in a hurry. This will help filling soybeans where the
rains did fall."

Check out our "Before the Forecast" report on potentially big rains
headed this way with Gustav's remnants in coming days--the heart of
which hits Thursday into Friday morning. Scattered showers are to
precede the main event Wednesday. We'll have more on our blog later
this (Tuesday) evening and on our late-edition of the Nine O'Clock News
after the Cubs game tonight beginning around or a bit after 10 p.m. See
you then--and thanks again to Walt Stagner and John Hazzard for their
reports on this evening's south and west suburban storms.

Tom Skilling

Photo courtesy of Walt Stagner, Looking east from Yorkville to Oswego

Thanks for joining us for this Tuesday edition of Before the Forecast!

For complete weather information, tune in to WGN News at 9pm and wgntv.com for Tom Skilling's Full and 7-day forecasts.

Tune in tomorrow for another edition of Before the Forecast, and as always continue
to watch WGN for more coverage: Morning, Noon & Nine.

It's been dry in Chicago and in many parts of the Midwest the last several weeks with
much of the Chicago area receiving less than half an inch of rain, making this the driest
Aug. 5-Sept. 2 period since 1933 during the "Dust Bowl."
All that may be about to change: There are growing indications that moisture from the
remnants of Gustav may interact with an approaching cold front to bring an extended
period of rainfall to the area.
Before the rain arrives later in the week, Chicago is in store for another sunny and very
warm day Tuesday. Monday marked the city's fifth official 90-degree high in a
heat-starved summer. It was the warmest Labor Day here since the thermometer hit 95
degrees on Sept. 5, 1983.

STORM BRINGS 117 M.P.H. GUSTS AND 14-INCH RAINS TO LOUISIANA
Gustav spared New Orleans a direct hit, but battered portions of southern Louisiana
with wind gusts as high as 117 m.p.h. and torrential rains that approached 15 inches at
Grand Isle. More than 1 million people were without power Monday evening with the
landscape littered with fallen trees. Gustav spawned at least 17 twisters from the
Florida Panhandle to Louisiana as it made a Labor Day landfall.
--By Steve Kahn, WGN Weather Center Meteorologist

Dear Tom,
I don't think we've hit a 100-degree high yet this year. What is the
likelihood we might still get one?
Amy Chatfield
Dear Amy,
Not only haven't we hit 100 degrees yet this summer, but the city's warmest
day so far has been only 91, something that has never happened here since
Midway Airport weather records began in 1928. Since then, a 92-degree high
in 1951, 1979 and 2004 reigns as the year's lowest maximum temperature. The
odds are very much against getting 100 yet this year. Chicago has logged
only six September 100-degree days since 1871, and none since it reached 100
on Sept. 7, 1960. The latest 100 on record here is Sept. 15, 1939, when the
mercury peaked at 102. The city's last encounter with triple-digit heat was
July 24, 2005, when it hit 102 at O'Hare and 104 at Midway.

There have been beautiful sunsets visible in many sections of the world in recent weeks
-- this one included. This photo comes to us from Paul Hadfield and was taken outside
of Mt. Auburn, Ill., Saturday evening (8/30). Our thanks to Paul for a spectacular shot.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune

Photo courtesy of Paul Hadfield, Mt. Auburn, Illinois