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The WGN Weather Blog has moved! We're now part of the Chicago Weather Center. You can find the new blog here: http://blog.chicagoweathercenter.com

Or you can visit the new Chicago Weather Center and find us under the tab of Weather News & Blog. Come on over to our new playground!
The National Oceanic and Atmospheric Administration (NOAA)--parent agency of the National Weather Service---is out with its 2010 Atlantic Basin hurricane season forecast and it raises warning flag for residents in the country's hurricane prone areas. The 2010 season is to be an active one--potentially "..one of the more active on record." says NOAA chief and under secretary of commerce for oceans and the atmosphere Dr. Jan Lubchenco. 
     The rapid demise of the current El Nino figures prominently in the agency's prediction. El Ninos often thwart Atlantic Basin tropical cyclone activity by increasing winds aloft over the tropical Atlantic. This has the effect of shearing developing tropical disturbances apart before they can organize into tropical storms and hurricanes. Thus, hurricane numbers go down in times of El Nino. The quiet nature of the 2009 Atlantic Basin hurricane season is a perfect example.  But with the current El Nino in full retreat--and the potential, according to longer-range coupled ocean/atmosphere models like NOAA's "CFS" (Climate Forecast System) model,  which attempts to predict weather trends on a seasonal basis, for a comparatively rapid swing from El Nino to La Nina conditions a possibility in the equatorial Pacific as the summer and coming autumn proceed, conditions grow more supportive for tropical cyclone (tropical storm and hurricane) development.
    We'll talk more about this in the days and weeks ahead. But this is NOT good news--and is particularly concerning given the catastrophic oil spill underway in the Gulf of Mexico.
    Read a full summary of NOAA's 2010 Atlantic Hurricane Season forecast here:

http://www.noaanews.noaa.gov/stories2010/20100527_hurricaneoutlook.html


Tom Skilling
  Heat built to summer levels Monday. The stunning shift of the past 36 hours away from the early spring-level chill which dominated so much of May to full blown summer heat culminated Monday afternoon in the Chicago area's first official 90-degree highs--the first to occur in May in nearly three years. The heat arrived amid the Chicago area's most humid air of 2010 with Gulf Coast level low 70-degree dew points and followed a record high morning minimum of 73 at the city's Midway Airport observation site. The previous warmest May 24 low had been 72-degrees in 1991. The combination of heat and humidity pushed some area heat indicies to 95-degrees at O'Hare--but as high as 100-105-degrees at the Chicago area's hottest local observation sites.
     Veteran National Weather Service observer Frank Wachowski reports to us the mercury first reached 90 at 12:42 p.m. at O'Hare and 1:05 pm at Midway Airport--the first 90s in well over 9 months since August 9 last year.
      The long term average date for Chicago's first 90-degree reading is on or about June 11 putting the current round of 90s into the Chicago area three weeks early.
     It's not common to see 90-degree temperatures in  May--but it's by no means rare either. Approximately three in 10 Mays records a 90-degree temperature.
     The longest string of May 90s extended across 10 days in 1977.

Other unofficial Weather Bug highs recorded Monday:

95-degrees    Darien, Des Plaines, Palatine
94                 Oswego, Highland IN, Evergreen Park and Elmhurst
92                Frankfort, Lemont
91 Pontiac

     Lake breezes have been tempering the heat along Lake Michigan Monday and will grow even more important in coming days. By Thursday, strengthening northeast winds will lock in forcing temperatures and humidities noticeably lower.
    More on the heat, the cooling expected with a back-door cool front late week and any prospects for a return to hot weather over the coming two weeks on Monday evening's WGN News programs at 5 and 9 PM.

Tom Skilling

    
   Our Skilling Storm Chase team is eastbound on I-44 just outside Springfield , Missouri intent on intercepting potentially strong thunderstorms later Thursday afternoon and evening near the Arkansas/Missouri border.  It's pouring on us and powerful t-storms are moving out of Arkansas across the Missouri border to our southeast. There's a severe thunderstorm watch out in that area.
    Our hope is to be able to show you storm activity still to evolve this afternoon and even ing on our 9PM News tonight.  
Oh my word--forgive us as we take a moment to catch our breath!! We've just emerged from a hair-raising, white knuckle trip through blinding thunderstorm downpours which obliterated visibility for more than 20 minutes as we made our way S L O W L Y through southeast Kansas. During that time, we literally had NO visibility---I mean visibility was ZERO--a situation complicated by continuous flashes of cloud to ground lightning, crashes of thunder, hail bombarded our vehicle creating a deafening roar. We are parked in a field outside just south of Norwich Kansas catching or breath and marveling we came through the last half hour in one piece.  Temperatures had dropped from a once muggy 82 to an almost chilly 57 at the height of the storm.  They recovered to 68 at the time of this blog's posting.
     Pam Grimes was our driver and how she managed to keep the vehicle on the road through what we just passed through is absolutely beyond me.  Our chase leader, Jim Reed, was in the driver's seat of our lead truck---we move in a caravan on five vehicles.  We wondered, when we first saw Jim's well traveled Ford Explorer, why there was a flashing light on top.  Now we know.  It probably saved our lives! By following that beacon, Pam managed to keep us on the road when the road was invisible to us through the downpours.
     Huge clouds of dust---probably the result microbursts--were evident in the distance as we emerged from this evening's storm. 
     Cameras were clicking and rolling all through the event. Photo journalists Steve Scheuer and Jordan Guzzardo as well as veteran Tribune photographer Zbigniew Bzdak have captured every moment on tape and in still form.  Check out video Wednesday evening on WGN News at Nine and see Zbigniew's photos at Chicago Tribune.com.  And a complete record of the Skilling Storm Chase is always available at wgntv.com/storm chase.

Tom Skilling
    
Skies as we proceed west are growing ever darker as we continue westbound on Highway 160 in Harper, Kansas. Warnings have been issued with the squall line we're approaching and, for the first time this trip, increasingly frequent cloud to ground lightning can be seen. A tornado warning has been issued based on a radar-detected circulation and the line has a history of large hail production. 
     Sky now black to the west.  Looks like this is going to get interesting!

Wednesday storm chase underway

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We're on the road west of Wichita heading for severe storms west of the city moving rapidly northeastward. Tornado watch is out and it's muggy, warm and windy and in the low 80s. 
   Wednesday greetings to all!  We arrived back in Wichita, Kansas around 1:30 am this morning after a day long trip out to the rolling plains of western Oklahoma-not far from the Texas Panhandle.  There, the terrain rolls gently and wheat fields extend to the horizon in all directions.  What an amazing place from which to watch the weather!  It's really quite beautiful!
    A tornado watch had been posted by the time we arrived Tuesday afternoon and towering cumulonimbus clouds would indeed breach the day's storm and cloud-thwarting cap and anvil out before the day was out.  The air was humid and warm--seemingly supportive of the storm development which occurred. The amazing thing in that part of the country is the absolutely unobstructed view one has of any storms which form.  But in the end, while severe severe weather warnings were issued in response to several of the more energetic thunderstorms which formed, overall, the day remained comparatively quiet. It was quite surprising to us that more lightning wasn't visible from some of the distant storms.  We had thought--and frankly anticipated-- we might see quite a lightning show at one point. That never happened.
     After spending the day and evening surveying that area, and after feeding our evening report back to Chicago by way of our satellite truck, our WGN team began the long trip back to Wichita in the late night darkness Tuesday evening.
 We had been so busy all day, we hadn't taken time to eat, other than for the snacks producer Pam Grimes had fortunately assembled for the trip, and were hungry for something more substantial to eat. We ended up stopping at a Sonic restaurant where we encountered a whole group of storm chasers who pulled in after their own long day on the road. The group included Reid Timmer, who is widely known from his storm chasing episodes which air on the 
Discovery Channel. What a nice group! There is amazing comaradery among the storm chase community and it was evident as all of us talked and exchanged stories on how things had gone that day and offered glimpses of the thinking on what might be ahead.  That group had apparently made their way to this region of western Oklahoma much as we had with the expectation of monitoring any storm development which might occur.
   Though the evening's storm evolution ended up following its own course--nature has a mind of its own, even in this era of spectacular computer models and observational tools--- there had actually been good reason to believe the region was an area in which storm development might take  take off in Tuesday's evening hours--and we did see and photograph some spectacular towering thunderstorms which included stunning anvils (the fan-out of the cloud tops which occurs as a storm's updrafts reach the top of the troposphere, through which temps drop with height, then spread out horizontally in a vast shield of ice crystals as the rising air encounters the warming temps of the stratosphere (the next layer up as parcels ascend through the atmosphere). 
     CAPES, an energy measure, had soared to 5,000 j/kg--amazingly high values which suggested that any trend toward storm development might well become fairly explosive.  The region was also juxta-positioned with the dry line and just west of the axis of the strongest low level southerly winds.  That's a region of "speed convergence" in the atmosphere--where fast winds encounter slow moving air and a pile-up takes place which encourages upwelling of the air--a critical step in storm development.  Upper air forecasts off our models had indicated jet stream winds were diverging over the region and that instability (the rate at which temps cool with height) was high.  All the ingredients appeared in place.  But the atmosphere doesn't always respond as one assumes it will--and that was the case Tuesday. There are triggers--or in this case, a lack of critical atmospheric triggers---required to contribute that final critical "kick" to initiate storm formation--- that aren't always easy to measure.  Nature still possesses its mysteries!
   We are to meet soon this morning with our storm chase leader Jim Reid and plan strategy for the day ahead. This area (Wichita) of southern Kansas is outlooked for possible severe weather development this afternoon and tonight--but so are nearby areas of Oklahoma and Missouri which are within driving distance.  We will satellite a report back to Chicago for the WGN Midday News and be heading off!  
    Check in here when you can!  We keep you posted on developments here in the field. We intend to be on the road traveling where any storms that develop take us. It's good having you with us!

Tom Skilling

What change from Monday! The sun's out brightly Tuesday and warming is underway. It's a stunning turnaround from Monday when southeast howled, skies were shrouded in clouds, there was drizzle and temperatures languished in the  60s.  Monday was one of those days which made a good thick jacket feel awfully good! 
    We're southbound in Oklahoma heading into a humid, energetic air mass advertised by the latest RUC model as likely to possess off -the- scale CAPE (atmospheric energy) values over 5,500 j/kg by later this afternoon!  That's an air mass even more energetic than yesterday's--when the atmosphere managed a cluster of supercells which spawned the multiple vortex twister we encountered. Among  the other big atmospheric changes we're noting Tuesday is the presence of a "cap"--a rain-inhibiting warm layer aloft which thwarts the ascension of air needed for cloud and storm formation and the fact the "dry-line", along which thunderstorms flared fairly early Tuesday afternoon has retrograded (slipped westward) into western Oklahoma and the Texas Panhandle.  Still, the RUC model suggests the cap is likely to break later this afternoon---a notion supported by our high-resolution RPM model, though RPM shows the cap breaking later--more toward 6 or 7 pm. 
      A dormant warm front divides powerful southerly winds, blowing at up to 40 mph, and ligher southeast winds.  There's split in the jet stream over Oklahoma, a proxy for regions in the atmosphere where air is rising.
      Here's what all of this seems to suggest---and what we'll be monitoring as we continue heading south in Oklahoma. It is the consensus view herer that the current rain-inhibiting cap is likely be breached late this afternoon or evening--a development which should allow towering, lightning-generating cumulonimbus clouds which, more than yesterday when they were shrouded in stratus, to appear dramatically on the horizon.
     Severe weather can't be ruled out, including twisters.  We'll keep you posted.
     We plan on our 5pm WGN News program to give you a look at our chase vehicles and the satellite truck from which we are uplinking our reports back to WGN.  And tonight at 9PM, our series on the revolution in meteorology continues.  We look at supercomputer modeling of the atmosphere and take you inside the National Weather Service's supercomputing facility outside Washington, D.C.  
     

     
There's nothing like an encounter with a multiple vortex tornado, especially when it chases you down the highway at 55 mph, to capture people's imagine and get the phones ringing. I talked this morning about our rendezvous with the twister Monday on the Fox News Channel's Happening Now program with Jane Skinner as well as with Greg Jarrett of WGN radio, Eric and Kathy and our own Mark Suppelsa on The Mix and with Robin Marsh, midday anchor of Oklahoma City's KWTV.  

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