Dear Tom,
Instead of rising, why does smoke from a chimney descend before a storm?
--Hilary Schnadt
Dear Hilary,
"When the smoke goes low, there will be a blow," and there is some truth to that proverb. In calm, dry weather, hot air from a chimney continues to ascend as long as its temperature is higher than that of the surrounding air. This is more pronounced during cool weather when the hot chimney air is most buoyant. The opposite situation prevails when a rain bearing low-pressure system approaches. Southerly winds ahead of the system bring higher temperatures and humidity. The warmer temperature weakens the current of hot air and, in addition, the smoke particles absorb moisture, become heavier and sink. A drooping smoke plume thus indicates warmer, damper weather and an approaching storm.
Instead of rising, why does smoke from a chimney descend before a storm?
--Hilary Schnadt
Dear Hilary,
"When the smoke goes low, there will be a blow," and there is some truth to that proverb. In calm, dry weather, hot air from a chimney continues to ascend as long as its temperature is higher than that of the surrounding air. This is more pronounced during cool weather when the hot chimney air is most buoyant. The opposite situation prevails when a rain bearing low-pressure system approaches. Southerly winds ahead of the system bring higher temperatures and humidity. The warmer temperature weakens the current of hot air and, in addition, the smoke particles absorb moisture, become heavier and sink. A drooping smoke plume thus indicates warmer, damper weather and an approaching storm.
