Folks, summer will be here before you know it! With that, as we all know, comes the annual season for those pesky pop-up thunderstorms we’ve all seen in the afternoon and evening. There’s nothing like sitting by the pool on a hot, sunny day and before you know it you’re hearing rumbles of thunder and suddenly down comes the pouring rain.
“Weather guy/gal only said 20% chance today!?” – You
“Yes I did. Forecast verified.” – Weather guy/gal (and another story).
So what happened? Well, these are called Air Mass Thunderstorms. In the summer months, around Kentucky and the entire southeastern U.S., it is typical see very hot and humid days, which are the perfect environment for air mass thunderstorms to generate.
During the afternoon the sun has heated the surface, through [do action=”ams-glossary-link”]insolation[/do], to hot temperatures which results in a convective nature of the lower atmosphere. This hot, humid air will form thermals which rise up into the atmosphere and condense and cool until cumulus clouds form.
If the thermal is strong enough, it will continue to rise and become unstable, allowing it to push far up into the atmosphere until ultimately a cumulonimbus cloud is formed. Once this occurs, well, we all know what happens from there: pouring down rain, lightning and gusty winds.
These thunderstorms are called Air Mass Thunderstorms because they form in the middle of warm, humid air masses which can settle over areas spanning hundreds of miles. They’re often called “garden variety” or “pop-up” thunderstorms as well. Meteorologists often refer to them as “ordinary cell” or “single cell”. Generally after the sun goes down in the evening, these storms start to lose their needed heat and [do action=”ams-glossary-link”]instability[/do], and die down. Here’s the definition from the National Weather Service glossary:
“Generally, a thunderstorm not associated with a front or other type of
synoptic-scale forcing mechanism. Air mass thunderstorms typically are
associated with warm, humid air in the summer months; they develop during the
afternoon in response to insolation, and dissipate rather quickly after sunset.
They generally are less likely to be severe than other types of thunderstorms,
but they still are capable of producing downbursts, brief heavy rain, and (in
extreme cases) hail over 3/4 inch in diameter.” –NWS Glossary
I don’t know about you, but after this long, cold winter we had, I’m ready for these pesky storms. However, keep in mind that these storms can be dangerous at times, so always stay weather aware.
Check back, I’ll be posting some more interesting stuff in the coming days.