How a Florida Afternoon Thunderstorm Forms

[swimaway19]

For the past few days as I have been sitting on the lifeguard stand at the pool, I have noticed a strange trend I hadn't seen before. The pool I work at is usually right on the line where the Gulf sea breeze and the East Coast sea breeze converge, with half the pool in the shade from numerous clouds, and the other half in the naked sunlight with no more clouds in the horizon facing the Gulf. As I sit, I see a narrow cloud column begin to billow sky ward, but within 5-10 minutes, it appears that the top has collapsed. Then, in another 15 minutes, the column appears to reform, this time a little wider, before it too collapses. Finally, on the 3rd or 4th build up, it appears that the cloud has a big enough base to support the column and the cloud begins to darken into a thunderstorm. Could someone tell me if this is normal for the seabreeze pattern thunderstorms in Florida, or if I am just losing my mind to the 95 degree heat?

[wjs3]

Swimaway:

It sounds to me like you are talking about typical breaking of the inversion...that relatively cooler air exists under realtively (for its altitude) warmer air and the realtively cooler air ha to break through before storms can get going.

When that inversion breaks, depending on the temperature profile of the rest of the atmosphere, you can get towering cumulus and cumulonimbus quite quickly.

To be more specific, you are seeing air rise, begin to condense and then hit the inversion, which weakens the inversion....but also stops the updraft...then a second updraft forms and weakens the inversion even more (additional updrafts are usually stronger as the higher surface temps make things more buoyant). Then, finally, a third or fourth updraft that is "warm enough" (and fighting a weaker inversion) blows right through the inversion.

Hope this makes sense...

WJS3

[swimaway19]

It does. Thank you very much!

[Wthrman13]

Hopefully not to confuse the issue, since what x-y-no said is completely correct, but even without the inversion layer, it is still possible to see the evolution that you witnessed. The first couple of attempts at thunderstorm development (what mets like to refer to as "convective initiation") that you saw were probably not wide enough to avoid entrainment of the drier and cooler air from outside the updraft. This entrainment reduces the buoyancy of the cloud and may also cause it to "pinch off" from it's source of warm moist air from near the surface. Each subsequent attempt at development will have an easier time, since, as x-y-no said, the atmosphere where the cloud rose has been modified. The wider the updraft on each subsequent attempt, the more protected the core of the cloud is from the entrainment of drier air from outside, and the more likely it is to maintain it's buoyancy and rise further, possibly producing a thunderstorm. Incidentally, this effect, combined with the difficulty of breaking through the inversion, is what often keeps thunderstorms from developing on days when, all other things being equal, a major severe thunderstorm outbreak would be possible, much to the chagrin of stormchasers like myself!

[swimaway19]

Thank you very much! I really appreciate the answers!