When "convective temps" are met, storms ignite!

HOUSTON - Sunday's line of heavy thunderstorms that swamped some areas of Houston was birthed out of the clear blue sky; literally. The combination of old outflow boundaries and plenty of unabated heating lead to an atmospheric explosion of intense thunderstorms.

Check out the radar images from Sunday:

Yesterday your author here arrived at work around 7 a.m. due to the showers and storms that rolled through very early Sunday. As the first round pushed to the coast it intensified as the boundary pulled up stationary right along the immediate coast. Areas from Galveston to Winnie picked up between four and seven inches of rain.

Finally around noon the storms had edged offshore and I saw a brief opportunity to run home, eat and perhaps sneak in a workout. For those that know me, I don't miss workouts! I knew I didn't have long. I was full well expecting more storms--big ones at that given the clear skies and rapid heating.

No sooner did I arrive home (near The Woodlands) the radar had gone from completely quiet with blue skies at noon to a massive complex of storms developing near Brenham by 1 p.m. I knew right then and there my workout was toast. I got back in the car and headed for the station. I knew it would be a rocky afternoon.

By 3 p.m. we were gearing up for a potential flood situation across the city of Houston.

So what happened?

Aside from the upper-level low to the west that provided the energy for storm development and old outflow boundaries (basically micro-scale cold fronts from decaying storms from earlier in the day), our atmosphere reached what we call the "convective temperature."

The convective temperature is the moment that the atmosphere is now warm enough to support thunderstorm development---meaning air can rise quickly into the atmosphere to support cloud and storm formation. 

Depending on the environmental conditions, the convective temperature can be a lot lower (if we have high dew points and a forcing mechanism like a front of an upper-level low) than if we had no such features nearby at the height of summer. That means with  dry, desert air overhead the convective temperature is a warmer than the high temperature for the day thus remaining rain free on a hot August afternoon.

Sunday's convective temperature was around 83 degrees. As the clouds cleared out and the ground heated up, our convective temperature was easily met and the result was atmospheric fireworks! Abundant low level moisture from the gulf and the upper-low to our west provided the forcing needed to ignite a volatile atmosphere into a frenzy of storms that dropped as much as 4 inches of rain in some parts of town in as little as 30 minutes.

Monday's set up is about the same except Houston is overcast and reaching the convective temperature, albeit a low temperature, may be a struggle. However if there is any sunshine at all by Monday afternoon, look out! We could be in for a repeat of big storms as the upper-level low passes overhead.

© 2017 KHOU-TV


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