The threat of severe storms this week peaks on Wednesday with storms that could produce strong winds and hail
This could be a busy week in Alabama and Tennessee weather with a threat of severe storms on Wednesday, and there could be another threat of severe weather over South Alabama this weekend.
Midweek storms pose a threat of mainly large hail and high winds; tornadoes are rarely ‘impossible,’ but in this case we believe the hail and wind are the two obvious factors.
The latest information on the threat can be found here on WHNT.com’s Forecast Discussion Page.
Why wind and hail?
Both strong damaging winds and hail are caused by the thermodynamics (think temperature/heat energy) of the atmosphere: not just the environmental winds.
Here’s how a downburst forms creating strong winds at the surface…
And here’s an animation of how hail forms…
So, about Wednesday’s storms…
The easiest way for us to ‘see’ if the thermodynamics of the atmosphere are capable of producing this kind of storm is with an atmospheric sounding: the information we get from a weather balloon.
Since we can’t launch balloons into the future, our computer models can at least simulate it for us; that gives us a good estimate of what future conditions will be like. Here’s one such example from Monday’s midday GFS model guidance. It’s a profile of the atmosphere forecast for 4 PM Wednesday.
So what are you looking at here?
TUTORIAL FROM WEATHER.GOV
The blue-dashed line I’ve used to highlight the freezing line is important, but so is that thin line in between the red (temperature) and green (dewpoint) lines that intersect it. That little thin line represents the ‘wet bulb temperature:’ the temperature that the air reaches when evaporational cooling takes place during precipitation – in this case, a storm.
This forecast is for a freezing level at 7,200 feet above the ground. That is LOW.
Back on March 19, 2018 when the massive hailstorm hit Cullman, the wet-bulb freezing level was around 9,000 feet above the ground.
No. We’re not forecasting more Mountain Dew-can sized hail on Wednesday; however, when freezing levels are this low, it’s easy to get some large hail in a few storms.
It wouldn’t be surprising to see a few of the Wednesday afternoon storms produce hail larger than a half-dollar or even a golf ball.
We’ll keep you posted on the threat!