We are still near ‘peak’ of tornado season in North Alabama and Middle Tennessee; the odds of tornado outbreak decrease significantly around here between May 6th and May 27th. Notice the wording there: ‘tornado outbreaks.
Alabama and Tennessee can have tornadoes at any time of year; but we are starting to shift focus away from powerful, dynamic storm systems that spin up multiple tornadoes in single day (days like April 18th in Mississippi with 44 total tracks) to organized areas of heavy summer-like storms that produce strong damaging downburst winds, hail, and flash flooding.
Interestingly enough, as ‘tornado season’ wanes, we see the literal peak of all severe weather occurring between May 20th and July 15th. That sounds much more like a plateau than a ‘peak,’ but it’s the fact that we have daily showers and storms producing strong winds and hail in small spots that make it that way.
The first round of this kind of weather kicks in on Thursday: a batch of heavy storms moving out of Mississippi and West Tennessee into the Tennessee Valley region may provide some heavy rain (more than 1”), gusty winds, and small hail Thursday afternoon and evening in particular. The over-all severe weather risk looks low for now, but a few storms could get stronger than the others. We’ll keep you posted!
Now is a good time to remind you that summertime storms can bring some of the worst weather you’ll deal with all year.
Worst all year you say?
Yep! Some of the nastiest storms of the year happen in the summer season, but they are not always ‘severe’ like the powerful, destructive storms of Spring and Fall (the ones that bring the extreme winds and tornadoes). Most of us never have to deal with a tornado; only 1% of Alabama’s land area was impacted by a tornado on April 27, 2011 (the largest, deadliest tornado outbreak in a generation).
The Storm Prediction Center’s severe weather climatology shows how the risk of severe storms (mainly from wind) actually increases from May through June and July over a big part of the Southeast:
Summertime storms work differently than those driven by dynamic jet-stream-driven storm systems, and it can be very, very difficult to ‘see‘ what they’re doing on radar because they aren’t spinning or causing long-term strong winds that are more easily tracked in the Spring/Fall storms.
A storm does not have to be ‘severe’ to bring strong winds that can break branches on trees, heavy rain that can cause flash flooding, and dangerous (deadly) cloud-to-ground lightning.
So how do they work?
Summer storms are more simple than the severe storms of the other seasons: updrafts and downdrafts. Hot, humid air rises (quickly) creating the storm, but eventually that air cools, condenses out water vapor, and gets too heavy for the updraft to hold. That’s when it crashes to the ground in what we call a ‘downburst.’ Those downbursts can fall to the ground at up to 100 miles per hour, and when they hit the ground all of that energy spreads out on the ground as damaging winds.
Sometimes these storms congeal into a large MCS: a mesoscale convective system. Those big masses of thunderstorms can do a lot of damage while producing only downbursts. One particular MCS from last summer stands out as a prime example of how nasty these things can be: the derecho of June 28, 2018.
Here’s the deal. It does not matter if the wind is swirling in a funnel with a Tornado Warning or if it’s blowing along the ground in a straight line; wind gusts that high are dangerous.
Anytime there’s a storm in the area, take it seriously: especially if there is a Severe Thunderstorm Warning!
You can get free lightning alerts, warnings, and notifications about storms in the general area with Live Alert 19!
Summer storms are notoriously slow movers. There’s rarely much of what we call a ‘steering current’ to move them along, so they can sit and rain. And rain. And rain. And rain.
That happened over Huntsville in August 2017, and the result was some incredible flooding at the foot of Monte Sano from Oak Park south to Blossomwood along Fagan Creek: WHNT.com Flash Flooding from August 10, 2017.
Lightning doesn’t mean a storm is severe, but it’s deadly anyway: All thunderstorms have lightning, but sometimes the lightning gets extreme. Summer storms can produce hundreds of lightning strikes over the span of a few minutes. Positive strikes that come from the tops of those storms (sometimes as high as 50,000 feet) are the most powerful; they’re the ones that cause the most damage, and they can also strike as many as 10 miles away from where rain is falling.
That’s called a ‘bolt from the blue,‘ and that’s why it’s critical to go inside anytime you hear thunder; you’re close enough to be struck by lightning!