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Watching the potential of severe storms closely

We are expecting the possibility of severe thunderstorms come Friday evening and overnight. There are some precluding factors in their ignition, however. Any one of the factors, or a combination of them, may spare us of a long Friday evening and overnight. Here are a few of my thoughts going through my head when it comes to forecasting Friday’ severe weather potential—it gets complicated. I also hope this blog gives you a little insight as to how hard it is to forecast severe thunderstorms (can be a real beast…and bust).

Morning thunderstorms are expected on your Friday. The atmosphere is set for a few of these storms to produce some lower-end severe hail. Good news, widespread severe weather is not looking very likely out of this first bout. In fact, this first bout will likely produce clouds that could place a cooling-veil over Northeast Kansas for a good chunk of the day.

You need heat to drive severe thunderstorms. Friday morning clouds may help to limit heating come Friday afternoon. Less heat means less fuel for thunderstorms. However, if we clear out earlier, then the surmounting heat could actually increase later afternoon storm chances. In either regard, we are expecting enough heat to provide at least sufficient fuel for potential storms by late Friday afternoon.

Sometimes you can get warm air to build up a littler higher in the sky. What this does is it puts a “lid” on the atmosphere. If this lid is not broken, then storms do not form. A lid is expected to form on Friday. However, there is a flip-side to the lid (no pun intended).

To some degree, a lid actually lets the atmosphere boil. If the atmosphere boils underneath the lid, and the lid is popped, then explosive storms can occur. Either the heat building underneath the lid itself, or a kick, is needed to cause storms to explode.

If we have enough morning clouds on Friday, then the heat underneath the lid may not be enough in-and-of itself to pop the lid. So, that means we may need a “kick” to get storms to blow. We do have a strong kick coming in by late Friday afternoon and evening.

Right now we think enough heat will boil underneath Friday’s lid; that, provided a kick, could realize some pretty strong storms by Friday evening. Should storms kick, they will likely become severe. Large hail and gusty winds are the main threats, but enough twist near the ground could help fix broad thunderstorm rotation to the ground in the form of a few tornadoes.

Even though Friday’s situation is complicated already, I can throw another monkey-wrench into the mix—morning storms can actually help create additional kick for new storms. Now, I said that morning storms can produce clouds that keep things cooler (keeping storm chances down), but they also can help increase storm chances, too. Sure, clouds can clear out, but the cool imprint of morning storms often gets mixed about in the atmosphere, too. The cool imprint of morning storms can actually help to provide a kick for new storms by late afternoon. As weathermen/women, we are trained to look for the imprint of morning storms (usually via radar). We have to keep a close lookout for these features Friday, too.

In short, it’s complicated. All of these features/variables have to be watched very closely by the time we hit late Friday afternoon across the area. The hope is that we have morning storms that really cloud things over and keep us cooler than currently expected. The cooler temperatures, and a lid on the atmosphere, would be ideal at lowering severe thunderstorm chances come Friday evening and overnight. Let’s hope this is the case.

Best,

Alex

By Alex Harrington

July 2, 2009

Lawrence Weather Watch

Discussion

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2 July 2009
at 12:10 p.m.

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mommaeffortx2 (Anonymous) says…

You just keep the storms gone please going camping this weekend no need to rain on my parade:)
2 July 2009
at 12:39 p.m.

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countrygirl (Anonymous) says…

Storms make it hard to keep the temp up in the smoker. Please no rain—bad for the ribs!
2 July 2009
at 12:44 p.m.

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oscarfactor (Anonymous) says…

Question: what exactly is “lower-end severe hail?” It seems to be an oxymoron.
2 July 2009
at 12:48 p.m.

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budwhysir (Anonymous) says…

All in all, forcasting weather is alot like forcasting your feelings for the next day. You can say what you want but when the time comes, it may be different. Just a thought. Oh, and to take care of a few problems listed. Just bbq them ribs in the living room and if yer goin camping, just stay in yer camper then it will be dry
As far as oxymorons, lower end severe hail would be the hail at the lower end of severe meaning that the severe part of this hail is on the lower end of severe.
2 July 2009
at 1 p.m.

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The_Original_Bob (Anonymous) says…

“Question: what exactly is “lower-end severe hail?” It seems to be an oxymoron.”

.25 - .50 inch, I think might be what he is saying.
2 July 2009
at 1:09 p.m.

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RETICENT_IRREVERENT (Anonymous) says…

lower-end severe hail…
It really hoovers when Mother Nature can't afford the good stuff.
2 July 2009
at 2:01 p.m.

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49aharrington6 (Anonymous) says…

Hi all,

“Quarter-sized hail” is lower-end severe (and smaller). Even coming down at 50-80 mph (+), quarter-sized hail won't dent things up too bad. Once you start getting to golf ball sized hail, then watch out. Right now, I don't think we'll have the energy for hail greater than quarter sized Friday morning.

Later Friday afternoon and evening, watch out. Latest indications still really point at a severe weather situation across much of Northeast Kansas. It is still too early to 100% bank on it, but all the ingredients are there for more of a “spring-esk” severe weather situation. Right now large hail (greater than golf balls) and destructive winds pushing 70 mph, wouldn't be out of the realm of possibility for Friday evening and overnight (if everything comes together). We cannot out-rule a few tornadoes either.

Of course, we've been through these situations many, many times before; but, with it being the start of a holiday weekend, I expect quite a few people traveling (that means lots and lots of cars and people outside). Pay close attention out there folks for the latest Friday evening and overnight forecast. With a little luck, maybe we'll see a bust.

I love the questions, btw.

Best,

Alex