Wednesday, June 12, 2013

Breakdown for tonight's severe weather, possible derecho

 First I want to start off with something another collegue of mine, Scott Sabol, recently posted.  I completely agree with it and URGE you to keep posted to the forecast because it will be changing hour to hour.   If we see storms pop this afternoon it will GREATLY affect how tonight will play out.
I always tell people: Overhyping the weather situation breeds conflict and frustration and ultimately apathy then dismissal. Hard to reestablish credibility when its lost. We at FOX8 will describe the weather situation like we see it with no hype or exaggeration. We always adjust the short-term severe storm threat hour by hour. The forecast on a day like today is a fluid one. Anticipate small scale changes and timing as the situation evolves this afternoon and evening
We are still under the Moderate Risk for severe weather for much of Illinois, Indiana, and Western Ohio.  The fact that we are on the far right side means two things.  This forecast only goes until 8AM tomorrow.  Then they have another forecast for tomorrow.  So means that the storms will be reaching this right edge late tonight since the storms are moving from West to East.
To start off the breakdown, we will look at the Tornado Outlook.  For this and the rest of the outlooks the percent is for an "event" (tornado, severe winds of 58+ mph, or severe hail of 1" or larger) within a twenty five mile radius.  There is also a black circle.  Those are areas that the events will be even stronger than the rest.  So for the Tornado Outlook, there is a 5% chance of a tornado within a twenty five mile radius.

We will likely break our nine month, four day Tornado Warning drought for Ohio.  When there is a strong line of storms you can easily spin up a quick, weak tornado.  Think of it like this... Imagine winds are going 80 miles per hour down your street, the winds moving down the next street over are only going 60 miles per hour.  The 80 mile per hour wind will want to curve over to the 60 because there is less mass there.  This can cause a quick instantaneous spin-up.  This is not the main threat for damage, the 80 mph would would be.
Speaking of the winds... here is the Wind Outlook.  Not surprised with this at all.  Winds will be the main threat for severe weather tonight.  When the storms roll through fast and nasty that wind out ahead of the storms is moving just as strong.  I would be sure to tie down any loose items outside now.  Maybe move the grill to the garage, put down patio furniture, flip the trampoline over now and put some weight on top of it.
And we finish off with the Hail Outlook.  You may be surprised that the hail is as highly warned.  If you remember last year, the derecho that plowed through Ohio had no hail.  You need the storm to be circulating within to keep bringing back up the hailstones and keep adding layers to them.  The derecho moves so fast that it doesn't have time to churn away... It just plows through.   Which brings up the conversation of ... will this be a derecho?

A derecho is a widespread, long-lived, straight-line windstorm that is associated with a fast-moving band of severe thunderstorms.
From what it looks like right now, I do not see a screaming line like last year, BUT that does not mean this will not be as bad.  I still think it could easily be classified as a derecho, but I see this more as a cellular storm structure at first, instead of a line, then slowly develop into a line... Here is why...

The atmosphere is just primed and ready to go.  We have hot temperatures to fuel the storms... especially this afternoon with a high near 90.  The liquid energy for storms, dew point, is already at 68 at 10AM.  If you watched the movie Twister, they made mention of the "Dewpoint is up to 70 sir" and as movies are NORMALLY not very accurate... that was and when you have a dewpoint of 70... you have lots of moisture.  As a matter of fact, if we have storms pop this afternoon, the chances for them to become tornadic is MUCH better than tonight.
So check out these winds.  00z is 8PM EDT (It is in Zulu time)  So you can see before 8PM we will have winds coming out of the SSW along the surface around 950 mb(on the side).  As you go higher up in the atmosphere (lower mb on the side) you can see the winds rotating to the WNW.  So as you go up into the atmosphere this afternoon the winds will be switching directions.  This is good for tornadoes and isolated supercell storms to form, but the question is will we have anything to trigger a storm to fire.  Once we get past 00z the winds generally all come from the West.  So straight line winds will be a huge problem.  Winds at about 600-450 mb are going over 50 knots.  When you have a strong downdraft the downdraft will pull those winds to the surface and along with the quickly moving storms... you will likely see severe winds at the surface of over 60 mph or stronger.

So this afternoon... if we see a few storms fire over Ohio, be on alert for hail, strong winds, and even a tornado cannot be ruled out.  The real threat for damaging winds will be tonight after midnight.  The energy with these storms will be building after sunset.
This is a future radar for 1AM Thursday morning.  The storms are just screaming through Ohio at that time.  Make sure to keep your NOAA Weather Radio on tonight.  I will be joining Bill Kelly for Team Overnights with this storm.  I will also try to post an updated Future Radar and any more thoughts on the storms later this afternoon, so be sure to check back in.  Until then... enjoy the heat and hit the pool (as long as there isn't a storm nearby).  Have a good one!

Andrew Buck Michael

PS Send in your storm photos on Twitter and Instagram using #OHStorm

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