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02/28/2012

Mid Evening Update On Wednesday's Severe Weather Potential

Whenever we have a chance of severe weather, I try to update you as frequently as time permits. Since we have a risk of severe weather tomorrow, let me give you the latest.

 

Please keep in mind, this is an update to my full blog. To read the more comprehensive severe weather outlook, please view my previous blog here...

 

http://fox41blogs.typepad.com/wdrb_weather/2012/02/severe-weather-risk-on-wednesday-my-thoughts-on-the-potential.html

 

Storm Prediction Center Severe Weather Risk Wednesday

 

Ever since our January event, we have had a lot of days with risks of severe weather! Wednesday is another...

 

SPC Categorical Risk Wednesday

Notice the slight risk includes our entire area Wednesday.

 

Spc 2 cat


 

SPC Risk


 

SPC Probabilistic Risk Wednesday

Notice the northwest part of our area is in the 15% chance while the southern and southeast part of our area is in the 30% chance.

 

Spc 2 prob

 

Severe Weather Discussion

 

One of the big things we discussed earlier is that two waves of storms will move across our area. One should affect our area from 2 am to around 7 am, then a much more questionable area between Noon and 4 pm Wednesday. Both will have wind energy to work with, but the storms overnight tonight will have a TON of wind energy to work with. The wind shear for tonight / tomorrow is called "Speed Shear" which is primarily supportive of damaging winds and hail, but does support a isolated tornado threat. Let me show you the energy / instability these storms have to work with.

 

GFS Instability By 7 AM Wednesday

Notice the GFS shows about 250 to 500 units of instability on the later edge of the "overnight" envelope.

 

Gfs CAPE 1

 

GFS Instability By 1 PM Wednesday

Notice the GFS shows very little recovery of the instability north of the river, with the best south of the Kentucky Parkways.

 

Gfs CAPE 2

 

 

NAM Instability By 7 AM Wednesday

Notice the more robust NAM shows instability values from 500 - 900 as we move toward sunrise.

 

NAM CAPE 1

 

NAM Instability By 1 PM Wednesday

Notice the NAM continues to show a moderate area of instability near 1700 units west of I-65 tomorrow afternoon.

 

NAM CAPE 2

 

The instability picture is very different on the NAM versus GFS. Both the NAM and GFS show a temperature of 67 - 68 degrees by midday Wednesday. The difference is the NAM holds the dewpoints a bit longer under nearly identical circumstances as the GFS. The NAM is known to have a high dewpoint bias and I think this may be showing up again. The odd part is one would expect storms to flare on the NAM in the higher instability, but look...

 

NAM Precipitation Through 7 AM Wednesday

Notice the NAM shows rain and t-storms in our area through around 7 AM Wednesday.

 

Nam_1

 

NAM Precipitation Through 1 PM Wednesday

Notice the NAM starts a reflare of storms south of the river near 1 pm Wednesday, but oddly nothing in the higher instability air.

 

Nam_2

 

NAM Precipitation Through 7 PM Wednesday

Notice the NAM shows a better chance of storms south of the Kentucky Parkways.

 

Nam_3

 

My Thoughts On Wednesday's Severe Weather Threat?

 

Let's start by talking about the early threat. It will be much colder in the morning than the warm part of the day on Wednesday. This means the storms won't be able to reach all the way to the ground for energy and we call these elevated storms. These elevated storms will have a ton of wind energy to work with and I would be surprised if we don't get a few going severe. From 4 AM - 7 AM appears to be the greatest threat for the overnight storms with damaging winds and hail as the primary threat. A quick spin-up cannot be ruled out, but doesn't appear to be the main threat.

 

AdvanceTrak

 

Now for the "secondary threat. There still appears to be a significant influence from the "subsidence" or sinking air tomorrow that is supressing t-storm development for the northern half of our area. I actually believe this concept. Remember storms really have to operate as a well oiled machine. All parts must be running perfectly for us to see severe weather events. If we have any area lacking, then the system never reaches potential. The weak link tomorrow appears to be the sinking air in the mid levels of the atmosphere. This sinking air will warm the mid levels of the atmosphere and limit the energy these storms have to work with. Plus the sinking air directly opposes the rising motion in these storms. This is not a well oiled machine that I am describing tomorrow. For this reason, I think this is NOT going to be an outbreak setup. The wind energy will support some warnings but I think the greatest risk is from Leitchfield, KY to E-town, KY to around Carrollton, KY. Hail and damaging winds would the primary threat, but an isolated spin-up can't be ruled out although that risk is lower. I think this second round is going to have a tough time amounting to a lot for Louisville from the data as I see it.

 

AdvanceTrak 2

 

AdvanceTrak 3

 

AdvanceTrak 4

 

 

Friday continues to look more dangerous to me for part of the Ohio Valley. Southern KY looks like it has the greatest threat, but this is one we must watch closely in the coming days.

 

 

 

Remember, I will have the most frequent updates for this potential severe weather on my facebook. It is a good way for you and your friends to stay plugged in to the latest...

 

https://www.facebook.com/pages/Marc-Weinberg/171330336238674


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