WKU Meteorology

Unseasonably warm conditions continue to be the story across much of the eastern half of the US, as seen in the surface temperature map provided by TwisterData.com for Thursday at 18z (1PM).  A large upper level ridge is parked over the area bringing high temperatures in the lower 80s and low temperatures in the 60s.  The record for yesterday (March 14^th) was 82 set in 1967 and yesterday’s high was 81.  These warm conditions will continue for the weekend and early next week.  These warm and moist conditions will also produce summer like storms.  Expect an increase in chances for your Thursday and Friday as an upper level disturbance moves through the area.  These storms will likely not be severe, but heavy rain and small hail are not out of the question.  Since the convection will be mostly unorganized you might want to check local radar for the next several days if planning outdoor activities.

By: Dustin Jordan

A band of heavy rain will move through this afternoon and evening bringing rainfall totals from 2-3 inches. small streams and creeks will likely rise quick later today.

Would not be surprised to see totals near an inch. The secondary low for Saturday appears to be Sunday timing instead with warmer conditions so no threat of frz rain. enjoy the rest of spring break!

2. Tuesday skies will be sunny with some southerly flow. I expect a quick warm-up with highs in the mid 60’s.

3. Another sunny day Wednesday with southerly flow lows will range from the mid to upper 40′s. Highs will be in the 60′s.

4. A split flow pattern evolves by mid-week with a cut-off low over the desert southwest and a front moving across the great lakes. Increasing clouds Wednesday night and southwest winds may keep temps in the 50′s.

5. The cut-off low forms a low over the Arkansas region Thursday. Severe weather stays south of our region since the low track is south. However periods of rain are likely from Thursday afternoon into Friday. Temperatures Thursday should rise into the 60′s before falling into the 40′s early Friday with highs in the 50′s on Friday.

6. Low level cold drills in by Saturday morning lows may be in the  low 30′s. Our frontal boundary moves south of the region, the most likely case is what the models are showing a sunny cold day Saturday. However I would not be surprised to see a secondary low along the front make a run at the region with a freezing rain/rain mix.

NWS report on the southern supercell from Friday

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE LOUISVILLE KY
432 PM EST Mon Mar 05 2012

...Damage Report for Simpson and Warren counties in Kentucky...

Damage Type: Straight Line Wind Damage

       Date: Mar 02 2012
 Begin Time:  4:48 PM EST
   End Time:  5:05 PM EST

Begin Point: 4 NNW Franklin
  End Point: 2 SE Alvaton

 Wind Speed: 80-90 mph

   Injuries: 0
 Fatalities: 0

Damage Type: Tornado

       Date: Mar 02 2012
 Begin Time:  5:05 PM EST
   End Time:  5:07 PM EST

Begin Point: 2 SE Alvaton
  End Point: 2 E Alvaton

   EF Scale: 1
 Wind Speed: 95 mph

Path Length: 2 miles
 Path Width: 60 yards

   Injuries: 0
 Fatalities: 0

Narrative:

Straight line wind damage along and north of the super cell moving
through Simpson County uprooting shallow-rooted hardwood and
softwood trees and destroying a tool shed on Evans Rd.  As it moved
into Warren county it damaged barn roofs and produced golf ball size
hail which penetrated siding on numerous vinyl sided houses.  As it
reached 961 east of Alvaton in Warren county, it spawned an EF1
tornado with winds estimated at 95 mph destroying a barn and tool
shed.

$$

WEW/RJS

Here are some youtube videos

http://www.youtube.com/watch?v=jWEeE8kgqoM

http://www.youtube.com/watch?v=sBZXKoOW7yk

CNN news article

http://www.cnn.com/2012/03/03/us/severe-weather/index.html?hpt=hp_t2

Here is a radar image from the Washington post and Stu Ostro of the weather Chanel.

This is an image of a supercell storm at peak intensity, you can see the hook portion heading into west Liberty.

Radar image. the different colars measure the wind sepped going from and toward the radar. Where they meet you have the tornado.

image from texas storm chasers

I would post more but I’m sure have many of the same searching methods as I do. I’ll post final numbers sometime next week.

The clipper will take a climatological track north of BG Sunday night. Louisville, Lexington and many of the tornado affected regions of east KY may see a inch perhaps a few of snow. For BG expect some scattered rain showers, maybe a little mixes in, temps stay above 32.

I’m signaling the all clear. I’ll post if anything on damage in the region later tonight or Saturday.

A tornado warning is in effect till 4:30.

tornado warning northwest warren untill 4:15, rotation with storm heading into southern warren as well. seek shelter now.

scattered supercells are forming and a PDS tornado watch is in effect till 9pm.

Can this set-up be compared to some legendary textbook outbreaks?

My answer is no but close. The warm sector in the April 1974 case was more pronounced with warm and moist air being a month later. However in terms of severe events this should be the top event of the year and perhaps of the past few years.

Why is that?  ( Model images are invalid for this post after 00z Saturday Mar 3rd.)

1. Powerful jet at the 250 mb pressure level. 110-130 KT with our region in the favored exit region ( ahead of the jet streak-strongest winds at the 250 mb level)

Decent 500 mb shortwave and vort max to our northwest.

our region is just southwest of the triple point (warm front, cold front low pressure center meeting spot) in the prime heating hours of the day.

A key indicator for me in terms of a tornado threat is the risk for updrafts into storms known as helicity.

Values around 150-250 m/s^2 are favorable for a tornado threat. In this case the entire is that then some. Wednesday values were from 400-600 m/s^2 but that was with less instability.

twister data is the source. I’ll double check to see if the site is added in the links section.

instability, a good measure of that is CAPE. Values from 1000-2000 J/KG indicate moderate instability sufficient for severe weather.

Another indicator is the lapse rate temp difference with height. In the case of tomorrow it will steep increasing the instability and promoting the large hail chance.

In terms of chasing there will be a lot of interest in the region but keep in mind storm motions will be very fast and these storms will be dangerous as well. Please do any chasing very safely.

I’m not going to discuss the Monday morning snow again till Sunday, severe weather is of most concern, please refer to last update. Forecast details in last post as well.