AMV depict pre-frontal trough

Atmospheric Motion Vectors are nicely illustrating the pre-frontal trough across Arkansas. Of particular interest is the illustration of the trough with height. For the low level winds (blue) the pre-frontal trough can be seen clearly...particularly in northeast Texas where southwesterly winds are occuring ahead of the trough and northerly winds behind the trough. Looking at upper level winds however (green, red, pink), most remain in a southwesterly direction, indicating that the trough aloft remains to the northwest. This makes sense because the frontal boundary will be tilted with height back towards the northwest. The screenshot is below. - Jason Bourne

1-minute satellite capturing front and pre-frontal trough

Looking at 1-minute imagery west of the HUN CWA the approaching cold front and pre-frontal trough are clearly visible and can be tracked with the data. The northeastern edge of the pre-frontal trough is moving into the HUN CWA and extends south and west through Mississippi and into Arkansas and Louisiana. Behind it...the actually cold front signaled by a drop in dewpoints is moving through central Arkansas. Surface observations are overlayed for illustration. Below is a still shot and a .gif to show the tracking ability with the one minute data. - Jason Bourne

Using 1 minute Satellite in desicion NOT to warn

Tracking a rapidly developing storm approaching our CWA,  on above 1 minute satellite imagery one can notice the rapid vertical growth slowing at the end of the loop as storm encounters less favorable lapse rates.  Decided NOT to issue a warning partly based on these visual cues.  Thanks Vis!
-Stormfront
PS-This storm had our HIGHEST prob. severe of the day by far.  In this environment it was tempting to warn based on that alone....

Verification of first OHX warning

A couple of Severe Thunderstorm Warnings (SVR's) have been issued for the OHX forecast area.  The first warning verified at 1934 UTC with several trees down, some that fell down on homes.  The following images show a rear inflow notch with a velocity max of 60 kts. This SVR was issued at 1923 UTC with an 11-minute lead time.

Prob Severe Qualitatively Helpful

With a low shear, low mid-level lapse rate environment today...ProbSevere has not been very high, and most storms have not been severe. However with the severe storm we did have...Prob Severe only topped out at 25%. This may seem like a poor performance however, when looking at ProbSevere qualitatively and not quantitatively a survey of the storms at the time showed every other storm less than 10 percent. That means that for the severe storm, despite having a low value of ProbSevere, it was still 2.5 times that of any other storm in the area. This still is useful information given the environment and actually added confidence to the warning decision because it was the best we had seen all day.

-Jason Bourne

Lone storm in Arkansas

One lone storm in southern Arkansas along a sagging cold front jumped in ProbSevere values (40%->50%->74%->90%), due to a strong normalized satellite growth rate, and a jump in total flash rate. This storm was just outside the SPC's wind and hail outlook.

Fig. 1: Strong ProbSevere values on an isolated storm in southern Arkansas.

Fig. 2: Our storm in southern Arkansas with the western edge of the SPC severe wind outlook (5%).

OHX: Severe Thunderstorm Warning

Our first warning for the day was issued northeast of the city of Nashville, where a jump occurred with the pGLM data. The SVR TSRA polygon was overlayed show how the lightning jump was used in the preceding scan.

 

The 4 panel below shows the Sig Probs only rose to 21%, but a distinct velocity maximum of 50-55 kts was occurring and the 1-min visibility nicely shows the strong updrafts with rapid cooling in the IR imagery.  This storm was was likely capable of damaging winds. 

-Yodamaster777

1 Min Visible Sat Shows Convection Developing on Outflow Boundary

We noticed an outflow boundary moving into our CWA from the Huntsville CWA to our south. Convection is developing along this line and is producing several cells that are generating quite a bit of lightning activity.

 
We issued a severe thunderstorm warning on one of the cells for Coffee, Warren, and Grundy conties that produced a significant lightning jump. The flash extent density value reached around 40. -JP

PGLM and 1-min Overshooting top HUN

Captured a good shot of 1 minute imagery with an overshooting top in the warning box. This was a good example of a line of storms moving to the northeast that all looked fairly equal for a while. Then there was this overshooting top that corresponded with a jump in the flash rate the corresponed well. In the end there was a report of quarter size hail with this storm but it was in a county that was in the far southeastern flank of the warning polygon. This did not line up with the storm but the blowoff from the storm is travelling to the southeast. It could be possible that hail from this storm was blown southeastward out of the storm and thus landing in the adjacent county. Or it could have been a suspect report. -Jason Bourne

NUCAPS theta-e Cross Section

We recently gained the ability to create cross sections through the NUCAPS swaths. This will be helpful for diagnosing phenomena such as boundaries and convective instability. The first image below is a plan view display of theta-e at 660 mb across the region. Obvious is the much cooler, drier air behind the cold front (low theta-e) with moist, warmer air ahead of it to the east (high theta-e). Also plotted is a line, denoting the location for which the cross-section (image below) was taken, through the cold front. The cross-section depicts theta-e vertically through the atmosphere. This provides another perspective on the cold front, which is obvious in the image.