Day 2 Wrap Up - LAPS Data Useful!

Looking back at today...I noticed that the storms initiated along the instability gradient that was evident in the LAPS CAPE data. Further east...into central NC...the storms strengthened and were more persistent/long-lasting. This is represented well in the Storm Total Precipitation (grey-shaded) in the image below.

KFCX/KLTX/KRAX Storm Total Precipitation overlaid onto LAPS CAPE.

After using LAPS data a couple of days in a row...I am convinced that it is useful in assessing the pre-storm environment. It may even be useful as the event evolves but I will have to assess that another day...

~Lilly Miller~

End of Day 2

Storms were slow to develop over the CAE CWA yet prob severe led the way in delineating the one and only severe storm that managed to develop.  Given the lack of activity we swapped to the ILM CWA and managed to double our severe storm count with another isolated supercell over SE NC.  Prob severe again did very well over the lifetime of this storm.

GOES CI struggled within a westerly low level flow regime across the western portion of the CAE CWA with at times moderate probabilities shown for convective initiation yet were largely overdone.

Finally, imagery adjustment for parallax shift can in some cases mask useful information as denoted in this blog post.

Tornadotod

Atmospheric Motion Vectors Change with Outflow Boundaries

The low level atmospheric motion vectors (based off of Visible Satellite Imagery) shifted with the storm outflow boundaries as they pushed across the area.

Also of note...the storm motion of the convective cells seemed to follow the AMV's even with sparse AMV data.

~Lilly Miller~

Beware the parallax...

Note how the adjusted parallax error VIS image below masks the non-adjusted VIS image.  Using just the parallax error adjusted imagery, one would have missed the rapid updraft growth taking place along the southern flank of this long-lived supercell storm.



Tornadotod

9 Sigma Lightning Jump!

In the upper right image, a 9 sigma lightning jump was noted with the Wake County, NC storm (near the Raleigh metro area) at 2218 UTC! This occurred as the storm had a Prob Severe value of 98%, and several area radars showed a three body scatter spike in the middle levels of the storm. This gave me very high confidence to issue a new Severe Thunderstorm Warning for this storm. JJW

Interesting SRSOS animation...check it out!

LTX composite radar imagery (40 dBZ+) overlaid on 1 min SRSOS enhanced VIS.  Note the continuous pulsing overshooting tops.

Tornadotod

Anson County Severe Thunderstorm Warning - Prob Severe Jump and Lightning Jump!

I issued a Severe Thunderstorm Warning for Anson County (and others) at 2149 UTC. The Prob Severe values jumped from 46% at 2144 UTC to 95% at 2146 UTC. The Prob Severe values remained high to warning issuance. In addition, there was a 3 sigma lightning jump with that storm at 2144 UTC and 2146 UTC. These jumps, combined with the three body scatter spike developing aloft, gave me high confidence to issue the warning. Update: 1.00" hail 3 miles SSE of Ellerbee in Richmond County at 2225 UTC. JJW

ProbSevere loses Satellite fields on storm

Interesting case with a storm today moving into the far southern portion of the Columbia CWA.

Early on at 1952 UTC, ProbSevere increased to 67% with strong/moderate satellite growth/glaciation rates and .73 in MESH, 32 fl/min.
 
By  2014 UTC, ProbSevere decreased to 19% due to falling MESH (.42 in) and flash rate (14 fl/min).

The next time (2016 UTC), however, the satellite fields dissapear (to N/A) from ProbSevere with this cell, leading to a drop in probabilties to 12%. The reasoning behind the loss of the satellite fields is unknown to the group in the HWT. The ProbSevere contour does appeared to grow, so it is thought that the object replaced the old sat fields with sat fields from a nearby storm, which read N/A. The ProbSevere developers can clarify.

Later, at 2046 UTC, MESH climbed back up to .78 in, and flash rate to 30 fl/min, both similar to what they were at 1952 UTC when the prob was 67%. However, at this time with the new "N/A" satellite data, the probability is only 50%. This implied to the forecasters that the lack of satellite fields in ProbSevere could forever hold down (compared to a similar storm with Satellite data) the probs for a given storm. This point can also be clarified by the developers.

ProbSevere and Lightning Jumps Coincide with Lifecycle of Supercell

An ongoing supercell pushed eastward this afternoon and started strengthening again. This strengthening was evident in both the sudden increase in ProbSevere Probabilities and with the Lightning Jump Detection Algorithm.

MRMS Composite Reflectivity (Top Left), MRMS MESH/Hail Track and Lightning Jump Detection Algorithm Underlaid (Top Right), MRMS Reflectivity at -20C (Bottom Left), MRMS Low and Mid-level Rotation Track (Bottom Right)

At 2042Z: ProbSevere Probability jumped up to 70% with 51 dBZ at -20C
At 2050Z: ProbSevere Probability spiked at 93% with a 7.0 Sigma Lightning Jump. There was also a 60 dBZ core at -20C and MRMS MESH showed 1.3".
The supercell pulsed down for a couple of scans then was back up to 94% ProbSevere Probability at 2108Z. This corresponded with a 5.0 Sigma Lightning Jump and a 61 dBZ reflectivity core at -20C. The best reflectivity both near the surface and aloft was lost by 2116Z, which corresponded with Sigma Lightning Jump decreasing to a value of 1.0.

The supercell went on to pulse in strength beyond this time with both ProbSevere and the lightning detection jump algorithm corresponding well with its varying strengths. The moral of the story here is that both the ProbSevere and Lightning Detection Algorithm gave me better situational awareness and increased my confidence when issuing a warning, especially since these were the highest values of both products that I had seen all afternoon.

~Lilly Miller~

Chatham And Wake County Severe Thunderstorm Warning - Prob Severe and Lightning Jump Helpful!

Here is the Severe Thunderstorm Warning I issued for Chatham and Wake Counties in North Carolina at 2136 UTC. The storm that was in the previous warning polygon weakened considerably, so that warning was not re-issued. However, the Prob Severe values jumped into the 80s and 90s in the time since, with a 96% value at the time of the warning issuance. In addition, a 4 sigma lightning jump was also detected right before warning issuance. These factors, combined with high reflectivity aloft from a neighboring radar (KFCX), helped give me more confidence to issue the warning. Update: 1.00" hail reported in Cary (Wake County) at 2204 UTC. Several other reports of 1.00" hail in that area. 1.75" hail reported in Apex (Wake County) at 2215 UTC. Ping pong ball size hail in Kerly (Johnston County) at 2310 UTC (warning in effect downstream of warning below later on). JJW