CI signature good at showing big convection in West Texas

Analysis of the CI and CI severe shows 80% and a drop back down to 75% (for CI) before convection developed. Storm is displaying strong hail signatures. We have extended warning for webb county.

 Interesting to see that at the same time we are watching a big line of convection south of the Corpus Christi radar that may be dumping heavy rain but, not  looking severe.

Thunder

Webb County, TX Storm Update

Overall, PROBSvr continues to show high probabilities of severe hail.  So far no reports have been received at the WFO, not surprising considering the low population density in this part of TX.  Otherwise, Lightning Jump data showed a 2 sigma increase approximately 20 minutues before warning went out the door.  Finding little utility with the Convective Initiation products so far.

 torman1

Latest update

As of about 19z:

Severe thunderstorm warning issued for large hail in the NW edge of the CWA, just south of KCZT.  Strong deep-layered shear (0-6 km layer), versus weaker 0-1 km values argues for hail producing supercells and possibly isolated downburst winds, versus tornadic storms.  Reflectivity jumps in the mid-levels on the KDRT radar seemed to portend a near-future jump in ProbSevere values for this storm.

A collision of a northward moving convergence boundary with the southward moving synoptic boundary at the eastern end of the CWA has touched off additional convection.  This is near a gradient zone in stability/shear.  Lightning flash rates/overshooting tops are not overly impressive, as of yet.  We'll continue to monitor.   - J-money     

Initial severe thunderstorm warning

Initial severe thunderstorm warning issued for Webb County in southern Texas @ 1859 UTC.  MRMS reflectivity at -20C now peaking at 61 dBZ with PROBSvr quickly increasing the probability of severe hail.  DFX radar currently in SAILS mode and additional volume scans provided little added value due to hail being the primary concern, at least initially.  That said, PROBSvr probability of severe seemed to be playing catchup as forecast decision to issue warning occurred prior to probabilities increasing significantly.

torman1

Environmental Analysis for Hail

Our initial assessment of the hail threat was from the 12z Corpus Christi sounding. We used it to assess hail growth zone height by sampling the -10C, -20C, and -30C heights AGL (this is approximately between 300mb and 500mb). The problem is this data is now 7 hours old and there are spatial limitations too, since this observation was taken almost 200 miles away from the storm we are particularly interested in. NUCAPS soundings would improve our assessment spatially since there is no sounding sight near our area of interest today. Also, the satellite pass that would provide NUCAPS data is timely, since it falls between radiosonde observation times. 300mb to 500mb is also the portion of the atmosphere that NUCAPS performs the best due to higher information content. This is very important in rapidly changing environments.

-dryadiabat

Prob Severe Compared to Reflectivity

Comparing the prob severe to radar reflectivity over time. We noticed the prob severe ramped up to 86% and then dropped back down to 31. Using some common radar analysis techniques this correlated well. The radar reflectivity jumped to over 50 dbz and then dropped down to 46 dbz.

Thunder

Initial blog post

Initial blog post:

Today's focus will be over extreme southern Texas as an outflow induced frontal boundary continues to sag south across the Corpus Christi and Brownsville CWAs. Ahead of this boundary, ample amounts of low-level moisture are in place with early afternoon dewpoints hovering in the lower to middle 70s. Latest 1-km SRSOR visible imagery from GOES-14 indicates plenty of low-level CU in place south of the boundary, however SPC mesoanalysis is already showing a moderately unstable airmass with MLCAPE values currently exceeding 2000 J/kg is some locations across far southern Texas.  So far, convection has been slow to kickoff in the unstable airmass south of the boundary, with the only notable convection of interest located along the Texas/Mexico border where the outflow induced front appeared to begin interacting with elevated terrain just west of the Rio Grande River.  That said, PROBSvr has been tracking this cell quite well so far, however probabilities for severe remain low at this time.  Also of interest is a northward moving outflow/differential heating boundary which will continue tracking north this early afternoon, before eventually colliding with the outflow induced frontal boundary approching from the north. As these two boundaries collide, expect developing/strengtheing convection as the airmass largerly remains uncapped per latest SPC mesoanalysis grapics.  Effective bulk shear of 40-45 kts remains more than supportive for severe development, however deep layered shear vector orientation along the effective outflow boundary may keep developing convection in linear segments.  Of interest however, Rapid-Refresh soundings from south-central Texas show deep inflow directly from the east with quick veering with height above 900-hPa. As a result...cannot rule out an isolated tornado or two, however very dry air aloft along with steep mid-level lapse rates will likely keep large hail and damaging winds the primary focus of severe weather concerns. 

torman1

Value of Parallax Correction

We just got started setting up our procedures in AWIPS II and got caught up in a discussion of the value of parallax correction. It is very obvious when you toggle between the two. The correction is very evident in the mid and especially the higher clouds. We're currently looking at thunderstorm anvils in the western part of Corpus Christi's forecast area. The correction removes some of the shadowing from these anvils that were projected onto the lower clouds. Also, we looked outside of the area we were focused in, up further north. The edge of the cirrus across portions of Iowa and Missouri shifted significantly between the standard visible image without correction, and the parallax corrected image. We can see where this would be most valuable with the derived products and ensuring their placement is accurate and lines up well with radar data.

In the above images, corrected is on the top and uncorrected is on the bottom. 



-dryadiabat

The Experimental Warning Program at the Hazardous Weather Testbed Begins

The 2016 Experimental Warning Program at the Hazardous Weather Testbed begins today and will run through the week of May 9, 2016.  The weather this week looks to be dominated by a cutoff upper level low over the Rocky Mountains into the western Central Plains, so much of the week will be spent in Texas.  Both groups of forecasters today are beginning their shifts in the Corpus Christie, TX WFO.  One group may move to Brownsville WFO if it looks like capping will be overcome/a forcing mechanism becomes apparent or to the San Antonio WFO if elevated convection looks to become more intense.  I will be supporting the NOAA/CIMSS ProbSevere product and my posts will focus on ProbSevere.

-Sieglaff

HWT 2016 GOES-R/JPSS Spring Experiment Begins Today!

The HWT 2016 GOES-R/JPSS Spring Experiment in Norman, OK begins today, 18 April, and will run through 13 May. Three NWS Forecasters and one Broadcast Meteorologist will participate in the GOES-R and JPSS product evaluations each week. Participants will utilize the experimental satellite-based products in a real-time AWIPS-II to issue experimental mesoscale forecast updates and severe thunderstorm and tornado warnings.

Products to be evaluated include:

• GOES-R Legacy Atmospheric Profile (LAP) All-sky Thermodynamic Products
• GOES-R Convective Initiation and Severe Convective Initiation
• Probability of Severe Model
• GOES-14 Super Rapid Scan Operations for GOES-R (SRSOR) 1-min imagery
• Atmospheric motion vectors (updating every 10 minutes)
• Parallax-corrected 1-min imagery
• Total Lightning using PGLM (in LMA networks)
• Lightning Jump Algorithm (using ENI)
• NUCAPS Temperature and Moisture Profiles (JPSS)

You can follow this blog for live updates and forecaster posts from within the HWT.

Bill Line, SPC/HWT Satellite Liaison