The top image is CIRA/NSSL WRF Simulated IR while the bottom image is observed IR around 22 UTC.  The simulated IR underestimated cloud cover over Oklahoma where a mid/upper low was centered.  The convection over the Rockies in Colorado and New Mexico as well as cooler cloud tops over eastern Texas and Louisiana were handled well by the simulated IR.  The convection near Lubbock, Texas was captured very well.
was handled very well by the simulated IR.  The band of

Based upon CTC rates around -20 to -25 C and initiation within a LAPS-analyzed region of approx. 2500 J/kg of CAPE, we warned on a cell that was developing around the Brown/Comanche/Mills intersection, expecting that strong cooling rates within an axis of (model-represented) good instability would at least result in a hail threat. However, the cell quickly weakened as it moved into the FWD CWA. Based upon recent sounding from MPEX in Seymour, TX, current atmospheric column across central TX may be too dry, resulting in growing updrafts entraining too much dry air and dissipating from negative buoyancy.

CTC Rate (SW portion of CWA)

LAPS-analyzed Instability

I was wondering why LAPS constantly showed weakening trends with discrete storms entering a north-south aligned CAPE tongue just west of KABI. Rapid strengthening occurred just after initiation:

LAPS 1km overlaid with reflectivity/VIS.

CAPE (LAPS) peaked in excess of 2000 J/kg in the area where storms were expected to move in. However, as seen below, storms gradually weakened during the following scans and so did the CAPE plume in LAPS:

The guess is that there was some strengthening of the dryline with enhanced postfrontal mixing occurring (personal talk). Also, there might be an evolving dryline bulge to the southwest of Dallas. Accompanied broadening area of backing winds is now present to the east/northeast of the decaying storms  and the focus for initiation of most intense storms in the next few hours remains next to the Dallas/Fort Worth area (as constantly seen in OUN WRF/LAPS). 2145Z features 15-20 kt SE-early surface winds in this area with rapid thunderstorm growth. Helge

A lightning jump of 18 Flash/Min to 40 Flash/Min between 1908 and 1909Z  with a second jump to 51 Flash/Min at 1912Z preceded a rapid increase in vertically integrated ice, MESH, and reflectivity at the -10C isotherm. A 1″ hail report was then acquired at 1926Z in Ratliff City.

The following plot shows the flash extent density trace for the storm approaching Ratliff City, OK. Focus on the timeframe between roughly 1900Z and 1930Z. Notice the strong jump between 1908Z and 1909Z.

MESH jumped from 0.63in (1910Z) to 1.10in (1912Z) to 1.26in (1914Z) with the last detection of 1.02in (1924Z) before dropping off thereafter. The following images show the jump from 1910Z to 1912Z.

Looking at the vertically integrated ice product…there was an increase in values from 14 kg/m2 (1908Z) to 20 kg/m2 (1910Z) to 32 kg/m2 (1912Z) with consistently high values above 30 kg/m2 through 1924Z. See the images below as the storm approached Ratliff City.

Regarding reflectivity at the -10C isotherm…there was an increase to 59dBZ  by 1912Z then 61dBZ at 1914Z (not shown).

Again, the 1″ hail report was acquired in Ratliff City at 1926Z which gives the lightning flash extent density tool a 17min lead time to the 1″ hail report.

RJM

The images at 19 and 20 UTC respectively depicted an area of drier air, most likely associated with a short wave on the back side of a mid/upper low over southwest Oklahoma. This wave seems to be enhancing cloud top cooling and convection generation over west Texas, near Lubbock.  We will keep a close eye on this feature to see if this wave will allow for explosive convection 22-01UTC near a dryline from near Childress to San Angelo with very unstable (2000-3000 J/kg) air near and east of the dryline. Michael Scotten

The cells that have formed in the western portion of the FWD CWA have so far been fairly pedestrian.  Initially, this was puzzling, as there appeared to be several favorable factors for more vigorous activity.  My partner here pulled up my favorite product, the LAPS CAPE analysis, and he may have found the answer.  The storms are forming along an instability gradient (the blue/green interface towards the bottom of the image), and moving eastward into an area that was worked over by morning convection (lighter blue colors).  So, they waddle along and weaken in the more hostile environment.  Mystery solved, at least partially!  Still expecting more exciting weather soon as a watch just went up.

CL

Thunderstorm coverage is expected to increase 21-02z across north and central Texas as daytime heating should erode capping. Think isolated to scattered supercells will develop near or just east of the dryline where best instability (2000-3000 J/kg) and increasing shear (0-6 km 30-55 kt).  Very large hail would be the main hazard with supercells, thought damaging winds and perhaps a tornado or two may occur as well. Highest storm coverage will most likely be across western north Texas and Oklahoma where capping is weakest closer to the mid/upper low.  The best chance for supercells with the biggest hail is expected over northwest Texas where best instability and shear are forecast. Across Oklahoma, weak capping and limited heating from ongoing convection are expected to limit the overall severe potential, though a stray damaging wind or hail report remain possible, mainly through 02z. With low LCLs and locally enhanced 0-1 km SRH values 150 to 200 m2/s2, short lived weak tornadoes are possible, mainly over central and eastern Oklahoma through 01z. Additional severe storms may develop farther south near or east of the dryline, across central and south Texas though stronger capping is expected to reduce the number of storms.  The supercells may evolve into mini squall lines/MCS clusters 01-03z as they move southeast and are expected to slowly weaken. However, damaging wind and large hail may the main hazards with any MCS.

We are setting up in the Dallas/Fort Worth CWA today, and expect some busy weather in a few hours.  So, I’ve been scanning the various products to get a general overview.  The SPoRT GOES RGB product is good to get a general sense of the airmass structure.  Decided to do a second post on it today to start off.

In the image below, the greenish yellow colors represent the more humid subtropical airmass, while the blue to red color is the drier, more continental airmass.  You can see the approximate position of the dryline at the interface of these colors.  Of course, the sounder is sampling the upper mid levels here (400-500mb) and doesn’t exactly correspond to the surface dryline…you can see this in the overlaid obs.  Still, this is a product that can give you a quick idea of the general airmass setup.

CL

As part of the Nowcast / Warning desk for FWD, it’ll be interesting to watch initiation along the northern portions of the tightening dryline this afternoon.

When comparing the simulated IR with the actual IR at 19Z, it appears the simulated is underdoing cloud-cover on the backside of the upper low (across NW TX / W OK). It then initiates convection across NW TX around 21-23Z. The possibility exists that across the northern portion of this region, around the Red River or so, heating might be overdone on the model, resulting in initiation too early / too widespread. It will be interesting to see how initiation occurs along the dryline today.

Picca

19Z Actual IR

19Z Sim IR

23Z Sim IR

The CTC algorithm missed a developing storm that went on to become a robust storm and prompted an experimental severe thunderstorm warning. The storm in question is highlighted below within the red hatching at 2114Z when visually it was very apparent the storm was rapidly intensifying.

The algorithm “missed” this developing storm mainly due to the algorithm defining the cloud type in the vicinity of the developing storm as thick ice and cirrus at 2032Z and 2045Z. This storm was likely within the thick ice and cirrus definition…and therefore was included in the ice cloud exclusion zone and not given a CTC rate.

This example merely illustrates that not all developing storms will be captured by the algorithm even if visually it looks to be clearly intensifying. This is especially the case in a situation where multiple storms are in one area.

RJM