All-Sky LAP CAPE and Boundaries

The All-Sky LAP CAPE product is rather useful as a quick and dirty SA tool to quickly identify boundaries and their approximate location/orientation. While the actual CAPE values given are not as important (perhaps better to rely on obs, mesoanalysis, and short-term models for that), the LAP product does very well with identifying the key location of the gradient and subsequent boundary. The boundary location in today's case is rather obvious, but this product will likely prove useful in more diffuse situations.

--Stanley Cupp

GOES-16 Sandwich Product showing a nice above anvil cirrus plume. ProbSVR showing 99% for large hail and Tor prob 5% with nice double rings.   GLM Min Flash area remained in place with overshooting top of this supercell.

ProbSevere Double Contour

A quick post regarding the ProbSevere 'double contour'.  New to the ProbSevere AWIPS-II display is an outer contour that indicates the ProbTor value for a storm outside of the inner contour (the inner contour is the maximum of ProbHail/ProbWind).  This double contour idea came from the forecaster feedback from the 2018 HWT experiment--as a means to have both severe thunderstorm warning and tornado warning guidance in a single display.  Today, forecasters have very active weather, with many storms (Figure 1).  The default for the double contour to appear is ProbTor >= 3%.  Forecasters have stated today they appreciate the ability to change the threshold for the double contour to appear.

Figure 1.  ProbSevere contours from a forecaster's AWIPS-II screen.  The inner contour is the maximum of ProbHail/ProbWind for the storm and the outer contour is the ProbTor value (displayed when ProbTor >= 3%).

ProbSevere

ProbSvr readout is becoming so long it is hard to fit within a 4_panel. It is not usable as a readout in a 9_panel due to the number of parameters being shown. Perhaps combine the LLAzShear into a single line such as (Max,LLA,MLA) (0.004/s,0.0002/s,0.005/s) to save space???

-- S Coulomb

NUCAPS Soundings

While it is very easy to plot forecast soundings from whatever model you may choose, NUCAPS provides yet another resource as an alternative to NWP. A strong thunderstorm formed in Mexico around 22z today, almost due west of Del Rio, TX. SPC mesoanalysis showed approximately 2000-3000 J/kg of MUCAPE in the vicinity prior to convection initiation (CI). A quick look at a 20z modified-NUCAPS sounding corroborated the SPC analysis, with ~2400 J/kg of MUCAPE at 20z. The NUCAPS data allow for a detailed analysis of the resulting profile and can be a useful alternative to model soundings, especially the modified products as they attempt to more accurately represent the boundary layer based upon RTMA data. The 20z NUCAPS had ample CAPE in the hail growth region along with 700-500 mb lapse rates in excess of 7C/km. Effective bulk shear in excess of 40 knots coupled with favorable thermodynamic environment likely resulted in this storm producing large hail as KMAF radar sampled greater than 60 dBZ at greater than 32K feet. ProbSevere hail output peaked at 97% (MRMS Mesh = 1.87") roughly 40 minutes after CI.

--Stanley Cupp

20z NUCAPS sounding near storm in Mexico


20z SPC Mesoanalysis MUCAPE and 0-6km shear (dot indicates point of CI)

Mexico splitter - Prob Severe and GLM data

Loop showing the evolution of a strong cell west of Del Rio in Mexico. Prob Severe values were dominated by Prob Hail in this case. This hail threat makes sense given mesoanalysis and storm mode, supported by 12z Del Rio sounding. Peak values around 97% occurred before the storm split, but after peak dbz values observed on radar. This makes sense considering the beam height at this range (165 mi from MAF) was showing the mid-level core at 30kft MSL - hail would likely have needed time to fall out from this height. This case could be useful for offices with high radar beam heights distant from isolated thunderstorms. Prob Tor did nudge up around the time of the storm split enough to show the 'double contour', however V data at low levels was not present.



Same storm now with GLM Event Density. This data showed a lightning decrease around the time that the storm split. Following the split, almost 0 lightning was observed in the southern cell, while the left split saw a spike in event density. The left split reinvigorated shortly after the split while the right mover weakened.



This is the same loop with radar overlaid that shows the storm split and this time flash extent density. Almost 0 lightning data seen in the south cell.

Brewster Co TX storm not so Punky but modified NUCAPS was

The modified NUCAPS sounding over Brewster Co TX was more representative of the actual conditions at 20Z versus the regular NUCAPS. A dryline was positioned very near the point of interest and convective initiation eventually occurred  near the boundary in ~1000 ML CAPE air around 22Z.



Modified NUCAPS sounding w/ surface Td near 47F. MLCAPE ~ 1000 J/kg.



Regular NUCAPS sounding w/ surface Td near 54F. ML CAPE ~2000 J/kg.



RTMA Td analysis. Point H is where the NUCAPS sounding was taken from.



GOES-16 RGB at 2150Z showing CI occurring near the dryline.

Best option available?

Below is an example of a case where prob severe my offer the best option for a warning decision. This storm is outside of the best RADAR coverage available; however, strong development has been seen on Satellite imagery for an extended period of time. In a case like this, the PROB Severe Algorithm may be the best option for a warning decision, based on the data available.

South Beach

GLM Min Flash Area...Best Practice

Figure A


Figure B

Best Practice:  Look at lower left image on both Figure A and B (GLM Minimum Flash Area), notice Figure B has interpolate turned on which makes the product less useful since outer edges also have minimum values.  The GLM Minimum Flash Area of interest jumped out much better on Figure A without interpolate turned on.

Week 2 of the 2019 EWP Underway

6 National Weather Service forecasters are in Norman, Oklahoma at the Hazardous Weather Testbed for the 2019 Experimental Warning Program--Satellite and Radar Convective Applications Experiment.  Monday is being used as a training and AWIPS-II product familiarity/procedure building day.  This will serve all participants well in the coming week as much more active convective weather is expected starting Tuesday.  Many satellite and radar products will be evaluated, including NOAA/CIMSS ProbSevere v2.  ProbSevere v2 explicitly produces probability of severe hail, severe wind, and tornado.  One element of focus for the 2019 evaluation is the inclusion of a 'double contour'--one ProbSevere contour that is the maximum of ProbHail and ProbWind for a storm and an outer contour that is the ProbTor probability for a storm.  The double contour approach was a widely requested enhancement by participants of the 2018 HWT EWP as a mechanism for forecasters to monitor severe wind/hail as well as tornado threat on a single display (often all tilts radar).

J. Sieglaff