Mesoscale discussion using All Sky and SPC mesoanalysis page

Favorable 0-6km shear aloft from SPC Mesoanalysis page above across FWS CWA



All Sky Total PW above shows deeper moisture in southern FWS CWA.



High DCAPE values across the FWS area per SPC mesoanalysis page above
Mesoscale Discussion...40-50kts of wind shear aloft and high DCAPE values show conditions favorable for severe winds to occur, mainly for locations where  All Sky total PW shows strong moisture gradient along surface front in southern part of the CWA.



This is a loop of radar and All Sky LAP CAPE.  Notice the higher CAPE values in the southern part of the CWA. This is were linear convection could grow upscale become surface based and capable of produce damaging winds. 

-Jake Johnson

ProbWind with report Leesburg VA

We had given some thought about operating in Kentucky or Virginia with one group today, so we have been paying a bit of attention in the eastern US.  One storm west of Washington DC had ProbSevere, specifically ProbWind rapidly rise this afternoon, while most storms had ProbWind remain 5% or less.  The figure below shows the rapid increase of ProbWind (blue, upper left) and the black line at 1905 UTC represents a wind report of trees down blocking a road.

ProbSevere time series from the ProbSevere website.  The upper left panel show the time trends of the various ProbSevere models.  Note how ProbWind rapidly increases between 1845 and 1900 UTC.  A report of trees down blocking a road was received at 1905 UTC.

-J. Sieglaff

AllSkyLaps_sfc900_vs_700-300 Comparison

Monitoring environment downstream of convection entering FWD forecast area around 1830 UTC on May 2.  Top image is the sfc-900 mb ALLSkyLaps PW illustrating higher moisture over southern portion half of the FWD CWA.  Bottom image is the 700-300 ALLSky Laps PW illustrating much drier air above suggesting convective instability.   SPC Mesoanalysis  RAP downdraft CAPE (not shown) also suggests axis of highest DD Cape in this region suggesting environment supportive for damaging winds as line segments moves across the FWD area later this afternoon.

- Quik Twip

GLM, Satellite, and Convection Initiation

For the first time this week, finally got a chance to examine CI using GLM data. I built a 4 panel that worked well for me (ENTLN CG and cloud flashes on each panel):

top L: 1 minute visible with flash extent density (FED) and event density (ED)

top R: 1 minute Vis/IR sandwich with 1 minute total optical energy (TOE)

bottom L: 1 minute Day Cloud Phase Distinction/Day Convection RGBs with average flash area (AFA)

bottom R: MRMS -10C reflectivity with minimum flash area (MFA)





Agitated cu developed just prior to this image at 1634z. These two images highlight the differences between FED (upper L of the top image) and ED (upper L of the bottom image). You'll notice that the flash extent density is much more muted than the event density. You can really hone in on the strongest initial convective cores with the ED and TOE compared to the FED.





Next two images are at 1651z with FED highlighted in the top image and ED in the bottom. Again, your eye is immediately drawn to the event density vs. the flash extent density. Also, your total optical energy corroborates with high values on the southern cell (at least with respect to electrical activity...radar showed both cores with similar 50 dBZ heights).





By 1725z, both event density and total optical energy are beginning to overwhelm and lose granularity. At this point, flash extent density highlights the more active cores. ED and TOE are both still useful, but the distinct advantages they showed earlier in convective evolution have degraded as convection has matured.





by 1929z, it's fairly obvious that the advantage TOE had in highlighting distinct cores early is no longer. While you can see smaller areas of enhanced optical energy, it is far noisier. We've noticed this throughout the week that TOE's usefulness seems to wane as convection matures and storms are extremely electrically active. Flash extent density seems to be a better choice at this point compared to event density, as was the case at 1725z.

A few of the biggest takeaways...Total optical energy (1 minute) serves a very useful purpose for CI as it can highlight areas of new updraft growth, but loses impact as storms become mature and lightning becomes well established across the area. Event density would seem to be a better choice for CI compared to flash extent density as well.

The four panel that I built I've found very useful for CI or subsequent new updraft development by combining the best of visible imagery, RGBs (are utilized to diagnose glaciation within clouds), and the MRMS -10C reflectivity. Time for more coffee.

--Stanley Cupp

All Sky Moisture Advection

All Sky Layer PW Surface-900mb                                               All Sky 900-700mb layered PW


700mb analysis from SPC Mesoanalysis, shows good warm air advection across Dallas/Forth Worth CWA.  The All Sky 900-700mb layered PW product shows good west to east moisture gradient across the central part of the CWA associated with the 700mb warm air advection signal. 

-Jake Johnson

GLM comparison for Line of thunderstorms

A linear storm was moving east across western FWS CWA producing 1" size hail.  Look at the cursor location, GLM Flash Extent Density and Event Density products were highlighting the most intense part of the storm better the GLM TOE product.  The GLM Total Optical Energy is preferred for initial storm development.  When thunderstorms become mature its best to use the GLM Flash Extent Density or GLM Event Density product to compare storms in the mature phase. 

-Jake Johnson

Prob wind - two cases with unexpected results.

Here are two cases where ProbWind produced surprising results. In the case above, a very strong wind signature descended from a linear storm segment. BV data near 80 knots in the lower 3 scans, however ProbWind was only at 71%. I would have likely issued a warning here without ProbWind, however the ProbWind data made me question mid-level winds within the thunderstorm complex.



In this case, a storm well behind the main outflow is identified. Prob wind is slightly higher here, at 74%, however the storm had no signs of imminent high wind in any of the lower tilt data. This case may have been a result of stronger mid level winds aloft affecting the prob output.

-Dusty Davis

May 2, 2019 ProbSVR Hail product for Comanche Co, TX

ProbSevere for Hail in Comanche Co, TX was showing very high probabilities looking at pink colored tracking outline in above picture, and picture below shows time series for hail probabilities. 

LSR report for 1.00 hail came in at 1:42pm in NWSChat...see text product below. 


-Jake Johnson

ProbDryWind?

I was talking with forecasters from Rapid City and Grand Junction offices.  They often experience dry microbursts.  ProbWind often does not do very well with these type of wind events.  This is something us (as developers) are aware of and are working on improving.  The setup and ingredients for these type of wind events are physically quite different than their more moist counterparts.  One forecaster suggested instead of trying to incorporate it into ProbWind and adding to the ProbWind readout, to make a new entry in the ProbSevere family--ProbDryWind.  This is an interesting thought and something we will need to ponder and discuss.  The forecaster added, he couldn't envision a day where you would need both within a CWA--the environments are very different and a separate display/readout would reduce confusion.

-J. Sieglaff

May 2, 2019 All Sky Total PW vs Merged Total TPW

Figure A

All sky continues to handle total PW better than CIRA Merged Total PW looking at the bottom two frames. Notice the westward expansion of better moisture in the All Sky which matches up with surface obs compared to much lower values further west on Merged Total PW.


Figure B

Looking at the lower left panel for CAPE in the All Sky product we see a well defined instability gradient in southern FWS area which has our interest for higher probability of severe weather. Storms across central and northern parts of Dallas/Fort Worth area will be elevated, however storms that develop in southern part of the CWA could become surface based along the instability gradient. 

-Jake Johnson


Figure C

RAP13 0-3km CAPE is favorable for surface based storms in far southern FWS CWA.