Good non-severe storm with agreement from radar/satellite products

One storm became near severe around 545 pm in EWX CWA. All parameters; lightning, ProbSevere and Dual-pol radar agreed on the evolution of the storm and expected impacts. Radar data suggested there to be equal wind and hail threat based on high ZDR and KDP within the core suggesting sub-severe hail. There was some notching in the back side of the storm's reflectivity as the front end of the storm surged eastward suggesting some wind threat. Lightning over this time had increase from 10 fl/min to 20 fl/min about 15-20 minutes prior to the development of some weak mid level rotation. As the storm cycled and weakened, so did the lightning and ProbSevere values. An uptick in GLM event density was followed by a slight increase in ProbSevere values toward the end of the loop.


KEWX 4-panel - Refl (UL), ZDR (UR), KDP (LL), CC (LR)


KEWX 4-panel - SRM (UL), V (UR), HC (LL), SW (LR)


GLM sequence of Gillespie County storm - 1-min(FED)(UL),AFA(UR),TOE(LL),EventDensity(LR)



ProbSevere time trends from http://cimss.ssec.wisc.edu/severe_conv/plots/PSplots.php?ID=176047

-- SCoulomb

AllSky LAP CAPE with 40+dbz radar overlaid

This loop shows how AllSky LAP CAPE behaved as convection evolved through the event. You can see which cold pools related to which thunderstorm events. Allsky Lap captured several of these cold pools including a large one over central texas.

Lightning Event Density As A Proxy For Storm Intensity

Lightning Event Density was mirroring the storm near point F for a fair amount of time. Notice how the prob severe graph almost directly correlates to the product. When Flash Event Density decreased, the Prob Severe decreased as well. Greater Flash Event Density seems to correlate to storm intensity.

Lightning Event Density Before Storm Weakens (Point F)

Lightning Event Density After Storm Weakens (Point F)



Trend-line for the storm...notice the drop-off that occurs when the flash event density decreases.

South Beach

GLM Event Density drop during supercell split and right move

This loop shows how event density evolved as a supercell rightmoved in west Texas. Another good example of GLM data showing a minimum during the most intense phase of convection. GLM data counts recovered somewhat toward the end of the loop.

-Dusty

All-Sky LAP PW vs. Merged TPW

There has been considerable examination of the All-Sky LAP products (PW and CAPE) this week, and for good reason - they're quite good. I wanted to take a quick look at how the All-Sky LAP total PW compared with the merged TPW product. The All-Sky product is on the left and TPW on the right. I overlaid the 20z 1 hour RAP PW forecast for comparison. Ignoring the higher resolution of the All-Sky, the very broad distribution of enhanced and depressed values are similar in location between the two products. However, the TPW values are considerably lower than both the All-Sky and the RAP forecast. Further, pulling the 21z SPC mesoanalysis PW shows that the All-Sky tends to be the better of the two satellite products.

The TPW seems good for very broad generalizations, but if given a choice between the two in operations, I'll take the All-Sky, All-Day Every-Day.

--Stanley Cupp

NUCAPS soundings comparisons for 5/2

This was the 12z Del Rio sounding.



This sounding is a modified NUCAPS near Del Rio. While the lower level structure was a bit different than the actual sounding, the observed sounding was taken several hours earlier before boundary layer modification.



This was an unmodified NUCAPS sounding from the same region. Boundary layer moisture is not captured nearly as realistically as the prior modified example. Overall, trust in the modified NUCAPS sounding data has increased dramatically after some exposure to it. I would say many forecasters need more experience learning about the soundings through simulations to trust the data more.

-Dusty

Merged-TPW compared to Sfc obs

The merged-TPW product compared well to the surface obs with 1) the strong gradient along the dryline 2) the lower PWAT values behind the MCS and 3) axis of greater PWAT along the immediate Gulf Coast. Actual values however were too high in the dry air (MAF/DFW) and too low in the moist air (DRT/CRP). Values compared to 12Z soundings at BRO the best.



-- SCoulomb

NEW NUCAPS

NUCAPS offer a way to get a vertical profile of the atmosphere across the US. However, in areas where soundings were not "retrievable" it can leave many of the products with large holes in them.



Default Output From NUCAPS on w/ vis satellite
A great application would be some type of algorithm that fills in the "data holes" Two ways to approch this would be:

1.  Linear interpolation between the grids
2. Use a model such as the RAP to fill in the gaps

A quick attempt at a combined product with the NUCAPs Forecast and the RAP.[/caption]
A smoothing of some sort would still benefit the product above, but this would be of great benefit to forecaster's trying to determine the afternoon environment. (Note: I think it would be beneficial to include a mask that said whether the data was from NUCAPs or a model in each location if a product like this was developed. All in all, this is a useful product, but it needs some further refining.

South Beach

AllSkyLAP doing a good job with extent of CAPE

The AllSkyLap CAPE captured the overall footprint of the CAPE when compared to the SPC mesoanalysis even down to the cold pool in the wake of the disorganized MCS north of EWX CWA. Values themselves were however much lower than actuality.


AllSkyLAP CAPE


SPC Mesoanalysis MUCAPE

-- SCoulomb

Del Dot CAPE in NUCAPS Forecast

NUCAPS forecast product unrealistically advects the CAPE east through the evening. In reality the CAPE axis extends along and east of the Rio Grande and will likely stay in place but slowly modify toward sunset. Also it might improve the product to interpolate or fill in the gaps with a model (actually Jake's comment) not mine.



-- SCoulomb

NUCAPS Modified Sounding Compared to Surface Obs

NUCAPS gridded 700-500mb Lapse Rate and Modified sounding points.  Lapse rates are favorable for storm intensification across the southern part of FWS CWA.


NUCAPS Modified sounding had 72/69 (temp/dewpoint), compared to closest surface METAR KLHB 74/69 (temp/dewpoint).  This sounding data showed un-capped and unstable environment supportive of surface based convection in southern FWS CWA.

-Jake Johnson

ProbSevere Trendmap for a splitting supercell

Graph of probsevere for splitting supercell discussed in earlier blog entries. These graphs are extremely useful to forecasters looking for trend analysis.

Possibly even more important could be their use in post-event analysis. For example, plotting lines on these graphs when LSRs came in, when tornadoes occurred, can give forecasters an idea of what the trends were showing in MRMS at the time of the impacts. The RealEarth viewer appears to allow you to view these graphs from object IDs back about 24 hours, however only the object ID shapefiles are available before that in time. It would be very useful for forecasters to have access to these time series plots for post event analysis - perhaps consider making them available for any object IDs up to a week old?

GLM behavior, overlaid with +40dbz/vis sat throughout a CI event and storm split

Full loop from CI through storm split. A good practice for GLM users overlaying with radar is to Alpha your color table below a certain range (in this case 40 dbz) to mask out low reflectivity values and focus on storm cores only. Because of the parallax error, the storm cores on GLM are displaced to the northwest of the radar cores - a hidden benefit for storm interrogation!

There are several things to note here. First is the onset of GLM data - this storm featured explosive development. The GLM data here is 5 min/1min update. Because of this, the upward trend is rather sudden - for early stages in deep convection it may be best to use 1 min data. As the supercell splits, the the different cores are most evident in the top left, which is Event density data. FED, AFA, and TOE do not snow this trend nearly as well. I chose not to include a loop of Minimum area, because this data was too low -resolution to capture details of different cores this close.



This is a longer loop of the same event showing the storm through its demise. You can see the Average Flash Area in the storm in the bottom left really increase as this particular supercell diminishes. This is consistent with the idea that shorter length lightning in the core ceases and most of the remaining strikes are longer flash events in the residual anvil.

-Dusty Davis

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.