Tuesday, May 7, 2019
Tornado Development in N LUB CWA - ProbSVR & NMDA Performance
When the reported tornado developed in Swisher County in the northern portion of the LUB CWA at 5:12 PM, it was preceded by increases to the ProbTor and AZShear products by several minutes. Initially, I believed these algorithms to be picking up on sidelobes in the lowest levels of the radar scans, as noisy velocity data was being recorded in areas where reflectivity values were small. You can see these artifacts in and around areas of purple haze in the animation below. However, these products verified their jumps with a brief tornado touching down. It was reported to look relatively strong while on the ground with multiple vorticies visible at the time. It was short-lived, however, seeming to dissipate relatively quickly after touchdown.
The NMDA also did well picking up on this circulation before tornadogenesis, but I had some questions regarding the data quality in the low-level detection prior to the tornado.
#ProtectAndDissipate
The NMDA also did well picking up on this circulation before tornadogenesis, but I had some questions regarding the data quality in the low-level detection prior to the tornado.
#ProtectAndDissipate
Lightning Jumps in Action
The storm near Tulia is...impressive. Aside from being a long-tracked supercell, the storm has been extremely active electrically. There have been several lightning jumps with this storm that appears to coincide with an increase in the strength of the mid-level mesocyclone. First we will take a look at an hour long loop (TL - Flash Extent Density overlay with Vaisala GLD, TR - Minimum Flash Area, BL - Optical Energy, BR - Mid-level Azimuthal Shear (3-6 km AGL) with New Mesocyclone Detection Algorithm Overlay) :
There are two jumps to take a look at, 1) between 21:29 and 21:40, 2) 21:55 - 21:20. Although the AzShear product doesn't show a strong mid-level meso developing, the number of positive CG flashes in the GLD data increases and we see continued small area flashes in the core. The more impressive jump is the second one; AzShear shows a much more pronounced area of positive shear, a long-lived NMDA indication (the circle with 4 pips on it), and overall smaller flashes in the area of that storm.
Shortly after the last jump (and not shown here), live stormchaser feeds showed a rapid strengthening of low-level features; well defined wall cloud, organized rotation, and frequent CG activity sending a flurry of stormchasers heading east to get out from under the storm...
-Dusty
There are two jumps to take a look at, 1) between 21:29 and 21:40, 2) 21:55 - 21:20. Although the AzShear product doesn't show a strong mid-level meso developing, the number of positive CG flashes in the GLD data increases and we see continued small area flashes in the core. The more impressive jump is the second one; AzShear shows a much more pronounced area of positive shear, a long-lived NMDA indication (the circle with 4 pips on it), and overall smaller flashes in the area of that storm.
Shortly after the last jump (and not shown here), live stormchaser feeds showed a rapid strengthening of low-level features; well defined wall cloud, organized rotation, and frequent CG activity sending a flurry of stormchasers heading east to get out from under the storm...
-Dusty
Line of supercells developing along dryline
Another loop of supercells developing along the advancing dryline as depicted by the AllSky H9 PW imagery.
GLM Helped Situational Awareness
GLM data helped me stay situationally aware as new updrafts quickly strengthen on eastern edge of CWA.
Issued a warning on this cell about ten minutes after upon continued strengthening in the radar fields and prob severe (hail/wind) values rapidly increasing (I find the time series plots very valuable). Given storm environment I expect the storm to continue to strengthen to severe levels.
-icafunnel
Evolution of ProbSevere
I am finding the all hazards version of ProbSevere to be extremely useful as a situational awareness and decision making tool. Here is a short animation of the evolution of ProbSevere thresholds for a storm near Kermit, TX.
Below is a timeseries for the same storm...
A loop of the ProbSevere thresholds provides a quick look at the potential hazards, but it becomes even more powerful when you combine it with the timeseries.
Below is a timeseries for the same storm...
A loop of the ProbSevere thresholds provides a quick look at the potential hazards, but it becomes even more powerful when you combine it with the timeseries.
Prob Severe Trends help with decision-making over rural area
Quick ramping up trend of TOR prob strengthened my confidence in this TOR warning in northern Pecos County, despite lack of reports from rural area. Jumped from 16% to 44% to 63% to 78% within 4 scans.
ZDR_Arcophile
ZDR_Arcophile
Web ProbSevere Table Cutoff
A small cosmetic issue, but I noticed that the Table Display from ProbSevere gets cutoff on the top row, and covers the axis information on the last row. Also had some difficulty zooming out at times, but may have fixed the issue but unselecting option to synchronize ranges.
#ProtectAndDissipate
#ProtectAndDissipate
Big, Bad Flash or Bad Big Flash...Update
Well, one piece of the puzzle was solved. A second large flash in the Minimum Flash Area product occurred between Lubbock and Amarillo, around 1500 km2. To see what was going on, we now take a look at the difference between GOES-16 GLM:
and GOES-17 GLM:
After a LOT of going back and forth, we realized that the color table for Flash Extent Density had the alpha at zero for anything around 1.0 to 1.244. SO, the previous example that showed no FED actually DID have data associated with the large flash; it was hidden (my bad!). Fixing the color table to plot any data greater than zero at the darkest color blue and...voila! The large flash now does show a FED of 1.0. So that problem is now solved.
However, there is still a question as to why that big area flash occurred where it did, when it did, and if it was actually as large of a flash as indicated. Still something to dig into further!
-Dusty
and GOES-17 GLM:
After a LOT of going back and forth, we realized that the color table for Flash Extent Density had the alpha at zero for anything around 1.0 to 1.244. SO, the previous example that showed no FED actually DID have data associated with the large flash; it was hidden (my bad!). Fixing the color table to plot any data greater than zero at the darkest color blue and...voila! The large flash now does show a FED of 1.0. So that problem is now solved.
However, there is still a question as to why that big area flash occurred where it did, when it did, and if it was actually as large of a flash as indicated. Still something to dig into further!
-Dusty
TPW Differences Along Dryline
The CIRA Merged TPW and All Sky LAP in the TX panhandle show some differences in the vicinity of the dryline at 19 UTC on 7 May. This is a cloudy region so the retrievals are either GFS (All Sky LAP) or advected polar microwave (Merged TPW), The All Sky LAP TPW shows a moist panhandle, with values in green / yellow (1" or above). The Merged TPW indicates lower values in green / purple, or about 0.7". Surface dewpoints range from 59-65 F, indicating moist air ahead of the dryline.
Surface GPS observations from Suominet at three TX stations in the panhandle (Amarillo - 1.0", Borger - 1.0", and Canadian - 1.1") lean closer to the All Sky LAP analysis. An hypothesis for the Merged TPW being low is dry retrievals from higher terrain to the west being advected into the moist sector.
JohnF
Surface GPS observations from Suominet at three TX stations in the panhandle (Amarillo - 1.0", Borger - 1.0", and Canadian - 1.1") lean closer to the All Sky LAP analysis. An hypothesis for the Merged TPW being low is dry retrievals from higher terrain to the west being advected into the moist sector.
JohnF
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