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

Posted in Forecaster Thoughts, GLM, Live Blogs, ProbSevere on by Brandon Smith.

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

Lightning Event Density As A Proxy For Storm Intensity

Posted in HWT, ProbSevere, Total Lightning on by Brandon Smith.

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

Viewing angle from different radars using AZ_shear is important

Posted in AzShear on by Brandon Smith.

The top image shows two discrete supercells in the center of the image.  Meanwhile the middle image is from KMXX radar which shows weak/harder to identify AZ_shear circulations for the two supercells.  Bottom image is AZ_shear from KEOX that has a different viewing angle that shows much more pronounced AZ_shear circulations.  A Best practice…for using the AZ_shear single radar product is for forecasters to use multiple radars for better situational awareness since some radars might not show that strong of a signature compared to others due to different viewing angles. -Jake Johnson

 

All-Sky LAP PW vs. Merged TPW

Posted in GOESR, Live Blogs on by Justin.

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

All-Sky PWAT

Posted in HWT, Live Blogs on by Brandon Smith.

The AllSkyLAP PWAT compared fairly well with surface conditions and the merged product however it struggled in the wake of the front/dryline and was too generous with the PWAT values when compared to earlier UA obs. Values in the warm sector were more representative (higher) than the merged product.

— SCoulomb

NUCAPS soundings comparisons for 5/2

Posted in Live Blogs on by Michael Bowlan.

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

Archive Event – AzShear

Posted in AzShear on by Brandon Smith.

The two images above…KMXX 0-2km AZ product had a bright spot before the velocity couplet developed later on the leading edge of the QLCS which is a helpful pro-active approach to watch this area for possible QLCS tornadic development. -Jake Johnson

Two images above…KEOX radar had a different viewing angle compared to KMXX and it actually showed a brightness in the AZ_shear product way before KMXX.  Its best to look at multiple single radars and look for developing AZ_shear circulations for better situational awareness. – Jake Johnson

Merged-TPW compared to Sfc obs

Posted in News on by Brandon Smith.

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