The Satellite Proving Ground at the Hazardous Weather Testbed

Wednesday, May 25, 2022

Convective initiation in the Hoosier State

One of the teams at HWT today is working in Northern Indiana. There is a tornado threat later, and the team is also working a DSS situation at a Fort Wayne baseball game. LightningCast is hitting on convective initiation in Kentucky and southern Indiana.

Figure 1: LightingCast contours, GOES-16 GLM flash-extent density, and GOES-16 ABI day cloud convection RBM over Indiana and Kentucky.

MAF Testbed Observations

ProbSevere v3

For the initiation of convective storms, I found that the ProbSevere performed the best over the other products available to me today. I have seen over the last couple of days that the best use of ProbSevere is the trend table. The steep increase in these total severe values support radar trends that suggest a warning is necessary. For the initial warning on severe storms, this was the best use.

The only negative to this product was the latency. While the latency was only on the order of 2-5 minutes, this was equivalent to appx. 2 radar scans that indicated to me ahead of time that this storm was strengthening. This can lead to some confusion especially if the storm is quickly pulsing and falling.

Additional upticks were noticed in subsequent SVR issuances throughout the afternoon that provided a nice heads-up in conjunction with the radar data. These were used in the context of the storm maintaining its strength after the storm was warned and again after the storm re-pulsed several minutes later.

It is also worth mentioning that the perceived threat of ProbSevere was also the shared opinion of the forecast (forecaster perceived threat for hail had the highest ProbS. probability). Once the storms reach the “cap” of their ProbSevere, it becomes of little use.

GLM

GLM was useful during convective initiation, but did best for storms that were already at the peak of the ProbSevere threshold. GLM showed additional pulses in a mature storm that had a 90% probability of being severe and added confidence to the warning forecaster that the storm had gained additional strength which manifested itself in larger hail for example.

It was however short-lived as the storm gained additional intensity but did not show the corresponding increase in GLM FED that one would expect. This was explained as a limitation due to the structure of a mature (and severe) thunderstorm.

Min Flash Area also reached its lower values on several storms which provided little to no additional data. Maybe this used in conjunction with total optical energy would be useful, but this yielded no significant results when investigating briefly.

PHS Model

The PHS model was very useful today ahead of convective initiation, but more so in an advective situation.

Instability parameters were observed as ongoing severe storms moved SW toward the established instability gradient. ProbSevere outlined areas are moving SW in the image below across an area of relatively high CAPE and low LIs. This provided useful information about the existence of a boundary and the motion of the storms along with the pre-conditioned environment.

The model did have limitations as the storms became ingested into the later runs of the model and the storms showed developed cold pools. The environment depicted in this situation had become dominated by nearby cold pools of incorrectly placed convection which limited the model’s usefulness.

LightningCast

Not much use of the lightning cast today due to the lack of CI within our CWA, but we did get a chance to look at the advection of lightning. In general, this proved to be a little too slow. It seemed the contours were tight to the storm and storm motion was rather slow, but the lead time on lightning detection was around 30-40 minutes. With an advecting storm, I would have expected this to be rather accurate to the 60 minute threshold that it attempts to achieve, but 30-40 minutes is still VERY useful for DSS and now-casting purposes.

NUCAPS

NUCAPS had some interesting results today, primarily in the way it reported green, yellow, and red data points. Some of the gridded data was unavailable for points with green-retrieval and this was puzzling because it would have indicated a dry slot over the DFW region that was evident in the water vapor and visible satellite. However, the data grid boxes were missing or contaminated with bad data over a mostly clear area. Areas with similar cloud coverage performed as expected. The pop-up skew-t continues to be the best tool in this suite of products, provided the data points are green-retrieval.

Optical Flow Winds

Not much use on the optical flow winds today due to the fact that ongoing convection muddied the data. Overshooting tops were visible for a brief moment, but quickly engulfed in strong storms and expanding anvils. The divergence field is really hard to gather meaningful intel from and the existing platform outside of AWIPS limits its overall usage. A suggestion in our group today was that divergence could be useful if the noise is limited. Perhaps remove values above and below a certain threshold. Instead of widespread values, draw attention to the important outliers.

- Overcast Ambience

Today’s details of products and warnings: Midland, TX

I found the PHS products useful for seeing the corridors of enhanced severe risk. They correctly showed that hail (or wind) was the highest risk compared to tornadoes.

ProbSevere was very useful with the trend lines. Again and again correctly identified risks as they occurred.

GLM showed strong ramp ups in activity prior to each severe issuance. No complaints here.

NUCAPS data was less useful, but with the skew-t pop up I was able to correctly see areas of mid level dry air. I did not use optical flow. Prob lightning was useful to see the first cells pop up but did not serve as much purpose after that with no known DSS opportunities.

Some Random Gu

Observations and DSS for Fort Worth, TX

AWIPS radar display over Texas. Synopsis - An upper level storm system and a cold front will bring a chance of showers and thunderstorms this afternoon and evening over the Forth Worth, TX area. Some storms could be severe with damaging winds and hail. Activity should exit to the southeast late tonight or early Wednesday morning.

VIS: Storms initiating in the NM/TX border. Anticipating a line of storms to develop along western TX and pushing southeastward.

Infrared.

DSS: Colonial Country Club - Charles Schwab Tournament - Forth Worth, TX

AWIPS radar display over Texas.

SPC Mesoanalysis: CAPE values of 2500+ J/kg, setting the stage for active convection this evening over much of TX.

SPC gives an enhanced risk of severe thunderstorms across parts of TX.

VIS @ 22Z: Storms maturing quite well in SJT.

Issued another DSS update about the likelihood of lightning passing over the property.

Polygon warning.

ProbSevere 3.

Vortex Power

Fort Worth ProbSevere

21:47Z: The 21:47 UTC Prob Severe with MRMS overlaid gave us situational awareness on where to focus our attention for severe storms. It highlighted two big cells southwest of our CWA, where the ProbSevere values approached 80 and 93%, respectively. The storm closest to our CWA had a 50 kt inbound velocity on the lowest scan.

Snowfan

Fort Worth NUCAPS

21:19Z: There was a NUCAPS passover around 1930Z over the Fort Worth area. One sounding in our southern CWA showed this:

The sounding showed MLCAPE of around 1500-1600 J/kg, with DCAPE values in excess of 1000 J/kg. Compared to the SPC meso page, these values agree quite well:

Snowfan

Fort Worth Optical Flow

20:45Z

Optical Flow winds indicate a broad south-southwesterly flow at mid-levels.

Snowfan

Fort Worth PHS

20:10Z: The PHS is showing a very unstable environment along/south of the outflow boundary, stretching southwest to northeast across the Fort Worth CWA. Temperatures are in the 80s south of the boundary with upper 60s to lower 70s dewpoints. North of this boundary, temperatures are in the lower 60s with lower 60s dewpoints.

Over time, close to 00-01Z, the boundary slides south and east toward the southern portion of the CWA, with SBCAPE over 2000 J/kg, STP values upwards of 3-5 (perhaps picking up on the better curved hodographs along the mesoscale boundary), and LI values approaching -8 to -10. The CAPE seems to match up very well with that seen on the SPC meso page. The SPC meso page had a higher STP southwest of our CWA at this time. This product helped me to focus on regions where new convection would likely form, good for situational awareness.