EWP Blog – Page 15 – Spring Experiments & Beyond

Collection of Day Two Thoughts

Posted in GLM DQP, GREMLIN, OCTANE Speed Sandwich, PHSnMWnABI, SPG2024 on May 21, 2024 by Kevin Thiel.

Day 2 has featured more convection, and has been a helpful day testing these products and how they help in warning operations. Although I might not feel confident making warning decisions solely based on any of these tools, I think that each tool provides a valuable piece of information.

Pre-Storm

To keep things short here with all the observations, PHS was very helpful today in showing how the QLCS situation would evolved with several areas of embedded rotation. Having CAPE with SRH together showed how these came together, and in conjunction with velocity highlighted rotation updrafts within PHS. This proved to be a helpful pre-storm evaluation. A few storms began rotating, and then everything began rotating as the PHS model indicated.

Observations Related To Warning

The developing squall had a linear appearance at first. As time progressed with more embedded areas of rotation, this became a lot less neatly organized.

Here is a look pre-warning for a tornado warned cell with ProbTor increasing up to almost 40 before moving off the point.

A zoom in on an impressive overshooting top. Sorry for the reverse loop.

Here is a V-notch like structure. Though it doesn’t correspond with a radar V-notch, it does indicate how strong an updraft this was.

And here’s the radar look of that, which appears to somewhat match the configuration seen aloft.

Interesting Signals

One thing to note early was that the PHS forecast had a lot of convective debris lingering in Iowa that was not present in reality. This does not appear to have impacted the instability parameters very much.

We’d mentioned looking at the dewpoints for the tendency for aggressive convection. But it only seemed slightly high compared to reality.

We did have a blob near Sioux City on Gremlin that didn’t really correspond with any signal on radar, and it didn’t seem to have satellite signal to go with it. Not sure where it came from, but we were able to see it was erroneous.

Here’s a look at GREMLIN with waves and wobbles following the GLM lightning.

Here’s another fun look at where it seemed the convection on the northern flank may have affected GLM quality with values decreasing on the north side. Note the reversed image loops.

Here’s an instance where GREMLIN’s max intensity happened before a lightning jump. Unfortunately this is reversed, but GREMLIN struggled to resolve an intensifying storm in the middle of the line.

Here is an example of GREMLIN losing a cell in 3 surrounding cells.

Kadic

Lightning Cast at Initiation near St Joseph MO

Posted in LightningCast, SPG2024 on May 21, 2024 by Kevin Thiel.

Wanted to provide an assessment of LightningCast on the cells developing on the KS/MO border. This is the same area of initiating convection previously mentioned in the “Tracking Convective Development…” blog post. This post will focus on the storms moving between Kansas City and St Joseph.

Lower probabilities for Lightning Cast (10% to 25%) began appearing for these particular storms as early as 1856Z. Probabilities for 10-flash began appearing after 1922Z.

The first cloud flash detected by ENTLN occurred at 1924Z. The first flash detection by GLM was at 1928Z. The first CG strike (NLDN) occurred at 1946Z.

All in all, Lightning Cast provided a considerable amount of lead time, which I found to be useful.

The Lightning Cast time series for KSJT (airport near St Joseph) also showed a steady increase as these storms approached and strengthened, with lead times. Probabilities increased above 50% about 10 minutes before flashes began being detected near KSJT.

–Insolation

OCTANE CTC/CTP Near St Joseph MO

Posted in OCTANE Speed Sandwich, SPG2024 on May 21, 2024 by Kevin Thiel.

Examining the qualitative appearance of OCTANE Cloud Top Divergence (CTD) and Cloud Top Cooling (CTC) products with storms near St Joseph MO.

First image: 2001Z. A series of updrafts is noted, several with mature CTD signals in blue/purple/red. Most notably is the signal over Leavenworth/Platte counties (largest CTD signal, near the bottom). The CTD signal here is large and mature, which implies a very strong updraft relative to the other storms in the area. The size of this feature does matter, as it implies the updraft (and thus the outspreading of the anvil) is very strong relative to the others. To add on to this, there is a CTC signal (green dot) associated with an overshooting top. This indicates that even though this storm has already produced a significant updraft, it continues to produce an overshooting top, implying the updraft is still strong and mature.

10 minutes later, things have changed. The image below is from 2011Z. Now, the CTD signal has spread out considerably and it appears the storm has past maturity. The more fragmented / strung-out appearance of the OCTANE CTD signal is a sign that the storm is likely weakening. There is also no longer a CTC signal associated with that particular anvil. Rather, it appears a new CTC signal (a new updraft) is going up on the southern flank. This is a sign that these storms are cycling and have more of a multicellular mode than a supercellular mode at the moment.

–Insolation

Using OCTANE cloud top divergence for severe development situational awareness

Posted in OCTANE Speed Sandwich, SPG2024 on May 21, 2024 by Kevin Thiel.

The OCTANE cloud top divergence product offered situational awareness in the development of a severe thunderstorm north of Kansas City. While the pink and purple values in the cloud top divergence increased, radar data at the base tilts showed little signal of intensification. There were signs of intensification aloft on the KEAX radar, but the OCTANE product allowed for a more easily available signal of growth aloft if the forecaster wasn’t moving through the radar tilts at the time. About 10 minutes after the first image below, a warning was issued as the storm aloft fully matured.

OCTANE Speed Assignments in Montana

Posted in OCTANE Speed Sandwich, SPG2024 on May 20, 2024 by Kevin Thiel.

An area of thunderstorms over southern Montana was examined using OCTANE and other satellite imagery.

Of interest in particular is the storm over western Big Horn County. The day cloud phase loop (bottom right) shows that this is a slow-moving thunderstorm, but there is also a bunch of patchy/streaky high cirrus moving much faster over top of it. Looking at the OCTANE speed sandwich (top left), it appears that the convective updraft was assigned the speed of the faster cirrus (yellow/orange, ~80kts). In reality, this updraft is moving much slower. For the sake of comparison and verification, notice the two updrafts over Stillwater County. These updrafts appear similar in nature based on the day cloud phase imagery, but the Stillwater County storms do not have any high cirrus contaminating the signal. As such, they are assigned a proper velocity on the OCTANE speed sandwich (green, ~30kts). There are also some artifacts in the divergence (bottom left) with the Big Horn County storm.

–Insolation

Learning the Ropes – GLM DQP Applications!

Posted in GLM DQP, News, SPG2024 on May 20, 2024 by Kevin Thiel.

GLM DQP: learning about its application – where data might be suspect or questionable. Where convection/GLM is along the line/boundaries could be such areas. Although not in Cheyenne’s CWA, saw an example over Cuba of pink pixels (at or near saturation), but could see lightning detection around it. This was an area near one of the boundaries (pink pixels were right along the line).

GLM DQP 1949Z over Cuba 20 May 2024 – pink (at or near saturation) pixels along boundary line

Forecaster Cumulus

GLM Glint in South America / Panama

Posted in GLM DQP, SPG2024 on May 20, 2024 by Kevin Thiel.

A glint was observed on various data sources tracking westward across northern South America and Panama between about 1630Z and 2000Z on May 24.

The glint is plainly evident on visible imagery (bottom right) and GLM Background (top right). On the GLM Data Quality, you can witness pixels that reach saturation over South America (directly related to the glint) — but there is also an area of convection that gets to near saturation over Panama. It appears that the most direct sun angle roughly coincides with the mature phase of these thunderstorms over Panama, leading to a period of near-saturation that eventually fades as the convection weakens. Convection can be confirmed by the presence of GLM flashes, but there does appear to be a relative min in GLM flash detections coincident with the near-saturation area.

–Insolation

Terraced SBCIN PHS Product in SW Kansas

Posted in PHSnMWnABI, SPG2024 on May 20, 2024 by Kevin Thiel.

At 22Z (5hr forecast) the PHS SBCIN product was showing a terraced appearance in SW Kansas. Maximum values were above 350, dropping to around 100 (blue/purple) a couple counties to the north. Between the two, there is the appearance that SBCIN decreases then increases again. Wanted to document this to see if there is a known cause for this appearance in the PHS data.

–Insolation

End of Day 1 Thoughts

Posted in GLM DQP, GREMLIN, LightningCast, OCTANE Speed Sandwich, PHSnMWnABI, SPG2024 on May 20, 2024 by Kevin Thiel.

Thoughts at the end of Day 1…

The LightningCast product I think would be VERY useful for DSS. Overall, when seeing it perform in real-time, the increasing LC probabilities seem to eventually correlate well with GLM flash density. I look forward to using the DSS form this week and seeing how that works for specific sites.

The GREMLIN product seems to be a great way to see the overall picture of precipitation (say, for a region). I think it struggles with precipitation intensity a bit (>45 dbZ) both for storm cells and for heavy stratiform precipitation. At the “storm” level, I have seen instances of the model not following the evolution well (either too intense or not enough).

For OCTANE, it was easier to pick out an example of CI and divergence with the IR versus the Visible products. I could use the direction product on its own in operations, but I really like having the speed, direction, and cloud top divergence all together in a 3 panel to identify convection.

PHS did a great job today identifying convective initiation when overlayed on visible satellite imagery. I look forward to seeing how this performs in other areas of the country this week.

Still learning how best to utilize the GLM DQP; but, when looking over Cuba, I was able to better understand how it locates areas where the data might not be the best. I hope to learn more about this product through the week and see more examples of its application.

Forecaster Cumulus

PHS Forecast For Supercell in Northeast Colorado

Posted in PHSnMWnABI, SPG2024 on May 20, 2024 by Kevin Thiel.

Have been looking at PHS data and forecasts in northeastern Colorado. In simulated composite reflectivity (bottom right), there is an indication of a supercell (perhaps right-moving) tracking eastward toward the CO/NE/KS triple point. PHS indicates that this supercell will be tracking into an increasingly favorable environment, and by 02Z, it will be entering an area with much larger CAPE and a nearby local maxima in STP.

Using more traditional mesoscale analysis (such as SPC) there are indications that this forecast is sound. For example, the 6hr SPC mesoanalysis forecast (valid 04Z) shows a supercell riding the northern gradient of an STP bullseye. Knowing that it’s often not the bullseye of a parameter to be concerned about, but rather the northern gradient, this has raised my interest as a forecaster.

To me, the PHS data provides additional confidence in the potential for this storm to become quite strong a few hours from now. Based on mesoanalysis, this storm could be capable of producing all hazards, with hodographs (SPC meso) and STP (both SPC meso and PHS) suggesting a tornado threat is absolutely there. I would probably use this information to start adjusting messaging, in sort of that in-between watch-and-warning paradigm.

–Insolation