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Severe thunderstorm and tornado warnings were issued partially driven by the increasing intensity of GLM FED. With the indication of a strengthening updraft due to increasing lightning activity atop the convergence signature on radar, a warning decision was made for both damaging winds and a tornado threat.
-Joaq
Developing convection along a surface front in eastern Kansas was producing signals in the OCTANE storm top divergence product, signs of glaciation, in the day cloud phase product, and increasing LightningCast probabilities. Along northern areas of the surface boundary, the divergence product and visible characteristics were stronger, while updrafts further south still struggled to sustain themselves. This may be due to residual convective inhibition evident on MCI ACARS soundings. Even about 20 minutes after these screen shots were taken, the GLM activity was fairly weak, while the storm top divergence only really showed showed up on storms near and north of the KC metro. While severe convection is still likely downstream, the OCTANE divergence product definitely highlights where better synoptic forcing is overcoming any convective inhibition.
-Joaq
PHS was a bit slower with the convection entering the DMX CWA compared to visible satellite initially. However, by 22Z it looks like it caught up!
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| PHS Composite Reflectivity overlayed on Visible Satellite (right) vs only Visible Satellite (left) |
Looking at 22Z (once the timing was better aligned), I was curious how the reflectivity in PHS looked compared to the radar. The overall shape and look of the broken line of storms lines up fairly well (even with the model smoothing things out). The intensity didn’t look like it matched up at first because I was looking for “red”. But, when using the sampling tool and seeing the values, the yellow-green colors in PHS indicated 63-67 dBZ (where the label DMX is in the image).
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| PHS Composite Reflectivity (right) versus KDMX radar reflectivity (left) |
Forecaster Cumulus
Honestly, for warning operations, I am used to using/focusing on the GLM Flash Extent Density and on the warmer color pixels and trends when lighting increases. I also wouldn’t consider myself an expert on lightning – I came into this HWT not having a lot of knowledge on the details of these products, the instrument, and the specifics of lightning. So, I am really grateful that I continue to learn more about this and GLM in general (thanks HWT and SMEs!).
GLM-DQP: It’s really useful to know where the subarray areas are, in case the GLM data looks “funky” (near/at saturation). I feel that this would not only be useful for my “home CWA” but also for when we back up other offices. It was also interesting that we (WFO DMX) found a case today where a storm passed through the subarray line and the GLM FED data pixels looked like it “dipped”, but the flashes stayed relatively the same (or even increased after passing through) when comparing with the ground network.
Forecaster Cumulus
It was interesting when comparing the Warning side of the house today versus the DSS side. When we (Cumulus and Kadic) were discussing this and picked two of the tools we used the most, there were similarities and differences:
For Warning Ops: OCTANE and LightningCast
OCTANE proved very useful in interrogating convection. LightningCast was also a helpful diagnostic tool in highlighting the potential for and track of intense convection when used with ProbSevere.
OCTANE:
Here’s a look at 2 particular instances from OCTANE:
A combination of cloud top cooling in OCTANE and subsequent divergence aloft was a helpful clue in assessing the potential of a storm that was distant from the radar. It was caught a little later in analysis, but OCTANE proved helpful in diagnosing the storm and deciding to pull the trigger.
This next instance was a warning that was issued solely using OCTANE and seeing how well it lined up with radar. The warning targeted the center of where the maximum storm top divergence was taking place, and then stretched down towards the south to account for parallax. The warning decision was made for the impressive cloud top cooling and pronounced divergence that appeared in the scans leading up to the warning. The panel on the top left shows the OCTANE speed, and it transitioned to a blue color leading up to the event.
LightningCast and Radar:
Below is the example of what MRMS looked like the moment DMXSVR005 was issued solely based on OCTANE. Much of the SVR encompassed the highest LightningCast values with a probability of 10 flashes of 70% in yellow and the various ProbSevere contours. Again, this highlights how useful these tools can be in performing storm interrogation. However, when thunderstorms are numerous, this may be a lot to run through. They are definitely useful tools in the tool belt, though.
For DSS: LightingCast (especially the Dashboard) and GREMLIN/GLM.
– LightingCast: I REALLY like the form and Dashboard. It helps focus on the DSS site specifically and organizes the data really well to where I would feel comfortable explaining/showing an EM the graph of lightning probabilities. Honestly, I could bring this back to my home WFO right now and use this for DSS events this summer. A couple things that could be added to make it even more awesome: adding more options for ranges (right now there is only 10 miles, perhaps adding 15 and/or 20 miles). Folks could then choose which to display in the graph. The other thing (fairly minor), perhaps reversing the size of the bubbles for the GLM data (smaller range, smaller bubble). But, this is personal preference – maybe if this could be customized by the user like the colors?
– GREMLIN/GLM: GREMLIN followed the storms a lot better today (seems to do better with more intense storms versus run of the mill/sub-severe ones). I used a two panel display with GREMLIN on the left and MRMS on the right with GLM and LightningCast and compared the two. I used time of arrival for the storms to 10 miles outside the DSS event and also at the site itself. GREMLIN was able to keep up with MRMS really well! I am becoming more and more convinced that this could be a really great product to help if a radar goes down or there is a radar hole (in data).
Overall, it seems as though OCTANE was used more for warning ops versus DSS, but LightningCast was used by both the warning operator and DSS forecaster.
Forecasters Cumulus and Kadic
GREMLIN continues to perform well with regards to the overall picture of precipitation and convection. In fact, in the example below, GREMLIN seems to be catching on to the northern extent of the line breaking apart and the southern portion becoming more intense. However, it seems to be a bit slower than the MRMS data.
LightningCast could be more useful in this case if the thresholds were modified (25 flashes versus 10) to better identify and focus on the more intense convection.
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| LightningCast overlayed on GREMLIN emulated radar (left) and MRMS Composite Reflectivity (right) |
Looking at the LightningCast dashboard for our DSS event, probabilities of lightning are increasing. I found that this is actually an easier way of being able to communicate lightning probabilities for a site (or a range around the site) versus using the map (seen above). This would allow me to let an EM or site official know that probability of lightning is near 80% for 10 miles form the site (within the next hour) and 50% at the site itself.
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| LightningCast Dashboard for Belin Quartet Summer Concert Series (Des Moines, IA) |
We provided valuable support. A message was sent nearly 45 minutes ahead of time following the issuance of a Severe Thunderstorm Warning to the west.
If our partners are simply looking to delay, LightningCast may also prove helpful in giving the all clear if you don’t see anything upstream on radar. The values react well as convection clears the site. This is also great in helping you know for sure when the last lightning flash took place, and it can help us give better information.
Forecasters Cumulus and Kadic
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.
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.
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.
Kadic
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
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.
–Insolation
