EWP Blog – Page 14 – Spring Experiments & Beyond

Using GREMLIN for Time of Arrival

Posted in DSS, GREMLIN, LightningCast, SPG2024 on May 22, 2024 by Kevin Thiel.

LightningCast has been running high near the PGA Tournament today near Fort Worth as a result of several thunderstorms around the region, but not over the region. As a result, decided to swap over towards trying to use GREMLIN to find the time of arrival of the boundary noted earlier.

So an attempt was made to highlight this in the DSS image to provide an estimate of when these hazards would arrive. Perhaps another proofread would’ve caught the initial typo from copying it over. However, a value of about 40 percent was noted. Partners still had information that storms would become increasingly likely over a narrower time frame in addition to the probabilistic information from LightningCast.

But nature had other plans with a strike and a few pulses of lightning over the event at the time this was “sent out”. An area of weak convection was in the area, and so I would’ve thought that this would not produce lightning.

Sneaking in information on the RGB evaluation, you can see how this was not a young storm and likely something in decay, and that may track with a bit of the surprise element.

Kadic

Speed of Incoming Surface Boundary

Posted in PHSnMWnABI, SPG2024 on May 22, 2024 by Kevin Thiel.

One of the things that we noticed was that it appears that model guidance is too slow dropping a weak surface boundary to the south. As a result the convection in model guidance is likely being developed too far to the north of what is likely to actually occur.

Below is the surface winds from the PHS model forecast from the 17z run for 20z. It has a boundary that is near or north of the Texas-Oklahoma border.

In reality, the boundary has been a bit further south. However, this has been the theme of the day, with convection generally advancing east faster than most high-resolution model guidance. Below are the surface observations across Texas showing how much further south the boundary is, in addition to the fact that the wind field is stronger than what PHS is indicating.

The image below has the forecast model composite reflectivity (top right) nearly a degree longitude to the west of MRMS radar reflectivity (bottom right).

This raises additional concerns, as out ahead of the convection, the PHS forecasts an increase in SRH. If this is unchanged considering the current placement of convection, it may indicate a greater probability of storms rotating. The fact that we’re also seeing a sharper boundary present in the wind field suggests we could also see stronger convergence along the band of developing convection than may be indicated within the PHS forecast.

Kadic

Using OCTANE to diagnose three convective environments along the Missouri border

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

Currently monitoring OCTANE data in the vicinity of the Missouri border at about 1850Z on Tuesday, May 24.

North of the border (far southwest Iowa) there is mature convection, with a clear signal for changes in direction and speed on the anvil (top two panes). The mature convection shows cloud top divergence, with new convection on the southern flank showing a sharp signal for cloud top cooling (bottom left).

There is an area of banded cirrus moving through the region just south of this. This cirrus shows up on day cloud phase imagery (bottom right) but also in the OCTANE speed product. Looking at satellite data qualitatively, it’s clear the cumulus field is much less impressive in this area. Convection is not yet initiating here. Surface observations don’t show a clear signal for a less favorable air mass, so it’s possible the mid-level conditions are not as favorable.

South of all of this, we are looking at a new area of updraft initiation occurring just on the Kansas side of the border. On conventional satellite imagery we can see updrafts reaching upper levels and shearing off (orphaned anvils) indicating true convective initiation is still a little ways off, but we are getting very close. There is a consistent signal on OCTANE cloud top cooling for some of these spotty updrafts. Comparing with conventional imagery, the OCTANE cloud top cooling signals provided 5-10 minutes of lead time on the orphaned anvils. This is useful information, as once these storms begin maturing, they may provide a little more lead time on the initiation of lightning in addition to just the initiation of mature updrafts.

–Insolation

Storm Hopping Over Subarray

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

We noticed a change in the storm on GLM as it tracked northeast. GLM seemed to decrease as the storm passed through the subarray region, but the number of flashes remained relatively the same according to the ground network. Knowing the location of this subarray and also comparing GLM to the ground network gave us confidence that the dip in GLM was not due to a reduction in flashes/storm intensity.

Cumulus and Kadic

GLM Trends In A Warning Decision

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

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.

OCTANE cloud top divergence also highlights the strongest thunderstorms in our CWA below.

-Joaq

Tracking Convective Development With OCTANE storm top divergence and LightningCast

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

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 vs Visible Satellite and Radar

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

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!

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).

PHS Composite Reflectivity (right) versus KDMX radar reflectivity (left)

Overall, I think PHS is proving to be valuable with CI (as seen in Day 1) as well as adjusting as storms evolve (such as timing in this case).

Forecaster Cumulus

Learning More About GLM and the GLM-DQP!

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

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

Warning vs DSS – “WFO DMX”

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

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:

As the line shifted east into the area, ProbSevere stood out, while the LightningCast steadily increased. The left hand panel depicts GREMLIN, and it properly highlights the southernmost storm as being the most intense. Unfortunately, not every storm that we issued warnings for got a specific screenshot, but when looking at LightningCast, areas that were likely to experience 10 or more flashes with a 70% probability seemed to correspond well with ProbSevere values would support issuing warnings.

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

Using GREMLIN and LightningCast for Warning Ops and DSS

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

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.

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.

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