LightningCast – Page 6

Utilizing OCTANE to Determine Failed Convection

Posted in LightningCast, OCTANE Speed Sandwich, SPG2025 on May 20, 2025 by Kevin Thiel.

Typically forecasters will utilize cloud top cooling and glaciation for an initial look into convective initiation. OCTANE cloud-top cooling clearly depicts the rapid intensification of an updraft with the quick change of colors (green to red). However, the OCTANE divergence component of this product helps to signify mature convection and a strong persistent updraft. Notice how there is no signal for cloud-top divergence (CTD) in the animated loop below (Figure 1). No signature for CTD and warming cloud-top temperatures became an apparent signature for failed convection.

Figure 1: OCTANE cloud-top cooling and divergence. Notice a rapidly developing updraft initiating south of the cluster of storms before it quickly warms as the storm fails to maintain strength.

Lightning cast clearly signifies a low probability for convection developing south of the main cluster. Additionally, day cloud phase distinction reveals an orphan anvil present in the storm that showed a quick signal for cloud-top cooling in the OCTANE product. Thus, failed convection led to no signal for a storm at the base reflectivity scan on radar.

Figure 2: Lightning cast V1 (left) and V2 (right), along with GLM Flash Extent Density and Day Cloud Phase Distinction RGB.

Figure 3: Local radar KILX base reflectivity at 0.5 degree tilt.

– Aurora Borealis

DSS messaging with the Lightningcast Dashboard

Posted in DSS, LightningCast, SPG2025 on May 20, 2025 by Kevin Thiel.

While doing the DSS for our event in Memphis (the Memphis Firework Preview Show 2) noticed a rather quick uptick in the Lightning V2 and eventually V1 probabilities about 45 mins or so prior to lightning strikes occurring near and around the site. This would give valuable lead time to any partner that was concerned about an outdoor event. It was made slightly easier to have confidence in this decision to mention an increased lightning threat especially looking at the line in satellite and on radar data.

– Sting Jet

LightningCast and GREMLIN Identifying Threats Fast w/ OCTANE Being Great with Initiation

Posted in GREMLIN, LightningCast, OCTANE Speed Sandwich, SPG2025 on May 19, 2025 by Kevin Thiel.

LightningCast seems to be doing its job quite well as it honed in on a small area in southeast KS with ample lead time (2042Z with more strikes appearing at 2056Z west of Jasper). This would be extremely useful for event deployments and getting ample lead time for our partners as seen below.

Regarding GREMLIN, it does a spectacular job identifying CI along boundaries (in this case, the dryline), somewhat ahead of time compared to MRMS reflectivity.

In this case, it appears to have picked up on more robust CI well ahead of time in TOP’s area. However, it does not appear to be super consistent later on with really capturing how robust some of these cells ended up later on, likely due to overall resolution of the product as well as lightning activity as these cells matured.

Lastly, regarding OCTANE, it did a great job on picking up a cell with ample cooling initially (reds and yellows) followed by strong divergence aloft (purples and pinks). This storm would go on to further intensify down the road.

This cluster of storms would then go on to produce multiple 60mph+ severe gusts.=

– Ryan Cooper

Day 1 GREMLIN and LightningCast

Posted in GREMLIN, LightningCast, SPG2025 on May 19, 2025 by Kevin Thiel.

Noticed that the meso GREMLIN was a little jumpy when it came to the apparent ‘strength’ of the storm. Tried to get a gif of it, but this isn’t the best…

Noticed that the CONUS did a better job of matching what the radar was showing (at this time frame). Same issues as above with the ‘jumpy-ness’. GREMLIN seemed to pick up more on the new convection (cell furthest to the south in image below).

When using ProbSevere with GREMLIN, can more easily see the slight shift in what it shows vs radar

LightningCast V2 appeared to consistently do a better job

– Lightning McQueen

LightningCast V1 vs V2

Posted in LightningCast, SPG2025 on May 19, 2025 by Kevin Thiel.

When initially getting into the Lightningcast product I noticed just some subtle differences between Lightningcast V1 (left window) vs V2 (right window) around the 1851Z timeframe to 1921Z. Near the Choctow and Pushmataha Counties had jumped up to 30% with even a small area of 50%, while the version 2 had a lower probability of lightning closer to 10-30% during that same timeframe. Will note on both, given the anvil cirrus from a strong storm off to the west may have been obscuring the area which looks like it lead to abnormally higher lightning probabilities than what otherwise would have occurred without the cirrus overhead. That being said, felt the Lightningcast V2 captured the threat better overall and kept the probabilities lower which would have lead me to not mentioning the area for thunderstorm probabilities just yet,

-Sting Jet

LightningCast Comparison

Posted in LightningCast, SPG2025 on May 19, 2025 by Kevin Thiel.

While the training touted cases where Version 2 (V2) of LightningCast had a clear lead time advantage over Version 1 (V1), many of the new cells I tracked today showed the opposite, with V1 showing higher probabilities sooner than V2.

It seemed like many of the cells were producing lightning very quickly after achieving even modest returns at the -10C level. In this case, the significant instability in the region today led to very rapid vertical cloud growth, which likely outpaced significant radar returns aloft. And while it is purely an educated guess on my part, that might have something to do with the weight given to the -10C reflectivity – if it needs a certain reflectivity threshold to really boost the probability, then the V2 product would be artificially slowing the increase in probabilities. Then in addition to waiting for the -10C reflectivities, you have to add in processing and dissemination lag time.

The V1 product, being based entirely on satellite data, was able to key in on just the rapid vertical growth and boost probabilities based on that alone, and not have to wait for the -10C returns to show up in MRMS.

Fig 1: Loop comparing LightningCast V1 (left) to LightningCast V2 (right)

Fig 2: Comparison of LightningCast V1 (left) and V2 (right) at 2041Z on 19 May 2025, showing V1 being first to have a 30% contour over the cell of interest in NW Arkansas.

Fig 3: Comparison of LightningCast V1 (left) and V2 (right) at 2046Z on 19 May 2025, showing both having a 50% at the same time, though V1 is larger in area.

Fig 4: Comparison of LightningCast V1 (left) and V2 (right) at 2051Z on 19 May 2025, showing V1 being first to have a 70% contour, while V2 still only has a small 50% area.

Fig 5: Comparison of LightningCast V1 (left) and V2 (right) at 2056Z on 19 May 2025, with the first GLM Flash Extent Density return (blue square) noted at 2059Z. Note that V1 had a 70% contour nearly coincident with the GLM Flash square, while V2’s highest return was still only 50%, and well displaced from where the lightning actually happened.

While I don’t doubt that the -10C reflectivity can help in many scenarios, on days like today it didn’t seem to help much, if at all, and in many cases the satellite-only V1 seemed to do a bit better. As I said, it’s my hypothesis that this is due to the rapid vertical development outstripping the production of -10C returns. Additionally, I would be curious if testing out MRMS Vertically Integrated Ice (VII) instead of -10C reflectivity would produce better results (if it hasn’t been tried already)

– Marko Ramius

Odd LightningCast Dashboard Reading

Posted in LightningCast, SPG2025 on May 8, 2025 by Kevin Thiel.

An odd or false reading from LightningCast occurred on the Dashboard readout on May 8, 2025. The IDSS event was the Southern Skies Music Festival in Knoxville, TN. The screenshot below shows the Max Lightning Potential (10-mile radius) increasing dramatically after 14:40 UTC while the other LightningCast options don’t suggest any potential for lightning (in next 60 minutes) until after 15:45 UTC and even then, the others didn’t have any probability over 30%. On the plainview map comparing LightningCast 1 vs LightningCast 2 (Figures 1, 2, 3), the contours finally overlap the 10-mile event ring by 20:31 UTC and match up with the Dashboard probability at the same time (See Figure 2). Discussions within the HWT noted the issue could likely be a domain or pixel issue for the Max P.

Screenshot of the LightningCast Dashboard for Southern Skies Music Festival on May 8, 2025 from 19:40 UTC to 21:25 UTC. Interesting to note the blue arrows pointing to high probability of lightning depicted by the Max while the others remained less than 10% until 15:45 UTC.

Figure 1: At 19:46 UTC, the lightning potential approaches the 10-mile radius when the Max probability suggests nearly a 50% probability of lightning in the next 60 minutes.

Figure 2: At 20:31 UTC, the 10 and 25 probability of lightning enter the 10-mile radius.

Figure 3: At 21:26 UTC is when the probability of lightning really tapers off, even the Max P version.

Loop of the LightningCast version 1 and 2 surrounding the Southern Skies Music Festival.

– Podium

Severe thunderstorm warnings ONLY using satellite data

Posted in GREMLIN, LightningCast, OCTANE Speed Sandwich, SPG2025 on May 8, 2025 by Kevin Thiel.

May 8, 2025 was an interesting day for the experiment because “WFO GSP” was not allowed to utilize radar to issue severe thunderstorm warnings. I relied heavily on OCTANE Speed and CTD/cooling products and GREMLIN for making these decisions. At first, I struggled a bit with mentally shifting everything to the southeast due to parallax. After I began to utilize the ENTLN data as a proxy for storm core, it was better to estimate storm location and movement (although still not perfect). By the end of the day, I ended up issuing seven severe thunderstorm warnings. I found myself relying more on the CTD and cloud top cooling panel than the speed sandwich. Since it was my second day using the OCTANE products, I was quicker at picking up on signals in the CTD panel that suggest the presence of stronger thunderstorms. Having the CTD in one number compared to having to mentally calculate it while using the speed sandwich was helpful when working in simulated operations when a couple seconds does make a difference. I also found GREMLIN useful as a situational awareness tool to help distinguish which cells should potentially be interrogated more.

Here is a loop of OCTANE Speed Sandwich and the CTD and CTC products from two severe thunderstorm warnings I issued. The severe thunderstorm warnings were issued for the same storm, with the second one being issued as the first one was expiring. Looking at the OCTANE data combined with ENTLN (Image 1), it was clear that the storm was taking a turn to the right. I don’t know the specific values that CTD was showing, but I do believe this storm had values of 4+.

Image 1: Two severe thunderstorm warnings in OCTANE SS and CTD/CTC with Lightning Cast v1 and v2 overlaid. ~21:20Z to 21:56Z

GREMLIN (Image 2) also subtly shows this change in direction. What is interesting is that GREMLIN using ECONUS actually maxed out with a value of 60.4 dBZ.

Image 2: GREMLIN loop for the same two severe thunderstorm warnings in Image 1.

Image 3: Severe thunderstorm warning with OCTANE SS and CTD/CTC. ~21:56Z-22:22Z.

Image 4: Severe thunderstorm warning for the same time but with GREMLIN.

Another severe thunderstorm warning I issued, was showing CTD values of 4+ that prompted a warning. In GREMLIN, the strength of this cell was not as obvious in the ECONUS version, but slightly more prominent in EMESO-2. GREMLIN shows these cells basically merging, but I don’t know if that was reality. Looking at these loops compared to the movement of the lightning data, I don’t think my strom track was very good. In cases where radar is unavailable, I could see other novice warning forecasters also struggling with identifying storm track and motion when using strictly satellite data and also trying to mentally correct for parallax. This may not be an issue for more experienced warning operators though.

– Golden Retriever Lover

Web based LightningCast for a DSS event

Posted in DSS, LightningCast, SPG2025 on May 7, 2025 by Kevin Thiel.

My office’s internet went down hard for the entire day, so I had to utilize a mobile hot spot. AWIPS in the cloud was very sluggish and unusable on the mobile hotspot so I opted to only utilize the web based tools for today.

With a focus on the Brisket Appreciation Society Annual Bash in Beaumont, TX, storms started to emerge to the west and southwest of the event around 2 PM. I found the DSS dashboard useful when monitoring the specific location, but I wanted to use the LightningCast map as well for overall situational awareness. It was a little difficult for me to find exactly where the location was, so it would be useful for the map to have a dynamic layer for the DSS events.

I created a public graphic around the time lightning started near the to move closer to the DSS event. I generally utilized radar and LightningCast dashboard for the DSS event for the messaging. I did not include an image of the LightningCast for the graphic because it was already above 80% when I created the image. Because of this, there was very high confidence that lightning would occur, with the goal of the graphic to inform people of the approaching storms and the associated hazards.

LightningCast (both v1 and v2) stayed very high during the entirety of the event. When looking at the DSS dashboard, the probabilities within for the event increased to >80% 30 minutes before lightning was within a 10 mile radius of the event. There was an issue with the 1 minute data that caused that dip to 0. However, the 1 minute data is very noisy, and in this case, is not an improvement when compared to the 5 minute data.

– Golden Retriever Lover

GREMLIN and The Orphan Anvil

Posted in GREMLIN, LightningCast, OCTANE Speed Sandwich, SPG2025 on May 7, 2025 by Kevin Thiel.

I experimented with GREMLIN for convective initiation on May 7, 2025. One feature that stood out and was briefly discussed amongst the developers and participants was an orphan anvil. The first animation below is the GREMLIN CONUS (bottom right), MRMS Composite Reflectivity (top right), and GOES-19 Channel 7 (bottom left) and the second animation is Day Cloud Convection overlaid with LightningCast. As you follow the anvil passing south of the Home (or the Hot Pepper Festival), GREMLIN continues to project it as a storm or at least a shower further east. LightningCast did well and held steady and kept the lightning potential with a set of updrafts to the west. Unfortunately, a meso-sector was not available at this time and thus could not compare the 1-minute data to the 5-minute data. On a side note, the MesoAnwhere did fairly well depicting the orphan anvil progressing eastward.

Images above show the orphan anvil being projected eastward and suggested by GREMLIN as a storm/shower but MRMS has no reflectivity. The lack of lightning probably hurt GREMLIN in this scenario and it was suggested by a developer that anvil temperatures can resemble cloud tops and most likely confused GREMLIN in this scenario.

MesoAnywhere showing the orphan anvil.