Utility of Parallax Corrected LightningCast Versus Non-Corrected within DDC

June 15, 2023 – Role playing as DDC, I was tasked with providing DSS for a (fictitious) grass fire near Meade, KS.

DSS: Grass fire near Meade, KS

For this DSS, requested information included lightning within 10 miles of the site, any significant changes in wind speed and direction, as well as other hazardous weather that would pose a risk to emergency personnel containing the fire.

Figure 1.

There was ongoing severe convection within the western half of the CWA by the start of my shift, and there was a high likelihood of this convection approaching the DSS site. As shown in Figure 1,  my datasets/tools of choice for tracking severe convection and lightning were as follows: GOES-East Mesosector LightningCast, MRMS Composite Reflectivity, ENTLN intracloud and cloud to ground lightning, surface observations, Time of Arrival Tool, Distance Bearing Tool, and Range Rings Tool.

Ground based lightning observations and LightningCast complimented each other nicely when assessing the potential for lightning at the site. Additionally, LightningCast picked up on additional agitated Cu well ahead of the main line of thunderstorms closer to the DSS Site. Using the Time of Arrival tool to track the main cluster of cloud to ground lightning associated with the severe convection was also very useful in providing information on potential to see most lightning via advection, in the absence of additional convective initiation and/or a rapid change in forward speed in ongoing convection.

Figure 2.

Some consideration was made to not “overwarn” on lightning potential as the main breadth of lightning would likely come from the severe convection still well off to the west. So with this particular scenario, I set an internal threshold of 80% within LightningCast to send a DSS message. The data readout of the parallax corrected LightningCast offered within AWIPS (not shown) was favored over the non-parallax corrected time series (Figure 2), giving higher confidence in the true probability of occurrence used within the DSS message. This gave around a 35 minute lead time before the first strike was detected within 10 miles of the DSS site. Had we used the non-parallax corrected readout values, lead time would have been much shorter, around 10 minutes using 1-minute imagery and less than 10 minutes using 5-minute imagery. This clearly demonstrates the value of using parallax corrected data compared to non-parallax corrected data when performing DSS.

Here was the DSS message sent at around 21:10 UTC:

Severe thunderstorms have developed around 50 miles to your west, and will likely move over your site between 5:15 pm to 6:30 pm CDT. There is a high chance for storms to remain severe by the time they reach your site, bringing very strong winds over 70 mph out of a direction ranging between northerly to westerly, large hail, heavy rainfall, frequent lightning. We still cannot rule out the potential for a brief tornado, although the chance for a tornado is much lower than previous hazards mentioned. Because of the approaching thunderstorms, the chance for lightning to occur within 10 miles of your site within the next hour (5:15 pm CDT) is over 80%.


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Low Probabilities of LightningCast Despite Observed Cloud to Ground Lightning Within Trailing Anvil / Stratiform Region

While providing (fictitious) DSS for a grass fire near Meade, KS on June 15, 2023, LightningCast was utilized in notifying the onset of lightning within 10 miles of the DSS site as a line of severe thunderstorms approached. Additionally, consideration was given to the potential for lightning cessation over the site in an effort to give information on potential for the “all clear.”

Figure 1.

LightningCast within the trailing anvil portion of the squall line steadily dropped off within the trailing stratiform region. However, these probabilities decreased when cloud to ground lightning was still being observed, with even some strikes occurring in probabilities less than 10%. This can be seen in Figure 1 in the far left hand portion of the animation with CG icons occurring within and outside of the lower contours of LightningCast.

This significantly lowered confidence in tracking the lower probability contours to give an estimated time of cessation.

Here was the DSS message sent at around 21:45 UTC:

As of 4:45 pm CDT, severe thunderstorms are 20 miles west of your site, and continue to approach your site. There is a very high chance these storms remain severe by the time they reach your site, currently expected between 5:15 pm and 5:45 pm CDT, bringing very strong winds over 70 mph out of a direction ranging between northerly to westerly, heavy rainfall, and frequent lightning. We still cannot rule out the potential for a brief tornado and large hail, although the chance for a tornado and hail is much lower than previous hazards mentioned.

Because of the approaching thunderstorms, the chance for lightning to occur within 10 miles of your site within the next hour (5:45 pm CDT) is over 99%.

It is worth noting that even after severe hazards associated with this line of thunderstorms have ended, there will remain over 75% chance of lightning over your site for an additional 1-2 hours, along with the potential for continued gusty winds over 20 mph ranging out of the southeast to northeast.


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BMX Severe Thunderstorms

Overall, I used OCTANE, PHS, ProbSevere 3 and LtgCast today. NUCAPS wasn’t really accessible. Worked the DSS event, an Air Show, which was canceled due to severe thunderstorms all afternoon producing tornadoes, large hail and damaging winds. DSS for this event would have been done days ago.

Below is a shot of LtgCast on a radar background and ELN measured lightning, the +/- are positive and negative ground strokes, and the cyan dots are in-cloud. It is interesting how the 75% probs lead out into southwestern Georgia though the showers there are more stratified and lightning isn’t expected, yet it gave about 45 minute notice of lightning strikes; that’s a good thing. But how useful is this? It predicted a few single lightning strikes tens of miles apart scattered across 100 miles which isn’t really useful; would you stop all outdoor activities across ¼ of Georgia for a few stray strikes? Would you clear the baseball field because a lightning strike will hit in the next hour somewhere within 50 miles? Not likely, but knowing there is some chance is valuable information for an event coordinator for risk analysis. If they can make minor changes to activities with little or no impacts, it helps, especially if it’s an area where lightning isn’t expected. What would be a big plus would be an estimate of flash density/frequency expected to go with the probs. That gets back to tracking the convective cells to predict areas of dense lightning. We have radar and ELN’s for that.

PHS composite reflectivity vs radar at 21Z… I find little value in the PHS composite reflectivity product. Below you see PHS composite reflectivity compared to the radar returns at 21Z. It’s not doing too well and I haven’t seen a time when it has done well predicting where the storms will be. The HRRR, NSSL WARF, HRef, NAM Nest and other high res models do much better.

PHS Bulk Shear 0-1 km below on the left and 0-3 km below on the right both show a line between areas of lower and higher shear along the boundary where the severe storms were tracking, but this occurred after the convection started. I don’t see a pre convection signal pointing to where the training storms formed.

The Bulk Shear 0-6 km below shows more promise with the 19Z  frame showing a boundary where the training severe storms formed/tracked (what did it look like at 16Z or 17Z?). I would need to see more of this pre convection to really make a judgment, and would need to see positive validation/verification to have any confidence in it as a tool.

– Super Bolt

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PHS Reflectivity Forecast Helping Out with DSS

The Panda Ceremony was held at the Jackson, MS Zoo on the evening of Wednesday, Jun 14, 2023.  Strong to severe storms were forecast throughout the afternoon and evening hours and the event coordinator requested DSS for lightning and any severe weather with as much lead time as possible.  Using the 14.16z initialization of the PHS reflectivity was useful in providing some timing details to the event coordinator (See Figure 1). It suggested a fairly robust storm to roll through the Jackson area by around 00z with the forecast reflectivity ranging from 50-65 dBz directly over the event site.  

The reflectivity forecast did well with depicting a fairly large storm to move across southern Mississippi but was a bit too north on the location.  Overall, the product was very useful in boosting the forecaster’s confidence in the convection timing to impact the event. See Figure 4 for a look a the verification.

Figure 1: Loop of the 14.16z PHS layer reflectivity had a large storm over Jackson, MS, and impact the event (black range ring) by 00z.

Figure 2: A DSS Graphic was issued shortly after 3 p.m. to highlight the timing and potential impacts of the Panda Ceremony.  The original image had the animated GIF above with the PHS reflectivity forecast.

Figure 3: This was the first of 3 graphics created for the event and this graphic highlighted the severe weather threat and timing.  Overlaid is the MRMS reflectivity greater than 35 dBz and OCTANE Winds.

Figure 4:  A loop of MRMS with ProbSevere and LightningCast shows some verification of the PHS reflectivity forecast shown above. This loop ends at 2232z.   

– Podium

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Verification of NUCAPS Soundings

Using the 1930z pass of the NUCAPS soundings during an SPC Moderate Risk was quite exciting.  The environment was primed for significant severe weather and having NUCAPS soundings available at the time of convection out of ahead of storms was beneficial. It provided additional confidence in the severity of the environment. 

As you can see from the satellite, soundings were unusable further north due to the ongoing convection and cloud cover. Thankfully clear skies prevailed from Jackson and southeastward providing some impressive sounding data to compare to SPC Mesoanalysis.  Sounding A was well in the warm sector and sunny skies and thus had the highest CAPE values and lapse rates. Sounding B was just to the southwest of the DSS event and was beginning to see some anvil over that location, but it still provided reasonable data and compared well with SPC mesoanalysis.    

Figure 1: Location of the NUCAP Soundings chosen to view and compare to SPC mesoanalysis. For reference, the range rings outline the 5 and 10-mile radius around a DSS event in Jackson, MS. 

Figure 2: Sounding A with a surface-based CAPE of 6004!

Figure 3: Sounding B with a modest 4079 surface-based CAPE.

Figure 4: SPC mesoanalysis Surface-Based CAPE and CIN at 20z on June 14, 2023.  The star is the DSS event location and the two dots are the estimated location of the soundings analyzed.

Figure 5: SPC Mesoanalysis 0-3km lapse rate (C/km) depicted lapse rates from 7.0-8.0. Once again, both soundings matched up well with SPS data.

– Podium

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PHS Blog Post AMA 6/13

PHS today was interesting given some of the local convective parameters. The main one that caught my attention was the lesser 0-6km bulk shear that it was giving just ahead of an incoming storm in the Oklahoma Panhandle. The PHS was around 20-30 knots whereas other guidance and SPC Mesoanalysis was showing 50+ knots. I did look at other parameters such as MUCAPE and SBCAPE for example and they were in the ballpark of other guidance including SPC Mesoanalysis.  If the PHS was correct then the storm mode would feature more multicell with some organization vs more of a discrete supercell mode so it was going to be interesting to see what would occur. 

What wound up occurring was a persistent long track supercell along with other convection which was anticipated given the PHS wind shear.  Overall, I was impressed with the PHS wind shear forecast as that tailored away any thinking that there may be additional supercells as additional updrafts would interfere with the intensification of other cells. The PHS however was around 1-2 hours slow with convection moving into the AMA CWA, however the composite reflectivity forecast did show more of a cluster of storms developing. The PHS was also showing a corridor of stronger 0-3 and 0-1 SRH which in reality the intense cell did move through and actually wound up producing a few tornadoes. The ProbTor was also showing tornado potential as high as 40% as it was moving through this corridor.  Overall, I was impressed with the PHS today and think that it could create good DSS messaging opportunities along with being skillful in Mesoanalysis.

PHS showing the lesser values of 0-6 bulk shear in contoured form

SPC Mesoanalysis depicting the 0-6km bulk shear at the same time

How the radar wound up turning out at 2130Z with the multiple cells

– Tor Nader  

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Day 2 Review of Products & Operational Applications

I took on the DSS role during today’s operational period. There were no afternoon NUCAPS-Forecast runs and the morning runs provided minimal coverage over the AMA CWA. So, I opted for PHS data today (namely SBCAPE) with MRMS 0.5 km Composite Reflectivity and ProbSevere overlaid (Figure 1) to diagnose the environment. Much of AMA was socked in by stratocumulus at the start of the operational period, but severe storms just to the west posed a concern as they tracked eastward into a gradually destabilizing environment.

Figure 1

The assigned DSS event was a hypothetical RC plane show at Texoma Municipal Airport (denoted by a yellow star in Figure 2). I was instructed to alert the hypothetical POC for the event when either of the following hazards were expected within 20 minutes: winds or gusts of 15 kts at the airport OR lightning within 10 miles. I used LightningCast probability contours along with ENI 5-minute pulse lightning plots (reddish orange tick marks) to monitor the proximity of lightning to the event range ring (Figure 2). I issued a DSS update with “lightning likely” wording after the LightningCast meteogram depicted a steadily increasing likelihood of lightning at the airport within an hour (Figure 3).

Figure 2

Figure 3

A LightningCast observation: the footprint of the 75% probability contour was much larger than the actual area in which lightning strikes occurred (at least according to ENI 5-minute pulse lightning) mainly in the anvil region. That said, GLM Flash Extent Density did indicate low-value pixels in the anvil region, so perhaps I missed some anvil lightning strikes by looking at just ENI 5-minute pulse lightning.

– Vort Max  

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HGX Convection impacting the Car and Truck Show in Burton, TX

Initial setup for the HGX vicinity showed several cells to the north and east of the DSS site, propagating southeastward. The strongest cell, pictured below, had a PSv3 of 73%, while PSv2 remained as 56%.

We issued a warning for a northern cell moving into the CWA into Madison county, based on a -70C cloud top brightness temp and PSv3 total prob over 70% (had been climbing from the 50s fairly steadily). But the cloud top shear noted by Octane was not strong (~20-25 kts), so the warning was very borderline. Just a couple scans later, it lost most of its texture on the vis imagery and lost its shear in the Octane direction product. Cloud tops warmed a bit as well.

00H NUCAPS-Forecast (NF) is showing moderate CAPE now (1st image below), which may help explain the messy sub-severe multicell clusters, but the forecast valid at 02z this evening shows a resurgence in the CWA (2nd image below).

Looking to our NW, one of the stronger cells is outside our CWA, but the Octane direction is showing good cloud top diffluence.

The PHS SCP forecast valid at 20z looks to be around 2-4 over our area, although this doesn’t match well with the SPC meso page SCP, which focuses high values W of our CWA.

The 21z PHS MUCAPE (15z run) looks like it has insane values of 6000-7000 J/kg near the coast and just offshore. This is much higher than the SPC meso page, showing 3000-4000 J/kg at most.

Looking at the optimal application of LightningCast, it seems that the point-based meteogram would work best for CI and in situ developing convection, versus storms propagating into the area. In our case here, at the DSS site, the point-based LC probs are low, suggesting little concern. But we can see from the GLM FED data that there are mature cells with lightning just to the NE that will probably move near the site in the next hour, which certainly poses a safety concern.

The NUCAPS sounding near Victoria (far SW CWA) showed a lot of CAPE and DCAPE, but a rather dry profile. This is confirmed by WV imagery over much of far S TX.

22z PHS Composite Reflectivity (above image) compared to 22z MRMS Composite Reflectivity (below image ) depicting PHS struggling on timing as the cluster of thunderstorms propagate from northwest to southeast.

Late in the event, this cell is showing slow strengthening on PS — currently both v3 and v2 have 40% total.

– Edgar and Harvey Specter

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MAF Convection

Convection has been slow to initiate in W TX, but we’re finally seeing some vertical extension and greater texture in the CU field on the NE side of the mountains. LightningCast is now showing higher probabilities in this area, after several scans of sub-50% contours.

We are seeing good destabilization. The PHS MUCAPE compares quite well to the SPC mesoanalysis.

LightningCast probabilities continue to climb, and we’re finally seeing a few flashes on GLM imagery.

Our LightningCast meteograms are finally showing some higher probs in the next hour near our DSS site in Fort Stockton.

We’re now seeing more defined features in the Octane imagery, including cloud top divergence signals and cooler brightness temps, down to -63C. But our ProbSevere markers remain low.

Looking at the NUCAPS-Forecast initialization at 19z, the mid level lapse rates are lower in areas NE of the higher terrain, where convection has been a bit slower to strengthen, as compared to the storms to our SW over Mexico, where MLLRs are higher.

The new TPW imagery from NUCAPS shows well the delineation of the moist air to the E and drier air to the W.

The PHS SHiP pattern looks good, but its magnitudes appear way off, compared to the SPC meso page and how SHiP is calculated.

Hail probs are exceeding 80% now on ProbSevere, although our GLM lightning is rather low! Interesting how assumed large hail presence doesn’t necessarily equate to classic charge separation that would prompt high electrification.

21z 700-500mb comparison of SPC Meso (top) vs 21z NUCAPS-Forecast (bottom)
    – Some differences in lapse rates between the two, with NUCAPS about .5-1°C/km  lower than SPC Meso page. 

ProbSevere, Octane, and IR imagery supports warning issuances for Reeves and Pecos counties.

With the warning now out for Reeves and Jeff Davis counties, this storm continues to exhibit high hail probabilities on PSv3.

Up to 120 kts of ST divergence with the warned cell (at about 50 kft).

Interesting how ProbSevere identifies objects. There appears to be 3 separate updrafts in Pecos county, however PS is seeing one object.

– Edgar and StormofCentury

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Examination of LightningCast and OCTANE in Idaho and Oregon

Near the Idaho/Oregon border, we observed splitting cells on the afternoon of Wednesday, June 7. We believe we were able to see the first hints of this process get underway with the help of the OCTANE product. Subtle gradients were observed on the left side of the main storm prior to the ultimate cell merger. 

In the image on page 2, we see a nice comparison using LightningCast between an environment characterized by cirrus contamination vs an environment that was not contaminated. On the eastern side of the CWA that was characterized by cirrus contamination, LightningCast probabilities peaked at 50% on a storm that ultimately produced lightning. In contrast, two thunderstorms to the west (developing in a clear, cloud-free environment) both saw LightningCast values exceed 80% on two storms that ultimately produced lightning.

Above, we see perhaps the first instances of a splitting cell in progress, and OCTANE helped give us a first indication of the split (upper left in particular)

Above: LightningCast Meteogram as of 2053z, depicting a small trend upwards, albeit extremely minimal, within the next 60 minutes for some lightning impacting the American Aquarium at Hayden Beverage in Boise (DSS location).

Above: 21z PHS shows development of convection in Owyhee and Twin Falls counties (southern BOI CWA) depicted by a red box; however, the 4 Panel Situational Awareness is indicating that doesn’t seem to be the case, with mere cirrus cloud development. Perhaps the timing is off?

Above: On the other hand, PHS is doing a fairly good job depicting the convection just east of the DSS site. Currently (almost 22z), a few decent cells depicted by ProbSeverev3 (right around 15-18% probability, where MESH values are just over 0.50”)

Above: 2123z: LightningCast indicating just above 50% probability of lightning within the next hour yet the Meteogram is well below 20% for the GOES East reading. It is suspected that this is because the AWIPS readout is Plax-Corrected, whereas the Grafana Meteogram may not be?

Just after 22z, Grafana Meteogram (above) shows GOES East  ProbSevere Lightning to be 67%. This latency further aids in the belief that the Meteogram is not Plax-Corrected.

As of 2220z, downward trend displayed with regards to the Grafana Meteogram (topped at 70%, now showing 54%). This is indicative of the cells east of Boise (DSS area) initially showing signs of weakening…HOWEVER…

Things are starting to get juicy at 2224z with ProbSevere v3 showing the cell south of Idaho City has increased to 36% probability (below).

– Bolt and Harvey Specter

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