OCTANE and a supercell

 Day 4 OCTANE

I had a severe storm in the southern part of the CWA that was a little pulse-y, and I found that I was able to look at OCTANE to see when it was on the way back up. Below, I have the OCTANE and radar at the same time stamp- OCTANE shows cooling cloud tops, and the ProbSevere MESH was 1.12”.

OCTANE product and base reflectivity at 21:25z, MESH of 1.12”

A short time later, the MESH jumped up to 2.17” and OCTANE depicted it as a mature cell.

OCTANE product at 21:33z, base reflectivity at 21:38z, MESH 2.17”

I don’t know if anyone reported how big the hail ended up being, but I wouldn’t doubt it was over 1.5”.

- Lightning McQueen

MesoAnywhere Appearance with Sharply Defined Convective Clouds

 More of a ‘gee whiz’ post than anything of true operational importance. I thought it interesting that while in many instances you don’t see a big change in the MesoAnywhere images from the ‘real’ GOES images at x1 and x6 minutes, vs the interpolated MesoAnywhere imagery, you can tell if you look closely at sharply defined convective clouds with ‘active’ cloud tops full of bubbling and roiling features. The real imagery (example in Fig. 1) will show features that appear somewhat sharper than the interpolated MesoAnywhere imagery (example in Fig. 2).

Fig. 1. 2126Z ‘Real’ GOES-East Day Cloud Phase Distinction imagery (Right).

Fig. 2. 2128Z Interpolated MesoAnywhere’ GOES-East Day Cloud Phase Distinction imagery. (Left)

- Marko Ramius

LightningCast Dashboard

 One of the more useful features for DSS messaging today was the Dashboard Request Form for values at our State Track Meet. Since we were operating under the assumption that the go or no-go threshold for this event was lightning within 10 miles, I liked using the dashboard but isolating the Max P 10-mile radius line in pink.

One note of feedback I had was to add some context for what we’re looking in each line at by noting where the data comes from in the legend. I was able to verbally ask a visiting scientist exactly what each line meant and where the data comes from, but this may not always be an option. The suggestion we came up with was adding (5-min, CONUS) and (1-min, MESO) to the legends circled in red so that it’s clear that the 5 minute data came from the CONUS satellite and the 1 minute data comes from one of the mesosectors.

- millibar

Lightning Cast: Real-Time Monitoring for DSS

 The LightningCast Dashboard is an excellent tool to monitor and predict the probability of lightning at a point, which allows us to easily provide decision support services (DSS) for outdoor events.

Here’s an example from today for the Clown Rodeo on the south side of Lubbock, TX:

Notice the LightningCast probabilities for both the ABI and ABI + MRMS generally remained between 0 to 20% during the duration of the event.

These probabilities were associated with developing cumulus clouds in the area, which can be seen in the Day Cloud Phase Distinction RGB:

Typically, if a meteorologist sees developing cumulus similar to shown above in the Day Cloud Phase Distinction RGB, this would result in an increasing concern for lightning at that location. However, it is challenging to quantify this concern and message it probabilistically to our partners. LightningCast gave us confidence to message our partners there is a low probability (10 to 20%) of any lightning strikes within the next hour.

-Vrot

Lightning Cast Differences With Pulsing Convection

 A weak line of thunderstorms developed and moved into the southern portion of Great Falls, Montana CWA (WFO TFX). Based on MRMS, the storms appeared to be weakening with MRMS and lightningcast V2 began to lower probabilities of lightning quicker than V1. However, slightly after the lightning decreased in V2, both versions increased probabilities of lightning within the next hour to above 90%. Maybe V1 does better with pulsing storms or maybe it was just a single case scenario where V2 dropped in probabilities during what it believed was decaying convection, when in reality it was pulse-like convection.

- Aurora Borealis

CONUS GREMLIN Handling Convection Worse than MESO for a Change Over Western Montana

 

Figure 1: CONUS GREMLIN. There is a lot of stratiform in TFX and MSO’s area, though it is not being reflected nearly as much as MRMS indicates in Figure 2.

Figure 2: WMESO GREMLIN. Although the Meso Sector doesn’t extend all the way north, it does a better job representing the arcing line of showers. Perhaps it has a tendency to do this on the edge of the domain?

Not a whole lot is happening across MT right now so I will shift my eyes to TX for a bit. OCTANE seems to be doing great with initiation across a puffy CU field across west TX in Figure 3.

Figure 3: Note the cooling tops across all the CU in the unstable environment. A few have already developed into robust storms.

Back to MT…

Cloud tops have cooled somewhat on the storm entering the southwest corner of the CWA with LightningCast increasing accordingly, Figure 4.

Figure 4: LightningCast V2 seems to be handling this better according to lightning obs.

Figure 5: Associated Radar

ECONUS GREMLIN also appears to have picked up on this well (Figure 6).

Figure 6: ECONUS GREMLIN

Figure 7: ECONUS GREMLIN continues to intensify accordingly with what radar and MRMS have.

Additionally, the parallaxing appears to be quite evident once again as shown in Figure 8 and 9. I’d imagine that it’s due to the ECONUS sector, but I am not totally sure. This would be a major issue in my CWA with flooding ops as the warnings tend to be very specific over slot canyon locations, and this could lead to a false alarm or a missed event entirely if we are solely relying on GREMLIN.

Figure 8: Notable parallax issues compared to where my SPS was issued.

Figure 9: Location of the storm according to the KTFX radar.

GREMLIN Goes Over 60dBZ?!

 A very interesting thing happened with the GREMLIN tool with today’s supercell southwest of Wichita Falls, TX. After a very strong upward burst in the updraft and surge in lightning activity, the CONUS GREMLIN actually showed simulated returns over 60dBZ, despite the product supposedly having a hard cap at that level. Simulated returns as high as around 64dBZ were noted.

Fig. 1. Clockwise from top left:GREMLIN GOES-East Meso1; MRMS Composite Reflectivity; GREMLIN GOES-East CONUS; GOES-East Meso1 Channel 13 10.35µm IR imagery.

Looking at the loop before and leading up to this time (Fig. 2), we see persistent high overshooting tops in the IR imagery, and even evidence of gravity waves surrounding propagating away from the core of the overshooting top. The Mesosector GREMLIN was a bit less and jumpy, but did eventually show consistently stronger simulated returns. Meanwhile, the CONUS GREMLIN would continue to consistently show strong returns at least approaching 60dBZ even after this loop. The GLM Flash Extent Density (Fig. 2 overlay) does show higher values in the frames leading up to GREMLIN going over 60dBZ.

Fig 2. Same as Fig 1, for a loop from 2024z to 2035z.

Fig 3. Same as Fig 2, with GOES-EAST GLM flash extent density overlaid.

- Marko Ramius

Getting Supercellular with Octane

 After about an hour or so of monitoring the storm to the north and west of the Dallas Fort Worth CWA we finally begin to see signs of a rather mature and intense supercell across portions of northern Texas. Taking a look at the Octane Speed Sandwich we can see clear signs of a much tighter shear gradient, which from my perspective shows a clearly intense supercell.

Figure 1: Octane SPEED Sandwich valid between 2000-2030Z.

Taking a look across some of the more typical radar 4 panels I use, Mesh has become maxed out around 2-2.5 inches, the vertically integrated Ice has become maxed out on the color bar, and finally the MRMS 30 min rotation tracks have begun to perk up with this storm. So while it was outside of our area of responsibility for warning operations, I would not have been shocked if the storm was either severe thunderstorm warned with a considerable tag or even tornado warned.

Figure 2: Four Panel with RALA in the Upper Left, MESH in the upper right corner, 30min MRMS Rotation tracks in the bottom right corner, and VII in the bottom left corner.  Valid times 2000Z-2052Z.

On the mesoanywhere Day Cloud phase distinction, we can also see the overshooting tops with this supercell producing some gravity wave like features, indicating a very intense storm. You can also note that the initial supercell had split with the left moving supercell now pushing across the Red River and into Oklahoma. This left moving supercell went on to produce several large hail reports.  

Figure 3: Mesoanywhere Day Cloud Phase Distinction Valid 2030-2056Z.

Finally as the storm began to push southeastwards this evening we did begin to see a weakening trend in the Octance SpeedSandwich product between the upshear and downshear strength which looks to have been a precursor to a weakening trend with the cell between 2130Z and 2230Z. Radar returns began to diminish shortly after this signature with the core of the storm beginning to collapse just as we ended the day.

Figure 4: Octane Speed Sandwich Valid between 2100-2130Z.

Figure 5: KFDR 0.5 Base Refelectivity, Valid between 2118Z-2217Z.

- Sting Jet

Storm Initiation for FWD and Gremlin gets Going

From a top down perspective looking at Octane products down to Gremlin and actual radar data from KFWS, it provides a clear picture of what you might want to be looking at as far as what the Octane products can show you and to take a targeted approach to potential warning operations. Taking a look at some satellite data, we can see two areas of interest to the north and then a second one to the west where strong Cloud top Cooling and Cloud top Divergence is seen. In addition to all of this, the greatest gradients from the Octane Speed/Direction images show a rather robust cell to the north and west of the Dallas Fort Worth CWA and this is the cell we will be focusing on.Figure 1: Four panel with Octane Speed Sandwich in upper left corner, Octane CTC/CTD with no smoothing upper right, Octane CTC/CTD High smoothing lower right, and Octance CTC/CTD Mod smoothing lower left. Times were between 1902Z-1932Z

Taking a look at the Gremlin data we can clearly see the MesoSector began to pick up on the previously mentioned cells and further strengthening of these cells located to the north and west of the Forth Worth CWA a few minutes prior to MRMS showing some reflectivities, as this initial CI began to strengthen further. We can also see a bit of a lightning jump with these cells as well.

Figure 2: Four panel with GREMLIN Mesosector on the top right, MRMS reflectivity on the lot left, ECONUS Gremlin with GLM flash density on bottom right and finally GOES Meso sector 3.9 Micron Imagery on bottom left. Times were between 1921Z-1945Z

Finally with radar returns finally noting a strengthening trend with the cell of note to the northwest of the Dallas Fort Worth Metro, and with the previous signals from the stronger cloud top cooling and resultant Divergence, we could infer if these storms did develop in our CWA that they had an increasingly likely chance to become severe within the next 30  minutes or so.

- Sting Jet

Filling in LightningCast Contours in AWIPS

 TFX was focused on DSS messaging since it became evident fairly early on in the day that we were not expecting severe convection. The event we had was a State Track Meet with a range ring of 10 miles. Since there were a lot of contours to look at, our group decided to load them as an image and play around with the fill value of the LightningCast probabilities for easier visualization of imminent lightning threat for our partners. To do this, we loaded LightningCast as an image, went into the Change Colors option of the Img LightningCast and set the 10/30/50/70/90 thresholds to match with the colors, including setting 0-10% as transparent. Then we overlaid MRMS on top of it and set everything below 20 dbZ to transparent so we didn’t get any noise from the light showers since we were more focused on the thunderstorms with higher dBZs.

Initial attempt at filling in the LightningCast contours.

Later on in the day, we settled on a less opaque version of the colorbars and we were able to save them such that others in the TFX group could use them on the AWIPS user account as “LightningCastFilled”. This allowed the reflectivity above 20dBZ to stand out more so partners knew where the heaviest rain was without it blending into the bright filled LightningCast.

Final decision on the colormap filling in the LightningCast contours overlaid with MRMS composite reflectivity above 20 dBZ.

Our group members also noticed the default Max and Min for both versions of LightningCast (when loaded as an image) were originally set in AWIPS to random numbers like -20 and 113. Version 1’s default range was different than Version 2’s which added to the visual discrepancy. Before we figured this out, the contours and images did not match up in space (i.e. the image went outside the contour for the same value), but turning on samples revealed they were the same value. In theory, these should be set to 0 and 100 given that LightningCast is a probability. Once we changed these values on the LightningCast Img product in AWIPS to be set to a range of 0 to 100 and reset the colorbar levels according to this scale, they matched up perfectly with the contours. Our suggestion for developers was to ensure the default for these is 0 to 100 in AWIPS if they were ever to be loaded as an image.

-millibar

Comparing LightningCast v1 and v2 in benign thunderstorms

Lightning is deadly even in "benign" thunderstorms. Some morning convection in Arkansas demonstrates the everyday value of having MRMS Reflectivity at -10C in LightningCast v2 (LCv2), compared to satellite-only LightningCast v1 (LCv1). 

The GOES ABI data is invaluable in the probabilistic LightningCast model, especially prior to convective initiation. But radar data sometimes (not always) provides a signal of convective weakening or decay prior to satellite data.

In this example, thunderstorms ongoing in southern Missouri and northern Arkansas weaken as the sun is coming up. In the animation below, LCv2 is on the left and LCv1 is on the right.

 
Towards the end of the period, when only one cell is present, we see that LCv2 reduces probabilities of lightning about 10-15 minutes prior to LCv1. This cell did not produce any additional lightning.

Figure 2: LCv2 (left) and LCv1 (right) contours, along with GOES-19 day-cloud-phase-distinction RGB and GLM flash-extent density (large blue pixels).

Other features that stand out are "stronger" false alarms in LCv1, compared to LCv2. The images below show these false alarm regions to the south (Figure 3) and south and east of the thunderstorms (Figure 4).

Figure 3: LCv2 (left) and LCv1 (right) contours, along with GOES-19 day-cloud-phase-distinction RGB and GLM flash-extent density (large blue pixels). Note the stronger false alarm in LCv1 south of the ongoing thunderstorms.

Figure 4: LCv2 (left) and LCv1 (right) contours, along with GOES-19 day-cloud-phase-distinction RGB and GLM flash-extent density (large blue pixels). Note the stronger false alarms in LCv1 south and east of the ongoing thunderstorms.

Overall, the radar predictor in LCv2 helps to reduce false alarms that occurred in LCv1.

 

Day 3 - The Train Is On The Tracks OCTANE

I definitely felt more comfortable using OCTANE today and now that I understand it better, I was able to look at it compared to 10.3 imagery and I found that useful in differentiating which storms were still strengthening.

Jason showed us how to play around with the color tables for the OCTANE product and basically invert them so that the purples/pinks (cooler colors) represent cooler cloud tops, and the yellows/oranges/reds are the divergence. Conceptually I think this makes more sense to me putting cooler colors = cooling cloud tops.

GREMLIN

I feel like I saw very mixed results with GREMLIN with this event. There were times when the meso performed the best I’ve seen it all week (below)

…and then just two minutes later, not so much.

I’m not sure what attributed to the sudden drop off on what on radar appeared to be the strongest storm.

Later, GREMLIN seemed to be doing very well with the areas of more stratiform precip, which I don’t believe I’d gotten to see up until this point. Was curious if it typically does better in that type of environment.

LightningCast

I wish I had grabbed more of the LightningCast plots since it was probably the product I was looking at the most since I was doing the DSS messages, but the plot below was the only one I did grab.

I was curious about the sudden dip in the V2 product because I don’t think I’d seen it be lower than both V1 before.

- Lightning McQueen

Warning Operations with Satellite Data Only

 In the absence of radar data, satellite data can be utilized for warning decision-making by utilizing a suite of satellite-derived products.

GREMLIN (synthetic composite reflectivity) used in tandem with OCTANE can depict an area of strengthening convection that would be capable of producing hazardous weather.

In the example shown below, OCTANE indicated strong cloud top divergence and GREMLIN showed increasing reflectivity, which resulted in increased confidence that convection is intensifying (as shown in this case). As a result, a special weather statement (SPS) was issued for a strong thunderstorm producing small hail and gusty winds. This storm would initially produce half inch to nickel hail.

Later on, cloud top divergence intensified further on the same thunderstorm:

Eventually, this storm would produce severe hail. This demonstrates the utility of monitoring satellite trends. If you have storm reports, you can use those trends to calibrate yourself on warning-decision making.

-Vrot

Warning Operations with Satellite Data Only - Part 2

 This is intended as a downstream follow-up to the first post of this name, which dealt with the issuance of an SPS for a cell north of North Platte, NE (Fig. 1).

Fig. 1: 1935Z OCTANE Speed Sandwich (top left) and OCTANE Cloud Top Cooling/Divergence for no smoothing (top right), low smoothing (bottom left), and high smoothing (bottom right) around time of SPS issuance.

As the cell continued southeastward, cutting across northern and eastern parts of Lincoln County, NE, the storm did increase modestly in satellite presentation. The OCTANE Speed Sandwich (Fig. 2, top left) showed some signs of strengthening in the form of displaying higher winds (oranges), indicating a storm growing a bit higher and tapping into stronger winds aloft. The OCTANE Cloud Top Divergence and Cooling views (Fig. 2, same as Fig. 1) was also intermittent cloudtop cooling (greens) over the expected updraft location, indicating continued upward motion and updraft maintenance, and the cloudtop divergence was showing pink to intermittent red, indicating moderate to occasionally strong divergence.

Fig. 2: 2014-2032Z OCTANE Speed Sandwich (top left) and OCTANE Cloud Top Cooling/Divergence for no smoothing (top right), low smoothing (bottom left), and high smoothing (bottom right) around time of SPS issuance.

As shown in Fig. 3, the GOES-East CONUS GREMLIN output was somewhat underwhelming, and the GOES GLM lightning data shows no appreciable increase, but the 10.35µm IR imagery showed clear signs of higher cloud tops.

Fig. 3: 2014-2032Z GOES-East GREMLIN (left) and 10.35µm IR imagery with GLM Flash Extent Density overlaid (right).

While the signs of strengthening could have been used to justify increasing the size of the hail on a follow-on SPS over the initial half inch forecast, in this forecaster’s opinion it would have been difficult to justify upgrading to a Severe Warning at this time.

Continuing on down the line, we see (Fig. 4) the OCTANE Speed Sandwich product show cloud top wind speeds at least maintaining, if not increasing a touch further, indicating at least maintenance of strength, if not a bit of strengthening. The Cloud Top Divergence continues to show moderate (purple) to intermittently strong (red) divergence, and the Cloud Top Cooling continued to show occasional upward bursts in the updraft region. These would indicate the storm is likely at least worthy of a high-end SPS, and may be approaching severe thresholds.

Fig. 4: 2039-2103Z OCTANE Speed Sandwich (top left) and OCTANE Cloud Top Cooling/Divergence for no smoothing (top right), low smoothing (bottom left), and high smoothing (bottom right) around time of SPS issuance.

The GREMLIN simulated radar output from the same time (Fig. 5, left) shows fairly consistent moderately strong returns, in the high 40s dBZ to near 50dBZ. And understanding that GREMLIN tends to underestimate real radar returns somewhat and applying a mental adjustment, we can assume the storm is on the strong side, and appears to be more consistently strong. While the GLM never got very high, during this time period it does finally perk up somewhat and show modestly higher values, indicating a bit stronger updraft and more cloud ice and mixed phase precip aloft.

Fig. 5: 2039-2103Z GOES-East GREMLIN (left) and 10.35µm IR imagery with GLM Flash Extent Density overlaid (right).

Again, it might be hard to justify a warning at this time based solely on the satellite and lightning data and the at-best marginal modeled environmental data (no radiosonde sounding data available). However, at 2058z there was a public report of 0.88” hail (nickle-sized), just below severe thresholds. Combined with the data showing a decently strong storm in the satellite data, and the inherent increased uncertainty in dealing with just satellite and lightning data in the absence of radar data, in this forecaster’s opinion receiving a hail report just below severe thresholds likely would have been enough to justify putting out a severe warning. The office did issue an LSR for a report of 1” hail from an NWS Employee just east of Maxwell at 2106Z.

- Marko Ramius

Using LightningCast and MesoAnywhere for Alligator Wrestling

 Since we are relatively limited with the products we can use today as the meso sector doesn’t fully extend down into JAX’s area, I will be mainly using LightningCast and MesoAnywhere today. We are able to use the CONUS sector for GREMLIN, though I’m not too sure how useful it will be today with good radar coverage via KJAX. However, there are some more storms moving in from TAE’s area and with KVAX out for the day, it could prove useful.

There is already some discrepancies with the event so far with LightningCast V2 being slightly more bullish with the threat at the Alligator Wrestling event this afternoon as shown below in Figure 1.

Figure 1: LightningCast V1 (left panel) compared to V2 (right panel).

The LightningCast dashboard also shows this discrepancy (Figure 2) with a notable spike in probabilities from V1 followed by a significant decrease and a pretty gradual increase for V2.

Figure 2: LightningCast dashboard comparing V1 (warmer colored lines) and V2 (green line) over time at the event.

Additionally, MesoAnywhere has proven useful since we do not have a meso sector today. I found that it has been pretty good identifying more dominant storms in decaying clusters with pretty good lead time compared to using 5min imagery. Pretty obvious that this would be useful, but I see it as a pretty great tool as a former Florida WFO meteorologist. A lot can happen in 5 minutes and I see this being quite useful for summertime pulse convection.

As of 4:10PM ET, Lightningcast V2 continues to remain more bullish than V1. Figure 3 shows the contours in AWIPS and Figure 4 shows the dashboard. Both versions appear to be on a steady incline, though V2 is noticeably higher.

Figure 3: AWIPS LightningCast with V1 on the left and V2 on the right. The 30% contour is noticeably further south toward the Gator Wrestling Match and also has higher probabilities off the coast of St. Johns county.

Figure 4: LightningCast dashboard showing the probabilities across each version. As of typing this, both have begun to even out.

However, it does appear that V1 did a better job at picking up on the lightning threat for a storm over in TAE’s area covering Berrien and Lanier counties in GA. In Figure 5 below, both versions had a 90% contour over the developing storm with lightning following not too long after.

Figure 5: LightningCast V1 and V2 indicating the threat of lightning for a storm over Lanier and Berrien counties in GA.

In Figure 6, LightningCast shows the threat decreasing accordingly with time as the storm begins to ingest some cooler air, likely outflow from the southern storms. This product appears to be quite good with initiation and I hope we get more cases like this over the next couple days.

Figure 6: The storm over Berrien/Lanier counties in GA showing less of a signal for lightning over the next 60 minutes as it weakens.

Regarding the Gator Wrestling, chances have decreased to zero over time. Both V1 and V2 remained on the lower end for probabilities and verified well with only one GLM strike within 10mi (Figure 7).

Figure 7: Not a whole lot going on at the Alligator Wrestling Match.