ProbSevere – EWP Blog

ProbSevere and LightningCast During Severe Warning Operations

Posted in LightningCast, OCTANE Speed Sandwich, ProbSevere, SPG2023 on June 15, 2023 by Kevin Thiel.

A moderate risk for severe storms was forecast for the Southern Plains with hail, wind, and tornadoes as significant threats. Storms quickly initiated in southwest Kansas (See Figure 2) and were ongoing when the testbed started at around 19z. Primarily used during warning operations were ProbSevere, LightningCast, and radar. Thrown in for good measure I used OCTANE to aid in storm motion and direction. ProbSevere was helpful in issuing warnings but was vital in assisting in the hail size mentioned in the warning text.

Figure 1: SPC Day 1 Outlook for June 15, 2023.

Figure 2: 2011z showing ProbHail with a MESH of 2.17” provided the confidence to mention 2-inch hail in the text. There were two separate storms that eventually merged later in the afternoon.

Figure 3: storms were beginning to merge and ProvSevere was as well and thus prompted just one warning instead of two.

Figure 4: New warning with ProbSevere now depicting just one storm.

Figure 5: Storms continued to merge and evolved into a wind signature more than a hail producer. Thus the ProbWind had a nice uptick to 68% at 2133z. Before this time it never rose bout 40%.

Figure 6: Once the convection evolved into a linear wind producer, LightningCast became helpful in how far east to extend the polygon. I used the 75% contour and issued a 60-minute warning.

Figure 7: Captured much of the event to show the evolution of convection and ProbSevere.

Figure 8: OCTANE aided in determining the area of cell merger in southern Grant and portions of Stevens Counties.

– Podium

6/15/23 HWT – AMA

Posted in NUCAPS, OCTANE Speed Sandwich, PHSnMWnABI, ProbSevere, SPG2023 on June 15, 2023 by Kevin Thiel.

What appears to be a nice distinction between sheared / lesser sheared convection across the Octane window. Stronger shear across SW OK producing much different appearance versus SW KS convection. Nice quick visual distinction for operational use. The idea of a quantifiable divergence contour and/or grid would be welcome also.

Octane data from Goes west meso sector was zoomed in along the inflow region across the SW OK supercell (not our CWA but I had to look). The upper right panel is the directional component and the color scale was changed to highlight approximately 210 – 150 degree range. The increasingly warm colors represent a backing of flow at approximately 4.5 kFt. This level of storm integration (if appropriate) would be advantageous to warning operations.

ProbSevere time series plots do not sample. I would like sampling tied to the cursor as in the parent CAVE window. The element assignment within ProbSevere did cause a problem with the time series information with a storm that strengthened on the southern end of a developing line. The storm initially had a defined area for the region of interest but once ProbSevere assigned it to the larger line the probabilities became much less representative. This impacted ProbTor values which were being monitored ahead of an eventual tornado warning in the Tx Panhandle. I was the warning forecaster today and used ProbSevere extensively for my decisions. It is not the deciding factor but it certainly weighs into the decision process.

PHS model output was interesting and the Updraft Wind element was noted as something not usually seen with model output. It was viewed initially but I didn’t monitor the model output once storms developed and warnings were being issued.

NUCAPS forecasts were unavailable until the very end of the operational window. I did view the 19z overpass soundings and found the familiar trends of errors at the boundary layer when compared to nearby surface observations. This limitation continues to impact my confidence in the product.

– jbm

6/15 HWT OUN SuperCell

Posted in OCTANE Speed Sandwich, PHSnMWnABI, ProbSevere, SPG2023 on June 15, 2023 by Kevin Thiel.

A very intense supercell formed across western portions of OUN CWA. This cell underwent many transformations including splitting and merging at other times. Octane was very interesting to watch as this cell went through the various processes before eventually producing a tornado. Octane was able to show the storm splitting before it occurred on radar. PHS was also showing corridors of stronger 0-3 and 0-1 SRH; SPC Mesoanalysis was showing this as well but I did like how the PHS was able to highlight exactly where these occurred. Seeing that and a near stationary boundary did increase my confidence that if a storm was able to latch on it would become tornadic. Probsevere/MESH did struggle to catch on to how large the hail actually was initially before finally picking up on the hail size.

4 Panel with Octane on the top row; appears to be two distinct divergence signatures occurring

Radar Loop of storm splitting shortly after Octane signature…. Notice how the left mover dissipates.

Using the 4 panel with Octane, IR and Day Cloud Phase it was also beneficial to see the upper divergence signature on Octane correlate with the cooling cloud tops of IR and Day Cloud Phase. Although it didn’t seem to create any additional lead time with that aspect; at least that I was able to notice. It was overall a very interesting storm to watch for this experiment.

4 Panel Intensification of storm. Note the rapid color gradient to blue (upper level divergence)on Octane towards the end of the loop.

Radar loop around the same time as the 4 panel above

– Tor Nader

6/15 Feedback for AMA

Posted in LightningCast, NUCAPS, OCTANE Speed Sandwich, PHSnMWnABI, ProbSevere, SPG2023 on June 15, 2023 by Kevin Thiel.

PHS

The surface based CINH at 20z lined up rather well with the satellite imagery showing the slightly more stable clouds over the eastern CWA.

When sampling an image versus contours, the contour sampling has the entire product name in the readout

PHS captured the initial convection just east of AMA well, even though the convection started an hour earlier than PHS indicated. Image on right is PHS SB CAPE and contours are PHS SB CINH. Home is roughly where the storm is located. Satellite image is around 1930z and PHS forecast is 21z when CINH dropped from 80j/kg to 40 j/kg.

PHS did a reasonable job predicting the general storm coverage by 21z from the 16z run.

Toward the end of the exercise, the storm coverage was well captured by the PHS 16z run. Should have taken this into account for my public graphics when describing the storm evolution.

NUCAPS

This is a NUCAPS sounding in the TX panhandle near AMA vs. a RAP40 sounding at the same point. The RAP has the same trend in the dew point profile as NUCAPS, but is lower.

Noticed the NUCAPS sounding didn’t have the lower dew points around 400 mb as shown in the special sounding. NUCAPS did have a hint of the weak cap near the surface though.

NUCAPS 700-500mb lapse rates from the gridded data was a constant 34.17 C/KM across the map.

NUCAPS forecast for ML CAPE was slightly less than what SPC mesoanalysis had at the same time of 20z.

NUCAPS ML CINH was higher than SPC Mesanalysis for 20z, with some parts of the CWA having almost 90j/kg of CINH south of Liberal, KS.

The 700-500mb lapse rates matched well with SPC meosanalysis for 20z.

OCTANE

OCTANE showed the cumulus developing along the dry line and warm front well. Can also distinguish which clouds are becoming taller.

OCTANE highlighted where convection was taller, and Lightning Cast started to show probabilities for those same updrafts.

ProbHail

Noticed what could be an above anvil cirrus plume with the storm in question. Prob Hail only had a 35% chance for severe hail at the time.

Prob Tor

Noticed the Prob Tor jumped up depending on what cells it was encompassing. Took three screen shots to denote the trend. Seemed reasonable for it to increase since the end cell was ingesting the dry line at the time the probabilities increased.

-Rainman

BMX Severe Thunderstorms

Posted in DSS, LightningCast, OCTANE Speed Sandwich, PHSnMWnABI, ProbSevere, SPG2023 on June 14, 2023 by Kevin Thiel.

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

PHS Reflectivity Forecast Helping Out with DSS

Posted in DSS, LightningCast, PHSnMWnABI, ProbSevere, SPG2023 on June 14, 2023 by Kevin Thiel.

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

Day 3 Review of Products & Operational Applications

Posted in OCTANE Speed Sandwich, PHSnMWnABI, ProbSevere, SPG2023 on June 14, 2023 by Kevin Thiel.

I took on the warning forecaster role during the operational period today. A supercell was underway at the start of the period, so I began by issuing a Severe Thunderstorm Warning. ProbSevere was (unsurprisingly) indicating a slam dunk for severe wind and large hail (Figure 1) but I noticed when sampling the ProbSevere data that MESH was slow to pick up on just how large the hail was with this storm. A broadcast meteorologist passed along a report of 5-inch hail at 2000z, but MESH did not indicate 4+ inch hail until 2020z.

Figure 1

I also noticed that PHS composite reflectivity was much too slow with the progression of convection across the SHV CWA. Below are a screenshot of PHS progged composite reflectivity at 21z and a screenshot of the radar 0.3 degree reflectivity at 21z. PHS expected the supercell of interest to still be located over the northeast portion of SHV (Figure 2) while in reality the supercell was about to exit the easternmost fringes of the CWA (Figure 3).

Figure 2

Figure 3

Once the aforementioned supercell exited the SHV CWA, we pivoted to the LZK CWA to monitor the ongoing convection there. I decided to interrogate the OCTANE products because I hadn’t looked at much satellite imagery thus far.

OCTANE was especially useful in two ways today:

OCTANE Speed indicated a storm split underway as two speed maxima can be seen in the red-orange hues (Figure 4, top left panel)
I tweaked the AWIPS colormap for OCTANE Direction to better depict the storm-top divergence occurring (Figure 4, top right panel)

Figure 4

– Vort Max

BMX Warning Met (West Sector) on June 14, 2023

Posted in ProbSevere, SPG2023 on June 14, 2023 by Kevin Thiel.

Our group role played as BMX during an anomalously conducive environment for severe weather consisting of very high instability and very high shear. My position was warning met, sectorized for the western half of the CWA.

ProbSevere helped considerably in triaging which storms deserved attention, and which storms were trending in such a way that warranted a warning decision and/or adjustment. A combination of several supercells that would merge with other cells and evolve into clusters and bowing quasi-linear structures made it difficult to have a comfortable handle on storm behavior and associated hazards. This was compounded by the fact that radar data from the favored radar site, KBMX, was dropping out at times. While other datasets were referenced (satellite, surface observations, storm reports, objective analysis, etc.), ProbSevere felt like it gave the biggest helping hand in warning decisions during this complex scenario.

Looking in the southwest portion of the CWA around 20:30 – 22:00 UTC, ProbSevere signaled the diminishing probabilities associated with a bowing segment that earlier resulted in an 82 mph wind gust within eastern MS as convection was decaying rapidly. This helped grow confidence in holding off on a warning as it entered BMX’s CWA.

ProbSevere also pointed at a cluster of storms increasing in potential for severe hazards. This was helpful given the noisy velocity data, higher than desired sample height (closest radar sampled ~5-8kft), and likely complications regarding wind vectors having some orthogonal component to the radar radial. Essentially, ProbSevere provided clarity and continuity in a noisy radar situation increasing confidence in storm behavior.

Having discussion with a developer, I expressed how useful it was to not only have a time series to view trends in overall probabilities of severe hazards, as well as of each hazard (i.e. hail, wind, tornado), but also time series of the data that drives the probabilities like those offered by CIMSS.

The above time series corresponds to the cluster of storms in southwest BMX around 20:30 – 22:00 UTC (link). Notice in the time series the local minima in probabilities within ProbSevere v3 around 21:00 UTC (~47%) followed by a notable increase in probabilities, exceeding 80% around 20 minutes later. This trend in local minima followed by increasing probabilities was more obvious than ProbSevere v2. Looking at the individual inputs, this was likely driven by an increase in things like Azimuthal Shear, VIL, MESH, Lightning attributes, along with other environmental attributes.

– 0SMBLSN

6/14/23 HWT – SHV

Posted in LightningCast, NUCAPS, OCTANE Speed Sandwich, PHSnMWnABI, ProbSevere, SPG2023 on June 14, 2023 by Kevin Thiel.

Operational window encompassed ongoing severe storms at the start of the period which moved eastward out of the CWA by mid afternoon. The resultant outflow boundary / cold front intersection to the west of the CWA become the focus regions for potential for renewed storm development.

NUCAPS 6/14/23 19z sounding south of the outflow boundary of interest compared to nearby surface observation showed a large discrepancy in observed surface conditions (90/72 at nearby ASOS). This raises considerable questions on how these soundings are to be best utilized in operations.

OCTANE was useful in monitoring the attempted updrafts along the outflow boundary. It seems to show updraft growth more clearly than the day cloud phase product. I would like to see these data incorporated into the LightningCast model as this product is also very good at highlighting potential areas for CI.

OCTANE output was also viewed in a region of a splitting supercell across western AR. Good conversation with developers on further development of the wind retrievals with observational data constructed hodographs being an operational request.

Utilized LightningCast to highlight the region of concern for new storm development. The storms did develop but it was a more gradual evolution. The highlighted region did verify as the region of development.

ProbSevere did a great job as a safety net for radar warning operations. The element trend window is a helpful addition. Talked with the developer on potential marking times along the time series where the element changes ID or grows in area to show when ProbSevere has merged or separated elements as this impacts resultant probabilities.

PHS model output from the 16z run was viewed online and compared to the corresponding HRRR. At the time of the exercise conclusion its solution had verified better on composite reflectivity than did the HRRR. A product in AWIPS highlighted regions where the fusion data is different than a zero hour model output would be beneficial for situational awareness and potentially for model output utilization.

– jbm

Probsevere and Octane

Posted in OCTANE Speed Sandwich, ProbSevere, SPG2023 on June 14, 2023 by Kevin Thiel.

Widespread severe storms have been ongoing over portions of the southeast CONUS nearly all afternoon. ProbTor was doing a decent job with picking up on a couplet in Montgomery county Alabama around 1950Z. Overall it seemed that ProbTor V3 was giving higher tornado probabilities than V2. It was noted that V3 is based off of the HRRR whereas V2 is based off of the RAP. So that was rather interesting to me that the HRRR was potentially picking up on better areas of rotation.

Image of ProbSevere with ProbTor in the bottom left

Loop of tight couplet that ProbSevere V3 was picking up on

The other really interesting feature I noticed on the part of Octane. The Octane vertical divergence fields which is noted by a sharp gradient of blue in the coloring. This was occurring around the same times as cooling cloud tops that were seen on IR imagery. This also seemed to be a precursor to when storms began to intensify on radar. Along with that intensification was when a better couplet began appearing on radar and an increase in ProbTor V3. Overall I thought that those three correlations were rather neat to see in real time. If this correlation does continue to show up then this has the potential to be another important feature of the Octane product.

Loop of Probsevere with intensifying cluster of storms

Still image of Octane showing the “Blue” Divergence aloft features

Loop of cooling cloud tops via IR