Category: ProbSevere

Can PHS Improve Mesoanalysis and Near Term Convective Forecasts?

Posted in DSS, LightningCast, PHSnMWnABI, ProbSevere, SPG2022 on by Kevin Thiel.

A large portion of the MKX CWA was included in a MDT severe risk, so by the start of the operational period, we had to assess the evolving severe threat spreading in from the west. Meanwhile, our DSS event was the Madison Jazz Festival, which entailed a focus specifically on south central Wisconsin. The PHS CAPE forecast appeared to be a noteworthy improvement from the CAPE fields on the SPC Mesoanalysis, along with the short-term forecast on that page.

Below are the 18z through 20z plots of MUCAPE, MUCIN and effective bulk shear from the SPC Mesoanalysis page.

Compare the above images with 4000 J/kg of uncapped MUCAPE to the PHS MUCAPE initialization at 18z and 2-hour forecasts (19z and 20z) below.

As you can see, while the SPC mesoanalysis was indicating 4,000 J/kg of uncapped MUCAPE, the PHS forecast showed CAPE decreasing across central and south central Wisconsin. This was an important and helpful piece of information for our DSS content for the Madison Jazz Festival.

The Day Cloud Phase RGB images below back up the PHS forecast vs the SPC mesoanalysis, as relatively flat Cu field over our area of interest actually dissipated between 20z and 22z.

Based on the PHS forecast combined with satellite analysis, we were able to focus the convective threat for the Madison area toward 6PM and onward, tied to the stronger forcing and better moisture arriving from the west where the ongoing convection resided closer to the cold front. It appears that the PHS sampling of moisture in the column applied to the near-term forecast strongly outperformed the SPC/RAP Mesoanalysis model background and OA algorithm.

Differences between the LightningCast (LC) CONUS and LC Mesos

Note below the CONUS scale (1st image) and Mesos (Meso Sector 2 on 6/15) had a different depiction of the lightning probability over northeast Iowa at 1911z 22Jun15. This was due to the time for a CONUS GOES-East scan to complete, vs. the much shorter time for a Meso sector, which in turn affects the LightningCast model. This is something to keep in mind when using the product.

ProbSevereV3 Trends for Severe Convection in Western/Southwestern Wisconsin

At 2106z, the ARX office had recently issued a Tornado Warning (2102z) for the northern cell with a high % on PSV3 and PTV3, per the noted superior calibration of the updated model vs. the V2. Could the PSV3 and PTV3 trend on this storm have assisted the radar operator in an increased lead time? As you can see below, starting at 2045z, there was a sharp upward trend in the ProbTor, to near 40% prior to 21z. At the least, this tool appears to be an excellent situational awareness tool, and may even be able to help lead time in some cases. It helped us in the MKX CWA regarding downstream warning issuances. In the event of an unexpected radar outage in a sparse radar coverage area, environmental analysis plus satellite interrogation with the utility of PSv3 could support successful radar warning ops in a less than ideal scenario.

– Hurricane84

Situational Awareness and Lead Time with LightningCast and ProbSevere/Tor

Posted in DSS, LightningCast, PHSnMWnABI, ProbSevere, SPG2022 on by Kevin Thiel.

Today’s experience landed us in MKX monitoring convective development potential across the western portion of the CWA, with a line of storms ultimately moving in from the west, and some risk of discrete cells persisting even after we ceased the experiment.

I took the opportunity today to set up procedures overlaying PHSnABI indices (CAPE) with satellite imagery (e.g. Day/Cloud Phase or Viz), to see how well it corresponded with convective development. Unfortunately I didn’t grab a screenshot, but it was a nifty display that I hope to use again. PHSnABI suggested that CAPE in some areas of the CWA was not as high as the SPC mesoanalysis or RAP suggested. We tried to investigate this using a combination of NUCAPS and model soundings and RAOB, but couldn’t figure out a reason for the CAPE depression before incoming storms grabbed our attention. Notably, the indices derived only from GOES agreed with PHSnABI about this depression, though we couldn’t figure out if it was correct. It seems likely the GOES ABI was driving the PHSnABI result.

My main takeaway the rest of today is how useful ProbSever, ProbTor, and LightningCast can be with approaching/developing convection.

LightningCast, combined with GLM data, was useful for IDSS imagery to depict position and potential of lightning (example DSS slide using these graphics provided below).  Storms never made it to our decision point prior to leaving the experiment, but lightning threat was usefully communicated to the simulated JazzFest event.

As convection developed, we also practiced relying on probSevere and probTor for lead time in anticipating warnings. The following shows an example where the probTor trends corresponded well with ARX’s actual decision to issue a tornado warning.

SImilarly, intensification of the convective line appeared to be well detected. In fact, depending on what threshold of the probSevere parameters is relied on (probably depends on environment and other factors), the escalating value could have given useful lead time for a severe issuance decision.

Although the main mode appeared to be a line of convection, there were positions along the line where tornado risk seemed to increase (evidenced by radar velocity). It was reassuring to see probTor pick up on the gradually increasing risk of tornadoes as well.

And one final note… lightningCast is fairly impressive in how it produces calibrated estimates of lightning occurrence using only a single time step of satellite imagery (though it uses several bands of the ABI). Naturally lightningCast has difficulty where a developing tower is obscured by an anvil overhead, as we saw in this example. But it was neat to see lightningCast immediately respond with a broader swath of high lightning probabilities the very first time that a tower poked above the anvil that previously obscured it.  The fact that it was hidden probably means lightning could have been occurring below the anvil with lower than ideal lightningCast probabilities (though non-zero, to its credit), but it was neat to see the immediate adjustment to the probability contours with new imagery.

– Buzz Lightyear

ProbSvr V3 ProbTor

Posted in ProbSevere, SPG2022 on by Kevin Thiel.

The LaCrosse office was busy today with multiple storms that exhibited rotation. ProbSvr/ProbTor was helpful in the case of situational awareness and triaging the storms. Below is an example of a case where ProbTor decreased significantly over a period of a few minutes. In this case, ProTor slowly increases over a 10-15 minutes as the storm exhibits some rotation. A lightning jump was also noted with the peak probabilities of ProbTor around 40% at 2016 UTC. All of the parameters decrease significantly over a 5-6 minute period of time by 2022 UTC (images of reflectivity and velocity are included below). The lightning decreases dramatically as seen in the chart below as does the azimuthal shear (based on the chart and 0.5 velocity). A severe was already out for this storm and ProbSvr remained high throughout much of the lifecycle of the storm. As the warning forecaster, it was nice to see the confirmation of the lower probabilities. A severe warning was already out and the storm was covered for those threats. It was nice to have the confirmation from ProbTor to turn my attention to other storms that may need a warning or be on the verge of warning issuance.

2016 UTC 0.5 Reflectivity

2016 UTC 0.5 Velocity

2022 UTC 0.5 Reflectivity

2022 UTC 0.5 Velocity.

– Marty McFly

Storm Movement and Severity at TAE

Posted in LightningCast, NUCAPS, PHSnMWnABI, ProbSevere, SPG2022 on by Kevin Thiel.

Down in Tallahassee, there are two boundary layers where storms are initiating or ongoing.  There is a lingering MCS that moved down from the Midwest overnight and a Sea Breeze. You can see the CAPE gradients along the both boundaries and how that progresses forward in time with both the boundaries interacting with one another.

17Z

18Z

19Z

This tracks very well when you overlay the visible satellite imagery with the PHS images as you can see the cumulus field along the CAPE gradient. This gives a good visualization of where storms are initiating along the Sea Breeze and the strongest storm movement along the MCS.
As these two boundaries move closer together they will be moving into a more favorable low level environment. It would be nice to have the Polar Orbiting Satellite NUCAPS sounding data available. This way we could verify lapse rates and what Prob Severe is giving us. While an upper level ridge is in place over the southern CONUS what sounding information we did have early on in the forecast period was very helpful as outside of the storm environment skies were clear. I was able to grab some gridded NUCAPS data that shows the diurnal destabilization of the low levels from 18Z. Now that it is 21Z, that data isn’t as helpful in either a warning or pre convective event because things could have changed drastically in the 3 hrs since the last Polar Orbiter moved through.
After overlaying Prob Severe with the PHS CAPE and Visible Satellite imagery, you can see your strongest storms along the CAPE gradient which tracks well. However, there are differences between Prob Severe Version 2 and Version 3.
A great example of the differences between PSv3 and PSv2 is with one of the strongest storms of the day for the Tallahassee CWA. Version 2 seems to try to highlight a hail threat at 48% while Version 3 has prob severe hail at 6%.  It seems that Version 2 is overestimating the Hail threat for this area. Especially given the subpar mid level lapse rates at 5 C/km or less, storm motion of around 5 kts or less and the upper level subsidence. The storm environment just is not conducive to produce quarter sized or larger hail.
– Cirrus Fields

Differences in Prob Severe v2 vs v3

Posted in PHSnMWnABI, ProbSevere, SPG2022 on by Kevin Thiel.

Some significant differences in probabilities for v2 vs v3. Noted on this storm in northern New Mexico. Not quite sure the reasoning for this large discrepancy.

Storm ID: 346478 in Northern New Mexico June 9, 2022.

Notable Differences in ProbSevere in the time series.

Storms going up right along forecasted boundary from PHS CAPE

Storms developing in Prowers County in southeastern Colorado.

– David Spritz

ProbWind and ProbTor Performance

Posted in PHSnMWnABI, ProbSevere, SPG2022 on by Kevin Thiel.

ProbSevere May Have Caught a Missed Severe Wind Event

The ProbSevere v3 drew attention to a cell near Bloomington, IN on the afternoon of June 8th. Specifically it was drawing attention to the wind threat with a high ProbWind percentage reaching 50% to 60%. However, radar interrogation was only initially yielding velocity of 30-40kts on the inbound side of the cell, sub-severe but certainly SPS worthy. There were a few scans yielding up to 45kts as well. So initially there was a little wondering why there was higher ProbWind percentages. Quick realization of the storm track being perpendicular to the radar beam could explain the lower velocity signatures here. Knowing this, ProbSevere and its ProbWind portion was drawing attention to a scenario that otherwise may have been missed if only looking at velocity data and not realizing the storm track relative to the radar beam.

ProbSevere v3 of “Bloomington Cell”

STP went up at 20Z coincident with new SPC mesoanalysis.

ProbSevere v3 readouts of “Bloomington Cell” at 1940Z

KIND Velocity signature of the “Bloomington Cell” @ 1941Z

ProbTOR Missed a Likely Tornado Event – First Example

At 2005Z the KIND radar showed a solid and persistent tornado signature on a cell near Shelbyville, IN. To go along with this in the overall outlook for the day was an MD highlighting the tornado risk and a Tornado Watch that included the southern half of IN. However, the ProbTor parameter did not tick up in response to the tornado signature on radar. The observed uptick at 2000Z, coincided with the intake of the new SPC mesoanalysis data that ProbSevere v3 ingests as described by the product’s providers. Even still, this uptick was small only amounting to a ~5% increase.
ProbTor only peaking at ~15%
 
The second image below may explain some of this away, showing that two individual cells were coalesced into a single storm identified by ProbSevere v3. These two cells were relatively close to each other, so much so that they did appear as one on MRMS data. However, the third image of SRM and V show the tornado signature associated with the northern cell. This combination, with the southern cell having a much lower tornado potential and being ingested by the northern cell may have played a role in lowering the overall ProbTor percentage.
ProbSevere v3 showing that cell being grouped with another to its south, could this have inhibited the increase in ProbTor?
 
SRM (left) and V (right) showing the TOR signature with this cell.
 
Multiple LSRs for wind damage were observed from this event, with a “tornado possible” added to the remarks.

The PHS SigTOR parameter also further supported the tornado risk during the 2000Z hour. The image below shows the PHS SigTOR parameter at 2000Z with ProbTOR percentages overlaid on top. The cell which produced the likely tornado east of Shelbyville, IN is sampled in the image with the ProbTOR only at 9%.

PHS SigTOR parameter pegging the area that produced a TOR. The cell highlighted with ProbTor readout produced the Tornado Warning referenced earlier.

ProbTOR Missed a Likely Tornado Event – Second Example

From roughly 2130Z to 2200Z, a supercell passing west to east through west-central OH showed a persistent meso signature as seen from the KILN radar in Wilmington, OH. This signature eventually depicted gate-to-gate shear and tornado warnings were issued for this cell. The same ongoing Tornado Watch from the prior example also covered this same region. Image three also shows the PHS SigTOR Parameter showing higher tornado potential in the region, although not directly overlaid with where the Tipp City cell was. However, the ProbTor parameter of ProbSevere v3 did not show a corresponding jump in tornado potential. Unlike the prior example which showed the ProbSevere v3 grabbing a second much weaker cell with the tornado producing cell, this was a discrete cell with no merger occurring.

Highlighted in the Tornado Warning issued by the Wilmington, OH office, was a tornado debris signature. The KDAY metar located just south of Tipp City also included “tornado” in the remarks signature, shown in image four.

KILN SRM and V showing tornado signature near Tipp City.

Time series of ProbSevere with persistently low ProbTor for tornado warned storm west of Tipp City.

PHS SigTOR Parameter highlighting higher tornado potential in the region with overlaid ProbSevere – ProbTor percentage for tornado warned cell by Tipp City.

The KDAY metar showed “tornado” in the remarks section for the cell passing through Tipp City.

– Trip

PHS, NUCAPS, Optical Flow, Prob Severe Fun

Posted in NUCAPS, Optical Flow Winds, PHSnMWnABI, ProbSevere, SPG2022 on by Kevin Thiel.

PHS and NUCAPS

Today worked out well with PHS and NUCAPS. NUCAPS data came in shortly after opening up our work stations. We decided to compare the output between PHS, NUCAPS, and SPC mesoscale analysis. The variable that we chose was surface CAPE.
They all seemed to match up well highlighting the higher instability to the south that would gradually  push north this afternoon. It was definitely a confidence builder in each product to see the agreement between them.

Optical Flow

We also decided to compare the Optical Flow winds to SPC mesoscale analysis. Once storms developed a bit more, you can pick out a slight directional divergence signal in the flow. Looking at SPC mesoscale analysis there is also directional divergence is present in the mesoscale analysis.
Overall looking at these two examples, using these tools together can be a way to verify information and give the meteorologist more confidence (or less) in a specific product to help them with forecasts, DSS, and warning operations.

Prob Severe

We were able to compare Prob Severe V3 to the time when there was an observed report and when the new tornado warning came with a radar observed tag due to a CC drop. The first image is when there was a twitter report of a tornado around 2142Z in SE Darke county.

At 2144Z the Prob Severe V2 tornado jumped to 21% while V3 only went to 6%.

The next image below is when the radar confirmed tornado was reported.
– Noctilucent & Matador

ILN HWT Blog Day 3

Posted in GLM, LightningCast, NUCAPS, PHSnMWnABI, ProbSevere, SPG2022 on by Kevin Thiel.

NUCAPS

Did finally get a chance to check out NUCAPS for today’s case as the timing and location of the data was more compatible. It was good info ahead of the storms as it showed the low LCL values (mainly noticed in the modified soundings), below 1000 ft which is what you want to see for potential tornadoes. Overall, liked getting to dig into the NUCAP soundings, but given the finicky timing and data quality, it’s not something I could use on a regular basis for warning operations. Would be better suited for short term forecasting or possibly as the mesoanalyst.

GLM & LightningCast

For GLM, I set the max value at 130. I originally set it to 65 as I had been using in the high plains the past few days, but for these midwest storms it seemed too sensitive. 130 was a good value for today, likely because of the larger and more numerous storms than I dealt with today versus the previous days.
Also tried out the parallax corrected LightningCast today. Liked that it gave a more accurate location when using it for a specific location such as today’s DSS event. While it was made to pair with radar, it was still useful when using it with satellite products – just had to take a few seconds to make the mental adjustments at the beginning.

PHS

Prior to entering the ILN CWA, the PHS STP showed an area of high STP values in and near Rush County, Indiana. The actual IND office did issue a tor warning for this area at 4 PM ET.
Over time, I did notice that for STP, really just the current hour and the next couple of hours were useful. Jumping to 3 or 4 hours ahead it seemed that the data was missing for areas I expected to see higher values. Once the next run came in and I went back and looked, the data was much better. For an example below, there was a vast difference for 21Z between the 18Z run and the 20Z run where the 18Z run for that time did not seem realistic but the 20Z run was more what I expected to see.
08.18 run for 21Z

ProbSevere

After talking with one of the ProbSevere people, was able to learn that the threshold for ProbTor is lower than that for Wind or Hail. For training purposes, it would be good to include this information to give a mental threshold for forecasters, such as an ongoing tornado would likely see a max of around 60% for ProbTor. It makes sense that the probs would be lower for tors just as they are for SPC outlooks where the tor percentages are also lower than that for wind or hail.
– Matador

Northeast Colorado Supercells

Posted in GLM, LightningCast, NUCAPS, PHSnMWnABI, ProbSevere, SPG2022 on by Kevin Thiel.

Nowcasting Supercell storm entering CWA: The loop of instability and SigTor highlight the southeast/south central CWA east of Colorado Spring, ahead of an already ongoing storm. North of this storm an environment of favorable instability exists up to about the latitude of Denver, with a significant drop off to the north.

When it comes to high and northern plains – parallax becomes an issue. In this case lighting was occurring just on the other side of the border with the CWA, so here are the two LightningCasts (with/without parallax correction) for comparison:

ProbSevere v3 increases correlating to entering a favorable environment

PHI localized CAPE corridor

New area of MFA suggesting spitting storm with new updraft core of the established cell. (1950 UTC)

Storm cell split denoted by MFA with two distinct areas of MFA in upper right panel. (2000 UTC)

Focused on the cell east of Denver – this cell and subsequent others that developed are in the favorable area of instability. Just to the north of Boulder we spotted a few cells that attempted to develop, however in the lower instability environment movement off the higher terrain resulted in these cells falling apart. Through the rest of the afternoon this area remained convection free.

Sig Tor blip. A SRVE like feature was observed but at this time convergence associated with this feature wasn’t favorably located under the updraft.

Cell developing east of Denver, noted by the MFA  in the upper right panel. (2020 UTC)

Cell rapidly develops in an area of localized higher instability denoted by the PHS values discussed earlier on.(2034 UTC)

The LightningCast has identified the left turning nature of the storm(s) east of Denver

An interesting note was comparing the differences between GOES East (left panel) and GOES West (right panel). These subtle differences can  be effective in analyzing the strengthening of a thunderstorm.

In the middle of METWATCH – NUCAPS became available (about 1 hour latency). The sounding below is a modified NUCAPS profile, depicting the environment in which our storms developed. Storm mode was supercellular with frequent spitting of cells.

-Mr. Bean

-2%hatched

CYS HWT BLOG Day 2

Posted in GLM, LightningCast, PHSnMWnABI, ProbSevere, SPG2022 on by Kevin Thiel.

LightningCast for storm approaching Scottsbluff

First instance of 50% contour 1831 Z
The lightning cast did build before backing off for a few frames, dropping below 50%, but jumps back up above at 1851 Z. From then until the first flashes of lightning, the probabilities continued to increase.
First instance of 75% contour 1906 Z
GLM denotes flash 1915 Z
So, lightningcast was able to indicate well ahead of time that we needed to keep an eye on that storm for lightning production as it approached the city.

GraphiCasts with ProbSevere and PHS

For today’s GraphiCast, decided to overlay ProbSevere V3 over visible satellite data to indicate the location of the stronger storms amongst all the clouds. The concern with using it for public graphics is whether the public will understand it. Went with a brief description that it indicates stronger storms for today, but would be curious to see how others message what probsevere means and then how the public may respond to it. I do like how it clearly shows the cells to watch out for.
To determine the time that storms would continue through, I only used the hourly PHS data which dropped off at 23Z. The images below show 20Z PHS vs 23Z. This timing for storms ending for the CYS CWA worked out well as the strong to severe storms exited the CWA by 2256Z with only a few isolated showers remaining for a short time afterwards.
20Z:
23Z: 
– Matador