Category: PHSnMWnABI

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

Day Cloud Phase Boundary noted on PHS CAPE forecast

Posted in PHSnMWnABI, SPG2022 on by Kevin Thiel.

A notable boundary seen over the southern CWA of LBF on GOES 16 Day Cloud Phase Distinction is also evident in the PHS CAPE forecast for 19-21Z over the same area. The evolution of this boundary could be key in determining future convective development later this afternoon/evening.

Day Cloud Phase Distinction 20Z

SFC CAPE PHS for 21Z forecast, top left panel.

Meteorologist David Spritz

PHS CAPE Gradient Use in Mesoanalysis

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

The PHS Sfc CAPE procedure was helpful in diagnosing the mesoscale environment. In particular, the depiction of CAPE gradients matched well with where the Day-Cloud-Phase Distinction showed where these boundaries lay as could be construed from the cumulus field.

The PHS Sfc CAPE depicted this surface boundary migrating southward through the central NE through the 21Z-00Z time frame. Observed cells moving left (east) off the boundary into a more stable environment as resolved by the PHS Sfc CAPE field all decreased in intensity and saw their convective updrafts weaken.

Seeing this after the first hour raised forecast confidence in the forecast thinking of today’s severe weather potential and was shared in a graphicast for this test case scenario.

PHS-CAPE-STP-PSv3 Procedure from 6/6 @ 20Z to 6/7 @ 01Z
Day-Cloud-Phase Distinction RGB at 20:06Z
– Trip

PHS CAPE Uses

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

Interesting item to note when analyzing PHS forecast CAPE over western South Dakota. This may be terrain induced, but the sharp gradient of CAPE values noted up and and down the western border of South Dakota.  This correlated fairly well with a strong storm or two in the western UNR CWA.

PHS CAPE sharpening gradient in the top left panel.

Wide view of storms in the area using PSv3.

Close in view of several storms on or near that boundary.

David Spritz

LBF Day 1 HWT Blog

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

Day 1

Acting as LBF
This image was used in a graphicast to which we then added areas of concern over the next several hours and storm direction.

PHS, ProbSevere

Enjoyed using PHS, especially getting the heads up at the beginning of today’s session to watch along the value gradients for stronger storms. That tip fit the bill for what we were seeing today and higher prob severe seemed to follow the gradient as well. I have not had much practice with version 2 of probsevere, so I cannot not really compare it to version 3. However, I did find version 3 useful today, especially with all the readout information breaking down the threat level for each type of severe hazard as well as mesh values.
2041 UTC
2141 UTC

LightningCast

From an IDSS standpoint, the Lightningcast is nice to use to give a heads up and see trends in lightning.
For GLM, I really liked decreasing the max value. Seems to work well in these smaller cells to highlight which cells to watch for.
– Matador

Greenville SC Observations

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

Synopsis: A deep upper low tracked slowly northeastward across Missouri today. The main cold front associated with this low moved across the Greenville, SC region. Along and ahead of the front, widespread showers and thunderstorms continued over western South Carolina for most of the afternoon and evening hours.

Our DSS messaging was for Softball Tournament Games located at Clemson University.

SPC Convective Outlook: Slight risk of thunderstorms over extreme northwestern SC, with marginal risk elsewhere.

Primary threat was wind flash flooding and wind with a chance of hail and a possible tornado.

Scattered showers and thunderstorms tracking northward across the forecast area.

IR imagery overlaid with lightning data.

Greenville ACARS sounding taken in 1910Z.

NUCAPS Sounding nearby Greenville.

Another NUCAPS Sounding nearby Greenville.

Mesoanalysis – Surface CAPE values ranging from 500 to 1,000 J/kg.

PHS showing similar instability parameters.

Watches/Warnings products issued throughout the day by WFO Greenville.

ProbSevere3: Low probability of severe weather, but sufficient enough for storm warning operations and convective maintenance situational awareness.

GLM Basic – Helped with operations as well as DSS.

GLM

GLM

Lightning Cast overlaid with satellite was helpful for enough lead time and confidence.

Lightning Cast overlaid with radar.

Lightning Cast overlaid with satellite.

Radar overlaid with Polygon Warnings issued throughout the day.

DSS update: A Flash Flood Warning was issued for Northwest South Carolina near Anderson county and remained in effect until 9:00 PM EDT.

Latest update on ProbSevere3 and tracking any nearby storms.

Latest update on GLM.

SPC Mesoscale Discussion. Thunderstorms intensified across northeast GA into upstate SC, near and south of a warm front that slowly lifted northward toward western NC.

Storm velocity showing gate-to-gate or small rotational couplets near Ware Shoals and Spartanburg.

Vortex Power

Monitoring convection in Louisville, KY CWA

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

After an initial batch of rain and embedded storms that are continuing to move across the easernt half of the LMK forecast area, there is a narrow corridor of partial clearing, behind which another band of convection is forming. It is somewhat apparent in the PHS fields (both CAPE and  STP) that there is better destabilization across western portions of the CWA under partial clearing.

Top left: PHS modeled CAPE at 20z. Top right: PHS moceled STP. Bottom left: GOES CAPE 20Z. Bottom right: GOES LI 20Z.

By 20Z, had issued a significant weather advisory for a cell in the northwestern and portion of the forecast area. ProbSevere began spiking, and GLM FED picked up while MFW decreased, indicating strengthening updrafts. Within the next 20 minutes, cells in the southeastern forecast area began exhibiting similar behavior, and I issued another advisory for those.

0.5 degree base reflectivity at 20Z overlaid with probSevere

4 panel GLM over IR at 20Z

ProbSevere was indicating more of a wind threat, and a secondary threat from hail with MESH up to a half an inch. Why did I not go severe? Base velocity was decent, up to 30kts on the 0.5deg tilt. Base reflectivity up to 50dbz was only apparent up through around 18kft. NUCAPS soundings from earlier in the day, courtesy of metop C, indicated a freezing level around 11kft, so I would believe small hail.

Mid morning NUCAPS sounding over central

By 2130Z, lingering activity is pretty much stratiform with just some embedded storms. Examining Day Cloud Phase Distinction (DCPD), and instability fields courtesy of PHS, we might figure out why. DCPD is indicating thick cloud cover over much of the eastern two thirds of the CWA. Meanwhile, CAPE and STP remain maximized closer to the western CWA boundary, under the area of clearing skies.

21Z DCPD

PHS 21Z modeled CAPE, STP (top) and GOES CAPE, LI (bottom)

19Z NUCAPS soundings (from the NOAA20 overpass) were largely unavailable over the CWA due to cloud cover.

A  Modified NUCAPS sounding out of SW KY indicates quite a bit of dry air at the midlevels, but also decent lapse rates and as much as 1500 to 2000j/kg of CAPE

For comparison, the regular, non-modified NUCAP profile at the same location was far less bullish with the instability.

A look at base reflectivity at 2130 indicates that trend towards mainly stratiform rain with embedded storms. In the eastern CWA, ProbSevere is still pretty enthusiastic about an exiting line of convection with probability ranging as high as 20 to 30%  for wind and even up to 20% for tornadoes. An examination of base velocity did indicate some inflow notches ahead of the line.

Base reflectivity with probSevere around 2130Z

However, with GLM FED remaining steady, and MFA on the larger side, the confidence in any real severe weather is waning.

– PoppyTheSmooch

ILX Ramblings

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

A comparison of NUCAPS at 19Z with observed/analysis products from SPC showed good comparison for both modified and unmodified data. Below shows the unmodified NUCAPS sounding that was “green” over the north-central portion of the ILX CWA. The MLCAPE was around 500 J/kg, with DCAPE around 690 J/kg, freezing levels just below 10,000 feet, and PW’s around 1.1 inches.

A modified NUCAPS sounding for the same location showed an uptick in MLCAPE to around 600 J/kg, along with similar PW’s, DCAPE and freezing level.

A comparison with SPC mesoanalysis at 20Z showed very comparable PW values, between 1.1 to 1.2 inches over north-central IL, and freezing levels between 10 to 11 kft. As for MLCAPE, it appeared that for both modified and unmodified NUCAPS, the observed was higher than NUCAPS, around 1000-1500 J/kg, perhaps not having a high enough surface dewpoint. As for 850 mb temperatures, they were comparable to those observed, in the 12-14 degC range. DCAPE was also comparable in NUCAPS with what the SPC mesoanalysis page was showing, between 600-700 J/kg.

With regards to lightningCAST, ProbSevere, and GLM, around 1932Z, once again the LightningCast was showing good lead time for areas downstream of storms. The main cell at this time I was watching was in the southeast Part of our CWA, which had a nice contour of 75% to the north and east of that cell extending well north of the storm core.

At 20Z, the Optical Flow divergence field appeared to match up well with observed convection at this time. It thus showed quite well with the shear field.

ProbSevere’s time series graph continues to show added value, allowing the forecaster to see the trend in a storm’s severity and probability of severe potential. This image was at 20:40Z.

Around 21Z, I noticed a jump in GLM FED for the area of storms in the northwest part of the CWA. Alongside this, the GLM TOE also increased, along with a decrease in MFA with the same storm cell. This area corresponded with increased flash rates in the EarthNetworks. I modified the GLM FED scale to 20-25 as a maximum to see the activity better, as well as lowering TOE to 50 as a maximum.

Around 22Z, the GLM TOE showed a good correlation with the 3 strongest storms based on dBZ and ProbSevere, one to the north, and two in the far southeast, bordering Indiana. For this display of TOE, I lowered the contours to a max of 50, which seemed to work well.

Around 22:12Z, the LightningCast showed an uptick in probabilities of 75% north of a cell that was starting to show towering CU on the day cloud phase. This was before GLM and ground-based radar showed uptick in lightning activity.

Are the edges of LightningCast contours related to the detection of GLM? See below image…The contours do not close off.

Snowfan