Author: Kevin Thiel

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

GLM – GOES-16 vs GOES-17

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

Differences between the GLM Flash Extent Density products from GOES-16 and GOES-17 were quite stark for convection occurring over the Cheyenne, WY CWA on June 7th.

The two animated gifs below highlight the difference in lead times for an observed uptick in lightning activity within a cell near Scottsbluff, NE. The first animation is of GOES-17 showing the uptick in lightning activity beginning at 1939Z. The second animation from GOES-16 shows the same uptick in lightning activity, except beginning ~5mins later at 1945Z. Interestingly enough, both satellite perspectives show the downtrend in lightning activity occurring at 1950Z.

GOES-17 GLM FED Scottsbluff 5-min improved lead time.

GOES-16 GLM FED Scottsbluff

The next three examples show sharp contrasting GLM FED intensities between GOES-17 and GOES-16 through the afternoon of June 7th. This first example focuses on a warned supercell just southeast of Scottsbluff, NE at 2022Z. The first image shows FED from GOES-17 showing much higher FED numbers, while the second image shows FED from GOES-16 not indicating any increased lightning activity. The third image shows a 4-panel layout of MRMS, MESH, VIL, and ProbSevere version 3 all supporting a supercell occurring. A subsequent report of 1.5” hail was observed from this warned storm.

The cause of this was shared from the investigators running the HWT this week, that GOES-17 had the better angle to see lightning activity in these supercells developing over the high plains of WY and NE. Whereas GOES-16’s perspective from further east had to punch through spreading anvils downstream of the main updraft that likely obscured the light emanating from the lightning, GOES-17 had a more side-on view of the updraft with less to no obscurations of light emanating from lightning occurring in the updraft. Unfortunately, GOES-17 CONUS view and the day’s mesosector from GOES-17 did not reach this far east and there are no satellite images displaying the different parallax views from GOES-16 and GOES-17.

GOES 17 GLM FED @ 2022Z “Scottsbluff Cell”

GOES 16 GLM FED @ 2022Z

MRMS – MESH – VIL – PROBSEVEREv3 @ 2022Z

1.5” hail report from this storm. Max MESH reached 2”.

The next two examples below each showcase three images each, a GOES-17 FED showing higher intensity lightning activity, a GOES-16 FED missing the higher intensity lightning activity, and a 4-panel layout showing MRMS, MESH, VIL, and ProbSevere version 3 highlighting the severe nature of the supercell.

An interesting follow-up to this in the future is to see how these two satellite GLM FED products compare in a low-storm motion environment where the spreading anvils at storm top flow in all directions. This could cause both satellites to have an obscured view of the convective updraft beneath, causing both to miss out on any increased lightning activity.

GOES-17 GLM FED @ 2016Z “Lance Creek Cell”

GOES-16 GLM FED @ 2016Z “Lance Creek Cell”

MRMS – MESH – VIL – PROBSEVEREv3 @ 2016Z

GOES-17 GLM FED @ 2026Z “Scottsbluff Cell”

GOES-16 GLM FED @ 2026Z “Scottsbluff Cell”

MRMS – MESH – VIL – PROBSEVEREv3 @ 2026Z “Scottsbluff Cell”

– Trip

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

NUCAPS uses in comparison between separate satellite passes

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

NUCAPS has been quite useful in comparison between previous passes. (Comparing the NOAA-20 modified and the Aqua), shows how an environment is changing to the south and southeast of the storm cell moving through Custer. We noticed a rapidly changing environment when compared to early afternoon convection. Sfc temperatures and mid level instability increased quite a bit as this storm moved off the higher terrain and into a more favorable mesoscale environment.

NOAA-20 Pass from approximately 19Z. On western SD/NE border.

Aqua Pass from approximately 2030Z. Same location. (On western SD/NE border.)

This increase in surface temperatures as the storm moves into a more favorable environment. Notable spike and jump in Hail core and probabilities.

A notable spike after 2130 for prob hail and prob severe.

-David Spritz

ProbSevere v3 and NUCAPS

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

When analyzing a thunderstorm developing over western South Dakota, a noticeable jump occurs near 20:25 – 20:30 UTC as seen on the ProbSevere Time Series. At this same time, there was a distinct uptick in lightning activity seen in the GLM 4 panel. This would correlate with a strengthening of the thunderstorm at this time. A modified NUCAPS sounding from around this time captured an environment favorable for further strengthening encompassed by steep mid level lapse rates and adequate instability. This thunderstorm was beginning to exhibit severe hail potential.

ProbSevere Time Series

GLM-16 4 panel

Modified NUCAPs sounding ~20 UTC

-2%hatched

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

Potential LightningCast limitations under convective debris

Posted in LightningCast, SPG2022 on by Kevin Thiel.

The first day of familiarization with the tools for the hazardous weather testbed and we were assigned the Louisville CWA to test a number of products on. The synopsis of the area’s weather features a line of convection moving in from the west with a Severe Thunderstorm Watch in place and several storms had already been warned on.

On the other side of the CWA, a few weaker cells had developed under a mix of sun and high clouds. It’s this convection across the eastern CWA that became the focus for today’s blog. We chose to target the LightningCast product because we noticed that although the -10C MRMS data would suggest lightning, the LightningCast data was actually much lower than anticipated (below 10 percent). Why was this the case?

After speaking with John Cintineo about this, and looking at the training that was provided for this testbed, it was surmised that this may be a case where convective debris or high clouds could mask the signal of weaker convection.

Eventually LightningCast did highlight this area with a lightning risk, but this case is relevant because if we are using this tool to aid in DSS to our partners, we must also identify some potential limitations.

Noctilucent/Mr. Bean

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