Author: Kevin Thiel

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

GLM and Minimum Flash Area

Posted in GLM, SPG2022 on by Kevin Thiel.

Lightning energy during the HWT was introduced in several different ways. Three of these were:

 

  1. Flash Extent Density
  2. Minimum Flash Area
  3. Total Optical Energy

 

For monitoring severe thunderstorms, Flash Extent Density seemed to be the most useful of the three.

However, all of the GLM products were what we focused on.

In order to obtain GLM lightning data on the grid or map, you had to obtain a Minimum Flash Area. It was interesting in the stratiform type storms that a wide area was displayed compared to the small area where the flash took place. In this case it was one cloud-to-ground lightning strike (CG).

This image is from the Bottom-Right panel (CG and Cloud Flashes):

This is the top-right panel (Minimum Flash Area):

This shows that one CG Flash can plot a large area on the Minimum Flash Area product. It seemed that this was necessary for other products to plot, such as the Flash Extent Density, but it may be a little bit of a distraction for the operational forecaster as it would seem to flash a bit (on and off if looping it) and for a much larger area than what was shown compared to the cloud Flash and CG plots.

– WeatherTed

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

Louisville KY WFO Observations During DSS

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

LightningCast

Immediately after coming online, there was the potential for heavy showers in my area of concern and a storm heading toward an established DSS Event. Initially, LightningCast showed a 50%-75% chance of lightning within the next hour, but this was monitored in successive frames as the trend continued downward.
This product gave me the situational awareness to immediately know that I should be interrogating a storm heading toward my DSS event without an in-depth analysis across multiple radar/satellite products. I continued to monitor the product as I got the rest of my AWIPS setup and I noticed the downward trend continued for my storm of concern. This simple display along with GLM flash data (on a 0-50 scale for this storm mode) gave me confidence in analyzing this as a low-end threat. This has an application in the operational shift change where a new forecaster can have two simple products loaded on a screen with rapid updates indicating that a DSS area is increasing or decreasing its likelihood of seeing lightning within the next hour. These two products in tandem are not only useful operationally, but as a base situational awareness tool.
Initial LightingCast/GLM view of the storm moving toward the DSS event area.
Visually the trend decreased after this initial probability. It would be very useful to have these plots available in AWIPS to view the increasing/decreasing probabilities associated with perceived storm growth and decay.
 
After the initial spike (which occurred as I was logging on), you can see that with no observed strikes and the probabilities staying constant, there was no initial concern.
The trend continued with a subsequent steady decrease in probability.
Another storm the south became the main concern with a Significant Weather Advisory (SPS) issued for its growth and subsequent wind threat. In this case, I think LightingCast is doing a good job at highlighting the advection and limiting the probabilities over my area based on its current (pictured) motion.
LightningCast and GLM plotted with a current storm motion and Time of Arrival tool to show that it is expected to miss the DSS event at this current time. However LightningCast did put the area in the 75% contour at 20:26Z
Our DSS event was impacted by a separate storm just north of this main storm at 20:33Z. There were no cloud flashes ahead of the CG strike and LightningCast did a good job of highlighting the area as potential increased at 20:26Z, but this was only a lead time of 7 minutes. After this observed CG strike, LightningCast dropped the probabilities to around 50% despite observed strikes occurring within the previously outlined 75% area. Thick clouds around the area from previous and advancing convection were observed over the entire area.
Lightning has been observed near the DSS Event ahead of any observed cloud flashes at 20:33Z. LightningCast only gave a 7-minute lead time with this quick-pulsing storm.
With lightning ongoing and observed within the 75% contour,, LightningCast dropped the probabilities to ~50% at 20:45Z.
This was the LightningCast trend at the time of ongoing, observed, lightning.
The trend remained steady after the lightning was observed and continued through the next couple of hours as the storm following this one weakened and moved over the DSS event area.

GLM

GLM performed quite well over the area today, especially as the storms were strengthening. The MFA and FED were again useful in identifying potentially stronger storms and where to focus my attention. This was again useful outside of supercellular convection. I was surprised with how well GLM performed with dense cloud cover from ongoing convection to the south and debris clouds left over from convection earlier in the day.
In dense cloud cover, MFA and FED were able to recognize an area of convection pulsing once it left my DSS event area. This could be useful in a similar situation where the organizer of an event recognizes increased lightning in their area and is looking to return to operations (most of the EMs and organizers have lightning notifications from several ground-based detection networks and frequently interrogate us about ongoing trends). I would be able to use this as a tool to see that lightning near the event is a continued concern because of potential backbuilding around a strengthening storm.
GLM suite showing a pulse in a storm near my DSS event area.
Overall, GLM was very useful in tandem with the LightningCast products for showing growth and decay in ongoing thunderstorms.
A strengthening storm to the south of my event area shows not only FED increasing, but also sees the LightningCast 75% contour expanding northward likely due to advection of the storm. The scale in this image is FED on a range of 0-50.

PHS

PHS again performed well on the 0-2 hour timeframe. The primary fields of interest were instability (CAPE, LI) and the SigTor parameter.
PHS model data with instability, LI, and SigTor. This is a model forecast of 1-hour for the 19Z time period which was initialization in our DSS simulation.
PHS was already highlighting the area of concern along a tongue of instability where storms were ongoing as of the 19Z 1-hour forecast. In subsequent frames, it shows the instability being maintained as storms move toward my DSS area despite thick cloud cover overhead. Based on previously discussed trends in observed lightning, it seemed it was accurately showing areas of marginal but sufficient instability.
One impressive feature of the PHS model was a thin line of instability on the back edge of convection. This area was a focus for several isolated thunderstorms behind the main line advancing through northern KY as of 21Z. This was a 3-hour forecast pictured above with highlighted areas of instability by low STP, highlighting an insufficiently sheared environment.
It is worth noting that within this study/testbed, we are looking in areas of Slight Risk or higher as highlighted by the SPC as our area of interest. In an operational setting, it is fairly uncommon to have severe weather events only when the area is highlighted in the Slight or higher category. Therefore, it is unlikely that the SigTor parameter would be useful outside of high-profile events. For example, at my local WFO, we have many severe weather days where we have very high CAPE, but very little in the way of shear. Since our primary concern is usually wind, I don’t think SigTor would be useful. It may be worth adding additional parameters highlighting various threat potentials (wind, hail, etc.).

ProbSevere v3

I was not the warning forecast in this instance, but I did notice that a couplet of rotation was observed on the MRMS rotation tracks. Based on radar data (it is worth noting that this storm was at a large distance from the radar), the couplet was well within the bounds of a rotating couplet with vertical continuity and frame-to-frame consistency.
However, ProbSevere only had a tornado probability of around 10% which should have been higher given the available radar data. This couplet was short-lived, but survived for a few frames after its initial detection. Probabilities did increase, but were not high enough for what I would have expected to be a weak tornado given the surrounding data.
ProbSevere 4-panel showing overall severe potential, hail, wind, and tornado probabilities. According to the data, all of the probabilities remained low, including TOR which should have been higher in this case. This is also supported with MRMS rotational measurements and KLVX radar data.

Optical Flow Winds

With the widespread convection across my area and the long-term cloudiness, I did find some correlation between the Optical Flow Winds and the strongest storms over my CWA (LMK). This was similar to the Birmingham area yesterday, but the stronger storms were not as pronounced in yesterday’s case. CAPE profiles were a little more pronounced today across central KY which likely contributed to this advantage. However, it was still hard to pick out the exact divergence value with these storms, but there were obvious hot spots that helped with situational awareness.
The strongest divergent cells were more obvious on the OFW display today and they lined-up with the strongest cells across the LMK CWA.

NUCAPS

NUCAPS data was unavailable today and the passes did not line-up with our area. Even if we had some data available, there would have likely been too many red-retrievals to make use of the soundings due to widespread thick cloud cover.
– Overcast Ambience

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