In the HWT this Thursday, we looked at storms which erupted in Montana. The storms took a little while to erode what little cap was there, and formed by early afternoon. There was an impressive MCV centered almost right over the Glasgow radar (KGGW). In addition, there was a short wave approaching from the west, and a frontal system in place complete with a warm sector over Montana.
Soundings in the area (Image 1) showed impressive CAPE, DCAPE, ample speed shear, marginal low level lapse rates, and impressive mid level lapse rates. We watched GOES satellite imagery in the area and saw several cells begin to develop all at the same time more or less along the warm front. Supercells eventually developed and moved slowly to the northeast.
Image 1 shows the KGGW sounding from 20210610/18Z.
During and after CI we watched how ProbSevere3 responded to the increasing severe threat. Here is a screenshot of one of the storms at 2144Z along with the ProbSevere2 and 3 readouts and the ProbSevere3 time series. This cell northeast of Glasgow showed some of the highest probabilities of the week for both algorithms, including a ProbTor of 22% according to the newer algorithm, and 7% according to the older one.
Image 2 shows storms over Montana and the ProbSevere readouts.
These LP storms were very photogenic- according to Twitter- and went on to produce monster hail larger than baseballs as well as tornadoes. In this instance, ProbSevere3 and 2 did a great job. Since ProbSevere3 is more conservative than 2, it is worth the time for forecasters to compare the 2 algorithms side-by-side once they are both available. This will help them calibrate their thinking as to what amounts usually produce certain amounts of wind damage, hail size, and tornadic activity. For example, just working with ProbSevere3 a few days, I know that a 22% tornado probability and 57% wind threat is very high, at least for supercells in the northern Plains in June.
Image 3 shows the storm reports for June 10, 2021.
As convection initiated, it took ProbSevere3 a while to find an “object”, and thus assign probabilities. It is possible the dry air as well as the heights at which the radar was hitting the storms played a role in us seeing reflectivity before probabilities started to come in. In addition, lightning took a while to develop, and this is also included in the algorithm.
When the storms were just developing and while they were discrete, ProbSevere3 did seem to encircle large areas of the storms and label them as one object. This has to do with the way the algorithm defines an object, and has improved since the last version. Still, it could be confusing to have one probability for several storms. While research continues on this, it underscores the fact that forecasters must use this as a tool in the toolbox and as a confidence-booster, not as an absolute last word on the severity of storms.
A moderate risk of severe storms capable of producing large hail, damaging wind gusts and tornadoes occurred across the Dakotas. My focus was in the Bismarck, ND CWA where storms were likely initiating in eastern MT and then moving into the very unstable environment across western ND. All of the higher resolution models were a bit late on storm initiation as storms began to fire between 3-4 PM CT. The experiment began around 2 PM CT, which allowed for mesoanalysis of the pre-convective environment.
A NUCAPS CONUS NOAA-20 pass occurred at 19z across ND and then again at 20z where the eastern edge of this pass overlapped with the previous pass across western ND. At 19z, a comparison was made between the NUCAPS profile and a nearby RAP sounding at the same time. Below Image 1 shows the locations of the NUCAPS profile versus the RAP sounding. This area was chosen as it was close to where the satellite was showing some potential for convective initiation and was just east of the dryline in the area where the better instability was to be present.
Image 1a shows the location of the chosen 19z NUCAPS profile.Image 1b shows the location of the chosen 19z RAP sounding.
Using sharppy the two profiles were then compared simultaneously. Both Images 2 and 3 show the two profiles, but image 2 will be highlighting the NUCAPS profile and associated instability values and image 3 will highlight the RAP sounding with associated instability parameters. Looking at the two profiles, there is not much difference in the mid to upper levels between the NUCAPS and RAP. However, the NUCAPS profile struggles more with the boundary layer features and temperature/dewpoint. Looking at observations, the current temperatures near that sounding location at 19z was 86 deg F with a dewpoint of 70 deg F. The RAP seemed to initialize these surface values pretty well and the thermodynamic profile east of the dryline, along with a bit of a capping inversion in place. Meanwhile, the NUCAPS profile struggled with the temperature and dewpoint, thus under doing the moisture and instability parameters. The CAPE values are noticeably different with the NUCAPS profile much lower with the instability due to these surface differences.
Image 2 shows the sharppy comparison of the 19z NUCAPS profile (colored) versus the RAP sounding (purple). The parameter values below are calculated based on the NUCAPS profile.Image 3 shows the sharppy comparison of the 19z RAP sounding (colored) versus the NUCAPS profile (purple). The parameter values below are calculated based on the RAP sounding.
After seeing the discrepancies with the observed surface values versus the NUCAPS profile, I decided to grab the modified NUCAPS profile for the same location for comparison. Image 4 shows this modified sounding with a 10 degree difference between the non-modified surface temperature. The modified sounding shows a 82 deg F surface temperature, while the original NUCAPS profile had 91 deg F. With the cooler surface temperature the modified sounding showed a similar inversion to the RAP sounding between 750-800mb. The dewpoint temperature also was better representative of the actual surface dewpoint, which helped increase the instability parameters significantly. NUCAPS profiles tend to be a tad lower on the CAPE values, so the fact that the RAP is still about 1000 J/kg higher is not a surprise. However, with no RAOB sounding available and comparing the RAP with the modified NUCAPS profile there is quite a bit of similarity between the two in terms of the thermodynamic profile. Lastly, as storms begin to fire in the next hour or so and no RAOB profiles closeby, it might be useful to compare and utilize the temperature heights (0, -10, -20, and -30 deg C) for radar interrogation as storms initiate. Knowing the RAP and modified NUCAPS profiles were similar then the heights from the temperature levels could also be compared. The RAP does show higher heights than the modified NUCAPS profile, so this is something to keep in mind and monitor as storms fire along the dryline.
Image 4 shows the 19z modified NUCAPS sounding plotted with NSHARP.
Keeping with the theme of NUCAPS, there was another pass at 20z further west (as mentioned at the beginning) that overlapped the 19z pass in parts of western ND. This included the town of Bismarck, where the office put out a special 20z RAOB sounding. Bismarck was a bit further east than the previous sounding, but was still in the very favorable environment. Images 5 and 6 show the comparison between the NUCAPS sounding at 20z and the RAOB Bismarck special sounding at the same time. Similar results can be seen between the observed sounding and NUCAPS profile where the CAPE values are again lower in the satellite derived sounding. This time the NUCAPS profile did a much better job with the surface temperature and despite the temperature profile being a bit smoother due to lack of detail in the boundary layer, the profile was overall pretty similar to the RAOB temperature profile. The dewpoint profile on the NUCAPS was much drier at the surface and therefore had a bit of a drier boundary layer than the observed sounding, which is likely why the CAPE values are also a bit lower.
Image 5 shows the sharppy comparison of the 20z NUCAPS profile (colored) versus the Bismarck RAOB sounding (purple). The parameter values below are calculated based on the NUCAPS profile.Image 6 shows the sharppy comparison of the 20z Bismarck RAOB sounding (colored) versus the NUCAPS profile (purple). The parameter values below are calculated based on the Bismarck RAOB sounding.
Once again the modified NUCAPS profile was compared (Image 7 below). The modified profile did a better job at showing the moisture in the boundary layer and attempted to pick up the dry layer at 650mb, which was actually at 700mb on the RAOB profile. Unfortunately, the temperature was too low and therefore the modified NUCAPS temperature profile shows a very sharp capping inversion that was unrealistic. Overall, the CAPE values did increase with the modified sounding versus the original NUCAPS profile and were closer to the observed sounding. Twice it has been noted that the heights of the temperature levels were closer between the non-modified NUCAPS profiles with the model/observed soundings. There may be some calculation in the modified sounding that is causing the heights to be lower and maybe unrealistic. In scenarios where there is a RAOB sounding, that is the best picture of the atmosphere you can get but it is great to compare the NUCAPS profiles for comparison to future events and potential trends in the satellite derived soundings.
Image 7 shows the 20z modified NUCAPS sounding plotted with NSHARP.
As storms began to initiate across eastern MT, both G16 and G17 GLM were utilized to look for lightning instances in the growing storms. Having both satellites can be super helpful, especially when one viewing angle may not see the strike, while the other does. This happened several times during storm initiation where one satellite would pick up a strike, while the other displayed nothing. Images 8-9 show this occurring twice in two different storms where each satellite picked up a strike that the other did not. As mentioned before, the viewing angle may not be in a good position for the satellite to see the storm’s top and therefore the strike is not bright enough to be detected. Along those lines, the scattering properties in the cloud are also not visible by the angle of the satellite’s view point and could cause the satellite to miss a strike. Lastly, there is a quality assurance that occurs for each product and if the strike wasn’t strong or long enough then the pixel could have been tossed out during this quality assurance. This is why it is so important to utilize both satellites when possible and it is a best practice to err on the side of whichever satellite is showing more lightning is probably more accurate.
Image 8 shows local radar and GLM flash points (top left), GLM minimum flash area and NLDN/GLD CG strokes (top right), GLM flash extent density and ENTLN CG/IC flashes (bottom left), and GLM total optical energy (bottom right). This image shows the G17 flash point and corresponding GLM gridded products, while G16 does not pick up on a flash point or any GLM lightning.Image 9 shows local radar and GLM flash points (top left), GLM minimum flash area and NLDN/GLD CG strokes (top right), GLM flash extent density and ENTLN CG/IC flashes (bottom left), and GLM total optical energy (bottom right). This image shows the G16 flash point and corresponding GLM gridded products, while G17 does not pick up on a flash point or any GLM lightning.
ProbSevere version 2 and 3 were compared through the afternoon. The trend continued with version 2 remaining about 20-30% higher in all categories except the tornado probs. Version 3 has leaned towards being slightly higher than version 2 when it comes to tornado probabilities. ProbSevere time series was utilized to track the southernmost storm along the line of storms headed into western ND during the mid afternoon hours. Both radars were pretty far away on either side of the storms, with Glasgow’s radar being slightly closer. The lowest elevation scan was at around 13000-14000 feet when velocity began showing a strong mesocyclone. Image 10 shows the time series of ProbSevere and the readout comparing version 3 with version 2. All four ProbSevere categories were steadily increasing through the last hour with version 2 remaining higher than version 3. Version 2 shows close to 100% probabilities for all but tornado, making this storm look like a slam dunk due to the environmental parameters. Meanwhile version 3 is slightly lower due to the fact that it can pick up on similar storms that occurred in a similar environment with little to no reports (from storm data). This is where version 3 adds in a bit more information to create more realistic probabilities.
Image 10 shows the ProbSevere readout for the tornadic storm in eastern MT, along with the time series showing steadily increasing probabilities of all threats. Note the lowest elevation scan with radar is at ~13500 feet.
Based on the strong rotation in Image 10, the tornado probabilities were close to 30 percent which is relatively high and should give a forecaster confidence on issuance with a lack of lower level radar scans. Chaser footage also helped to back the need for a tornado warning with images of wall clouds, funnels and more being reported from multiple sources. Image 11 shows the time series for ProbSevere along with multiple other parameters. One thing that was interesting to see was the tornado probability drastically dropped in version 2 but remained steady in version 3. Since version 2 is heavily using az shear, you can see the drop in MRMS az shear (red line on second plot down on the far left), which could be correlated with that probability drop in version 2. Also, the MLCIN is slowly increasing (blue line on second plot down on the far right) and could be playing a bit of a role in this drop as well. This is where version 3 might have a leg up on version 2 when it comes to tornado probabilities.
Image 11 shows the time series of version 2 and 3 of prob severe probabilities along with various other useful parameters.
Lastly, the optical winds were utilized to see the winds at the top of the storm. Image 12 shows the optical wind field for 200-100mb. You can see the cooler cloud tops in satellite below the wind field and then the associated diffluence aloft. This is an indication of the very strong supercell that is showing no signs of weakening anytime soon. Also, it is of note that there is another cool cloud top signature a bit further to the northwest associated with another strong supercell with diffluence aloft. The optical wind fields are useful in knowing what is going on aloft and the potential strengthening or even weakening of a storm.
Image 12 shows the 200-100mb layer of optical winds over the supercell in eastern MT.
An approaching short wave trough as well as a remnant MCV moving through the area helped trigger thunderstorms over the upper Midwest. Convection developed over Minnesota during the afternoon and evening hours. Storms did not become severe near the Grand Forks, ND CWA until late in the afternoon.
The upper Midwest is near the extent of coverage for both GOES 17 West and GOES 16 East. This made it a good chance to compare how the GLM lightning products were affected by this issue. Research has shown flash densities for both satellites diminish in this area, well away from the nadir of both satellites.
Image 1 shows Flash Extent Density for GOES 17 on the left, and GOES 16 on the right.
The character and quality of the Flash Extent Density (FED) returns from each of the satellites can be seen, with GOES 17 showing a slightly westward tilt, and an eastward tilt in the returned grids for GOES 16. The strongest storm in north central Minnesota has a higher and possibly better return on 17 than on 16.
Image 2 shows Minimum Flash Area for GOES 17 on the left, and GOES 16 on the right.
Values of Minimum Flash Areas from the satellites were quite different in some cases, and were also skewed as a result of the distance from the nadir of each satellite. Placement of the flash areas also differed from “viewing” angle.
Image 3 shows Total Optical Energy from GOES 17 on the left, and GOES 16 on the right at 1958Z.
Total Optical Imagery (TOE) was also skewed. It is interesting to note that the pixels of TOE in far southeastern ND change from minute to minute, as seen in Images 3 and 4. At 1958Z, GOES 17 had an area of TOE returns along the ND/SD/MN borders, while GOES 16 had 2 separate areas, one in southern ND and one in west central MN. By 1959Z, both GOES 17 and 16 agreed that there were 2 separate TOE returns in this region.
Image 4 shows Total Optical Energy from GOES 17 on the left, and GOES 16 on the right at 1959Z.
Pulsing storms were occurring today across the Grand Forks CWA, but not much in the way of severe storms early this afternoon. However, storms began to intensify on radar at the eastern edge of the CWA and approaching the western edge of Duluth’s CWA in north central Minnesota. A few tools were analyzed during this process to help identify why storms were suddenly increasing in strength. Mid-level water vapor satellite analysis with 500mb RAP heights showed a potential shortwave moving across the area and helping to intensify storms for a brief period of time.
Image 1 shows a loop of the mid-level water vapor from GOES-16 satellite, along with 500mb RAP heights with a few weak disturbances aloft.
A comparison of a model sounding with the NUCAPS profile (non-modified vs. modified) was done in order to see the environment these strong to severe storms were heading into later this afternoon. There were subtle differences, but overall the model vs. satellite profiles were pretty comparable. Instability values were higher with the RAP mainly due to the fact that it had a 5 deg F warmer surface temperature. But both profiles were similar with the dewpoints and overall the thermodynamic profile of semi-steep lapse rates along with no capping inversion. With the observed surface temperatures warmer than the RAP had by 3-4 degrees, we decided to check out the modified NUCAPS profile to see if it had warmer temperatures. The modified NUCAPS profile had the same temperatures as the RAP at the surface and was much closer in comparison. However, both the model sounding and NUCAPS sounding were off by 3-4 degrees F on the actual surface temperature, so mental modifications were made to realize the instability was likely more than given with these profiles.
Image 2 shows a combo overlay in sharppy of the 19z RAP sounding (colored) and the 19z NUCAPS profile (purple).Image 3 shows a combo overlay in sharppy of the 19z NUCAPS profile (colored) and the 19z RAP sounding (purple).Image 4 shows the19z modified NUCAPS profile from NSHARP.
The storms were relatively weak for much of their lifespan, but around 4:30 PM CDT a few cells intensified. A storm in Beltrami County near Red Lake, MN grew steadily in intensity, as seen below with the ProbSevere 3 time series. Wind was the main concern, with plenty of dry air noted on both the NUCAPS and RAP soundings. DCAPE ranged from 800-1100 J/kg on these soundings as well.
Image 5 shows the northernmost storm in question, which had a Severe Thunderstorm warning at this time. The ProbSevere 3 Time Series shows how it ramped up with time.
Overall probabilities that the storm was severe can be seen in Image 6, which shows the ProbSevere readout for the storm. Both ProbSevere 2 and the newer ProbSevere 3 showed an overall severe probability of 65% and 61%, respectively. The wind threat is lower with ProbSevere 3, which had it at 44%, as compared to Prob Severe 2. This is consistent with the research that has shown the newer version is more conservative than the old version. Research also shows that the newer algorithm output is closer to what actually happens historically, i.e., about 44% of similar storms produced wind damage according to Storm Data.
Image 6 shows the readout comparing the overall severe, hail, wind, and tornado threats from both ProbSevere 2 and ProbSevere 3.
Scattered strong to severe thunderstorms were popping up along the eastern ND and MN border today. However, these storms were struggling to become severe at times with a majority of the cells pulsing up and down. A NUCAPS pass around 19z provided gridded satellite observations and forecasts for the area to compare with SPC’s mesoanalysis page. The gridded NUCAPS at 19z shows CAPE (Image 1) values ranging from 500-1500 J/kg in the area mentioned above with little to no CIN (Image 2) present based on the gridded NUCAPS data. Image 3 below shows the SPC 19z CAPE/CIN data along with the forecast over the next 6 hours (through 01z). When comparing the 19z SPC mesoanalysis to the gridded NUCAPS, there was not much difference between the two with both showing higher CAPE values further south into Nebraska and Kansas. The gridded NUCAPS for CIN seems a bit erroneous with really no signature for -50 or less of CIN, which is present in the SPC mesoanalysis. This is likely due to the lack of detailed boundary layer features with NUCAPS and the fact that it may likely wipe such smaller inversions.
Image 1 shows the 19z gridded NUCAPS for CAPE.Image 2 shows the 19z gridded NUCAPS for CIN.Image 3 shows a loop of the MLCAPE/MLCIN forecast values for 6 hours (through 01z) from SPC’s mesoanalysis page.
Looking into the forecasted parameters from NUCAPS, there is a much higher bias in the CAPE values. However, they did a great job at pinpointing an area of higher instability to watch for storms to potentially become more severe with time. The overall CIN forecast looked as if it may start to increase further west near Grand Forks later in the evening, but in central MN where the corridor of CAPE values were higher remained uncapped. As time progressed through the afternoon a few storms did start to intensify and become severe across north central MN with a few severe wind reports. A few lingering surface boundaries were present, along with a weak shortwave at 500mb helped to enhance the storms a bit. I do feel the NUCAPS forecast values for CAPE were a bit too high in comparison to the actual environment and should definitely be compared to model data.
Image 4 is a loop of the 19z gridded NUCAPS forecast of computed CAPE over the next 6 hours (through 01z).Image 4 is a loop of the 19z gridded NUCAPS forecast of computed CIN over the next 6 hours (through 01z).
Lastly, the location of storms yesterday provided the chance to compare the GOES-16 and GOES-17 GLM products with one another. However, image 5 shows the extent of the two satellites and GOES-17 was right on the edge of where storms were across the Upper Midwest. As you get further away from the satellite and towards the edge of its coverage, you can start to notice more of a tilt in the gridded data. This may cause some erroneous data as seen in comparison with GOES-16. Comparing the GOES-16 data (Image 6) with the GOES-17 data (Image 7), there is a better display of the minimum flash area and lightning sizes with the GOES-16. You can see GOES-16 shows more of a mixture of shorter and longer flashes (purple and yellow colors), while GOES-17 sees strong shorter flashes (yellow colors). Also, the further away the satellite is to the storms the more likely the flash extent density may be less accurate. This is likely due to the storms being on the edge of the satellite’s reach. Therefore it is important to check out both satellites when possible, but take into account where the storms are in respect to the satellites coverage.
Image 5 shows the areal coverage of GOES-16 (left) and GOES-17 (right).Image 6 shows GLM through GOES-16 with the local radar (top left), minimum flash area (top right), flash extent density (bottom left) and optical energy (bottom right).Image 7 shows GLM through GOES-17 with the local radar (top left), minimum flash area (top right), flash extent density (bottom left) and optical energy (bottom right).
Here are a few more supplemental images of the GLM GOES-16 satellite versus the GOES-17 with similar concerns as mentioned above.
Image 8 shows GLM through GOES-16 with the local radar (top left), minimum flash area (top right), flash extent density (bottom left) and optical energy (bottom right).Image 9 shows GLM through GOES-17 with the local radar (top left), minimum flash area (top right), flash extent density (bottom left) and optical energy (bottom right).
Are the modified soundings realistic above the mixing layer?
Modified – Note the unusual dry layer around 500 MB.Unmodified – Note the dry layer around 500 MB isn’t there.More visually attractive on the SHARP.py vs. NSHARP in Awips.
Comparing soundings across the Northern Plains, and Upper Midwest. (Eastern Mt to the Arrowhead of Mn)
Today we focused on the slight risk across the southeast, specifically WFO Jackson, MS. During the afternoon hours, a small linear complex was coming across northern LA towards Jackson’s CWA. Right before the CWA line, there was a wind report of snapped tree limbs of 3” diameter from Monroe Airport. There was also a measured gust from the airport of 41 mph. The velocity on radar had ~60 knot outbound winds at around 14,000 – 15,000 feet, which easily could have produced a few severe gusts to the surface. The gifs below show the linear line of storms and the associated velocity as the system moved over Monroe Airport in northeast LA with the wind report at 1952z and then continued to enter western MS.
Image 1 shows a loop of radar reflectivity with prob severe overlaid and Image 2 shows the velocity associated with the radar loop.
In this situation, prob severe was not doing as good of a job on picking up on these “stronger” winds. Image 3 below shows the time of the wind damage report and 41 mph gust at the airport in northeast LA, but prob severe and prob wind are both only picking up about 20% probability of this potential. Almost two hours later, the line of storms are a bit weaker on reflectivity but just as strong or even stronger on velocity. Note, the storms were also closer to the radar at Image 4, so the stronger outbound velocities were closer to the surface. So this led to wondering is prob severe a good indicator for straight line winds?
Image 3 shows the prob severe time series at the time of the damaging wind report at Monroe Airport in northeast LA.Image 4 again shows a prob severe time series for the same line of storms about two hours later and approaching the western MS border.
Prob severe utilizes azimuthal shear which as seen in the Images 3 and 4 below are not present with solely outbound velocities and little to no inbound present. This is common for straight line wind scenarios, but not super helpful in terms of how prob wind is calculated. Also, the prob severe is an object oriented product that utilizes reflectivity for these objects. In this scenario, the reflectivity definitely began to weaken but velocity did not. The toughest part was the prob severe began to decrease over the two hour time span shown above, but yet several damaging wind reports of roofs blown off and trees/power lines down led me to believe the probability of prob wind should have remained constant or increased over time.
While investigating the prob severe I also took a look into the lightning characteristics within the line as you can see in the GIF below (Image 5) that there is the formation of some trailing stratiform on reflectivity. A still image was taken (Image 6) to show how the lightning began to extend westward into the light stratiform. The flash area (top right of the four panel) shows the darker purple color extending westward, which indicates the storm mode is more of that light stratiform rain with longer flashes extending through it rather than the intense small flashes within the leading line. This can be helpful in time when you may have a DSS event and the main line has passed through, but lightning is still present in the trailing light rain. Pairing the ground networks with the GLM extent and area allows a forecaster to give DSS on the latest CG stroke within the large area.
Image 5 shows a four panel with reflectivity (top left), GLM flash area (top right), GLM flash extent (bottom left) and GLM optical energy (bottom right). The ground networks have been added to the flash area with CG strokes and then over the flash extent with polarity and cloud flashes.Image 6 shows the same four panel layout as described in image 5, but as a still image. This shows a great use of GLM for examining storm mode and flash extent, along with DSS uses of CG strokes within the large westward expanding extent of flashes behind the main line of storms.
Lastly, there was a NUCAPS CONUS NOAA-20 satellite pass at around 19z, which was well before the line of storms made it to the western Jackson CWA line. No special radiosonde launches were made by local offices, so the next best observational guess of the atmospheric profile would be from satellite. Model soundings were also available to compare at the time. A RAP sounding at 19z was taken just east of the western MS border (see Image 7 below for location of this sounding) and a very nearby NUCAPS sounding was also retrieved for comparison (see Image 8 below for location of this sounding).
Image 7 (left) shows the location of the retrieved 19z RAP sounding (circled in white) and Image 8 (right) shows the location of the retrieved 19z NUCAPS sounding (circled in white).
The soundings (Image 9 and 10 below) looked fairly similar between the model and satellite profiles; however, there were several major differences that played a key role in changing the instability parameters. The NUCAPS sounding was still slightly too low of a surface temperature with 86 deg F versus the RAP’s 89 deg F. Surface observations from 19z at that location showed a temperature of around 91 deg F. Also, the surface dewpoint was far too low on the NUCAPS profile at the surface as it was 5 degrees below the current observation at 19z. Meanwhile, the RAP was only one degree lower than the current surface dewpoint. These subtle differences caused significant variations in the CAPE values.
Image 9 shows the 19z RAP sounding through sharppy.Image 10 shows the 19z NUCAPS sounding from sharppy.
After realizing the NUCAPS profile was not accurately depicting the surface temperature/dewpoint, I decided to see what the modified sounding might look like through NSHARP. Image 11 below shows the modified NUCAPS sounding through NSHARP with a much cooler surface temperature of near 80 deg F. This was almost 10 deg below the actual surface temperatures and 6 deg below the original NUCAPS profile. The boundary layer was not representative due to this drastic difference and therefore the modified sounding had to be thrown out of the comparison.
Image 11 shows the modified 19z NUCAPS sounding shown through NSHARP.
Lastly, with knowing the line of storms were headed into the area of interest I decided to see how the forecast products were looking. Unfortunately, I did not get to save the images off in time as the forecast images disappear from AWIPS when the next pass occurs. So I was left with the web-browser version which is only in a gridded format. Unfortunately it is very difficult to depict changes in this format, whereas in AWIPS you can interpolate the image and smooth the results for a more concise display of values. Image 13 shows the comparison of the web-browser gridded format versus the AWIPS smoothed version for the West Coast pass of the NOAA-20 satellite.
Image 13 shows the gridded NUCAPS CAPE forecast for 6 hours in the future from the web-browser (left) and the same exact data and image displayed in AWIPS smoothed (right).
Our team, as WFO/JAN, chose the setup for the Mississippi Pickle Fest at 1150 Lakeland Drive Jackson, MS as our IDSS location today (Tue, 08 Jun). Per SPC Outlooks, the Jackson area was on the “edge” of the Marginal Risk Area for severe weather. As operations began for today, a thundershower was noted to the SW of Jackson, moving NE toward the IDSS location of interest:
KDGX reflectivity at 1926 UTC, with shower SW of Jackson/Pickle Fest. Range rings at 5/10/20 miles.GLM and NLDN Lightning at 1932 UTC, showing electrical activity in thundershower SW of Jackson, MS.
A modified NUCAPS sounding from near Jackson, MS (which became available later), indicated plenty of instability/CAPE (2000-3500 J kg-1), suggesting that the thundershower would be maintained as it advected toward the Pickle Fest location. This would be a good time for a “heads-up” to the event venue or EM. The unmodified NUCAPS sounding (not shown) still suggested sufficient instability aloft for the storm to maintain itself.
The ProbLightning product on the Web, somewhat surprisingly, still showed only ~25% chance of a GLM lightning flash within the next 60 minutes at 2001 UTC, but this had increased to 75% by 2026 UTC:
By 2029 UTC, the electrical activity was nearly overhead:
Interestingly, the NUCAPS forecast CIN was forecast to increase over the next couple of hours (valid 22UTC, below), after the storm passed, but ahead of another, stronger line further upstream (not shown).
Based on this, and the rapid collapse of electrical activity within the shower around 2110 UTC, a reasonably confident “all-clear” could have been given to the venue at that time…or at least until the upstream line approaches in a couple of hours, assuming it holds together.
Today operations were centered over Bismarck, ND, where a large storm complex was in progress much of the day. The storms developed near a warm front, and benefitted from an approaching short wave trough as well as orographic lift and differential heating. You can see the extent of the anvils from storms centered over southern ND and northern SD. This complex dominated the local environment and seemed to take advantage of most of the local instability.
The new optical flow winds tool uses 1-minute imagery from GOES-16/17 ABI imagery to provide high resolution wind estimates at 2-km resolution using an optical flow technique. You can plot the winds in different layers, from 1000-800mb up to 100-50mb. As you can see, it is mainly the higher level winds that were plotted above the anvil plumes, and show the divergence at the higher levels of the storm.
Optical flow winds over storms in southern ND on the afternoon of June 8, 2021.
Taking a look at the SPC mesoanalysis at 300mb for this time, you can see the speeds and directions roughly match the 400-200mb winds plotted on the optical flow plots.
SPC 300mb analysis including heights, divergence, and winds at 2100Z.
Winds closer to the surface did not plot as much, mainly owing to the dense cloud cover the satellite was seeing. After some discussion, surface plots were added to the 1000-800mb layer, which helped to orient forecasters. Forecasters still need to mentally adjust the satellite imagery which was overlaid for parallax.
Optical winds with station plots added.
I think the optical wind flow could be useful to investigate storm strength and maintenance. It could be helpful in both warning operations and for IDSS purposes. The storm complex in question lasted for at least 12 hours, and produced wind damage, large hail, and torrential rains leading to flash flooding.
