Tuesday, June 2, 2015
Overshooting top in SRSO, no algorithm trigger, parallax error
SRSO vis channel showed an overshooting top (Fig 1: Gif Loop) in McLean Co, but the overshooting top detection algorithm did not make a detection on this feature. This was useful information in that it showed it wasn’t vigorous enough to actually be quantified as strong enough to be detected. Also noticeable was the 1 minute lightning was displaced south of the overshooting top feature, but aligned with the radar echo. After discussion with Chris S. the displacement seems to be a result of parallax error. –Cattywampus
Shadowing on vigorous updrafts evident on 1 min sat imagery
Late afternoon shadowing shows vigorous updrafts and associated 1 min flashes within individual cells over east central Montana. Rapid refresh of the ENI lighting data correlates nicely with the satellite sequence to show organized storms generating north of Billings.
John Pendergrast
Overshooting top algorithm in Montana
At roughly the same time as our big convection was happening with the high reflectivity and climb in lightning frequency, the overshooting top algorithm was triggered.
Image from 2210z.
Jason Williams
CI Probability Along Outflow Boundary
The CI probability product keyed in on some convective development along an outflow boundary from a storm moving southeastward across Morton County. It went from 43% at 2145Z over northern Grant County to 68% at 2200Z. Comparing the product to radar reflectivity, there were dBZ values over 50 just east of Heart Butte Dam at 2151Z and the cell continued to intensify for the next few scans.
I think that this data would be more useful during warning operations if it was available every 5 minutes versus every 15.
(Click image to see animation)
(Click image to see animation)
-Helen Hunt
I think that this data would be more useful during warning operations if it was available every 5 minutes versus every 15.
(Click image to see animation)
(Click image to see animation)
-Helen Hunt
Thoughts on 1min SSRO Data and Severe Weather Forecasting and Ops
Having the 1 min satellite data was vital to my knowledge of the environment and subsequent warnings. Here’s how.
I was able to identify boundaries important to convection and initiation across northwest NE. There were limited obs there, but it was clear from the satellite imagery. With the one minute satellite data I was able to find the 6 min satellite derived wind data. This data was a check to the models. The RAP had 0-6km shear AOA 30 kts, this suggested that multicell would be the dominate storm mode. The satellite obs suggested that there was actually a H3 jetlet moving into the area. The winds associated with this max increased the 0-6km shear to around 45 knots with near 0 surface winds across western NE.
I developed a thought that the storms would initiate across eastern WY and then move into western NE and intensify. I thought that the jetlet would cause the storms to become stronger and more supercell in nature until it moved out of the area. This in fact happened. This lead to a small window ~2 hours of supercells with large hail. Knowing that the boundary to the north was stationary and cu was starting to initiate along there, suggested that we would could see a short tornado threat as well. Storms that formed or road the boundary showed rotation. With lightning jumps and the one min overshooting tops data, I decided to issue a tor. My thought was that with a long lived overshooting top and a collapsing reflectvity core, that the updraft intensified, leading to more stretching of vort in the storm and possibly the RFD coming down. Knowing that 12kft was my lowest tilt, I decided the environment and radar signature may be enough to warn, No idea if it verified, however without the one minute data looped, I would not have been able to see fine details that suggested what was actually going on
I was able to identify boundaries important to convection and initiation across northwest NE. There were limited obs there, but it was clear from the satellite imagery. With the one minute satellite data I was able to find the 6 min satellite derived wind data. This data was a check to the models. The RAP had 0-6km shear AOA 30 kts, this suggested that multicell would be the dominate storm mode. The satellite obs suggested that there was actually a H3 jetlet moving into the area. The winds associated with this max increased the 0-6km shear to around 45 knots with near 0 surface winds across western NE.
I developed a thought that the storms would initiate across eastern WY and then move into western NE and intensify. I thought that the jetlet would cause the storms to become stronger and more supercell in nature until it moved out of the area. This in fact happened. This lead to a small window ~2 hours of supercells with large hail. Knowing that the boundary to the north was stationary and cu was starting to initiate along there, suggested that we would could see a short tornado threat as well. Storms that formed or road the boundary showed rotation. With lightning jumps and the one min overshooting tops data, I decided to issue a tor. My thought was that with a long lived overshooting top and a collapsing reflectvity core, that the updraft intensified, leading to more stretching of vort in the storm and possibly the RFD coming down. Knowing that 12kft was my lowest tilt, I decided the environment and radar signature may be enough to warn, No idea if it verified, however without the one minute data looped, I would not have been able to see fine details that suggested what was actually going on
June 2 — Flash Density Color Curve Comparison (CYS)
There has been some question as to the utility of the current default Flash Density color curve or developing different color curves to help forecasters pick out the highest flash densities.
Here is an example of high flash densities we saw this afternoon (2146 UTC) in the CYS CWA, looking at the default color curve and one of the possible options:
The image on the left is the default color curve, with the right image one of the options. The problem with the right image is the use of blue/green shades and red/orange shades for those that are colorblind. Those colors can cause problems in figuring out the highest flash rates without use of the sampling tool. Being a non-colorblind person, I prefer the right image as I was able to pinpoint the highest rates quickly. It is still a good idea to use the sampling tool with both color curves to ensure finding the highest rates.
CoonieCatEye
Here is an example of high flash densities we saw this afternoon (2146 UTC) in the CYS CWA, looking at the default color curve and one of the possible options:
The image on the left is the default color curve, with the right image one of the options. The problem with the right image is the use of blue/green shades and red/orange shades for those that are colorblind. Those colors can cause problems in figuring out the highest flash rates without use of the sampling tool. Being a non-colorblind person, I prefer the right image as I was able to pinpoint the highest rates quickly. It is still a good idea to use the sampling tool with both color curves to ensure finding the highest rates.
CoonieCatEye
CI-East: Success and Failure all in one.
This is a case where I found CI to be helpful in helping focus attention where there was nothing on radar but it was showing potential for convective development. Fig 1 shows a swath of about 23% over Kidder Co and about 33% over Burleigh Co to the West at 21:15z. About a hour later at 22:22z (Fig 2), we saw development on radar over Kidder Co but nothing over Burleigh which had the higher probability. This was helpful in this case because I was not anticipating development in this area, but the CI helped grab my attention to watch this area. –Cattywampus.
Fig 1: CI-East over Burleigh and Kidder Co
Fig 2: Convective development over Kidder at 22:22z.
Fig 1: CI-East over Burleigh and Kidder Co
Fig 2: Convective development over Kidder at 22:22z.
RUC – vs – NUCAPS soundings over SE Montana
Comparison of relatively uncontaminated areas from RUC and recently available NUCAPS ahead of encroaching cloud cover show temperature and moisture profiles similar with slightly higher PWAT on the RUC due to low level moisture contribution. NUCAPS indicated 500 MB temperatures around 2C warmer than the RUC likely leading to more convective inhibition than the RUC was showing.
John Pendergrast
June 2 — Rapid growth of 2 supercells across northern CYS CWA
We have been seeing amazingly rapid supercell growth of two cells, one just north of Guernsey and a second near Lusk since 2045Z. Both cells have also shown rapidly increasing severe probabilities. The Overshooting Tops algorithm was also indicated with the Lusk cell.
The 1-minute GOES-14 visible satellite is showing both supercells very well (L). The two pink overlays indicate the increasing severe probabilities. The southern cell north of Guernsey was up to 90 percent, while the cell near Lusk was at 76 percent. Since 2107Z, the Lusk cell severe probabilities increased to 89 percent at 2110Z. along with several CG lightning strokes. The 2107Z Flash Density (R) was up to 17/minute with the Gurensey cell, and 10/minute with the Lusk cell.
CoonieCatEye/MacGyver
The 1-minute GOES-14 visible satellite is showing both supercells very well (L). The two pink overlays indicate the increasing severe probabilities. The southern cell north of Guernsey was up to 90 percent, while the cell near Lusk was at 76 percent. Since 2107Z, the Lusk cell severe probabilities increased to 89 percent at 2110Z. along with several CG lightning strokes. The 2107Z Flash Density (R) was up to 17/minute with the Gurensey cell, and 10/minute with the Lusk cell.
CoonieCatEye/MacGyver
More thoughts on LAP CAPE in Montana
Above are radar images from BYZ at 2035z and 2119z, on top of LAP-derived CAPE (valid at 2000z). Convection that began to develop in a local min of CAPE quickly intensified as it moved into a local max. Again, the LAP-derived CAPE seems to be doing very well in assisting with short-term trends.
Jason Williams & John Pendergrast
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