[21:00 UTC] Convection has been ongoing across western and southern portions of the Duluth MN for several hours now during peak diurnal heating. Activity continues to track northeast through the area in an environment characterized by sufficient instability with SBCAPE between 1500-2000 j/kg, as depicted by SPC mesoanalysis. NUCAPS soundings showed a slightly more unstable environment with SBCAPE of nearly 2500 j/kg, but NUCAPS sounding Sfc LI, PWAT, and SBLCLs were generally in fairly good agreement with the traditionally-used SPC mesoanalysis. SB CAPE and LI would suggest that convective activity will maintain itself through the next several hours before it gradually enters a more unfavorable/unsupportive environment across the northeast after approximately 23:00 UTC or so. It should also be noted that there appears to be a non-zero tornado threat as SB LCLs are fairly low and surface backing remains fairly pronounced. Although speed shear is not particularly strong and/or robust, the low level directional shear will likely allow for some rotations within updrafts that move through this area. Best chances will exist across north/west parts of the local area. Will continue to monitor development and evolution for possible warning issuance.
It should be noted that having the ability to "point-and-click" to retrieve a sensed sounding in an area of interest is extremely useful. There is always a bit of QC that goes into any data/situation analysis, but to be able to see a sensed sounding in an area that otherwise would not have such data would be very beneficial in an operational setting.
Rosie Red
Thursday, May 24, 2018
DLH - Warning Issued based on ProbSevere
What I found interesting was that the storm to its north seemed to look stronger with higher values of GLM flash extent density & total power, as well as higher reflectivity values. However, ProbSevere values were much lower with this storm with ProbWind the only field of interest up around 58%.
GLM 4 panel animation:
CI Probability: Some questions (and another potential use)
We've evaluated CI Probability products this week, with some mixed results, but that has me thinking (which, as my wife will attest, is usually not a good thing)...
Have CI developers noted any correlations between the % shown and how quickly cells with reflectivity values > 35 dBZ develop?
One of my co-evaluators noted a small area of 90% CI Prob yesterday and within a few minutes, a strong cell developed.
I have observed several areas where there were consecutive CI Prob % in the 40-70 range within which convective cells developed, but that process took a little longer, closer to 20-35 mins.
It may seem intuitive that a 90% CI Prob area would generate convective cells quicker than an area where the CI Prob potential is in the 40-70% range, but is this really the case? Maybe this is one use for the CI Prob product that could/should be explored further.
And, how long does an area need to be highlighted with a decent (50%) CI Prob before a forecaster should be confident enough in the development of a cell with reflectivity values > 35 dBZ? Our evaluation group hasn't been able to answer that question during this week of testing.
- Thomas Bell
Have CI developers noted any correlations between the % shown and how quickly cells with reflectivity values > 35 dBZ develop?
One of my co-evaluators noted a small area of 90% CI Prob yesterday and within a few minutes, a strong cell developed.
I have observed several areas where there were consecutive CI Prob % in the 40-70 range within which convective cells developed, but that process took a little longer, closer to 20-35 mins.
It may seem intuitive that a 90% CI Prob area would generate convective cells quicker than an area where the CI Prob potential is in the 40-70% range, but is this really the case? Maybe this is one use for the CI Prob product that could/should be explored further.
And, how long does an area need to be highlighted with a decent (50%) CI Prob before a forecaster should be confident enough in the development of a cell with reflectivity values > 35 dBZ? Our evaluation group hasn't been able to answer that question during this week of testing.
- Thomas Bell
GLM, Flash Centriod Density
I used the flash centriod density over the radar to pinpoint quickly where the strongest storms were located in a shield of cloud cover. GLM data on the other screens were increasing a bit too. This area is capped for now. But models have the CAPE growing and the CAP breaking in a few hours...so we have time before these storms may become severe in a better environment.
-Penny Gardens
NUCAPS Comparison
I was curious to see differences in the Improved Latency vs. Modified soundings.
IL sounding has CAPE 707 CIN-53
Actual meso matched up.
Here is the Modified sounding. CAPE 707 CIN -53 Everything matched up when I checked K index, PW, LCL.
I looked at other soundings comparing the IL and modified and I found they matched up well. But I decided to look at the modified soundings to be sure.
I also used a couple of the procedures with NUCAPS overlayed with the LI. This was a good comparison to see where I needed to focus in on vs. where the green soundings were.
-Penny Gardens
IL sounding has CAPE 707 CIN-53
Actual meso matched up.
Here is the Modified sounding. CAPE 707 CIN -53 Everything matched up when I checked K index, PW, LCL.
I also used a couple of the procedures with NUCAPS overlayed with the LI. This was a good comparison to see where I needed to focus in on vs. where the green soundings were.
-Penny Gardens
Sioux Falls, SD Discussion
Looking at the environment prior to convection. Sioux Falls has a slight risk for the western half of the WFO area.
All Sky CAPE shows high values of 1000-2500 j/kg. Compared to the Mesoscale on SPC it's 4500 j/kg or higher. Ignoring the values, you can see the upward trend of increasing CAPE on All SKY.
All layer PW on All SKY shows lots of moisture available 1.2 to 1.7! It is more detailed where the highest values are located.
PW values of 1.2 to 1.3 on the mesoanalysis.
-Penny Gardens
All Sky CAPE shows high values of 1000-2500 j/kg. Compared to the Mesoscale on SPC it's 4500 j/kg or higher. Ignoring the values, you can see the upward trend of increasing CAPE on All SKY.
All layer PW on All SKY shows lots of moisture available 1.2 to 1.7! It is more detailed where the highest values are located.
PW values of 1.2 to 1.3 on the mesoanalysis.
-Penny Gardens
AllSkyLAP LPW with Differential Water Vapor RGB
I'm trying a 4-panel with AllSkyLAP Sfc-900mb LPW (top left), AllSkyLAP 900-700mb LPW (top right), AllSkyLAP 700-300mb LPW (bottom left) and the Differential Water Vapor RGB product (bottom right).
Note the differences in the bottom two images over the eastern Dakotas. There are some mid-level clouds showing up on the Differential Water Vapor image, obscuring the view. Is there a layer of dry air below those higher clouds? The AllSkyLAP 700-300mb LPW product seems to think so. I'm not sure if this due to the model background being used under the thicker clouds or if the cloud retrieval process is working its magic and is accurate. It would really be nice to get some sort of "ground truth" to determine how accurate the AllSkyLAP 700-300mb LPW product really is in this area. The same could also be said across northeast MT and northwest ND, but one can actually see that the model background is being used there. It is harder to make that determination across the eastern Dakotas.
It may actually be beneficial if the model background in AllSkyLAP products stood out a little better to highlight "use data with caution" areas for forecasters. Otherwise, because of the blending being done, a busy forecaster might mistake these areas for real, satellite-observed data.
- Thomas Bell
Note the differences in the bottom two images over the eastern Dakotas. There are some mid-level clouds showing up on the Differential Water Vapor image, obscuring the view. Is there a layer of dry air below those higher clouds? The AllSkyLAP 700-300mb LPW product seems to think so. I'm not sure if this due to the model background being used under the thicker clouds or if the cloud retrieval process is working its magic and is accurate. It would really be nice to get some sort of "ground truth" to determine how accurate the AllSkyLAP 700-300mb LPW product really is in this area. The same could also be said across northeast MT and northwest ND, but one can actually see that the model background is being used there. It is harder to make that determination across the eastern Dakotas.
It may actually be beneficial if the model background in AllSkyLAP products stood out a little better to highlight "use data with caution" areas for forecasters. Otherwise, because of the blending being done, a busy forecaster might mistake these areas for real, satellite-observed data.
MRMS Reflectivity at -10 C vs. First GLM Flash Centroid vs ENTLN
[19:30 UTC] Convection is well underway in the upper midwest as of this writing with activity beginning to overspread western and southern portions of the Duluth CWA. Decided to take a look at MRMS reflectivity at the -10C isotherm (which is often used as a proxy for initiation of electrification within a developing shower/storm). Although not always the case, previous studies have suggested that the -10C reflectivity of 35 dBZ can be used as a threshold for there to be lightning present within a cell. Certainly there is probably a range that could also be used as a proxy, but for these purposes decided to look for 35+ dBZ on MRMS at the -10C isotherm.
For the developing cell of interest, the first 35+ dBZ on the -10C isotherm appeared at 1830 UTC. 4 minutes later, the first GLM Flash Centroid was noticed with the cell and the first flash event density also appeared. Decided to take a look at the ENTLN ground-based detection as well, and as it turned out, the first cloud flash was detected at the same time the first GLM flash centroid appeared.
For the developing cell of interest, the first 35+ dBZ on the -10C isotherm appeared at 1830 UTC. 4 minutes later, the first GLM Flash Centroid was noticed with the cell and the first flash event density also appeared. Decided to take a look at the ENTLN ground-based detection as well, and as it turned out, the first cloud flash was detected at the same time the first GLM flash centroid appeared.
Fig. 1: MRMS Reflectivity at -10C isotherm at 18:30 UTC
Fig. 2: MRMS Reflectivity at -10C isotherm at 18:34 UTC
Fig. 3: GLM First Flash Centroid Density at 18:34 UTC
Fig. 4: ENTLN First Cloud Flash Lightning Plot at 18:34 UTC
Rosie Red
GLM first identified developing storm in WI
1923Z: Weak storms continue to develop across MN & WI in the absence of any major forcing feature & marginal instability. While we're acting as WFO DLH I noticed an area of increasing GLM fields in central WI shortly before 1900Z where otherwise no other convection was ongoing. While there is an 8 minute gap in the 1-minute satellite data from 1858-1906Z the IR values really didn't begin to pique my interest until 1910-1915Z. Also, a noticeable increasing lightning trend with ENTLN data wasn't really noticed until 1905-1910Z as well so GLM was able to capture the initial electrification of this storm with few minutes extra lead time. On a day like today when monitoring areas of cumulus for the first convective echoes to develop, GLM (especially GLM total energy) was especially useful.
Peter Sunday
AllSkyLAP Layer Showalter Index: First Impressions
A first look at the AllSkyLAP Showalter Index (SI) product and comparison with the SPC Mesoscale Analysis SI product yields a few observations/thoughts.
1. The color scale seems inverted to me. The negative SI values should grab one's attention, so perhaps they should be in the brighter (yellow/orange/red) colors?
2. Until GOES-17/GOES West comes online, I would use this product (and all AllSkyLAP products) with a lot of caution over the west due to parallax and lack of data. We can see some of this in the NW corner of the first image below.
3. The AllSkyLAP SI again has areas across the central and northern Plains (NE-SD-S MN) that are significantly different (greater negative values) than what is displayed on SPC's SI product at approximately the same time, especially across SD/S MN. However, it actually captured gradients across IA and MO pretty well...and values there were similar to what are shown on SPC's SI product.
4. Certainly be aware of where there are clouds/precip, as SI values will not match SPC's SI product values. This is the case in the image below across northeast MT/northwest SD and northern/cntrl MN.
- Thomas Bell
1. The color scale seems inverted to me. The negative SI values should grab one's attention, so perhaps they should be in the brighter (yellow/orange/red) colors?
2. Until GOES-17/GOES West comes online, I would use this product (and all AllSkyLAP products) with a lot of caution over the west due to parallax and lack of data. We can see some of this in the NW corner of the first image below.
3. The AllSkyLAP SI again has areas across the central and northern Plains (NE-SD-S MN) that are significantly different (greater negative values) than what is displayed on SPC's SI product at approximately the same time, especially across SD/S MN. However, it actually captured gradients across IA and MO pretty well...and values there were similar to what are shown on SPC's SI product.
4. Certainly be aware of where there are clouds/precip, as SI values will not match SPC's SI product values. This is the case in the image below across northeast MT/northwest SD and northern/cntrl MN.
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