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Severe WX Severe threat 3/30-3/31

CheeselandSkies said:
Models have been all over the place, widespread disagreement model to model and run to run. Only now starting to get any sort of trend one way or the other.
Click to expand...
Just your typical March Model Madness.

Models really didn’t have a handle on 3/14’s threat until a couple of days before. It looked like a moisture starved QLCS event. Then real time sampling of the lead primer wave and surface/moisture obs put it in the other direction. Then the HRRR started showing a full on supercell outbreak as we got closer.
 
ColdFront said:
Just your typical March Model Madness.

Models really didn’t have a handle on 3/14’s threat until a couple of days before. It looked like a moisture starved QLCS event. Then real time sampling of the lead primer wave and surface/moisture obs put it in the other direction. Then the HRRR started showing a full on supercell outbreak as we got closer.
Click to expand...
Begun, the March Model War Madness has

yoda GIF
 
A new run of the WRF-ARW model, using 06Z GFS initial conditions. It is centered on Memphis, TN, and has a 9 km resolution and a window of about 700 miles square.



Much more explosive convection firing than in previous runs of this model. This looks to promote a more multicellular mode than in previous runs. As you can see, there is still some space between the cells, though, so this could be the worst case scenario of many semi-discrete cells firing in the OWS. Not good.

test091.gif


The SCP shows a HUGE area (ridiculous really) above 10+ on the scale with some areas over 25+. This is looking like a very dangerous setup potentially.

test012.gif



The low-level Storm Relative Helicity is also alarming, with large areas over 350 m^2/s^2 and some areas occasionally topping 500. And remember, this is the lowest 500m (a metric you won't find many other places), so this is the tornado-prone part of the atmosphere. More and more concerning!

test013.gif



In particular, the Hodograph Curvature Area Index (a measure of how curved hodographs are) does a really nice (and scary!) job resolving tight rotation of supercells through MS, TN, and AL.

test015.gif



The Wind Gust Potential algorithm is designed to predict maximum wind gusts over a given area. It is similar to DCAPE but is measured in MPH. It mixes down a proportion of winds higher in the atmosphere, based on the low-level lapse rates in a given area. I've also overlaid the front/boundary detection algorithm (in golden) and the tiny hodographs overlay. If you look closely, you can see a couple of cells the model is trying to resolve put out possible gusts of 70+ across northern MS and AL.

test022.gif



Finally, the Tornado Risk Index is a composite parameter that factors in STP (fixed version), SCP, helicity, shear, and a couple of other factors and scales it on a scale from 0 to 10. In addition, areas with elevated chances of significant tornadoes (EF2+) get hatched. It looks increasingly like a large area in the middle and South of the country may have an opportunity for significant tornadoes. The peak Tornado Risk is N MS/W TN/N AL, where pockets of 8 out of 10 appear.

test024.gif


It still looks somewhat conditional, but it looks a LOT less conditional than yesterday. It looks like the ingredients are coming together for a potentially significant outbreak spanning multiple days. I think a large part of the current Enhanced Area will be upgraded eventually to a Moderate, and the Slight risk on Monday will be partially upgraded to Enhanced.
 
wx_guy said:
A new run of the WRF-ARW model, using 06Z GFS initial conditions. It is centered on Memphis, TN, and has a 9 km resolution and a window of about 700 miles square.



Much more explosive convection firing than in previous runs of this model. This looks to promote a more multicellular mode than in previous runs. As you can see, there is still some space between the cells, though, so this could be the worst case scenario of many semi-discrete cells firing in the OWS. Not good.

View attachment 37525


The SCP shows a HUGE area (ridiculous really) above 10+ on the scale with some areas over 25+. This is looking like a very dangerous setup potentially.

View attachment 37526



The low-level Storm Relative Helicity is also alarming, with large areas over 350 m^2/s^2 and some areas occasionally topping 500. And remember, this is the lowest 500m (a metric you won't find many other places), so this is the tornado-prone part of the atmosphere. More and more concerning!

View attachment 37527



In particular, the Hodograph Curvature Area Index (a measure of how curved hodographs are) does a really nice (and scary!) job resolving tight rotation of supercells through MS, TN, and AL.

View attachment 37528



The Wind Gust Potential algorithm is designed to predict maximum wind gusts over a given area. It is similar to DCAPE but is measured in MPH. It mixes down a proportion of winds higher in the atmosphere, based on the low-level lapse rates in a given area. I've also overlaid the front/boundary detection algorithm (in golden) and the tiny hodographs overlay. If you look closely, you can see a couple of cells the model is trying to resolve put out possible gusts of 70+ across northern MS and AL.

View attachment 37532



Finally, the Tornado Risk Index is a composite parameter that factors in STP (fixed version), SCP, helicity, shear, and a couple of other factors and scales it on a scale from 0 to 10. In addition, areas with elevated chances of significant tornadoes (EF2+) get hatched. It looks increasingly like a large area in the middle and South of the country may have an opportunity for significant tornadoes. The peak Tornado Risk is N MS/W TN/N AL, where pockets of 8 out of 10 appear.

View attachment 37539


It still looks somewhat conditional, but it looks a LOT less conditional than yesterday. It looks like the ingredients are coming together for a potentially significant outbreak spanning multiple days. I think a large part of the current Enhanced Area will be upgraded eventually to a Moderate, and the Slight risk on Monday will be partially upgraded to Enhanced.
Click to expand...
Phenomenal writeup per usual. Some of the model runs, like I said above, have just truly been a sight to behold, and this one in particuar that you posted is no different, due to just how widespread the CAPE, as well as the parameters are. Time to strap in for Sunday, as well as next week.
 
US_Highway15 said:
Phenomenal writeup per usual. Some of the model runs, like I said above, have just truly been a sight to behold, and this one in particuar that you posted is no different, due to just how widespread the CAPE, as well as the parameters are. Time to strap in for Sunday, as well as next week.
Click to expand...
Thanks, appreciate the compliment!

The HRRR will be starting to come into focus later today, and I'm super eager what it shows. The story across the center of the country might be the same as what the mid-South and Deep South will experience afterwards.
 
While the main surface low has flown off into Lower Michigan by 21Z Sunday, leaving a SW-NE oriented boundary that you'd think would be quite parallel to the upper-level flow (unfavorable for a supercellular storm mode), the 12Z NAM appears to be developing a secondary surface low in southern Illinois between then and 00Z Monday, which must be where all the SRH is coming from.

Pulled a couple of "PDS TOR" soundings off the run valid at 00Z Monday, one in southwest Indiana and another in *naturally* northern Mississippi. Paging @JPWX, turn off your tornado magnet.

nam_2025032812_060_34.9--89.29.pngnam_2025032812_060_38.78--87.04.png
 
wx_guy said:
A new run of the WRF-ARW model, using 06Z GFS initial conditions. It is centered on Memphis, TN, and has a 9 km resolution and a window of about 700 miles square.



Much more explosive convection firing than in previous runs of this model. This looks to promote a more multicellular mode than in previous runs. As you can see, there is still some space between the cells, though, so this could be the worst case scenario of many semi-discrete cells firing in the OWS. Not good.

View attachment 37525


The SCP shows a HUGE area (ridiculous really) above 10+ on the scale with some areas over 25+. This is looking like a very dangerous setup potentially.

View attachment 37526



The low-level Storm Relative Helicity is also alarming, with large areas over 350 m^2/s^2 and some areas occasionally topping 500. And remember, this is the lowest 500m (a metric you won't find many other places), so this is the tornado-prone part of the atmosphere. More and more concerning!

View attachment 37527



In particular, the Hodograph Curvature Area Index (a measure of how curved hodographs are) does a really nice (and scary!) job resolving tight rotation of supercells through MS, TN, and AL.

View attachment 37528



The Wind Gust Potential algorithm is designed to predict maximum wind gusts over a given area. It is similar to DCAPE but is measured in MPH. It mixes down a proportion of winds higher in the atmosphere, based on the low-level lapse rates in a given area. I've also overlaid the front/boundary detection algorithm (in golden) and the tiny hodographs overlay. If you look closely, you can see a couple of cells the model is trying to resolve put out possible gusts of 70+ across northern MS and AL.

View attachment 37532



Finally, the Tornado Risk Index is a composite parameter that factors in STP (fixed version), SCP, helicity, shear, and a couple of other factors and scales it on a scale from 0 to 10. In addition, areas with elevated chances of significant tornadoes (EF2+) get hatched. It looks increasingly like a large area in the middle and South of the country may have an opportunity for significant tornadoes. The peak Tornado Risk is N MS/W TN/N AL, where pockets of 8 out of 10 appear.

View attachment 37539


It still looks somewhat conditional, but it looks a LOT less conditional than yesterday. It looks like the ingredients are coming together for a potentially significant outbreak spanning multiple days. I think a large part of the current Enhanced Area will be upgraded eventually to a Moderate, and the Slight risk on Monday will be partially upgraded to Enhanced.
Click to expand...
Went ahead and sent a heads up to a friend I got out in Western KY by the lakes. The 0-500 SRH is off the scale shown near him.
 
CheeselandSkies said:
While the main surface low has flown off into Lower Michigan by 21Z Sunday, leaving a SW-NE oriented boundary that you'd think would be quite parallel to the upper-level flow (unfavorable for a supercellular storm mode), the 12Z NAM appears to be developing a secondary surface low in southern Illinois between then and 00Z Monday, which must be where all the SRH is coming from.

Pulled a couple of "PDS TOR" soundings off the run valid at 00Z Monday, one in southwest Indiana and another in *naturally* northern Mississippi. Paging @JPWX, turn off your tornado magnet.

View attachment 37549View attachment 37550
Click to expand...
Well that's less than ideal. What's up with these secondary lows (March 15th and this event lol)
 
Hey all, I'm preparing to run a 1 km ultra high resolution run so we can see things like Updraft Helicity cores and things like that (you can't really do that at 9 km resolution, it all just smears together and loses information). But because 1 km has soooo many grid points, it's impossible to do over a large area. So I'm really curious -- what area do you think would be best to center the run on? It'll probably be 200 miles square max at the most because I don't want it to run for days. I understand you may want it centered over your neighborhood, but realistically, where is the best place to center it to capture the most useful data? I'm thinking either Nashville, Birmingham, or Memphis (I've focused on those a lot lately!), but any other ideas? Consensus?
 
No Moderate Risk yet but updating wording certainly suggests it's coming.
 
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