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18-20 March 2012 severe prospects


tornadotony

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I don't normally post for anything this far out, and specifics will not be provided in this post. But the GFS and the Euro have both been consistent in bringing a powerhouse jet ashore sometime a bit after St. Patrick's Day. How it evolves changes from run to run, but there have been two constants in this equation.

1) Very powerful jet.

2) Wide open Gulf, extremely warm/humid central/eastern United States, with that airmass locked in place in the previous days.

It's too early to even highlight regions that might be threatened. It could be anywhere from the southern plains to the lower Lakes or even the upper Midwest. But combining the two above constants does not typically end all that well, and this time frame bears very close watching through the week and next weekend.

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If you don't mind me asking, Could you show maps of this?

First system is the upper level low centered in SW Saskatchewan and the second comes out of that vigorous mid/upper level jet streak into Southern CA, and you can see how they are close to merging together into one beast of a trough (the 528 dm heights are connected between both jet streaks, previously, there was a ridge between the two systems). In that case, the second, more powerful jet streak would possibly lead to a powerful shortwave impulse ejecting out from underneath the trough sometime between 174 and 216 hrs, inducing rapid, potentially intense surface cyclogenesis, beneath a broad-based and likely somewhat negatively tilted trough, which would spell big trouble in all likelihood for somebody.

Both systems have huge warm sectors to work with.

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First system is the upper level low centered in SW Saskatchewan and the second comes out of that vigorous mid/upper level jet streak into Southern CA, and you can see how they are close to merging together into one beast of a trough (the 528 dm heights are connected between both jet streaks, previously, there was a ridge between the two systems). In that case, the second, more powerful jet streak would possibly lead to a powerful shortwave impulse ejecting out from underneath the trough sometime between 174 and 216 hrs, inducing rapid, potentially intense surface cyclogenesis, beneath a broad-based and likely somewhat negatively tilted trough, which would spell big trouble in all likelihood for somebody.

Both systems have huge warm sectors to work with.

Thank you for posting that. Now I was also looking at the Euro, and it seems to show only a single system during that time frame, but it doesn't really eject at all, and ends up being cut off at 216 hr. Now, as I understand it, the Euro sometimes has problems modeling the ejection of a shortwave onto the Plains. Is that correct, and may the Euro's depiction of the low getting cut off be therefore in error?

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The Euro develops some kind of insane blocking that prevents the trough from ejecting fully, it has a closed off 582 dm ridge across the NE at 240, which seems pretty unrealistic, even with the extent of this torch. I mean, 570 dm heights into Hudson's Bay in March? Come on...

If that first wave comes in like the GFS progs, it will likely suppress the ridge somewhat and allow the second upper/mid level trough to eject more fully, and, as I mentioned, it is close to merging the two storm systems together.

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The Euro develops some kind of insane blocking that prevents the trough from ejecting fully, it has a closed off 582 dm ridge across the NE at 240, which seems pretty unrealistic, even with the extent of this torch. I mean, 570 dm heights into Hudson's Bay in March? Come on...

If that first wave comes in like the GFS progs, it will likely suppress the ridge somewhat and allow the second upper/mid level trough to eject more fully, and, as I mentioned, it is close to merging the two storm systems together.

You're right. That would be one heck of a torch. Heck, it was considered notable down here during last summer in Memphis when the 500 hPa heights got up to 592 dm over us, as they did on a number of occasions. 582 dm and 588 dm heights were the minimum rule over us, making for an absolutely baking summer. I'm guessing the reason the Euro has a tendency to hold back the shortwave is because it tends to build up too strong of blocking.

I suppose it remains to be seen exactly where this unified trough would set up. If it's large and broad, though, then it would likely affect a large area of the country.

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As we've been discussing over in Central/Western for a few days now, the stage being set over the course of this next week is rather extraordinary for mid-March. Ignoring the potential for big fireworks once the trough ejects, it's noteworthy enough just to look at the surface dew points and SBCAPE progged over much of the central U.S. each afternoon this coming week (starting Tuesday). I can't remember ever seeing a sloshing dryline with high instability hanging out over the Plains and upper Midwest day-after-day prior to late April... until now.

Like Tony said, extended, broad eastern CONUS ridging that draws in unseasonably-rich low-level moisture this early in the season is a huge red flag all on its own. In all likelihood, the only way to "avoid" a high-impact event over the next 7-14 days will be for the omega block solutions to verify, preventing the longwave trough from ever translating past the Great Basin prior to lifting/shearing out.

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As we've been discussing over in Central/Western for a few days now, the stage being set over the course of this next week is rather extraordinary for mid-March. Ignoring the potential for big fireworks once the trough ejects, it's noteworthy enough just to look at the surface dew points and SBCAPE progged over much of the central U.S. each afternoon this coming week (starting Tuesday). I can't remember ever seeing a sloshing dryline with high instability hanging out over the Plains and upper Midwest day-after-day prior to late April... until now.

Like Tony said, extended, broad eastern CONUS ridging that draws in unseasonably-rich low-level moisture this early in the season is a huge red flag all on its own. In all likelihood, the only way to "avoid" a high-impact event over the next 7-14 days will be for the omega block solutions to verify, preventing the longwave trough from ever translating past the Great Basin prior to lifting/shearing out.

It really is extraordinary. We never really had a winter, and now we're entering a May-type pattern.

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As for the later system, 00z went south, ends up closing the low, but it still ejects and you still get an ugly setup across the Plains/Ozarks on the 19th/20th/21st, and this is with the 582 dm line into Ontario and a closed off 585 ridge in the NE...

This concerns me significantly, as we still are seeing a volatile setup even with the omega blocking solution in place...

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As for the later system, 00z went south, ends up cutting off the low, but it still ejects and you still get an ugly setup across the Plains/Ozarks on the 20th/21st, and this is with the 582 dm line into Ontario...

In other words, we're still gonna wanna take it with a grain of salt.

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In other words, we're still gonna wanna take it with a grain of salt.

Yes, of course, given we're 8-10 days out, but I think my concern just went up a bit seeing a potentially significant setup with the trough ejecting even with Euro-like blocking in place. (I.E. I'm looking for trends in one direction or the other for this system at this point).

Right now I'll focus on that lead wave, which looks to be a possible setup in itself, if the upper support arrives in time to help erode the cap.

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The 00z GFS looks extremely impressive for Monday 3/19... no other way to put it. Simply a textbook early spring dryline setup for central and western portions of NE/KS/OK/TX. No reason to get into details given the timeframe and wild swings in the evolution of this trough, but the main takeaway is that the GFS has moved back toward ejecting it in a timely manner.

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Anything for the Ohio Valley/Great Lakes region in the next few weeks???

You don't need to post multiple question marks :D

But, yes, I think there is a definite possibility.

And...yeah, what brett just mentioned looks ominous (keep in mind Brett that this ridging on this run is even more impressive than the Euro, more blocking and still a dangerous looking situation), it is not often you see that much CAPE show up on the GFS 192 hrs out...wow...

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You don't need to post multiple question marks :D

But, yes, I think there is a definite possibility.

And...yeah, what brett just mentioned looks ominous (keep in mind Brett that this ridging on this run is even more impressive than the Euro, more blocking and still a dangerous looking situation), it is not often you see that much CAPE show up on the GFS 192 hrs out...wow...

Exactly... one would assume that a less extreme Omega pattern would lead to less meridional flow and slightly better moisture. Eagerly awaiting the Euro, though it's going to be harder to stay awake that long from here on out!

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Anything for the Ohio Valley/Great Lakes region in the next few weeks???

It's still too early to know what the evolution of this storm is going to be, so what we've talked about being shown on St. Patrick's Day and beyond has potential for pretty much anywhere between the Appalachians and the Rocky Mountains. As we get closer, we should start being able to pin down specific regions most likely to be affected.

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Exactly... one would assume that a less extreme Omega pattern would lead to less meridional flow and slightly better moisture. Eagerly awaiting the Euro, though it's going to be harder to stay awake that long from here on out!

There's very minimal capping as well.

Allow me to add to my previous post, it is exceedingly rare to see that much CAPE show up on the GFS at 192 hrs in a relatively uncapped warm sector...

And even with all these systems, the Gulf remains virtually untouched.

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There's very minimal capping as well.

Allow me to add to my previous post, it is exceedingly rare to see that much CAPE show up on the GFS at 192 hrs in a relatively uncapped warm sector...

And even with all these systems, the Gulf remains virtually untouched.

That last point certainly supports the idea of multiple rounds in the latter half of the month.

Oh boy, now we're back into the watching and waiting game. By the time we get to the event, I wouldn't have been thinking about anything but models and potential. :P

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I don't normally post for anything this far out, and specifics will not be provided in this post. But the GFS and the Euro have both been consistent in bringing a powerhouse jet ashore sometime a bit after St. Patrick's Day. How it evolves changes from run to run, but there have been two constants in this equation.

1) Very powerful jet.

2) Wide open Gulf, extremely warm/humid central/eastern United States, with that airmass locked in place in the previous days.

It's too early to even highlight regions that might be threatened. It could be anywhere from the southern plains to the lower Lakes or even the upper Midwest. But combining the two above constants does not typically end all that well, and this time frame bears very close watching through the week and next weekend.

Honestly I can not remember a time period of extended above normal temps/moisture flowing northward for so many days in advance of this trough. I mean some of the instability numbers that the GFS is putting out before this would be exceptional for severe weather this time of the year and mind you it is the GFS which has a tendency to grossly underdo instability in the early season. A closer to reality image would be the NAM, an example of the potential amount of instability for the region later this week is as follows:

wrfGL_0_cape_72.gif

If someone posted this without a date I would say Late May or Early June. To have 3000 J/kg of CAPE this far north this time of year is absolutely extraordinary, and one would imagine as you go on further in time closer to this system next weekend these numbers would have the potential to go up even higher given the continual flow out of the gulf plus the upper-level cooling advancing in with the trough. Like you say it is hard to pinpoint an area right now but to see the stuff we are seeing in the models looking ahead one would certainly be concerned about a significant outbreak within the 5-10 day range, maybe a couple outbreaks.

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Honestly I can not remember a time period of extended above normal temps/moisture flowing northward for so many days in advance of this trough. I mean some of the instability numbers that the GFS is putting out before this would be exceptional for severe weather this time of the year and mind you it is the GFS which has a tendency to grossly underdo instability in the early season. A closer to reality image would be the NAM, an example of the potential amount of instability for the region later this week is as follows:

If someone posted this without a date I would say Late May or Early June. To have 3000 J/kg of CAPE this far north this time of year is absolutely extraordinary, and one would imagine as you go on further in time closer to this system next weekend these numbers would have the potential to go up even higher given the continual flow out of the gulf plus the upper-level cooling advancing in with the trough. Like you say it is hard to pinpoint an area right now but to see the stuff we are seeing in the models looking ahead one would certainly be concerned about a significant outbreak within the 5-10 day range, maybe a couple outbreaks.

Great post. Reminds me a bit of April 9th/10th last year thermodynamically, except three weeks earlier...

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