Central/Western Summer Medium/Long Range Discussions

[CoastalWx]

Pattern could be pretty good for severe with a trough digging into the west coast in the 11-15 day.

[andyhb]

Pattern could be pretty good for severe with a trough digging into the west coast in the 11-15 day.

 

Yeah I will say that the pattern developing on the ensemble 8-10 day means (all of them actually) would also be very favorable heading into May.

[tornadotony]

General rule of thumb: after a long cold spell, never get excited about the first system to bring severe prospects, especially if it doesn't looks like it's a one-and-done deal.  The first system often serves the role of a sacrificial lamb, lacking impressive results but drawing moisture northward and leaving a favorable ridge configuration for major moisture advection with the next system.

[brettjrob]

General rule of thumb: after a long cold spell, never get excited about the first system to bring severe prospects, especially if it doesn't looks like it's a one-and-done deal.  The first system often serves the role of a sacrificial lamb, lacking impressive results but drawing moisture northward and leaving a favorable ridge configuration for major moisture advection with the next system.

 

I can definitely see the 4/23-25 system serving to prime the pump for another wrn CONUS trough over the 5-7 days that follow, should one develop.

 

I'm not yet convinced moisture will be a crippling issue next week, though it certainly could be. For all this season's frustrations thus far, one thing I've noticed is that moisture return ahead of a given trough has tended actually to increase in the guidance as we move from this (D8-10) range into the shorter range. That being said, my broken-record complaints about severe drought over the Panhandles and surrounding regions still stand, particularly in reference to Wed 4/23. My best guess would be that if the system isn't too progressive and this becomes a two-day setup, then moisture may not be a problem on Thu 4/24 over the central to eastern part of the Plains (owing both to the land type/lesser drought and the extra day of recovery). The 12z GFS pretty much shows that scenario.

[thewxmann]

This upcoming setup reminds me of 4/6/06. It literally wreaks of moisture mixing out.

[Stebo]

This upcoming setup reminds me of 4/6/06. It literally wreaks of moisture mixing out.

Lets give it a few days before you downplay the potential with something like moisture mixing out. It is still too early to get an idea of the strength of the moisture return into the plains.

[Quincy]

This upcoming setup reminds me of 4/6/06. It literally wreaks of moisture mixing out.

Totally different setup. No cutoff bowling ball sitting over PA/NY.

Interestingly enough, 4/6/06 was a decent 200+ severe report day followed by a significant tornado outbreak on the 7th further east.

[andyhb]

The first system often serves the role of a sacrificial lamb, lacking impressive results but drawing moisture northward and leaving a favorable ridge configuration for major moisture advection with the next system.

I can definitely see the 4/23-25 system serving to prime the pump for another wrn CONUS trough over the 5-7 days that follow, should one develop.

 

[1900hurricane]

Really digging that look over the Gulf of Alaska in the chart above.

[Thundersnow12]

0z GFS pretty impressive verbatim for next Thursday. Long way off obviously.

[andyhb]

I like how it shows a string of pearls on the dryline on the convective precip simulations.

[andyhb]

So the 00z Euro shows a near 200 kt upper jet streak in the N Pac coming in behind this trough, that is unbelievable (oh and 135+ kts at 500 mb).

 

Also, taken verbatim, western/central KS looks pretty nasty on Wednesday with a relatively wide instability axis and some very strong low level shear (it fires storms on the dryline too from the looks of it). That said, I won't be surprised if this slows down and Thursday becomes the main day.

[HM]

The long wave pattern to end the month could be worse, really. Below are some quick analog sets for certain factors...how did these play out in the Plains overall?

 

Global SST / ENSO (best matches): 2002, 1997, 1994, 1991, 1972 and 1957

Honorable mention global SST: 2009, 2004, 1986, 1982. 1977, 1976, 1965 and 1963

MEI SHIFT: 1997, 1986, 1982, 1972, 1965 and 1957

QBO (loose with shear patterns. * denote the closest matches) / ENSO: 2009*, 2004, 2002, 1997, 1991*, 1986*, 1976*, 1972*, 1968, 1965, 1958* and 1953

 

It seems like 1972, 1997, 1991 are some the strongest matches. We certainly, severe-wise, aren't behaving like 1991 so far.

[HM]

Really digging that look over the Gulf of Alaska in the chart above.

 

Yeah, the late April / early May pattern is looking pretty alright right now on the latest GEFS/EPS. Stronger than usual EML-advection pattern with a tendency for a trough in the western USA is a good start! The issue of blocking and trending cooler/drier is a concern, but that pipeline could be directed toward the Northeast.

[Radtechwxman]

Im def liking the look of the long range on models. gfs consistently is showing another even more potent system around April 30th-May 1st. and this system would likely have a better thermodynamic environment to work with, with better moisture in play with less systems traversing through the gulf and robbing the moisture. also looks like a powerhouse jet is trying to work its way down from the gulf of Alaska. as far as next week there will def be some severe weather but how widespread and how severe is the main question. the system has a lot of potential with a nice neg tilt trough and moderate 850's to the SSW. moisture is my main concern. im afraid of these systems preceding this storm will rob our moisture feed. gfs could be overdoing dew points again. hard to say this far out. it is a waiting game now

[tornadotony]

Yeah it's really starting to look like a sustained pattern change in the long-range.  The details aren't important right now.  What's important is that the GFS and Euro are showing hints of a pattern with the general longwave trough sitting over the west and shortwave after shortwave impacting regions between the Plains and Appalachians, with each wave lifting off w/o scouring the Gulf.  The long-range pattern reminds me a lot of 2010, which was dead as a doornail until 4/22 and then lit up at an absolutely torrid pace.  The ENSO phase is different (we were transitioning out of strong Nino toward mdt-strong Nina in 2010), but I wouldn't be shocked if we have a number of significant severe events from late April through May that impact anywhere from the Plains to the SE up to the Great Lakes.

[andyhb]

Currently, Wednesday looks like one of those days where capping is making things uncertain, but if storms go on the dryline, look out. The parameters by 00z Thursday are just nasty on the GFS and Euro. Obviously smaller scale details, like the lead vort that looks to eject ahead of the main trough, will become finer tuned as we move closer in, but I'm noticing that instability seems to be increasing with every run, not to mention that D2 also has a good amount of potential depending on how the main s/w rotating around the base of the trough behaves.

[Thundersnow12]

Currently, Wednesday looks like one of those days where capping is making things uncertain, but if storms go on the dryline, look out. The parameters by 00z Thursday are just nasty on the GFS and Euro. Obviously smaller scale details, like the lead vort that looks to eject ahead of the main trough, will become finer tuned as we move closer in, but I'm noticing that instability seems to be increasing with every run, not to mention that D2 also has a good amount of potential depending on how the main s/w rotating around the base of the trough behaves.

 

Yeah Weds looks much better on the 12z GFS compared to the 0z run, much tighter dryline, better instability etc

 

Haven't seen these colors since last May

 

[andyhb]

Yeah Weds looks much better on the 12z GFS compared to the 0z run, much tighter dryline, better instability etc

 

Haven't seen these colors since last May

 

gfsSGP_con_scp_156.gif

 

Great cross-overs there, >60˚ veering between 850 and 500 mb along the dryline.

[bdgwx]

I'm trying to find a late April or early May analog that best matches the 12Z GFS for the 4/23-4/25 time range. Any ideas?

[andyhb]

Euro is still way more amplified with the northeastern troughing compared to the GFS.

[brettjrob]

I'm trying to find a late April or early May analog that best matches the 12Z GFS for the 4/23-4/25 time range. Any ideas?

 

Without digging into the details, I'd say 5/4/07 had some similarities to 4/23 on the 12z GFS. Naturally, though, picking analogs from memory alone usually biases toward significant events (memorable) rather than duds (not memorable). Just one to look at.

[andyhb]

Euro is also still showing an extremely intense N Pac jet streak migrating through the Aleutians through 192 hrs, probably several standard deviations above normal, and it is dropping into that trough setting up to the west of British Columbia. It's also of note that there is high latitude blocking into the NW Territories preventing the western troughing regime from devolving.

 

There's also a ridge beginning to funnel large amounts of moisture into the south central/southeastern portions of the country.

 

Edit: Wow at 216...

[thewxmann]

Lets give it a few days before you downplay the potential with something like moisture mixing out. It is still too early to get an idea of the strength of the moisture return into the plains.

 

Well, the GFS & Euro love the idea of maintaining an sfc anticyclone over the NE GOM for several days leading up to the event. Given the drought, that could be a deal breaker WRT moisture.

 

Tony probably has the right idea here. The first system is likely to be a significant severe wx producer but the better widespread tornado chances for chasers will probably wait for subsequent systems.

[bdgwx]

Without digging into the details, I'd say 5/4/07 had some similarities to 4/23 on the 12z GFS. Naturally, though, picking analogs from memory alone usually biases toward significant events (memorable) rather than duds (not memorable). Just one to look at.

 

I know what you mean. It is hard to remember the duds. The 4/6/06 date someone else threw out looks pretty darn close even though it is almost 3 weeks removed which probably doesn't matter that much.

[Chicago Storm]

Euro is still way more amplified with the northeastern troughing compared to the GFS.

Yep.

 

Wed is still the day on the 12z, but with DP's generally <60F it's sort of meh.

[andyhb]

Yep.

 

Wed is still the day on the 12z, but with DP's generally <60F it's sort of meh.

 

FWIW none of the other guidance is as amplified with that either, with more progressive flow.

[andyhb]

This keeps looking more impressive with every run.

 

[Quincy]

Yeah it's really starting to look like a sustained pattern change in the long-range. The details aren't important right now. What's important is that the GFS and Euro are showing hints of a pattern with the general longwave trough sitting over the west and shortwave after shortwave impacting regions between the Plains and Appalachians, with each wave lifting off w/o scouring the Gulf. The long-range pattern reminds me a lot of 2010, which was dead as a doornail until 4/22 and then lit up at an absolutely torrid pace. The ENSO phase is different (we were transitioning out of strong Nino toward mdt-strong Nina in 2010), but I wouldn't be shocked if we have a number of significant severe events from late April through May that impact anywhere from the Plains to the SE up to the Great Lakes.

Strictly looking at tornado reports, this year very closely matches to 2010 as well. Trends are certainly encouraging toward the end of this month.

[Stebo]

Well, the GFS & Euro love the idea of maintaining an sfc anticyclone over the NE GOM for several days leading up to the event. Given the drought, that could be a deal breaker WRT moisture.

 

Tony probably has the right idea here. The first system is likely to be a significant severe wx producer but the better widespread tornado chances for chasers will probably wait for subsequent systems.

 

Yes and Tony's idea I agree with, but it isn't mixing out of moisture like you mentioned yesterday, that would be more of a lacking of quality moisture depth moving that far north to begin with.