Central/Western Medium-Long Range Discussion

[andyhb]

I haven't seen them; why are they "wow"?

 

A lot of western troughing/ridging over the eastern 2/3 of the country. Speaking for possible severe wx implications of course.

 

I apologize for the initial vagueness there.

[icebreaker5221]

A lot of western troughing/ridging over the eastern 2/3 of the country. Speaking for possible severe wx implications of course.

 

I apologize for the initial vagueness there.

 

Ok cool, thanks!

 

I'd also say that the 11-15day GEFS mean has some potential - I can picture a few embedded shortwaves digging nicely out of that trough in the TX/NM/OK region with decent return flow out of the Gulf. 

 

[Stebo]

I am getting very interested in the period around and after April 7th. Looks like a wholesale pattern change with a prolonged trough in the west and a ridge in the east. I could certainly see this period yielding some potential systems of interest with a high ceiling at that.

[1900hurricane]

As am I. Even at the tail end of fantasyland for most of the operational models, the change is already starting to be picked up on. It might be time for me to start looking at my schedule and seeing what I might need to do to free up a day in the future.

[Srain]

If this pattern does indeed develop, the first full week of April may have some potential...severe weather wise across our Region.

 

 

[brettjrob]

Cautiously optimistic that at least some changes are afoot for the medium range. It seems unlikely that the months-old Hudson Bay vortex will break down anytime soon, and most (maybe all?) of the guidance agrees on that point. That might put somewhat of a cap on just how favorable the pattern can become, particularly being that it's still early in the season, when higher-amplitude troughs tend to be preferred for substantial Plains events. Any progress is welcome, though.

[Quincy]

Maybe we'll get some early to mid-April action down in Dixie Alley, where they're climo-favored anyway. That area was eerily quiet until April 27-28 last year.

[andyhb]

Just to tease Brett, the 12z Euro had the best High Plains setup I've seen in several years on D9-10.

[brettjrob]

Just to tease Brett, the 12z Euro had the best High Plains setup I've seen in several years on D9-10.

 

https://discoveringdifferent.files.wordpress.com/2014/04/and-its-gone.jpg

 

At least there's something to watch early-mid next week. If that turns into 3-4 days of a sloshing dryline as the trough junks out too far west, though, full ragemode may commence.

[brettjrob]

The 8-9 April event notwithstanding, the medium range (D6-15) currently looks remarkably active on the guidance. Pretty much a parade of significant disturbances crashing onto the west coast and translating across the CONUS without any crazy amplification east of the Plains to scour moisture out of the Gulf. The interval between systems and associated moisture return to areas well north of the Gulf could potentially be an issue, but otherwise, this is shaping up to be the most active April for this subregion since 2012 -- as of now, anyway. If this pattern materializes despite the continued record +PDO, I'll be mighty impressed.

[Quincy]

Say hello to the PAC ridge again ~April 15-19. It's been on the ensembles for quite some time. It's still a bit muddled how the pattern with respect to severe evolves after that, but at least it appears likely the ridging should break down fairly quickly.

[brettjrob]

Say hello to the PAC ridge again ~April 15-19. It's been on the ensembles for quite some time. It's still a bit muddled how the pattern with respect to severe evolves after that, but at least it appears likely the ridging should break down fairly quickly.

 

Yeah, I don't know if I could've jinxed it better if I tried. Moisture return will in fact be a problem tomorrow, and then the STJ closed low starts filling to the point where shear over the warm sector is unremarkable by Sun-Mon. The much-advertised big trough next week is now but a whimper, and another positive-tilt one at that, most likely. With shortening wavelengths and multiple attempts at cutoffs, who knows what the medium range will bring... but with the raging +PDO showing no signs of abating, it's hard not to panic when you see that Pac ridge even try to start settling in.

 

But if recent GFS QPF over TX/OK between now and Tuesday verifies, I guess I can wait a bit. #payitforward

[andyhb]

But if recent GFS QPF over TX/OK between now and Tuesday verifies, I guess I can wait a bit. #payitforward

 

April showers bring May...tornadoes?

 

I don't think it is any time to panic. I've seen a number of mets with a mid-April lull as far as activity goes. There also hasn't been a dominant -EPO showing up on the ensembles to reinforce the E Pacific ridging being forecast (knock on wood). Even if a -EPO does develop, the wave shortening you mentioned will mean that it won't have the same effect that it did back in winter. There have been a number of very active May/June periods in particular where the EPO was predominantly negative.

[brettjrob]

The past 10 days have been among the best we've seen in years for drought relief in the most dire areas, as long as you're not in the western Panhandles or SW KS.

 

 

The active STJ looks to continue unabated into next week. If not for the substantial Great Lakes/Northeast troughing, there'd probably be one or more major severe weather days on the southern Plains next week. It's been way too long since the southern branch has been remotely active like this, with energetic waves translating across N Mexico and the Desert SW. If this can continue into early-mid May (big "if"), this would most likely be the best southern Plains season in several years, particularly out west.

[andyhb]

The active STJ looks to continue unabated into next week. If not for the substantial Great Lakes/Northeast troughing, there'd probably be one or more major severe weather days on the southern Plains next week. It's been way too long since the southern branch has been remotely active like this, with energetic waves translating across N Mexico and the Desert SW. If this can continue into early-mid May (big "if"), this would most likely be the best southern Plains season in several years, particularly out west.

 

Might want to look at the 12z GFS/Euro for Friday. The Euro is particularly impressive.

[brettjrob]

Might want to look at the 12z GFS/Euro for Friday. The Euro is particularly impressive.

 

Yeah, there's certainly some potential on multiple days; didn't mean to dismiss it entirely. And if the downstream troughing trends weaker on subsequent runs, there could end up being a higher-end day after all.

[Quincy]

After being stuck in model fantasy land, now inside of 10 days we have model support and agreement of some ridging in the east. We'll see if this comes into fruition. If so, we could see some enhanced severe activity into early May.

[brettjrob]

By 48 hours from now, the drought across most of OK and N TX will have been beaten into submission to the point that minor to moderate long-term hydrological impacts are all that remains. Even farther W into the Panhandles, this drenching should probably ensure average-or-better evapotranspiration for awhile. Bring on May, and good riddance to this active but underwhelming April.

[andyhb]

By 48 hours from now, the drought across most of OK and N TX will have been beaten into submission to the point that minor to moderate long-term hydrological impacts are all that remains. Even farther W into the Panhandles, this drenching should probably ensure average-or-better evapotranspiration for awhile. Bring on May, and good riddance to this active but underwhelming April.

 

Most ensemble guidance indicates some form of western troughing developing towards the end of the first week of May (possibly with periodic shortwave ejections in advance), looks fairly promising at this time.

[Quincy]

Most ensemble guidance indicates some form of western troughing developing towards the end of the first week of May (possibly with periodic shortwave ejections in advance), looks fairly promising at this time.

It's encouraging now to see this signal prevalent on a majority of the ensemble members, of both the Euro and GFS.

 

Finer details are a long way from being resolved, but after a momentary break in the action, we could see severe threats begin to ramp up again. (I think there is some thunderstorm potential by this Sunday/Monday, but something more significant likely holds off until later next week or the weekend that follows)

[brettjrob]

I can't be the only one getting concerned about the "jet disappearing into Canada act" (ala May 2009/2012) that seems to be a theme on MR guidance. There may be several days of semi-interesting high CAPE/low shear potential next week, and there's always a chance one of those days could emerge as more significant. But if we're talking amplified western CONUS troughing and large-scale organized threats, it seems we might be waiting until closer to mid-month, at least.

[Quincy]

I can't be the only one getting concerned about the "jet disappearing into Canada act" (ala May 2009/2012) that seems to be a theme on MR guidance. There may be several days of semi-interesting high CAPE/low shear potential next week, and there's always a chance one of those days could emerge as more significant. But if we're talking amplified western CONUS troughing and large-scale organized threats, it seems we might be waiting until closer to mid-month, at least.

Have to admit I'm getting a bit concerned. I'd much rather have an overall favorable pattern than a couple of days that may or may not produce.

The trend with the ensembles has been to knock the flow relatively zonal, but with positive height anomalies and pushing the jet north later into May. Although the 00/30 EC ENS showed more West Coast troughing by day 15, the ensembles have had poor consistency and verification beyond day 10 over the past several weeks. If you believe the CFS, it also shows signs of death ridging by mid-May.

Looking at some more data throughout today and after the Euro Weeklies come out, I'll be ready to put a May tornado outlook together.

[Chicago Storm]

Don't expect another worthy chase day for me until mid-month. Upcoming pattern until that point really doesn't look like anything more than run of the mill sort of events, though as Brett stated, something interesting could pop up on short notice.

[Ian]

CFS has been nice looking final third of May lately which is good for us except it probably will verify as a Great Lakes low. Also, CFS.. lol.

[Thundersnow12]

The CFS is changing run to run and even isn't in line with the GFS/Euro.

 

Victor Gensini and myself are heading up trip 2 with CoD and we leave 5/15 and we both think it looks quite good at this stage and are very optimistic. 

[andyhb]

The CFS is changing run to run and even isn't in line with the GFS/Euro.

 

Victor Gensini and myself are heading up trip 2 with CoD and we leave 5/15 and we both think it looks quite good at this stage and are very optimistic. 

 

I saw his latest ERTAF and he had the week from the 9th to the 16th as above average for activity.

[Thundersnow12]

I saw his latest ERTAF and he had the week from the 9th to the 16th as above average for activity.

 

He will also be going above normal for the week to follow that as well. 

[Ian]

The CFS is changing run to run and even isn't in line with the GFS/Euro.

Victor Gensini and myself are heading up trip 2 with CoD and we leave 5/15 and we both think it looks quite good at this stage and are very optimistic.

Def ensemble support for mid month. CFS is a joke.. Sorta. More trough runs than ridge runs.

 

Overall I'd be rather positive at this pt. Think after 'break' we see another active stretch which rarely fully disappoints this time of year. What April was lacking should be more available, plus April made do with a fairly unsupportive CONUS pattern overall.

[Quincy]

I think there are some encouraging signs. Here is the 500mb mean analog pattern for mid to late May, using the top 5 analogs from the GEFS 6-10 day forecast. It actually lines up very closely to the 00/30 Euro Weeklies projection for the time period, only slightly further east (even better) with the ridge axis.

 

I whipped together a quick May tornado forecast here. A little bit more cautious of an outlook than for April, but I wouldn't be surprised if there was a bigger event somewhere in the second half of May.

[Indystorm]

Good research, Quincy, on your tornado forecast.  I suppose it is always more difficult to forecast trends with tornadoes than what a hurricane season might look like as Dr. Gray at Colorado State and others have done well in advance.  My concern for May at least with recent model runs is the apparent lack of a strong jet stream in the CONUS.  That, of course, can change.