andyhb

How's the euro look compared to the GFS?

Looks pretty favorable as well, although it was further south for Tuesday last night (closer to the Red River Valley).

Take this with a grain of salt, but...

Popping 6/24/03, 5/3/99 and 4/26/91 in SARS on the same sounding? Not bad.

Tuesday next week is looking like a pretty legit threat at this point for somewhere in the Plains. Seeing some pretty top-tier instability/moisture values for late April, which makes sense with that lead shortwave this weekend assisting with poleward moisture transport.

Oddly, it's falling directly on the 25th anniversary of 4/26/91.

The 12z EPS looked pretty substantial to me, especially in the 7-10 day period, as did the 12z Euro op. The trough at 192-216 hrs would likely have a more significant potential since that lead wave helps advect mid 60s dews into the Plains (sacrificial lamb more or less). Then there's also that fact that it looks to reload right behind that.

Well that's an interesting #1 analog (some other big periods there too especially in the Plains)...

Things seem to be shaping up for a more favorable look later next week into the following one with multi-model/ensemble consensus of a western trough (and currently a rather progressive regime) setting up shop. Would have to think there would be one or more setups in the Plains if that ends up coming to pass, perhaps even on the more robust end assuming seasonable moisture return (which doesn't look to be out of the question). Not a huge fan of the Hudson Bay troughing that persists, but otherwise things are certainly looking more active for the tail-end of April.

*sigh*

Not sure I've ever seen a signal this strong from the CFSv2 SCP chart for 3 days in a row...especially this early in the season.

Pulled a sounding off the 12z Euro at SGF at 180s and it was pretty incredible. Very steep mid level lapse rates (SBCAPE near 2000 J/kg) with SRH in excess of 650 m²/s² and just a huge sickle shaped hodograph. Hopefully we get some more agreement among guidance for this period in the coming days, because it looks like it could shape up to be a more significant event assuming even rather marginal moisture return (given the impressive thermodynamics aloft).

Figured I'd bump this to let everyone know that the gaps in the ABC 33/40 coverage (on John Brown's Youtube page) of this event are going be filled in over the coming days since Bill Castle found it. The morning coverage (of the intense QLCS that swept through the state) between 3:30 and 6:00 AM is already uploaded.

https://www.youtube.com/watch?v=SGqjHgLzibY

https://www.youtube.com/watch?v=aZ9S0rFhRHw

Euro + EPS + Euro parallel (and the UK now that it has gotten in range) have been consistently hitting this potential for several days now. A lead shortwave trough ejection and strong lee cyclogenesis looks to occur March 7th (Monday) leading to a strong southerly LLJ of 40-50+ kts encouraging BL dewpoints to rise into the lower 60s across OK and KS ahead of a very sharp dryline. While this moisture may seem rather meager, keep in mind we're also looking at EML-assisted mid level lapse rates of 7.5-8+ C/km with this event, so that should be enough for moderate destabilization assuming some decent insolation (may need to watch for moisture mixing if it turns out to not be overly deep). This will also lead to a rapidly moistening BL further south for the next day.

On day 2, the primary upper impulse looks to eject towards the Rio Grande Valley as the low level jet strengthens in excess of 55 kts across E TX, the Arklatex and LA. While the flow does appear to be a bit meridional, there is certainly enough of an upper level jet component ejecting ahead of the trough to encourage storm development out ahead within a potentially very unstable warm sector (strong low level shear as well with backed SSE/SE surface winds underneath the aforementioned LLJ). If this setup turned out to be just a bit less amplified and/or meridional, we'd be talking some serious potential given the amount of instability that looks like it could be present (still think there is quite a bit of potential how it sits now). We'll see what happens as it is still a week out.

Definitely looks like the first more significant threat may be on the way with more possible afterwards given GWO progression through at least phases 8-1 and a shift towards a +EPO (Gulf of Alaska trough) through the first two weeks of March. CFSv2 chiclet chart has been lighting up March for the better part of a month now, so this definitely seems to have some legs. Quite a contrast to the past 3 Marches.

If I were a chaser/living in OK/KS/N TX, I'd be keeping an eye on next Monday with the Euro's idea of a strong lee cyclone developing in response to that negatively tilted shortwave trough ejection. Healthy EML overspreads the dryline leading to a pretty wide axis of moderate destabilization along with great directional shear in the lowest 3 km (12z run via 180 hrs).

https://twitter.com/antmasiello/status/698172872704028672

Brilliant,   

Bug report: I think the SCP algorithm on the site needs a tweak.

Then it comes down to what character the trough ejection assumes, and whether it will be sheared out if the ridge amplifies too much ahead of it, or whether it amplifies too much and becomes too meridional.

This looks to be what most recent guidance has suggested.

Continued strong signal from the EPS and GEFS for a large western trough developing later next week, thanks to a very impressive jet over the Pacific and a lack of a blocking ridge along the W Coast. Favorable teleconnections with troughing in the Gulf of Alaska (+EPO and -PNA) look to be in place to get this moving into the CONUS.

Wouldn't be surprised if 2015 has at least one last go of it in the severe department should this end up verifying, especially considering the location of the SE ridge axis out ahead and what may be quite a moist warm sector (especially by December's standards) by the time the upper level jet pushes eastward of the Rockies. Deep moisture trajectories on the Euro look pretty prototypical for what you would want to see in a cold season event, coming right through the Caribbean. Then it comes down to what character the trough ejection assumes, and whether it will be sheared out if the ridge amplifies too much ahead of it, or whether it amplifies too much and becomes too meridional.

This is of course barring any complications from the active southern stream, i.e. shortwaves disrupting the return flow. The more reliable Euro has not been showing this to the extent that the NA models have though, thus has more instability. Regardless, as usual this time of year, the biggest question is always moisture quality and from what I'm seeing, this system does have a reasonably good chance of achieving that. With a very potent jet like this moving onto the W Coast, that is definitely an eyebrow raiser.

HGX had quite the discussion for Mon/Tues in their most recent AFD.

THE PATTERN WILL BEGIN CHANGE SUNDAY INTO MONDAY AS A DEEP PACIFIC
NORTHWEST TROUGH DIGS SOUTH INTO THE GREAT BASIN...SURFACE PRESSURE
GRADIENT TO ORIENT MORE ONSHORE EARLY NEXT WORK WEEK. STRENGTHENING
SOUTHERLIES THROUGH MID NEXT WEEK AHEAD OF WHAT IS PROGGED TO BE
A FAIRLY PROGRESSIVE STORM SYSTEM. THIS SYSTEM IS CURRENTLY MODELED
TO BE QUITE IMPRESSIVE...ESPECIALLY FROM A DYNAMIC STANDPOINT. THE
TROUGH IS FORECAST TO EVOLVE INTO A DEEP CLOSED-OFF LOW THAT WILL
BARREL OUT OF THE LOWER ROCKIES EARLY TUESDAY AND BE EAST OF US
BY MID TO LATE WEDNESDAY. UNLIKE RECENT SYSTEMS WHOSE ENERGY
TRAVELED OFF TO THE NORTHEAST...THIS LATEST TROUGH IS FORECAST TO
DIG WELL INTO NORTH CENTRAL TEXAS AND PROVIDE VERY ROBUST MID TO
UPPER LEVEL SUPPORT FOR VERY ACTIVE WEATHER. A 40-60 PLUS KNOT LOW
LEVEL JET WILL COME ACROSS THE FORECAST AREA EARLY TUESDAY...GENERATING
AN HIGHLY-SHEARED WIND PROFILE (RIGHT CURVED HODOGRAPH WITH 0-1KM
PLUS 200 SRH) THAT...IF THESE DETERMINISTIC MODELS GET IT RIGHT...
EQUATE TO A SEVERE WEATHER OUTBREAK MID-MONDAY THROUGH TUESDAY.
OTHER INGREDIENTS THAT ARE WORTH MENTIONING ARE COLUMN MOISTURE
AT...OR SLIGHTLY UNDER...2 INCH PWATS THAT IS NEAR MAXIMUM CLIMO
VALUES FOR MID- NOVEMBER...NEAR 1K TO 1.5K J/KG SB CAPE VALUES
(MID-UPPER 30 K INDICES)...AND A SIGNIFICANT SPLIT JET STRUCTURE
TUESDAY MORNING TO PROVIDE THE NEEDED UPPER LEVEL EXHAUST. ALL
TOLD...IF RUN-TO- RUN NWP CONSISTENCY HOLDS UP THROUGH THE WEEKEND
...THIS WILL BE ANOTHER IN A STRING OF SEVERE WEATHER OUTBREAKS
FOR US HERE IN SE TX. OF COURSE...WE ARE DISCUSSING DAYS 5 AND 6
SO CERTAINLY THERE IS MUCH TIME TO TUNE THE FINER DETAILS.
CONSIDERING WHAT THE 12/12Z DETERMINISTIC MODELS ARE OUTPUTTING...
THIS SYSTEM WOULD POSE A MORE OF A DAMAGING STORM WIND AND TORNADO
THREAT...VERSUS THAT OF FLASH FLOODING...STRICTLY DUE TO ITS VERY
PROGRESSIVE NATURE.

FWIW, the message I'm getting from basically every AFD I've read (OAX, EAX, TOP, LSX, SGF, ILX, DMX, etc.) is concern for just how dynamically impressive this system is, as I've stressed from the beginning with this thing. Troughs like this can and often do pull a lot out of very little thermodynamic wise. Then you start concerning with areas that actually have appreciable buoyancy like closer to the 500 mb low. I also noticed that the Euro was showing some better 700-500 mb lapse rates further south on Wed, although still very little CAPE.

I wouldn't be surprised if this thing peaks severe wise on Wed from 12-18z over the E Plains and Lower MO Valley. Both the Euro and GFS are showing some appreciable instability there closer to the triple point where colder 500 mb temps will result in steeper mid level lapse rates on the nose of the LLJ.

So, the last few ECMWF runs have looked interesting about 6 days out.

Instability looks rather low, what was once looking like a solid warm sector has shrunk into almost nothing.

A lot of tornadoes only reach their peak strength briefly. Moore 2013 was rated EF5 based on the damage to (IIRC) Briarwood Elementary School alone. 

This was changed upon further survey. Several homes that were bolted down to their foundations were swept away and these received an EF5 rating. Briarwood was discovered to have had multiple construction flaws and was downgraded.

Expecting a 2013-like fall any year would be a tall order, considering that year had not one but two really significant severe events (10/4 and 11/17). However, I would lean more on the active side this fall given that previous ones heading into Ninos have featured some substantial fireworks and especially if this new regime that has taken over the E Pacific continues deeper into October/November (i.e. Gulf of Alaska/western N. America trough).

Was there actually 200+ MPH winds?  I heard it was widespread 150 MPH winds, maybe 190 MPH tops.  Early reports said EF-4.  But because the tornado was so expansive, might as well make it a cat 5.  Conspiracy!

The EF5 rating was at least partly based (haven't read the survey in awhile) on manhole covers that were thrown from their locations and also concrete parking stops.

Seems to be the suggestion of a rather strong shortwave trough dropping SE out of the Gulf of Alaska towards the early part of next week via the deterministic guidance (supported a pronounced lowering of the heights across the Prairie Provinces and N Plains on the ensembles in this same timeframe). Northern stream has been quite active this summer so this doesn't seem to be too farfetched. Does seem that there may be some low latitude troughing that could cause problems with moisture availability though.

The next 7-10 days aren't looking too promising, at least anywhere in the Plains. The fat lady may have been warming up as the June 4-6 sequence concluded and we didn't even know it at the time.

 

After an exceptionally active April-May pattern wise, it's not too surprising. That said, it is still June, and there will still be tornadoes on various days. And "real" setups can't be ruled out north of I-80 even heading into late June and July.

Yeah that whole idea fell apart fast. Looks as if we'll go all of Spring and June without a high risk or PDS watch at this juncture.

Just a few thoughts about the 00z guidance (focusing on the operationals):

There are two camps in this set of model runs. One, consisting of the Euro and GGEM, is more progressive with the closed low that breaks off the main northern jet branch in the NW in a couple days (this is mainly due to it not retrograding west as far) and eventually leads to a rather messy, disjointed troughing across the N tier of the CONUS late next week since the aforementioned low does not phase very well with the incoming southern stream that undercuts the Aleutian ridging.

The other, potentially more volatile scenario is shown by the GFS and likely an extrapolated UK. These two model retrograde the closed low far enough so that it is not picked up by the northern stream for a slightly longer period of time (both in a similar position at 144 hours). It then (on the GFS) is picked up by the northern stream afterwards and phases with the southern branch more effectively, eventually leading to a very potent shortwave trough ejecting across the Northern Plains around D8-9 with some extremely impressive wind fields for June (and likely higher end severe potential as it seems a large reservoir of seasonably high instability will be in place for whatever does come down the chute then).

In conclusion, while it seems all guidance would indicate at least some severe possibilities late next week (as they have for several days now), it's going to be crucial to monitor the evolution of this closed low off the West Coast over the next few days as it could have major implications downstream for the northern CONUS. Should also add that the northern stream shortwaves that eventually lead to the closed low being picked up are also highly important. Overall, a lot of moving parts and it should be awhile before anything is settled on.