andyhb

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

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.

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

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).

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.

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.

Some of these longer range GFS/ensemble runs as of late have really fallen into the "holy crap" category.

Man 18z GFS has a trough with a 90 kt 500 mb and 120+ kt 300 mb speed max moving across the Northern Plains next week, that would be seriously impressive.

What I seem to be seeing on the recent ensemble guidance is a tendency to shift high latitude ridging eastward over central Canada past the first week of June. Should this happen, it would likely open up an opportunity for the Aleutian low to slide east and allow a relatively open path for its associated jet to the West Coast (with an accordingly active pattern downstream).

-EPO block is going to be a problem through the next week at least, need that to break down/slide east a bit so the jet from the Aleutian low can advance east. Until then, might be more nickel and dime setups vs. bigger events.

We still haven't had that bigger event/outbreak to accent the season yet. There will likely be moisture in spades, just a question on whether the Pacific cooperates. A northern shift will help with the EML situation, with more favorable 700 mb trajectories.

June 1957 and June 1958 also had some bigger events in the N Plains and Upper Midwest (F5 in Fargo on 6/10/57 and F5 in Colfax, WI on 6/4/58).

Late May-June 2004 showing up a ton in the CPC 8-14 day analogs today.

Not sure about the Euro weeklies, but the monthly forecast from the CFSv2 for June looks pretty favorable currently. Strong northern stream on the 200 mb U-wind anomalies plowing into the Pacific NW with net troughing in the Gulf of Alaska, cool temp anomalies across the western/central CONUS and warm in the east.

I'll send him an NARR loop of late May 04 if it helps.

Mark can you hack Ian's computer?

Might want to mention that there is a very nice W TX/E NM setup showing up next week (5/19) on the 12z GFS.

Gonna need a pretty deep eastern trough to have any appreciable affect on the Plains this time of year.

12z GFS certainly appears to show a fairly healthy EML being advected over the warm sector Friday night looking at 700 mb RH. Significant increases in instability through the day Saturday as opposed to previous runs (18z/00z/06z) despite some early convection still being there. Also appears to show stronger wind fields.

Well, the 00z Euro looks pretty similar to 12z at first glance through most of the fields. H85 temps/winds in particular are almost identical to the 12z run at 00z 5/17. Will get a look at the morning convection/EML situation a bit later. The 12z run did have widespread favorable thermodynamic profiles across a large chunk of the warm sector at 18z, 00z was partially contaminated by convection (not from the morning).

Will probably start a dedicated thread to this tonight, but yeah the 18z/00z GFS runs would certainly not have too high of a ceiling. The 12z Euro would be very volatile though, whether that goes towards the GFS tonight is the question. The 00z UK is in, although I can't see any of the wind fields on it for that timeframe so that's a bit of a mystery of what everything actually looks like. I'll also add that the hits seem to keep on coming with repeated western troughing on most ensemble guidance/etc. I'd have to think that something bad (or good, for chasers) is going to happen (in spite of the 5 fatalities over the weekend) one of these times if this type of pattern continues. That's not to mention all of the flooding.