andyhb

Need to start paying attention to Sunday in the Upper Ohio Valley. Incredible soundings for the region coming off the 00z NAM/NAM 3 km and both of them have a string of supercells/bow echoes in the area.

Not to be overdramatic, but that 00z HRRR run is quite possibly the most dangerous looking solution I've seen from that model since maybe 4/27-28/2014, and possibly even back to 2011. The number of supercells it has interacting with an extremely favorable low level environment is pretty unreal. It's not alone in upticking the apparent threat at 00z, either. Taken face value, we're easily looking at a high risk setup, but I can definitely understand if SPC wants to delay an upgrade until the situation is more certain tomorrow morning in case any convection decides to blow up on the warm front potentially limiting its movement north (but, at the same time, I could very easily see one at 06z).

The combo of low level moisture and hellacious low level shear is at a level seldom seen here. The possibility of multiple bands of convection interacting with this environment assuming things stay at least semi discrete certainly has me thinking that there could be a) an expansion of the ENH/MDT east to account for sig severe storms moving across MS after dark into AL and b) potentially an upgrade to the current MDT in the D1.

My concern would go even higher if something like the 06z NAM were to verify with more SW 500 mb winds atop a raging southerly/even slightly backed LLJ. The amount of veering with height in the lowest 3 km and a rapid increase to near 60 kts at 850 mb is sure to send SRH values skyrocketing perhaps even higher than current model progs. I'll say right now that 4/2/17 didn't look as favorable as this on a synoptic scale, but as always, the mesoscale will make or break it.

That is all going to be very bad for the Missouri/Red/Platte River flooding later on.

First time starting a thread here in awhile, but this deserves attention. Models have converged on a volatile scenario for Saturday (4/13), with a potent mid level trough shifting into the S US, yielding a strong surface low lifting into the Arklatex and ample moisture advecting north with a 50 kt LLJ towards the I-20 corridor in E TX/LA/MS. Forecast soundings across guidance indicate potential for significant severe/tornadoes with very strong low level shear and large hodographs/amounts of low level moisture both near the warm front and the open warm sector, with also hints of an EML in the early day to limit junk convection. Number one concern right now would be storm mode, but I have pretty good suspicion there will be at least some discrete convection in the open warm sector.

Synoptically there are some similarities to the 4/2/2017 tornado event (high risk in a similar location) and also the 11/21-23/1992 event (three day tornado outbreak across the southern US with a similar looking synoptic trough), with the possibility of after dark problems in MS/AL. SPC currently has a 30% risk for D4 and 15% risk for D5.

Still quite far out, but the ensemble guidance is honing in on a the potential for a large longwave trough moving into the Central US in the middle of next week and it would certainly have severe potential, possibly into the reaches of this sub-forum. There have been some pretty nutty operational runs the last couple of days for that timeframe, and the CFS chiclets also have had a signal for the 4/16-4/19 period for awhile now. Fits with a -AAM tendency over the next week and a ridge amplification N of Hawaii.

Also I get the feeling several of those F4+ tornadoes might be downgraded on the current EF-scale, although Fujita and co. surveyed this thing themselves.

I think the snow maps from the 12z Euro need to be posted for posterity's sake. That is just ungodly what it does for IA/WI/MI.

We turn the calendar to April and a massive -NAO shows up. Oy f***ing vey.

Well that 12z Euro run was a disaster to say the least.

This is why we need severe wx to blow all the pollen away.

New seasonal forecast for AMJ from ECMWF looks active in terms of -PNA/pattern favouring cutters and severe wx.

Poll is now closed for this. Most popular vote was 1200-1300.

Tweeted about the new March seasonal forecast from ECMWF for AMJ and it looks active.

Well so much for tomorrow's threat with the early contamination, looking like further south in KY/TN/MS/AL might have a better shot now with the limited destabilization further north.

To further the notion, yeah those are multiple fast moving supercells there, it's not picking up on a squall line.

I tend to put a lot of weight in the 500 mb setup assuming thermos are adequate in these kinds of cases. This 500 mb setup with a powerful vort lifting ENE out of a mean positive tilt long wave trough, with an elongated west-southwesterly upper level jet and the surface low position, is notorious in the Great Lakes for significant severe weather events.

12 hours ago, Hoosier said:

What are your thoughts on the substantial weakening of the surface low on approach?  I am thinking it may not hurt because it could result in somewhat less forcing.  

Yeah I’m thinking the same thing, plus it’s the position that I’m paying attention to mainly since it is still a pretty strong surface low despite being filling.

Pretty anomalous setup for March here for NM and W TX tomorrow. Strong signal on the CAMs for a supercellular storm mode initially and those could be tornadic judging by the wind fields. Going to be a question of how much moisture can be advected in there before initiation. Current obs closer to the Gulf Coast show mid-upper 60s dewpoints becoming entrenched near the Rio Grande Valley in south-central TX. Given the strength of this cyclogenesis/low level wind field, I would not be shocked to see 50s dewpoints common in E/SE NM, which, given the terrain, would amount to a fairly substantial amount of CAPE.

Slow moving closed lows like this tend to perform well in the High Plains.

Might be a decent shot at severe weather in the subforum on Thursday looking at recent guidance as very strong wind fields (broad 55-65+ kt LLJ) and cold air aloft overspread mid-upper 50s dewpoints (perhaps low 60s further south towards the OV). Could be one of those events where you have a large amount of instability concentrated in the low levels.

These types of events tend to do some dirty work in this region.

Paul Roundy was my OU advisor's phD advisor. This is another shot across the bow regarding this upcoming severe wx season.

Wrong system @AfewUniversesBelowNormal

The SPC outlook is for 3/9, which is the shortwave before the one you keep posting maps for.

MLCAPE is already >1500 J/kg over a sizable chunk of the risk area at 17z so that element is basically checked off going forward. Going to come down to storm mode and whether the storm relative wind profiles are favorable enough for longer lived/strong mesocyclones (read: if the surface winds can remain at least southerly).

*looks at end of the 12z Euro*

*sees massive AK/Beaufort sea ridge and downstream Hudson Bay low/TPV*

Y'all rang?

New CPC monthly outlooks should be out today I think.

Ship sinker on the 12z Euro for next weekend, thing deepens 31 mb in 24 hrs between 168 and 192 to 973 mb over southern Superior.

2015 with more dry air aloft probably would’ve had at least two high risks in May.