Significant severe weather threats 4/8-10

[OKpowdah]

The persistent low index blocking pattern that has lent itself to a frigid end to winter and start of spring is finally nearing an end.

 

An oldie but a goodie reference: Namias, J., 1950: the index cycle and its role in the general circulation. J. Meteor., 7, 130-139.

 

Likely culprits to our extreme blocking ... the prolonged easterly QBO and a final "warming" that resulted in a strong wave-1 response in the stratosphere.

 

The AO has been down in the deepest darkest depths of the basement for a while now. There is unanimous agreement in the GEFS for a world-class reversal in the NH annular mode ... i.e. a rise of over 6SD in 10 days!!! That's pretty amazing.

 

 

 

Tropical forcing has been persistent near the dateline over the last month, but a new MJO wave is forecast to cycle through phases 3-4-5 over the next two weeks, triggering a wave response that will have significant implications in the mid latitude pattern.

 

All the energy trapped in the Pacific jet gets ejected eastward and dumps into the western US. The GEFS and ECMWF are in fairly good agreement on this pattern development with just differences in the timing. Notice on the spaghetti plot, there are just some minor phase shift differences from the Pacific across the CONUS. Pretty impressive agreement actually for day 8.

 

 

 

 

Really impressive jet structure. Notice dual jet support over the Plains with the strong Pacific jet diving into the backside of the trough over the western US and the polar jet across the Great Lakes and Northeast intensified by the tightened temperature gradient in the high index pattern.

 

 

In terms of severe weather potential, the rain storm this week also doesn't hurt ... adding moisture to the boundary layer.

 

By the weekend, looking at large scale moisture convergence from the Gulf to the polar front across the Midwest and Northeast.

 

 

A lot of good stuff coming together to support a rapid increase in Springtime severe weather activity over the Plains by early next week!

[andyhb]

It appears the 12z GFS OP is on the progressive side of its ensemble suite, which is to be expected.

 

Great analysis here, I like the points about the system this week providing some drought relief and perhaps enhancing the boundary layer moisture, of course, it helps when you have the Gulf/Caribbean essentially flowing into the Plains by late this weekend as currently suggested.

 

The MJO rotating into phases 3-5 at high amplitude is also telling into what type of potential this new pattern may hold.

[harrisale]

GFS now hinting at Tuesday (the 9th) as something to watch as well.

[andyhb]

I did a quick modification to emphasize the impressive upper level setup on Tuesday over the I-35 corridor and east on the 12z GFS, needless to say, that right rear/left front setup is pretty clearly evident.

 

[OKpowdah]

Tricky dealing with separate impulses in the overall ejection of energy into the southwest. That will be the culprit of run-to-run differences.

 

In the meantime, how's this for pattern similarities? Obviously differences in the time of year can't be entirely ignored, but this pattern certainly falls into one category that is historically favorable for significant events:

 

On the left is the 12z GFS forecast for 12z Monday ... on the right is May 24th 2011

 

[andyhb]

You might want to look at the lead up to 4/26/91 as well although this has the pattern shifted north a bit.

 

[andyhb]

12z Euro still ejects the trough in pieces beyond 168, although I'd imagine there's a dryline setup on both Monday and Tuesday before that happens taking verbatim.

[OKpowdah]

That's a beautiful 500mb mean from the 18z GEFS.

 

Large spread in the MSLP along the lee of Rockies. The mean doesn't even say much at this point.

 

 

[OKpowdah]

71.4% of the variance in the ensemble SLP forecasts by day 6 is related to how cold air damming develops along the lee of the mountains in eastern CO and Wyoming. We want that CAD to be weaker, with lower pressures extending northward along the lee of the Rockies.

 

[OKpowdah]

00z GFS is definitely impressive. Less upper level confluence to the north/northwest, so surface pressures are lower, lot less of that CAD.

 

Would like to see the energy in the trough more consolidated, with a tighter, deeper surface low.

[andyhb]

Would like to see the energy in the trough more consolidated, with a tighter, deeper surface low.

 

It tightens up by Tuesday, and it shows with the low level wind response, with a 60-70 kt LLJ over the Arklatex eastward to the Lower MS Valley.

[brettjrob]

This run almost makes Monday look like 11/7/11 with more CAPE. I can't find much to complain about, unless one is expecting an historic blockbuster outbreak, which might require stronger kinematics. While the GFS finally has a hint of run-to-run consistency since 12z today, it appears the UKMET and GGEM are not at all onboard yet with its solution, so the roller coaster continues at least a couple more days.

[andyhb]

Well, instead of going against the GFS on Monday, the Euro decided to one-up it, or perhaps two-up it, vigorous, low amplitude, negatively tilted H5 trough with a powerful 50+ kt LLJ feeding north to the east of the dryline and a sfc low below 990 hPa in the Eastern TX Panhandle.

[OKpowdah]

That is one stout LLJ. Perfect height falls. Deepening sfc low. This is a picture of something big

 

[andyhb]

That is one stout LLJ. Perfect height falls. Deepening sfc low. This is a picture of some big

 

f144.gif

 

Yeah, there's not a whole lot wrong I can find with that solution, including the moisture flow from deep in the Caribbean.

[OKpowdah]

Classic

 

[wxmeddler]

Looks fantastic for this range. Helluva cap, Classic Loaded Gun. Maybe a little increase in the 850-700 jet but I can't complain too much here.

[It's Always Sunny]

I think Missouri could be in for something interesting from what I'm looking at.

[CoastalWx]

71.4% of the variance in the ensemble SLP forecasts by day 6 is related to how cold air damming develops along the lee of the mountains in eastern CO and Wyoming. We want that CAD to be weaker, with lower pressures extending northward along the lee of the Rockies.

 

EOF_4fig_NCEP (2).gif

 

Sam, what's the link for these products again?

 

Nice disco.

[andyhb]

Looks fantastic for this range. Helluva cap, Classic Loaded Gun. Maybe a little increase in the 850-700 jet but I can't complain too much here.

GFS_OKC_04-03-13-00z_04-08-13-18z.JPG

 

I do remember seeing quite the impressive sounding off of Twisterdata near Wichita Falls from the 00z GFS on Monday evening (00z 4/9).

 

There's 3000 J/kg of CAPE with an LI of -9 to -10 in this area with storm initiation.

[OKpowdah]

Sam, what's the link for these products again?

 

Nice disco.

 

Thanks man.

 

Here's the link http://dendrite.somas.stonybrook.edu/CSTAR/Ensemble_Sensitivity/EnSense_Main.html

[OKpowdah]

12z GFS worlds apart from the 6z run lol. And the ECMWF still stands alone. It's gonna be a long 5 days lol

[OKpowdah]

12z GFS loses all the confluence to the north. So we don't have to deal with the pesky CAD, but we would like SOME confluence because that focuses upper level forcing further south and raises pressures to the northeast (effectively tilting the isobars over the southern Plains and helping to back low level winds)

[lowleveljet]

12z GFS loses all the confluence to the north. So we don't have to deal with the pesky CAD, but the we would like SOME confluence because that focuses upper level forcing further south and raises pressures to the northeast (effectively tilting the isobars over the southern Plains and helping to back low level winds)

 

Looks like a good return of moisture in eastern ok & most of arkansas with dewpoints in the 60's with afternoon temps in the mid 70's Tuesday afternoon.

[OKpowdah]

FWIW, the FIM, initialized off the 00z GFS, really keys in on Tuesday.

 

[JoMo]

12z GFS Looks like Monday on the dryline in central and western Oklahoma. That's been somewhat consistent. Tuesday is where things get a bit unclear. 

[CoastalWx]

Thanks man.

 

Here's the link http://dendrite.somas.stonybrook.edu/CSTAR/Ensemble_Sensitivity/EnSense_Main.html

 

Thanks man! Keep up the good work.

 

BTW, since you like mesoscale, check out the wake low near KGPT!

[andyhb]

Still not a lot of agreement at all with the 12z Euro in, although both the GFS and Euro have trended away from the early closing off of the upper level low, they are still drastically different with what happens after that. The Euro keeps a lot of the confluence over the Northeast (and the cold air damming to the leeside of the Rockies), which the GFS had little of at all as Sam mentioned.

[patrick7032]

I'll load some point soundings and images at work tomm...but here are a few soundings from the 18z GFS...for Wichita Falls...Fort Worth...and Oklahoma City.

[JoMo]

It changes each run though. Severe storms then snow..... in mid-April on tonight's 00z GFS.