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andyhb

Central/Western Medium-Long Range Discussion

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The 00z Euro had a very impressive system late next week. The models have been toying with a large upper trough dropping into the west for some time now, and recent ideas have suggested a pretty robust ejection, with today's 00z suite being the strongest so far. Certainly something to keep an eye on for further continuity in later runs.

 

There are two important things to watch first, one being the s/w dropping SSE towards the Gulf Coast early next week, which may have a substantial impact on moisture quality, and then the closed low migrating eastward and devolving into an open wave, after which the stronger impulse moving in from the Pacific NW drops in behind. 

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Still need some pieces to come together better than advertised on the Euro/GFS, but can't help but think that Wednesday into Thursday of next week has some potential from Oklahoma/Kansas into the mid-Mississippi valley.

With a fairly deep trough digging, it's going to come down to timing of shortwave energy, surface low development/placement and richness of low-level moisture. Right now, the GFS shows a marginal setup with a strung out low, while the Euro is a bit more robust and shows a nice low-level jet ramping up.

Let's see how the forecast evolves this weekend.

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October 9th, 2001 being the number one analog explains the Oklahoma bullseye. Also, October 4th, 1998 is up there.

 

The H5 pattern somewhat resembles each of those. The important thing to keep in mind is that moisture was unseasonably rich for both events, particularly 1998. Unless we can manage widespread 65-70 F Tds along the dryline and avoid mixing issues, the usual mid-level thermal issues of autumn will likely be a limiting factor.

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The H5 pattern somewhat resembles each of those. The important thing to keep in mind is that moisture was unseasonably rich for both events, particularly 1998. Unless we can manage widespread 65-70 F Tds along the dryline and avoid mixing issues, the usual mid-level thermal issues of autumn will likely be a limiting factor.

 

That was one of the strange things about the 11/17 outbreak last year, the lapse rates that day were one of the things leading to that thermodynamic environment being more volatile rather than less. Helps when you have an absolute powerhouse of a system with a strong mid level dry punch of course.

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It's looking like a relatively small area across southeastern Kansas and far northern Oklahoma will see a somewhat favorable overlap of instability, forcing and wind shear on Wednesday. With that said, as mentioned earlier, there are still some red flags that we may be looking at another underperforming setup.

While the GFS and Euro both show a surface low near the OK/KS border Wednesday afternoon and some backing low-level winds near a quasi warm front, we're just looking at a 1002mb low. Nothing like the more dynamic systems we saw last fall. While there's some moisture, the model consensus is only for mid-60s dew-points. The GFS spitting out some dews around 70 in the warm sector is likely overdone. We're looking at a relatively broad trough with no well defined shortwave energy being focused on one area. While the upper level flow is decent and the risk area is placed on the right-front jet quad, the low and mid-level winds aren't terribly impressive either,

A few pieces there and and a few others likely lacking. Should still be interesting, but again, over a small area and the severity of any storms may be limited by several factors. Thursday looks to have more instability, but the shear pattern becomes more perpendicular to the front. Then, the trend continues to be toward a cold front or elongated low working as the main forcing mechanism.

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00z NAM is awfully bullish now for Tuesday as well as Wednesday. Not sure how serious to take it, especially when it's showing a warm front all the way back into Nebraska Wednesday afternoon. Unless the GFS/Euro ramp up, may have to toss the NAM yet again.

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The latest Euro and parallel GFS are slowly coming into agreement with a full latitude trough across the Central US as the AO drops extremely negative by October standards early next week.

 

 

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That's a real humdinger on the 00Z ECMWF there. I'd get excited for that. Agreement between GFS and ECMWF are pretty bad going into the medium range though. The 7-10 day means over the CONUS are pretty much polar opposites right now.

 

BzW03zhIUAAkj41.jpg

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That's a real humdinger on the 00Z ECMWF there. I'd get excited for that. Agreement between GFS and ECMWF are pretty bad going into the medium range though. The 7-10 day means over the CONUS are pretty much polar opposites right now.

 

Agreement with the GFS is essentially non-existent with the other three main globals, the GGEM and UK also have a substantial trough dropping into the Central US this weekend.

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Looks like a decent setup for severe weather for October.  We'd probably want to see greater height falls (as a rough proxy for surface pressure falls) to really back surface winds enough for widespread tornadoes, but that LLJ is nonetheless impressive.  Bares watching.

 

post-378-0-57001200-1412707771_thumb.gif

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Not only that, but the pattern across the N Pacific looks to become increasingly volatile over the next while with a series of strong systems making their way into the Gulf of Alaska region and a corresponding strong negative height anomaly off the NW coast, so the active period might not be over with this system.

 

You can see it there on the Euro run with another very strong impulse in behind the trough of mention.

 

Euro is showing CAPE of 1500-3000 J/kg over central and southern AR @ 150 hrs.

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Looks like a decent setup for severe weather for October.  We'd probably want to see greater height falls (as a rough proxy for surface pressure falls) to really back surface winds enough for widespread tornadoes, but that LLJ is nonetheless impressive.  Bares watching.

 

attachicon.giff144.gif

We will be watching the oscillating boundary across Texas this weekend as the remnants of Simon pass across the Southern/Central Plains. The NW Gulf should be wide open with a strong southerly flow and the 5H low is nearing 3 standard deviations below normal via the 12Z Euro. Certainly worth monitoring.

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Agreement with the GFS is essentially non-existent with the other three main globals, the GGEM and UK also have a substantial trough dropping into the Central US this weekend.

Wouldn't put much weight into the GFS solution considering the AO and NAO are sharply negative.  Doesn't favor the progressive pattern.  Makes sense that the 3 main globals are showing substantial troughing in the Central U.S. 

 

ao.sprd2.gif

 

nao.sprd2.gif

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I almost hate to mention it with so much uncertainty almost a week out, but the recent ECMWF solution shows some similarity to the system from November 1992. I highly doubt something near that magnitude will occur, but it certainly has intrigue. It'll be interesting to see how the solutions evolve over the next several days.

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Looks like the 00z GFS came significantly toward the other guidance, although it is still more progressive than them.

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Definitely resembles a Nino like pattern with active subtropical jet.  I thought it was interesting that NOAA said they're not expecting an abnormally cold winter East of the Rockies like last year.  

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Definitely resembles a Nino like pattern with active subtropical jet.  I thought it was interesting that NOAA said they're not expecting an abnormally cold winter East of the Rockies like last year.  

 

They weren't expecting it last year either. Nino climo suggests it will be milder, either way.

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A welcomed change is ahead for the Pacific NW into N California as the pattern changes increasing a tropical connection from the Central Pacific and a zonal flow brings welcomed rains to a Region that has been very dry.

 

 

sat_wv_hem_loop-12.gif

 

 

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A welcomed change is ahead for the Pacific NW into N California as the pattern changes increasing a tropical connection from the Central Pacific and a zonal flow brings welcomed rains to a Region that has been very dry.

 

Hopefully the active jet sets up just a little bit further south than that this winter so central CA can get into the action.  Of course it's still too early for that right now, climatologically speaking. 

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A firehose of Pacific moisture looks to bring sorely needed lower elevation rains and higher elevation snows to the Pacific NW and portions of California over the next week. The pattern appears to transition as a -AO/-EPO/+PNA regime develops and may bring our first real shot of cold Continental air very far S into Northern Mexico and Texas as we begin November.

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A firehose of Pacific moisture looks to bring sorely needed lower elevation rains and higher elevation snows to the Pacific NW

 

 

5-10 inch rain amounts have affected the Pac NW. This weekend another 1-3" should affect the Pacific coast ranges. Apparently, the Hurricane Ana remnants will affect the Pac NW on Monday. I'm glad to see the Pacific coast get some rain. Not much for California though.

 

Halloween-November 2nd seems to be cool and dry east of the Mississippi. That's over 168 hours though. It really doesn't seem too weird, perhaps just the first temps below 32 degrees for northern areas.

 

post-1182-0-77735000-1414185304_thumb.jp

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Deep tropical moisture could be headed for the Southern Plains due to some EPAC tropical activity.  Both the Euro and GFS are moving the current disturbance in the EPAC into Mexico.  A trough across the Central U.S. draws that moisture up and into Texas and surrounding states in the 8-10 day frame.    

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Deep tropical moisture could be headed for the Southern Plains due to some EPAC tropical activity.  Both the Euro and GFS are moving the current disturbance in the EPAC into Mexico.  A trough across the Central U.S. draws that moisture up and into Texas and surrounding states in the 8-10 day frame.    

The chatter picked up again today from the various Texas WFO's regarding this potential. 93E is looking better by the hour and the 12Z guidance would be a welcomed relief to what has been an extremely dry October across Texas.

 

 

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Surface high pressure just off the SE Coast would also funnel in some Caribbean and Gulf moisture for Southern Plains and the Gulf Coast.

 

gfs_mslp_pwata_namer_29.png

 

gfs_mslp_pwata_namer_31.png

 

gfs_mslp_pwata_namer_34.png

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Looking ahead some, the next trough should start carving itself out across the central part of the country this weekend and going into next week. Of particular interest to me is the initial shortwave disturbance currently progged to eject into the southern plains Saturday. Even though the airmass across the southern plains and lower Mississippi Valley is going to need some major modification between now and then, guidance seems to think enough time will elapse to offer up some surface instability in the warm sector of the developing storm system. With adequate surface instability and wintertime dynamics, it looks like we might have our first real chance at some severe weather in quite a while.

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As andyhb mentioned in the Texas thread and we have been mentioning since last week concerning the severe potential in the busy pre Thanksgiving timeframe, the GFS is suggesting a robust 5H shortwave crossing our Region during the upcoming weekend. If the Gulf opens up as some of the guidance is suggesting, we could see a rather impressive severe weather threat across portions of the Southern Plains into the Northern Gulf Coast.

 

 

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Yep, I've been keeping an eye on it as well. I missed andyhb's post with the convective outlook in the Texas thread, but I figure I'll post it over here if just for posterity's sake. Predictability Too Low >> Probability Too Low any day of the year.

 

day48prob.gif

 

ZCZC SPCSWOD48 ALL
ACUS48 KWNS 171000
SPC AC 171000

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0400 AM CST MON NOV 17 2014

VALID 201200Z - 251200Z

...DISCUSSION...
MODEL CONSENSUS IS THAT UPPER PATTERN WILL BEGIN TO DEAMPLIFY BY
THURSDAY /DAY 4/ AND TRANSITION TO A MORE PROGRESSIVE REGIME WITH
SEVERAL LOWER-LATITUDE IMPULSES EXPECTED TO MOVE THROUGH THE SRN
THIRD OF THE COUNTRY. AN INITIAL LOW-AMPLITUDE SHORTWAVE TROUGH
SHOULD MOVE THROUGH THE SRN PLAINS AND LOWER MS VALLEY
THURSDAY...BUT IT CURRENTLY APPEARS MOISTURE RETURN WILL REMAIN
SOMEWHAT LIMITED FOR AN ENHANCED SEVERE THREAT.

FRIDAY /DAY 5/ COLD FRONT IS EXPECTED TO MOVE SWD TOWARD THE COAST
AS SHORTWAVE RIDGING BUILDS OVER THE SRN PLAINS.

SATURDAY /DAY 6/ MODELS HAVE TRENDED TOWARD SIMILAR SOLUTIONS WITH
SPEED AND AMPLITUDE OF A MORE SUBSTANTIAL SHORTWAVE TROUGH THAT WILL
MOVE INTO THE SRN PLAINS SATURDAY AND CONTINUE INTO THE MS VALLEY
LATER SATURDAY NIGHT. GIVEN THE ANTECEDENT FRONT IS NOT EXPECTED TO
PENETRATE THE GULF...MORE SUBSTANTIAL MOISTURE RETURN AND
INSTABILITY SHOULD OCCUR IN ADVANCE OF THIS FEATURE SUPPORTING
POTENTIAL FOR A MORE ROBUST SEVERE THREAT FROM TX INTO A PORTION OF
THE LOWER MS VALLEY. AN ENHANCED SEVERE RISK AREA WILL LIKELY BE
INTRODUCED ON THE NEXT 4-8 UPDATE FOR A PORTION OF THIS REGION IF
MODEL ENSEMBLES CONTINUE TO DEMONSTRATE CONSISTENCY.


FOR DAYS 7-8 SOME SEVERE THREAT WILL PROBABLY DEVELOP THROUGH SRN
PORTIONS OF THE GULF COAST STATES AND INTO THE CAROLINAS.

..DIAL.. 11/17/2014

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