January 28-30 Severe threat. S Plains to TN valley to SE

[OKpowdah]

Stuck in northwest flow for the next week, any current weather discussion here at OU has not been able to escape the use of the word "boring". However, a change is gonna come.

 

One of the distinct characteristics that I'm seeing of the pattern over the next week is that within this wave system, the sub-polar vortex over eastern Canada and the Northeast overwhelms the ridging over western North America. I compared it to RKW theory and the balance of vorticity in the system ... In this case the stronger trough leads to the eastern edge of the ridge slowly getting broken down ... can watch packets of anticyclonic vorticity erode away and get sucked underneath the trough

 

This is also why I have been very cautious about getting excited about any storm prospects for the East. Essentially we have a smooth long wave trough with periodic impulses of stronger flow consequence of s/w ridging swinging south of the trough and increasing mass gradients ... NOT conducive to amplifying disturbances for the East.

 

Anyway, back to the point -- this is NOT a stable pattern. Eventually, all the anticyclonic vorticity with the western ridging will get eroded southeastward ... probably by the end of next week as indicated by the long range models.

 

The immediate result will be a warm up for most of the Plains for a day or two.

 

The second result will be opening up the CONUS to Pacific disturbances ... with the blocking ridge now out of the picture.

 

IMPORTANT -- All the while, we still have the sub-polar vortex sitting off the northeast, over Newfoundland and the North Atlantic ... the effect being persistent background upper level confluence over the Great Lakes, Northeast, and eastern Canada.

 

I could see the first in the series of disturbances off the Pacific being a significant storm for the Ohio Valley to Northeast next weekend as some ridging still stands in the West.

 

However, as the pattern shifts to more of an RNA configuration by the following week, the next s/w (around January 28) could have a chance to dig earlier into the central Plains ... then remember the confluence to the northeast to keep the short wave from breaking north and maintain upper level dynamics ... could be a significant winter storm for someone to the north and perhaps a thunderstorm/rain threat for someone to the south.

[baroclinic_instability]

I definitely have my eye on the potential lee cyclone day 9+ per GEFS and to a degree the ECMWF Ensemble, but the GEFS goes back to another NE US vortex heading into week two. 

[Srain]

The trends via the 12Z GEFS and the CPC Super Ensemble reanalysis suggest we may well see a return to a ‘colder’ and stormy pattern as we head into the late January/early February time frame.

 

[andyhb]

12z/18z GFS and many of the ensemble members really going big with that second storm system around the 28th-30th.

[baroclinic_instability]

The trends via the 12Z GEFS and the CPC Super Ensemble reanalysis suggest we may well see a return to a ‘colder’ and stormy pattern as we head into the late January/early February time frame.

 

01192013 12Z GEFS 12zgfsensembles500mbHeightAnomalyNA276.gif

01192013 12Z GEFS 12zgfsensembles850mbTAnomalyNA276.gif

01192013 CPC Super Ensembles 500hgt_comp_sup814.gif

Still a ways to go, but the ECMWF still slides in that vortex over the Hudson Bay. EC Ensemble isn't quite as aggressive, but I would prefer to see it a bit west or it will be more of the same waves in NW flow for much of the Plains.

[andyhb]

Snippet from new Day 4-8:

BY SUN/D6 INTO MON/D7...THERE IS CONSISTENCY IN DROPPING A STRONG   SHORTWAVE TROUGH OR UPPER LOW SWD ACROSS THE GREAT BASIN...THEN   MOVING IT INTO THE PLAINS OR MS VALLEY ON TUE/D8. THERE APPEARS TO   BE SUFFICIENT TIME WITH FAVORABLE LOW LEVEL TRAJECTORIES TO BRING   SUBSTANTIAL MOISTURE NWD ACROSS THE GULF OF MEXICO AND INTO ERN TX   AND ACROSS THE GULF COAST STATES. THE LIKELY JUXTAPOSITION OF STRONG   FLOW ALOFT OVER A SUFFICIENTLY BROAD MOIST SECTOR SUGGEST THAT   SEVERE WEATHER WOULD BE LIKELY IF THIS SCENARIO OCCURS.   HOWEVER...WILL WAIT FOR MORE RUN TO RUN CONSISTENCY FROM THE VARIOUS   MODELS BEFORE INTRODUCING ANY POTENTIAL SEVERE AREAS THIS FAR IN   ADVANCE.

[OKpowdah]

Snippet from new Day 4-8:

 

Pretty impressive wording actually

[andyhb]

D7 out from SPC, focused on AR and vicinity.

[Indystorm]

As always consistency in model runs and multiple model agreement are keys, but from this distance this event does look impressive.

[brettjrob]

Euro is awfully impressive on moisture return, with the 60 F isodrosotherm on D7 along the I-70 corridor. GFS slightly less aggressive.

 

OTOH, the trough is positive-tilt and there are a fair number of solutions with a strung-out sfc low. Still lots of details to work out, but in terms of moisture, this looks like an opportunity you don't get every January.

[thewxmann]

The positive-tilt ejection issue is really getting old. Thankfully models will have no clue for several additional days, most likely.

[andyhb]

00z GFS kinda flubs it initially and then really gets going with the second wave, putting the entrance region of a 150+ kt, slightly west-southwesterly H3 jet streak over LA, MS and AL as the right exit region of the lead jet streak departs. There is widespread instability with 1000+ J/kg of CAPE (a max of almost 2000) and -4 or less LI's spread as far east as Western AL, while placing a 40-50+ kt southwesterly LLJ over the area with SSW to southerly sfc winds, which can easily work in the Deep South.

 

00z GGEM, on the other hand, looks to have a threat as early as Monday on the dryline in eastern OK (check the precip maps on Meteocentre). It ejects the trough as one piece and eventually has a 984 mb sfc low over the Great Lakes by 144.

 

00z Ukie is positive tilt, somewhere between the GFS and GGEM, but bombs the initial low into a 987 mb cyclone over Western IA by 144, and the height falls would suggest a favorable environment for severe essentially all the way to the Lower MS Valley/Mid South area, provided good moisture return, which, I must say, appears likely with this quick torch progged across the model suite.

 

00z Euro is somewhat similar to the GGEM, it's the furthest north of the models, and does eject the trough in one piece.

 

So clearly, there is a large range of solutions here, until the two primary anomalies that make up this system are fully analyzed, among other things, there likely will be large differences. Given the likely unseasonably warm environment ahead of it, this bears watching.

[SquatchinNY]

This potential looks really interesting.

[Srain]

The 12Z Operational GFS is rather impressive and certainly lend credence to this event offering a potential high impact scenario for this time of year.

[Ground Scouring]

Given the predominance of the Hudson vortex that seems likely over the next several days, I think that the models are not likely to deviate from the positively-tilted solution with several shortwaves rounding the base of the vortex. Given both the strong, elongated forcing and the the 850-mb vector relative to the front on the GFS and ECMWF solutions, the blended mean tends to favor a possible damaging-wind event more than a significant tornado threat. However, the amount of moisture return and the projected PWAT could mean both a damaging-wind and a heavy-rainfall event for the mid-Mississippi Valley. As to the timing, I tend to favor the somewhat-slower ECMWF as the past few weeks have trended toward slower ejection and less-progressive upper-air solutions. So I think the most likely timing for a substantial event will be day six and early day seven, though undoubtedly this estimate will change as will the targeted areas as the pattern becomes clearer on initializations. But the overall trend definitely favors a large wind and rain (likely flooding) threat with prolonged precipitation due to high PWAT. However, the pattern is not so great/ideal for widespread, strong tornadoes.

[Srain]

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
1057 AM EST THU JAN 24 2013

VALID 12Z SUN JAN 27 2013 - 12Z THU JAN 31 2013

MEDIUM RANGE MODELS AND INDIVIDUAL ENSEMBLE MEMBERS CONTINUE TO
SHOW A MODERATE AMOUNT OF SPREAD AND IN SOME CASES MEANINGFUL RUN
TO RUN CHANGES WITHIN A MORE AGREEABLE MEAN FCST OF A WEST COAST
TROF BECOMING STEADILY BROADER AS ITS AXIS TRAVELS TOWARD THE
CNTRL OR E-CNTRL CONUS.  WHILE THERE ARE CURRENTLY SOME DETAILS IN
THE LATEST OPERATIONAL SOLNS THAT COULD MERIT PARTIAL WEIGHTING IN
A DETERMINISTIC FCST THROUGH AT LEAST DAY 5 TUE... RELATIVELY POOR
MODEL CONTINUITY THUS FAR RECOMMENDS HOLDING ONTO A MORE
CONSISTENT 00Z GEFS/ECMWF ENSEMBLE MEAN BLEND FOR THE DAYS 3-7
FCST UNTIL THE MODELS STABILIZE.  THE ONE SIGNIFICANT ADJUSTMENT
IN THIS SOLN REFLECTS GUIDANCE AS A WHOLE TRENDING FASTER WITH THE
FRONT DROPPING FROM WRN CANADA INTO THE NRN TIER CONUS EARLY NEXT
WEEK.

GUIDANCE BEGINS TO DIVERGE DURING THE FIRST HALF OF THE PERIOD
ACROSS THE WEST AS THE 00Z ECMWF/CANADIAN TREND FASTER WITH THE
TROF DUE TO FLOW STREAMING SEWD ALONG OR INLAND FROM THE BC COAST
HAVING A MORE EWD COMPONENT THAN IN THE 00Z/06Z GFS OR 00Z UKMET.
IN ADDITION THE 00Z ECMWF HAS THE MOST AMPLIFIED DEPICTION OF
ENERGY ROUNDING THE UPSTREAM EPAC RIDGE BY LATE MON INTO TUE.
OVER RECENT DAYS THERE HAS BEEN A HINT OF SOME SWWD ELONGATION OF
THE OVERALL TROF EVEN TO THE POINT OF FORMING A CLOSED LOW EVEN IF
ONLY BRIEFLY.  WHAT OPERATIONAL SOLNS HAD SHOWN THIS IDEA
PREVIOUSLY HAVE TRENDED AWAY.  SOME 00Z ENSEMBLE MEMBERS STILL
SHOW THIS SCENARIO THOUGH... WITH CMC MEMBERS SHOWING THE HIGHEST
PERCENTAGE AND ECMWF MEMBERS THE LOWEST.  TELECONNECTIONS RELATIVE
TO THE EPAC RIDGE HAVE SUPPORTED SOME SWWD ELONGATION OF THE MEAN
TROF BUT LATEST D+8 MEANS INDICATE THAT THE RIDGE MAY NOT REMAIN
SUFFICIENTLY STRONG TO SUPPORT TOO MUCH SWWD ELONGATION OF THE WRN
TROF.  LESS ELONGATION IN THE 06Z GEFS MEAN VERSUS THE 00Z RUN
ADDS MODEST SUPPORT TO LEAN AWAY FROM THE SLOWER/AMPLIFIED SIDE OF
THE SPREAD.

DIFFS IN THE HANDLING OF LEADING WRN CONUS ENERGY AND UPSTREAM WRN
CANADA FLOW RESULT IN SIGNIFICANT DETAIL/TIMING DIFFS FOR CNTRL
PLAINS TO UPR GRTLKS SFC LOW PRESSURE AROUND LATE MON THROUGH LATE
TUE... BUT THE VARIED SOLNS DEVELOP SURPRISINGLY GOOD CLUSTERING
BY EARLY DAY 6 WED.  ASIDE FROM THE 00Z CMC THE MAIN THEME IN
OPERATIONAL SOLNS IS FOR A STRONGER/SLOWER PLAINS SFC LOW THAN
SEEN IN THE LATEST ENSEMBLE MEANS.  IT WOULD NOT BE SURPRISING TO
SEE AN EVOLUTION SOMEWHERE BETWEEN THE OPERATIONAL AVG AND
ENSEMBLE MEANS BUT RECENT GFS/ECMWF/CMC RUNS HAVE NOT STABILIZED
ENOUGH YET TO STRAY FROM THE ENSEMBLE MEANS WITH MUCH CONFIDENCE.

BY DAYS 6-7 WED-THU THE DIFFS ALOFT AFFECT TIMING OF THE COLD
FRONT CROSSING THE ERN STATES AND EXISTENCE OF A FRONTAL WAVE.
THE 00Z/06Z GFS THAT WERE SLOWER/MORE AMPLIFIED ALOFT OVER THE
WEST ARE SLOWEST WITH THE COLD FRONT AND SHOW A FAIRLY STG WAVE
LIFTING NEWD TOWARD THE NERN COAST.  THE 00Z ECMWF/CMC ARE ABOUT A
DAY FASTER WITH THE FRONT AND SHOW MINIMAL WAVINESS ALONG IT.
GIVEN THIS SPREAD AND PRIOR CONTINUITY... THE ENSEMBLE MEANS THAT
ARE BETWEEN THESE TWO EXTREMES PROVIDE THE MOST APPEALING SOLN AT
THIS TIME.



EXPECT BELOW NORMAL TEMPS OVER MOST OF THE WEST ESPECIALLY AFTER
SUN... WITH THE SRN HALF TO 2/3 OF THE REGION LIKELY TO TREND
DRIER BY THE LATTER HALF OF THE PERIOD.  RAIN/SNOW OVER THE WEST
IS NOT FCST TO BE EXCEPTIONALLY INTENSE IN GENERAL BUT SOME
LOCATIONS IN FAVORED TERRAIN MAY STILL SEE DECENT MULTI-DAY
TOTALS.  CNTRL-ERN AREAS WILL SEE A PRONOUNCED WARMING TREND AHEAD
OF THE INITIAL WRN SYSTEM BUT COOLER AIR WILL SPREAD EWD WITH
TIME.  AREAS FROM THE N-CNTRL PLAINS INTO THE UPR GRTLKS MAY
EXPERIENCE A PERIOD OF WIND-DRIVEN SNOW IN THE FIRST HALF OF NEXT
WEEK DEPENDING ON CNTRL PLAINS TO UPR GRTLKS SFC EVOLUTION.
BEHIND THIS SYSTEM THE CORE OF COLDEST AIR SHOULD BE OVER THE NRN
PLAINS/UPR MS VLY BY TUE-WED.  GULF INFLOW AHEAD OF THE TRAILING
COLD FRONT TRACKING TOWARD/THRU THE EAST SHOULD ENHANCE RNFL OVER
SOME AREAS FROM THE MS VLY EWD BY TUE-WED.  THERE IS CONSIDERABLE
UNCERTAINTY ON AMTS DUE TO DIFFS IN FRONTAL TIMING/WAVINESS...
WITH AN ENSEMBLE MEAN PREFERENCE BETWEEN THE FASTER/LIGHTER ECMWF
AND SLOWER/HVY GFS EXTREMES.

RAUSCH
 

[lowleveljet]

Well, the 12z Euro cuts off a big ole low with the west coast trof and hangs it up in so cal thru early Thursday. Massive shift from the 00z run as well as the 12z runs of the GFS and even the GEM.

[andyhb]

Well, the 12z Euro cuts off a big ole low with the west coast trof and hangs it up in so cal thru early Thursday. Massive shift from the 00z run as well as the 12z runs of the GFS and even the GEM.

 

Still clearly some details to be worked out, considering there are multiple jet disturbances that will be involved here, it appears that model consistency with the evolution of the trough following the West Coast portion will need to wait.

 

Still a large range of solutions on the 12z ensembles

[thewxmann]

I like how the 12Z GFS shifts towards the 0Z Euro solution, while the 12Z Euro does something that would enrage all extreme weather lovers.

[bubba hotep]

Well, the 12z Euro cuts off a big ole low with the west coast trof and hangs it up in so cal thru early Thursday. Massive shift from the 00z run as well as the 12z runs of the GFS and even the GEM.

 

The 12z Euro looks a lot like the FIM from yesterday at 12z, which looked a lot like the 18z GFS from the day before

 

 

18z GFS from day before yesterday here

[Ground Scouring]

I like how the 12Z GFS shifts towards the 0Z Euro solution, while the 12Z Euro does something that would enrage all extreme weather lovers.

In these cases, the GFS usually tends to latch on to a cut-off low more slowly than the ECMWF but comes around in the end. The 12Z ECMWF is in this case showing a much more modulated upper jet with a less-progressive shortwave pattern, concomitant with a much colder pattern in the Northeast by day six and beyond. I think the shift has some historical support based upon past model trends in these situations. Also, the colder look in the Northeast follows some recent indices elsewhere in the world, though the 12Z ECMWF in my view also underplays the subtropical jet. Thus, though I think that the set-up favors the slower, more cut-off ECMWF solution, the ECMWF looks to be too slow with the low beyond day 4. Keeping the H5 low west of S CA does not seem reasonable to me. I would lean toward a position over the Dakotas by late day 4 and afterward. But the overall trend points to an elongated low as seen on the 12Z GFS; the strong ridge over the E Pacific does not favor a very consolidated vortex, so the severe-wind threat, while appearing just as high as I originally assessed, comes with a low risk of strong tornadoes as mentioned.

Anyway, a big tornado outbreak in N AR/MO/IA in January would be almost unprecedented, save some examples like those of 01/03/1950, 01/ 01/24/1967, and 01/07/2008. The CIPS analogs actually show a low supercell risk in five days.

[brettjrob]

I like how the 12Z GFS shifts towards the 0Z Euro solution, while the 12Z Euro does something that would enrage all extreme weather lovers.

 

Well the 00z GFS is now onboard with that enraging solution. This trough translates through the Plains with relatively low amplitude and disorganized low-level cyclogenesis, followed by more disgusting northwest flow for the foreseeable future.

[tornadotony]

12z, 18z, and 00z GFS bring back the motherload of severe wx next week.  The CIPS analogs include the significant-violent tornado outbreaks of 1/12-1/13/2005, 2/28-3/1/2007, 2/5-2/6/2008, 1/3/2000, 3/9/1992, 1/3/1982, and 2/10/2009.  In terms of wintertime setups, that's a creme de la creme sort of lineup.  The 00z GFS throws even more fuel into this fire by bringing 60°F+ dewpoints to Terre Haute, IN, by 06z Wednesday morning and 65°F dewpoints all the way to I-40 in AR and southern west TN.  Add onto all of this the fact that the Euro did not have nearly the impressive cutoff in the SW and (contrary to previous posts) often seems to be too prone to cutting off the jet in the southwest with these major troughs, I really am beginning to lean toward a greater likelihood that something significant is going to happen Tues/Wed, perhaps across an area as widespread as from nrn IL all the way across MO and AR, ern KS and OK, NE TX, nrn LA, TN, KY, a good chunk of IN, MS, AL, GA, and maybe the Carolinas.  I won't totally bite just yet, but the odds of this system being significant are increasing.

[Chicago Storm]

As I posted in the Lakes/OV thread...

 

Not really sure what to think yet.

 

Obviously some runs (Such as the GFS) have shown nice severe potential for a large area, with chase potential...While you have some runs (Like the 12z ECMWF) that have a weak wave with far less potential. Given the poor performance of guidance pre-sampling this season we'll likely have to wait until Sunday for a better idea.

[prinsburg_wx]

0z CMC is now onboard with the GFS with a larger area of severe weather...imo, the euro has fallen short of it's usual stellar performance alot this winter...atleast in my area anyway.

[Hoosier]

12z, 18z, and 00z GFS bring back the motherload of severe wx next week. The CIPS analogs include the significant-violent tornado outbreaks of 1/12-1/13/2005, 2/28-3/1/2007, 2/5-2/6/2008, 1/3/2000, 3/9/1992, 1/3/1982, and 2/10/2009. In terms of wintertime setups, that's a creme de la creme sort of lineup. The 00z GFS throws even more fuel into this fire by bringing 60°F+ dewpoints to Terre Haute, IN, by 06z Wednesday morning and 65°F dewpoints all the way to I-40 in AR and southern west TN. Add onto all of this the fact that the Euro did not have nearly the impressive cutoff in the SW and (contrary to previous posts) often seems to be too prone to cutting off the jet in the southwest with these major troughs, I really am beginning to lean toward a greater likelihood that something significant is going to happen Tues/Wed, perhaps across an area as widespread as from nrn IL all the way across MO and AR, ern KS and OK, NE TX, nrn LA, TN, KY, a good chunk of IN, MS, AL, GA, and maybe the Carolinas. I won't totally bite just yet, but the odds of this system being significant are increasing.

Yeah, the Euro has actually trended away pretty hard from the cutoff solution if you compare the 12z Thu/00z Fri/12z Fri runs. Not sure what to think about the severe threat this far north and east (how often can you get excited 4 days out in January?) but overall chances do appear to be on an upward trend.

[Stebo]

Yeah, the Euro has actually trended away pretty hard from the cutoff solution if you compare the 12z Thu/00z Fri/12z Fri runs. Not sure what to think about the severe threat this far north and east (how often can you get excited 4 days out in January?) but overall chances do appear to be on an upward trend.

 

The dynamics most certainly will be in place, it is whether or not we can get some instability into the picture up this way. I am with Tony on this though, if what the models right now sans the Euro verify, it could very well be a top end type day for the Southern Plains and extending into the Mid MS valley regions.

 

Edit: as soon as I posted this the Euro has now trended toward the GFS tonight.

[Hoosier]

00z Euro is looking like another step away from the cutoff solution so far. Whether it's enough for something big, we'll see.

[Stebo]

00z Euro is looking like another step away from the cutoff solution so far. Whether it's enough for something big, we'll see.

 

It did at 96hr, then 120hr came out and it was pretty much wtf.

[tornadotony]

And welcome to the table, 00z Euro.

 

http://www.instantweathermaps.com/ECMWF-php/showmap-ecmwf.php?run=2013012600&region=USA&var=GRD_850mb&hour=96

http://www.instantweathermaps.com/ECMWF-php/showmap-ecmwf.php?run=2013012600&region=USA&var=GRD_850mb&hour=120