May 15th - 20th Plains Storm/Severe disco

[Stebo]

..SHORTWAVE TROUGH PRESENTLY NEAR THE CALIFORNIA COAST  

 

PREFERENCE: 2/3 NAM TO 1/3 ECMWF  

CONFIDENCE: ABOVE AVERAGE  

 

MODELS ARE IN AGREEMENT IN ALLOWING THE TROUGH TO REACH THE  

CENTRAL/SOUTHERN ROCKIES BY MIDDAY THURSDAY...BY WHICH TIME THE  

GFS ALLOWS FOR AN AREA OF CONVECTIVE GRID-SCALE FEEDBACK TO PHASE  

WITH THE LARGER TROUGH BEFORE ENTERING THE PLAINS...RESULTING IN  

GREATER EASTWARD MOVEMENT OF ITS ASSOCIATED DRYLINE BY 12Z FRIDAY.  

GIVEN AN ABSENCE OF SUPPORT FOR THIS SCENARIO AND THAT THE  

COURSER-GRIDDED GFS IS MORE PRONE TO SUCH ERRORS COMPARED TO THE  

HIGHER RESOLVING GUIDANCE...ITS SOLUTION IS DISCOUNTED.  

OTHERWISE...THE NAM/ECMWF HANDLE THE TROUGH COMPARABLY...WITH THE  

HIGHER RESOLVING NAM SLIGHTLY MORE PREFERRED THAN THE SLIGHTLY  

LESS RESOLVING ECMWF.  

 

Yeah that QPF bomb definitely reeked of convective feedback.

[ZackH]

..SHORTWAVE TROUGH PRESENTLY NEAR THE CALIFORNIA COAST  

 

PREFERENCE: 2/3 NAM TO 1/3 ECMWF  

CONFIDENCE: ABOVE AVERAGE  

 

MODELS ARE IN AGREEMENT IN ALLOWING THE TROUGH TO REACH THE  

CENTRAL/SOUTHERN ROCKIES BY MIDDAY THURSDAY...BY WHICH TIME THE  

GFS ALLOWS FOR AN AREA OF CONVECTIVE GRID-SCALE FEEDBACK TO PHASE  

WITH THE LARGER TROUGH BEFORE ENTERING THE PLAINS...RESULTING IN  

GREATER EASTWARD MOVEMENT OF ITS ASSOCIATED DRYLINE BY 12Z FRIDAY.  

GIVEN AN ABSENCE OF SUPPORT FOR THIS SCENARIO AND THAT THE  

COURSER-GRIDDED GFS IS MORE PRONE TO SUCH ERRORS COMPARED TO THE  

HIGHER RESOLVING GUIDANCE...ITS SOLUTION IS DISCOUNTED.  

OTHERWISE...THE NAM/ECMWF HANDLE THE TROUGH COMPARABLY...WITH THE  

HIGHER RESOLVING NAM SLIGHTLY MORE PREFERRED THAN THE SLIGHTLY  

LESS RESOLVING ECMWF.  

 

Lol... you posted that at the right time 

[ZackH]

Central NE on Thurs has sleeper potential per NAM.

[andyhb]

Secondary sfc cyclogenesis on Monday with the Euro, the first wave essentially departs into the Great Lakes and leaves the second one to work on it's own (nice LLJ response as well).

[baroclinic_instability]

Central NE on Thurs has sleeper potential per NAM.

A few high based cells possible W of LBF, but dews east of the dryline in the low 60s won't cut it. Pretty marginal skinny cape profiles and effectively no shear above 700 hpa per NAM. Still better than the nothing, but I don't think it would be chase worthy, IMHO. But then I am not a chaser

[andyhb]

Saturday risk shifted north, Sunday added.

 

DAY 4-8 CONVECTIVE OUTLOOK     NWS STORM PREDICTION CENTER NORMAN OK   0355 AM CDT TUE MAY 14 2013      VALID 171200Z - 221200Z      ...DISCUSSION...   MEDIUM-RANGE MODELS CONTINUE TO GENERALLY AGREE WITH THE ADVANCE OF   A WRN U.S. TROUGH ACROSS THE ROCKIES EARLY IN THE PERIOD...WITH   ASSOCIATED CONVECTIVE/SEVERE POTENTIAL RAMPING UP ACROSS THE PLAINS   AS THE TROUGH APPROACHES DAY 5 /SAT. 5-18/.  DETAILS REMAIN   UNCLEAR...BUT CURRENT INDICATIONS ARE THAT THE GREATEST THREAT MAY   OCCUR A BIT FARTHER N ON DAY 5 THAN PREVIOUSLY FORECAST -- I.E. FROM   NRN KS NWD INTO SD.  CAPPING SUGGESTS THAT INITIATION MAY BE   HINDERED UNTIL LATE AFTERNOON...AFTER WHICH SUPERCELLS SHOULD   INITIATE INVOF A DRYLINE/PRE-FRONTAL TROUGH AND THEN SHIFT EWD   THROUGH THE EVENING HOURS.  LARGE HAIL AND DAMAGING WINDS WILL   LIKELY BE THE PRIMARY THREATS...ALONG WITH ISOLATED TORNADOES.      AS THE UPPER TROUGH AND ASSOCIATED SURFACE SYSTEM CONTINUES EWD DAY   6 /SUN. 5-19/...SEVERE POTENTIAL APPEARS LIKELY TO CONTINUE -- FROM   IA SSWWD ACROSS WRN MO/ERN KS AND INTO THE NWRN OK VICINITY.  STORMS   -- POSSIBLY ONGOING IN SOME AREAS EARLY IN THE PERIOD -- SHOULD   INCREASE DURING THE AFTERNOON...BRINGING CONTINUED THREAT FOR LARGE   HAIL AND DAMAGING WINDS ALONG WITH ISOLATED TORNADOES.      MODELS BEGIN MORE SUBSTANTIAL DISAGREEMENT THROUGH DAY 7 AND   BEYOND....AND THUS WILL RESTRICT AREAL OUTLINE OF SEVERE POTENTIAL   TO DAYS 5-6 ATTM.      ..GOSS.. 05/14/2013

[ZackH]

A few high based cells possible W of LBF, but dews east of the dryline in the low 60s won't cut it. Pretty marginal skinny cape profiles and effectively no shear above 700 hpa per NAM. Still better than the nothing, but I don't think it would be chase worthy, IMHO. But then I am not a chaser

Oh def no tornado potential but if its on the way to where we are going anyways.... You know

[brettjrob]

Secondary sfc cyclogenesis on Monday with the Euro, the first wave essentially departs into the Great Lakes and leaves the second one to work on it's own (nice LLJ response as well).

 

Yeah, Monday might actually be the best-looking day on the Euro, at least W of the Ozarks. Interesting and potentially extended active period coming up finally, but timing will be key each day.

[Chrisrotary12]

Landing in Kansas City Thursday evening.  Looking at north/central Kansas Friday.  Southwestern/central Kansas for Saturday.  And then north/central Oklahoma for Sunday.

 

Thoughts?

[nrgjeff]

Welcome (in advance) to my hometown KC! Sounds like a good plan Fri/Sat. Depending on evolution of system, Sunday might be good up near OMA and possible outflow boundaries, esp if cap pulled north in wake of Saturday. That's based on the Euro. Closer to your return flight too, lol. Good luck!

[Chrisrotary12]

Welcome (in advance) to my hometown KC! Sounds like a good plan Fri/Sat. Depending on evolution of system, Sunday might be good up near OMA and possible outflow boundaries, esp if cap pulled north in wake of Saturday. That's based on the Euro. Closer to your return flight too, lol. Good luck!

 

We will be out on the plains until the 26th.  

 

Here's to hoping the CF does not push too far south and some moisture can return for next week.

[OKpowdah]

Wow, just now "discovering" the COD page for model guidance. Really impressive.

 

New go-to for me. http://weather.cod.edu/forecast/

[Ian]

GFS not the best timing for Sat but a few storms better than none. Looks like it's going to try to pull a Euro after given the trough orientation.

[OKpowdah]

12z GFS. Pretty impressive upper level divergent pattern over western KS Saturday evening

 

[Chrisrotary12]

12z GFS. Pretty impressive upper level divergent pattern over western KS Saturday evening

 

gfsSGP_250_spd_108.gif

 

Ya. Southwestern KS, east of the dry line looks nice Saturday evening.

[HM]

12z GFS. Pretty impressive upper level divergent pattern over western KS Saturday evening

 

gfsSGP_250_spd_108.gif

 

That caught my attention too. I do echo Brett's concerns about mixing out a bit ahead of the dryline in this area with the best moisture shifting east of the best low and mid level jets. Having said that, it still appears to be quite ominous for SW KS / NW OK and the threat could go all night for someone. So while areal coverage could be limited Saturday, I think a smaller-scale outbreak of tornadoes is possible if 1 or 2 nasty supercells get going.

 

We are getting to that range where the details matter but far enough away for models to screw them up. Counting down the days....

[ZackH]

For what its worth, here's the best CIPS Analog for Saturday's event:

 

6/13/2001

 

[HM]

Basically, all the "problems" with Saturday could be fixed with a faster arrival of the wave across the S-C Plains.

[Thundersnow12]

That caught my attention too. I do echo Brett's concerns about mixing out a bit ahead of the dryline in this area with the best moisture shifting east of the best low and mid level jets. Having said that, it still appears to be quite ominous for SW KS / NW OK and the threat could go all night for someone. So while areal coverage could be limited Saturday, I think a smaller-scale outbreak of tornadoes is possible if 1 or 2 nasty supercells get going.

 

We are getting to that range where the details matter but far enough away for models to screw them up. Counting down the days....

 

It will be interesting to see how SPC handles say Thursday-Sunday because you're going to have environments conducive for good supercells over a wide area but right now it looks like the cap might keep in check a wide area of lots of storms. You have great directional shear Thu/Fri with more a westerly component aloft. The question will be do we get storms in these enviroments. The LLJ progged on the 12z GFS into sw KS saturday afternoon/evening is very ominous to say the least and one or two supercells could take full advantage of that. 

 

Not overlooking tomorrow either from CDS-LAW-ABI. 

[brettjrob]

Basically, all the "problems" with Saturday could be fixed with a faster arrival of the wave across the S-C Plains.

 

Strongly agree. The GFS has unfortunately trended the opposite direction over the past 24 h, but it's tough to identify an overall trend in the full set of guidance. My hunch, for what little it's worth, is that the timing will be slow enough to leave us wanting for deep-layer shear, and for the cap to be a serious concern.

[HM]

Strongly agree. The GFS has unfortunately trended the opposite direction over the past 24 h, but it's tough to identify an overall trend in the full set of guidance. My hunch, for what little it's worth, is that the timing will be slow enough to leave us wanting for deep-layer shear, and for the cap to be a serious concern.

 

A major disagreement exists among the models in the Northeast Pacific-western North America sector. If the "second piece" waits to drop in, then the first wave will have more room to amplify and slow down. Notice last night's ECMWF blasted in the next wave quickly into the Pacific NW by 00z Sunday, in full. Today's 12z GFS sort of splits this next wave, sending some of it into the first trough and holding back the rest. So with that solution, there isn't a substantial kicker and it is by far the slowest solution of all the data right now. The GGEM today is like the GFS but then goes one step further to allow the two waves to interact much sooner over the NW. I would say the 12z UKMET looks like the 00z ECMWF. 

 

 

Plenty of room for changes with this complex interaction unfolding in the Northwest for sure.

 

 

By the way, the "second wave" is not the big closed low that drops into the Pacific NW early next week. Compare the models between 12z Sat and 12z Mon to see what I mean.

[HM]

It will be interesting to see how SPC handles say Thursday-Sunday because you're going to have environments conducive for good supercells over a wide area but right now it looks like the cap might keep in check a wide area of lots of storms. You have great directional shear Thu/Fri with more a westerly component aloft. The question will be do we get storms in these enviroments. The LLJ progged on the 12z GFS into sw KS saturday afternoon/evening is very ominous to say the least and one or two supercells could take full advantage of that. 

 

Not overlooking tomorrow either from CDS-LAW-ABI. 

 

My focus has been mainly on the big players in the pattern and the S-C Plains. From looking at that mostly, I can tell you that we are likely not done seeing changes yet in regards to timing and placement of features (see my response to Brett). Until this interaction is resolved properly with reasonable model agreement, I can't really comment on where the best areas will be. And even then, I would rather you guys tell me, not the other way around.  

 

I wish everyone the best of luck with their forecasts/decisions.

[HM]

Amazingly, the operational GFS is actually faster/less amplified than the new 12z ensemble mean/most members. The 12z GFS and the 00z ECMWF are so polarized that NCEP decided to do this:

 

...MEDIUM WAVELENGTH TROUGH DEVELOPING OVER THE WESTERN U.S...

PREFERENCE: BLEND OF 12Z NAM AND 00Z UKMET/CANADIAN

A PROGRESSIVE TROUGH WILL AMPLIFY AS IT ENTERS THE WESTERN U.S.
ENSEMBLE PLOTS SHOW GFS MEMBERS DIGGING ENERGY MORE SHARPLY INTO
THE BASE OF THE TROUGH OVER SOUTHERN CALIFORNIA AND BAJA WHEN
COMPARED TO THE EUROPEAN AND CANADIAN ENSEMBLE SYSTEMS. THE 00Z
OPERATIONAL GFS HAD BEEN LESS SHARP THAN ITS ENSEMBLE
MEMBERS...BUT THE 12Z RUN TRENDED SHARPER/DEEPER. THE 00Z
ECMWF...ON THE OTHER HAND...STANDS OUT AS BEING THE MOST DAMPENED
SOLUTION IN THAT PORTION OF THE TROUGH. THE PARENT SHORTWAVE WAS
IN ZONAL FLOW OVER THE PACIFIC THIS MORNING...GIVING LITTLE
SATELLITE REPRESENTATION TO SUGGEST FAVORING ONE MODEL OVER
ANOTHER. FOR A CONSENSUS SOLUTION...BLENDING THE
NAM/UKMET/CANADIAN WILL FORM A SOLUTION IN BETWEEN THE GEFS MEAN
AND ECMWF ENSEMBLE MEAN.

WE ALSO NOTE A LEAD SHORTWAVE THAT WILL LIFT THROUGH THE NORTHERN
ROCKIES ON DAY 2. THIS ONE DOES HAVE A MARKED DRYING SIGNATURE IN
WATER VAPOR IMAGERY OVER THE PACIFIC. THE NAM DOES NOT APPEAR TO
HANDLE THIS WELL. IT CONTINUES TO BE AN OUTLIER IN TAKING A
DAMPENED FEATURE QUICKLY EASTWARD AND INDUCING A SURFACE RESPONSE
AFFECTING ND/MN ON DAY 3. THE GLOBAL MODELS ARE PREFERRED FOR THE
LEAD WAVE.

From what I have of the new 12z ECMWF, it is holding onto the 00z idea pretty much.

[Ian]

Strongly agree. The GFS has unfortunately trended the opposite direction over the past 24 h, but it's tough to identify an overall trend in the full set of guidance. My hunch, for what little it's worth, is that the timing will be slow enough to leave us wanting for deep-layer shear, and for the cap to be a serious concern.

SW KS could have some pretty sizeable temp/dp spreads too it seems. Euro gets it to like 95+... tho it never fires anything around there so maybe moot.

[ZackH]

SW KS could have some pretty sizeable temp/dp spreads too it seems. Euro gets it to like 95+... tho it never fires anything around there so maybe moot.

 

I really believe the SW KS spreads could be a by product of the convective feedback the GFS has been having.  That drier surface-850 mb air that is being advected in due to the anomalous mesolow formed over the TX panhandle earlier in the period would cause higher spreads/LCLs.

[Ian]

I really believe the SW KS spreads could be a by product of the convective feedback the GFS has been having.  That drier surface-850 mb air that is being advected in due to the anomalous mesolow formed over the TX panhandle earlier in the period would cause higher spreads/LCLs.

yeah perhaps. i think i agree with spc areal outlook more than that play for now. plenty of time to change though.

[ZackH]

yeah perhaps. i think i agree with spc areal outlook more than that play for now. plenty of time to change though.

 

The target is a tough call for right now... because if the LCLs are lower down there its definitely the play, but North Central KS into NE may be the smart play.

[andyhb]

Amazingly, the operational GFS is actually faster/less amplified than the new 12z ensemble mean/most members. The 12z GFS and the 00z ECMWF are so polarized that NCEP decided to do this:

 

Yeah the Euro has been very persistent with this idea of weakening the upstream ridging as the trough attempts to amplify (although not much else agrees with it). The 12z GGEM, fwiw, is an I-35 and east special from the looks of it on Sunday, with a 40-50 kt LLJ to the east of the dryline in KS/OK.

[baroclinic_instability]

It will be interesting to see how SPC handles say Thursday-Sunday because you're going to have environments conducive for good supercells over a wide area but right now it looks like the cap might keep in check a wide area of lots of storms. You have great directional shear Thu/Fri with more a westerly component aloft. The question will be do we get storms in these enviroments. The LLJ progged on the 12z GFS into sw KS saturday afternoon/evening is very ominous to say the least and one or two supercells could take full advantage of that. 

 

Not overlooking tomorrow either from CDS-LAW-ABI. 

I see numerous slight risks with well placed hatches for all days beginning Sat. None of the progs in any way suggest widespread sig severe given marginal mid level/upper level flow/shear and midsummer like capping across much of the southern plains.

[baroclinic_instability]

Wow, just now "discovering" the COD page for model guidance. Really impressive.

 

New go-to for me. http://weather.cod.edu/forecast/

Not cluttering the thread, but yeah, mouseover for frames? Yes please. Ewall is still my all-time favorite, but it has its limitations, especially with respect to random/odd times the data begins streaming in depending on run (i.e., it isn't consistent), low res data for larger scale plots, and lack of thermodynamic plots. COD looks like, I may have to revisit it.