Jump to content
  • Member Statistics

    17,603
    Total Members
    7,904
    Most Online
    ArlyDude
    Newest Member
    ArlyDude
    Joined

May 19 threat in chaser land


Ed Lizard

Recommended Posts

  • Replies 203
  • Created
  • Last Reply

Its early, but I'd think if the GFS is close in and close to OKC would be the place to be. The amount of 3 hour rainfall that falls between 7 pm and 10 pm CDT suggests initiation very near 7 pm Thursday, and OKC GFS forecast looks decent for severe.

post-138-0-71052100-1305659044.gif

post-138-0-63152800-1305659058.gif

Link to comment
Share on other sites

A note from the Wichita NWS...

GFS CONTINUES TO BE THE FASTER OUTLIER COMPARED TO ALL OTHER MEDIUM RANGE GUIDANCE WITH RESPECT TO SYNOPTIC FEATURES. CONSEQUENTLY...GFS IS MOST BULLISH WITH MOISTURE RETURN AND FARTHER EAST WITH DRYLINE POSITION. FURTHERMORE...GFS WAS TOO FAST WITH THE LAST SYSTEM TO AFFECT THE AREA LAST WEEK. THAT SAID...AM TENDING TO FAVOR THE ECMWF/UKMET/CANADIAN/NAM CONSENSUS.
Link to comment
Share on other sites

The NAM has shifted the triple point markedly SE over the past several runs, which is a concerning trend, albeit one that I'm skeptical of at the moment. This is the reason for the strongly-capped sounding at ICT on this run, as they're actually within the diffuse warm frontal zone rather than solidly within the warm sector. Forecast soundings farther W -- say, at Medicine Lodge -- show a more favorable environment that compares with the GFS forecast for ICT.

A growing concern of mine is that the best deep-layer shear could remain a bit dislocated NW of the warm sector, as model trends continue to point toward the H5 low taking a slower and more northerly track. My Plains chasing "benchmark" for H5 trough axes and/or closed lows is the Four Corners area, and once again, 2011 is proving that such a track just wasn't meant to be this year. Not all is lost, of course, as 40-50 kt mid-tropospheric flow can still be more than adequate for late-season tornadic supercells. What gives me pause is that CAPE may not be particularly high for this event, and so I'd ideally like to see mid-level flow more on the order of 50-60 kt up and down the dryline.

The slight pulling back of the trough on this morning's runs also has some unfortunate implications on the low-level response. The NAM depicts a weaker surface low with weaker and less-backed surface winds, and the LLJ is also a bit anemic and slower to back over the course of the day.

If I'm allowed one more gripe, it's the poor mid-level lapse rates and resultant "skinny CAPE" profiles. On the sounding I linked above, one can see that parcel buoyancy actually decreases with height between roughly 600 mb and 500 mb. This is yet another issue that owes to the less progressive and more northerly trend, and could become a bigger problem if that trend continues.

Link to comment
Share on other sites

Cancel, 5/19, I like the 5/23- 5/26th\ much better for tornado potential. I don't go tornado chasing unless I can drink in my hotel room and for the tornado to chase me.

Until the Euro decides to cancel that, which it's starting to already if the trends don't turn around.

Link to comment
Share on other sites

17/00z NAM reverses most of the bad trends on this morning's run and indicates a fairly potent triple point setup somewhere in C or W KS. Everything looks pretty good for tornadic supercells. We just need the warm sector to expand eastward a bit, and another 500-1000 J/kg SBCAPE along the dryline wouldn't hurt, either. Hopefully, the NAM is underestimating surface temperatures, which would alleviate both of these issues.

Link to comment
Share on other sites

New SWODY2 features hatching along the length of the DL, with 30% probs focused near the triple point in KS. If I'm not mistaken, Mr. Darrow is one of the more conservative forecasters, as well.

ACUS02 KWNS 180502

SWODY2

SPC AC 180501

DAY 2 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1201 AM CDT WED MAY 18 2011

VALID 191200Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL AND

SRN PLAINS...

..CNTRL/SRN PLAINS

00Z NAM/GFS ARE VERY SIMILAR IN THEIR PROGRESSION OF UPPER TROUGH

ACROSS THE INTER-MOUNTAIN REGION INTO THE CNTRL/SRN ROCKIES BY THE

END OF THE PERIOD. ALTHOUGH BOTH MODELS ARE SLOW TO MOVE THIS

FEATURE INTO THE HIGH PLAINS EACH IS VERY CONSISTENT REGARDING THE

EJECTION OF A STRONG SPEED MAX THROUGH THE BASE OF THE TROUGH ACROSS

NERN NM INTO SWRN KS BY 20/00Z. AS A RESULT...DEEP LAYER SHEAR IS

EXPECTED TO INCREASE AS 50-70KT AT H5 BEGINS TO OVERSPREAD THE

DRYLINE AT PEAK HEATING. LARGE SCALE FORCING DICTATES THAT A

PRONOUNCED DRYLINE SHOULD EXTEND SWD FROM A SFC LOW OVER SWRN

KS...ALONG THE TX/OK BORDER INTO NWRN TX. WITH STRONG BOUNDARY

LAYER HEATING EXPECTED ALONG/WEST OF THE WIND SHIFT SFC PARCELS

SHOULD EASILY REACH THEIR CONVECTIVE TEMPERATURE AND ISOLATED

THUNDERSTORMS SHOULD DEVELOP AFTER 21Z. WITH MULTIPLE DAYS OF SLY

FLOW ACROSS THE PLAINS AND MORE FAVORABLE TRAJECTORIES ACROSS THE

GULF OF MEXICO...IT APPEARS BOUNDARY LAYER MOISTURE WILL MORE

READILY REFLECT A MODIFIED MARITIME AIRMASS WITH SFC DEW POINTS

EXPECTED TO RISE THROUGH THE MID 60S SOUTH OF THE WARM FRONT. BY

PEAK HEATING THE WARM FRONT SHOULD HAVE RETREATED TO NEAR I-70

ACROSS KS AND THIS SHOULD SERVE AS THE FOCUS FOR THE MORE

CONCENTRATED SEVERE CONVECTION DURING THE LATTER HALF OF THE PERIOD.

LATEST THINKING IS ELEVATED CONVECTION WILL BE ONGOING AT THE

BEGINNING OF THE PERIOD ACROSS THE CNTRL PLAINS ALONG NOSE OF LLJ.

AND ELEVATED INSTABILITY COULD EASILY SUPPORT MARGINALLY SEVERE

HAIL...OR PERHAPS AN ISOLATED EVENT IN EXCESS OF ONE INCH.

HOWEVER...THE GREATER SUPERCELL SEVERE THREAT WILL EVOLVE AFTER 21Z

ALONG THE DRYLINE OVER SWRN KS INTO WRN OK. THIS WILL BE DRIVEN BY

STRONG HEATING WHICH SHOULD YIELD SBCAPE VALUES IN EXCESS OF 2000

J/KG ALONG WRN PLUME OF RICHER MOISTURE RETURN. FORECAST SOUNDINGS

STRONGLY SUGGEST SIGNIFICANT HAIL IN EXCESS OF 2 INCHES MAY BE NOTED

WITH THESE SUPERCELL STRUCTURES. OF PARTICULAR CONCERN WILL BE JUST

EAST OF THE DRYLINE ACROSS SWRN KS INTO NWRN OK WHERE BOUNDARY LAYER

RH VALUES WILL SUPPORT LOWER CLOUD BASES. THIS MOIST ENVIRONMENT

WILL FAVOR TORNADO DEVELOPMENT AS MID LEVEL SPEED MAX OVERSPREADS

CONVECTION DURING THE EVENING HOURS. SEVERE THREAT SHOULD

CONCENTRATE ALONG THE WARM FRONT AFTER DARK AS LLJ IN EXCESS OF 50KT

IMPINGES ON E-W BOUNDARY.

..MIDDLE ATLANTIC

SLOW MOVING UPPER LOW WILL BE SHUNTED EAST INTO THE DELMARVA BY

20/12Z. THIS FEATURE HAS INDUCED STRONG AFTERNOON CONVECTION ALONG

THE ERN PERIPHERY ACROSS THE MIDDLE ATLANTIC THE LAST FEW DAYS AND

SHOULD DO SO AGAIN THROUGH DAY1 INTO THE DAY2 PERIOD. DIURNAL

HEATING WILL PROVE INSTRUMENTAL IN ROBUST THUNDERSTORM DEVELOPMENT

BENEATH COLD MID LEVEL POCKET. A FEW STORMS MAY PRODUCE HAIL OR

GUSTY WINDS.

..DARROW.. 05/18/2011

Link to comment
Share on other sites

I'm starting to sense some disappointment in the 12Z GFS and NAM, as far as anything big and exciting.

Also tomorrow looks more like Nebraska/Wyoming/South Dakota instead of Kansas/Oklahoma.

So it sounds like the system has shifted north over the last day or so? Before, MKX was doubting any severe weather potential. this morning, they said it is possible, if not likely, Saturday and Sunday. I'm not thinking much of Saturday, but could be decent Sunday with the cold front barging in.

Link to comment
Share on other sites

I'm starting to sense some disappointment in the 12Z GFS and NAM, as far as anything big and exciting.

Also tomorrow looks more like Nebraska/Wyoming/South Dakota instead of Kansas/Oklahoma.

We'll see.

Lapse rates are as sucky up there as they are along the dryline.

Link to comment
Share on other sites

I'm starting to sense some disappointment in the 12Z GFS and NAM, as far as anything big and exciting.

Also tomorrow looks more like Nebraska/Wyoming/South Dakota instead of Kansas/Oklahoma.

At this juncture I would respectfully disagree. The wind profiles in KS are looking to be excellent. If there are any breaks in the clouds and more instability is able to take hold, KS could get lit up as instability and mid level lapse rates are the only question marks. The NAM is notorious for underestimating instability. The NAM also still had the triple point in north/central Kansas last I checked which would make the northern target you spoke of crap. GFS is the outlier and I wouldn't look much at its more northern track at this point. The euro and the NAM are fairly close. I'm cautiously optimistic as even conservative forecasters are jumping on board. If there isn't much crap vection and the clouds fall away in places in the morning, we could be looking at a very active day. The favorable shear will possibly spawn a handful of tornadoes even without extreme instability, they just may not be as strong or long lived. Just my two cents.

Link to comment
Share on other sites

So it sounds like the system has shifted north over the last day or so? Before, MKX was doubting any severe weather potential. this morning, they said it is possible, if not likely, Saturday and Sunday. I'm not thinking much of Saturday, but could be decent Sunday with the cold front barging in.

Sunday looks decent for sure with the GFS consistently showing an 80kt H250 jet moving through the Great Lakes around peak heating. Instability is kind of "eh" and shear profiles are rather unidirectional but I tend to think that there could at least be a forced line of convection considering the upper level support.

Link to comment
Share on other sites

At this juncture I would respectfully disagree. The wind profiles in KS are looking to be excellent. If there are any breaks in the clouds and more instability is able to take hold, KS could get lit up as instability and mid level lapse rates are the only question marks. The NAM is notorious for underestimating instability. The NAM also still had the triple point in north/central Kansas last I checked which would make the northern target you spoke of crap. GFS is the outlier and I wouldn't look much at its more northern track at this point. The euro and the NAM are fairly close. I'm cautiously optimistic as even conservative forecasters are jumping on board. If there isn't much crap vection and the clouds fall away in places in the morning, we could be looking at a very active day. The favorable shear will possibly spawn a handful of tornadoes even without extreme instability, they just may not be as strong or long lived. Just my two cents.

Agreed, and even when you go that north you get into a little more meridional flow and veering from 500-200MB, so it could be more jumbled up there.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.

×
×
  • Create New...