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Severe Weather Thread (April 26 - May 3)


David Reimer

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Wow... Strong Rotation is evident on the OUN Radar West of Ponca City and that's 100+ Miles north... The NWS irritates me sometimes with there lack of wanting to issue warnings for reason beyond my understanding...

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Can we cut the criticism of NWS offices please.

I'm not criticizing...but the apparent debris signature does indicate a likely miss on that. Hoping it wasn't a big deal. Actually...I'm usually the one happy to see OUN holding off on TORs during a lot of these situations where its easy to start warning early and often.

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Reminds me a bit of Harrisburg NC on March 3. RAH issued a TOR

for a circulation approaching their CWA, but GSP did not warn the same

one as it was exiting theirs. Ponca City is right on the edge of OUN's

area, and Tulsa issued a warning for their first county. I guess OUN

figured it was too late by that time.

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SEVERE WEATHER STATEMENT

NATIONAL WEATHER SERVICE TULSA OK

1120 PM CDT MON APR 30 2012

OKC113-117-010445-

/O.CON.KTSA.TO.W.0020.000000T0000Z-120501T0445Z/

OSAGE OK-PAWNEE OK-

1120 PM CDT MON APR 30 2012

...TORNADO WARNING REMAINS IN EFFECT UNTIL 1145 PM CDT FOR PAWNEE AND

WESTERN OSAGE COUNTIES...

AT 1115 PM CDT...POTENTIAL TORNADIC CIRCULATIONS WERE LOCATED

ALONG A LINE EXTENDING FROM WESTERN OSAGE COUNTY TO WESTERN PAWNEE

COUNTY...MOVING EAST AT 35 MPH. TORNADOES MAY FORM RAPIDLY ANYWHERE

ALONG THIS LINE!

THIS STORM WILL OTHERWISE REMAIN OVER MAINLY RURAL AREAS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

NIGHTTIME TORNADOES ARE ESPECIALLY DANGEROUS...TAKE COVER NOW! IF YOU

WAIT UNTIL YOU SEE OR HEAR IT COMING...IT MAY BE TOO LATE TO GET TO A

SAFE PLACE!

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Didn't see this posted (I apologize if it already was) but Medford's Mesonet gusted up to 84MPH. Pretty freaking impressive!

MEDF.met.gif

Other notable Mesonet wind reports include Hollis, OK at 76 mph, Minco, OK at 75 mph, and Fort Cobb, OK at 64 mph. Sheesh!

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Did not know what a heat burst was until tonight, looks like they are extremely rare!

yep, they don't happen with many storms, due to how they rapidly dry-mix air to the surface from storms as dramatically like a chinook. but when they do, you could see temps rise as much as 20-25C in minutes and then drop back down within an hour or so.

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yep, they don't happen with many storms, due to how they rapidly dry-mix air to the surface from storms as dramatically like a chinook. but when they do, you could see temps rise as much as 20-25C in minutes and then drop back down within an hour or so.

Heat bursts used to be thought as rare, but since the explosion of ASOS/AWOS in the late 90s and mesonet sites, they are far more common than once thought.  The are often quite localized so we just missed them more in the past.

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DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1258 AM CDT TUE MAY 01 2012

VALID 011200Z - 021200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE ERN DAKOTAS AND

NEB...NERN KS...IA...MOST OF MN AND WRN WI...

...SYNOPSIS...

A LOW AMPLITUDE SHORTWAVE TROUGH WILL MOVE FROM THE MO VALLEY ENEWD

ACROSS THE OH VALLEY REGION DURING THE DAY...HELPING TO MOVE

MOISTURE AND INSTABILITY NEWD WITH A THREAT OF SEVERE HAIL AND WIND.

MEANWHILE...A MORE SUBSTANTIAL UPPER TROUGH WILL MOVE INTO THE NRN

PLAINS WITH LOW PRESSURE DEEPENING ACROSS THE DAKOTAS INTO WRN MN

SWWD ACROSS NEB. BOTH SHEAR AND INSTABILITY WILL BE FAVORABLE FOR

SEVERE STORMS

...MID MO INTO THE UPPER MS VALLEY...

SCATTERED WARM ADVECTION STORMS MAY EXIST ACROSS MN AND IA EARLY

NEAR A WARM FRONT...WITH A MARGINAL HAIL THREAT. THEN...STRONG SLY

FLOW WILL BRING MID 60S F BOUNDARY LAYER DEWPOINTS NWD INTO THE

REGION...CREATING STRONG INSTABILITY OVER THE WARM SECTOR.

CONVERGENCE WILL INCREASE ALONG THE COLD FRONT/SURFACE TROUGH. GIVEN

LITTLE IF ANY CONVECTIVE INHIBITION...STORMS SHOULD ERUPT BY

21Z...BEGINNING OVER NRN MN NEAR THE SURFACE LOW...THEN FARTHER SWWD

ALONG THE SFC TROUGH. WIND PROFILES WILL FAVOR SUPERCELLS...WITH

VERY LARGE HAIL LIKELY.

LOW LEVEL SHEAR MAY BE ENHANCED OVER CNTRL/NRN MN DUE TO THE EFFECTS

OF EARLY CONVECTION AND WHERE A WARM FRONT WILL HOLD. AS A

RESULT...A FEW TORNADOES MAY OCCUR. A STRONG TORNADO CANNOT BE RULED

OUT IF LOW LEVEL SHEAR ENDS UP BEING AS STRONG AS SOME OF THE NAM

FORECAST SOUNDINGS INDICATE. HOWEVER...THERE ARE VARYING MODEL

SOLUTIONS...AND WILL MAINTAIN ISOLATED TORNADO THREAT AT THIS TIME.

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Looking at surface obs, I'm having a hard time picking out the surface warm front that is supposed to be the focus of tornadoes around or North of the MSP area. But I am just an amateur. I might be able to pick out something in Wisconsin running towards Lake Superior, and from the low in NCen SD towards the ND/MN/Canadian triple point, but nothing around or North of MSP that is real obvious on cursory inspection.

ttd.gif

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Looking at surface obs, I'm having a hard time picking out the surface warm front that is supposed to be the focus of tornadoes around or North of the MSP area. But I am just an amateur. I might be able to pick out something in Wisconsin running towards Lake Superior, and from the low in NCen SD towards the ND/MN/Canadian triple point, but nothing around or North of MSP that is real obvious on cursory inspection.

It is subtle, but it most certainly is there. Not all warm fronts are extremely backed in the low levels like you may get with deeper cyclones. It certainly is a progressive wave/cyclone scenario here, but the warm front should still provide an environment favorable for tornadoes if the low clouds can sufficiently mix out by later afternoon. It certainly won't be a tor outbreak though. I am thinking discrete initiation followed by a QLCS later evening as the storms trek through MN, but it is definitely going to be a relatively significant potential early season event for MN (my home state).

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Anyone else notice twisterdata and a few other sites haven't updated since the 11z RUC run? I believe it's because the RUC replacement (RAP) started today at 12z. Wonder how long it will take for some of these favorite sites to switch over to the new RAP input. You would think twisterdata would have been on top of that.

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Anyone else notice twisterdata and a few other sites haven't updated since the 11z RUC run? I believe it's because the RUC replacement (RAP) started today at 12z. Wonder how long it will take for some of these favorite sites to switch over to the new RAP input. You would think twisterdata would have been on top of that.

Ah, thanks for bringing this up. I forgot this was today. SPC meso has the new information listed as RAP too.

"The SPC runs a comprehensive surface objective analysis scheme called SFCOA. The system runs at the top of each hour, using the latest 40km RAP forecast grids as a first guess. Next, the surface data is merged with the latest RAP forecast/analysis upper-air data to represent a 3-dimensional current objective analysis. Finally, each gridpoint is post-processed with a sounding analysis routine called NSHARP to calculate many technical diagnostic fields related to severe storms."

http://www.spc.noaa....r/mesoanalysis/

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