Possible Severe Event - 4/30 to 5/3

[KWT]

Yep thats the case, though the 1987 storm was a very powerful extra-tropical system, it had wind gusts of upto 90kts over the UK, upto 110kts in the channel and it caused huge damage!

Anyway no hints of any convection yet but it will come eventually later this afternoon.

[Bunkertor]

SPC AC 011730

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT THU MAY 01 2008

VALID 021200Z - 031200Z

...THERE IS A MDT RISK OF SVR TSTMS FROM SERN MO/SWRN IL SWD INTO
ERN TX/LA/NWRN MS...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS A LARGE AREA CENTERED
ALONG THE MS VALLEY...

...SYNOPSIS...
MID AND UPPER LEVEL TROUGH/LOW CENTERED ACROSS THE PLAINS EARLY IN
THE PERIOD IS FORECAST TO MOVE SLOWLY EWD TOWARD THE MO VALLEY WITH
TIME. AS THIS OCCURS...SURFACE COLD FRONT -- TRAILING SSWWD FROM A
LOW INVOF THE MID MO VALLEY -- WILL ALSO PROGRESS EWD/SEWD...MOVING
INTO/ACROSS THE MID MS VALLEY REGION WHILE SHIFTING MORE SLOWLY SEWD
ACROSS THE ARKLATEX REGION AND VICINITY.

ALONG WITH FAVORABLE SHEAR AS A RESULT OF STRONG DEEP-LAYER WIND
FIELD ACCOMPANYING THE UPPER SYSTEM...PERSISTENT NWD FLUX OF
LOW-LEVEL MOISTURE BENEATH FAIRLY STEEP MID-LEVEL LAPSE RATES ALOFT
SHOULD YIELD AN ENVIRONMENT FAVORABLE FOR A POTENTIALLY-SIGNIFICANT
SEVERE WEATHER EVENT -- CENTERED ON THE MID MS VALLEY REGION.

...MS VALLEY REGION FROM SRN WI/ERN IA SWD TO E TX/MS/LA...
THUNDERSTORMS SHOULD BE ONGOING AT THE START OF THE PERIOD ALONG THE
SURFACE FRONT -- LIKELY FROM NRN AND WRN MO SWD TOWARD ERN OK.
THESE STORMS -- AIDED BY MOISTENING/DESTABILIZING ENVIRONMENT AND
FAVORABLE SHER -- WILL LIKELY REMAIN LOCALLY SEVERE THROUGH THE
MORNING. BY EARLY AFTERNOON...COMBINATION OF WARM SECTOR HEATING
AND MOISTENING BENEATH FAVORABLY-STEEP MID-LEVEL LAPSE RATES SHOULD
ALLOW ONGOING STORMS TO INCREASE IN BOTH COVERAGE AND INTENSITY.

THOUGH STRONGEST FLOW ALOFT WILL SPREAD ACROSS NRN PORTIONS OF THE
OUTLOOK AREA...SHEAR MORE THAN SUFFICIENT FOR SUPERCELLS WILL LIKELY
EXTEND ACROSS A LARGE PORTION OF THE WARM SECTOR -- FROM E TX/NRN
LA/WRN MS NWD. ATTM...IT APPEARS THAT THE MOST FAVORABLE
SHEAR/INSTABILITY COMBINATION WILL EXIST BETWEEN 02/21Z AND 03/03Z
FROM ROUGHLY CENTRAL IL/SERN MO SWD ACROSS ERN AR/NWRN MS. ALONG
WITH POTENTIALLY A MORE LINEAR ZONE OF STORMS -- WITH EMBEDDED
ROTATION -- INVOF THE SURFACE FRONT...MORE ISOLATED STORMS ARE ALSO
EXPECTED TO DEVELOP WITHIN THE WARM SECTOR INVOF MORE SUBTLE
BOUNDARIES. GIVEN THE DEGREE OF LOW-LEVEL SHEAR AND DEWPOINTS WELL
INTO THE 60S ACROSS A LARGE AREA...TORNADOES -- A FEW POTENTIALLY
STRONG/LONG-LIVED -- ARE ANTICIPATED. DEGREE OF INSTABILITY ALSO
SUPPORTS LARGE HAIL AND LOCALLY-DAMAGING WINDS WITH
LONG-LIVED/WELL-ORGANIZED STORMS -- BOTH LINEAR AND CELLULAR.
CONVECTION SHOULD CONTINUE SHIFTING EWD ACROSS THE MS VALLEY THROUGH
THE EVENING/OVERNIGHT...AND THOUGH A SLOW DECREASE IN SEVERE THREAT
IS ANTICIPATED WITH THE LOSS OF DAYTIME HEATING...SOME THREAT WILL
LIKELY PERSIST THROUGH 03/12Z.

...IA/SRN WI/NRN IL EWD INTO SRN LOWER MI/NWRN OH...
WHILE LESSER INSTABILITY IS FORECAST ACROSS THIS REGION COMPARED TO
AREAS FURTHER S...SHEAR WILL BE MORE THAN SUFFICIENT FOR
SEVERE/SUPERCELL STORMS. WITH LOW-LEVEL FLOW BACKED NEAR/E OF
SURFACE LOW ACROSS IA DURING THE AFTERNOON...TORNADO THREAT MAY
EXTEND NWWD INTO THIS REGION DESPITE THE LIKELIHOOD OF LESSER
INSTABILITY. OTHER SEVERE/SUPERCELL STORMS WILL LIKELY OCCUR EWD
ACROSS THE MIDWEST/LOWER GREAT LAKES...WHERE PERSISTENT WARM
ADVECTION IS ANTICIPATED.

..GOSS.. 05/01/2008

[Ed Mahmoud]

GFS forecast sounding for Tulsa late afternoon/evening looks interesting...





Of course, GFS forecasts only very isolated action in Oklahoma, so that may be the case of a lot of unused potential.

[Ed Mahmoud]

Dryline through Wichita, and mixing through Manhattan now. It should retreat this evening ahead of the big rain action, but any daytime, good visibility supercells for our English visitors should be East of I-35.

[tornado92]

BBC page found on Google says Mr. Fish is famous for saying a hurricane wasn't headed for the UK. Technically correct, but a gale center with hurricane force gusts apparently did hit the next day, back in 1987. Mr Fish claims he was responding to a woman calling about a Florida vacation, and he did advise of strong winds.-

True, for English viewers, there was a documentary on this a few months ago on ITV. I happened to watch it.

Anyway, I've heard the action today would probably be Eastern Kansas.

[KWT]

Yep Ed best veiws will be just to the east of the dryline which is where the chasers are setting themselves up today.

There is alot of instablity progged over OK but its going to be very questionable if the cap breaks there or not, if it does then there may be a few isolated powerful supercells.

[Ed Mahmoud]

Yep Ed best veiws will be just to the east of the dryline which is where the chasers are setting themselves up today.

There is alot of instablity progged over OK but its going to be very questionable if the cap breaks there or not, if it does then there may be a few isolated powerful supercells.

I hope our visitors get a good show, but it seems like much of the action will be after dark.


I haven't spent much time in Missouri, tomorrow's target, but I get the impression the added topography and vegetation makes it not quite as ideal as the steppes of Kansas for storm spotting.

[KWT]

Yeah they will certainly chase tomorrow given there is a mod risk present as well but the terrain isn't the best ever.
Hopefully convection will kick off before dark, though may take till 5-6pm local time for that to really get going I suspect given the cap.

[KWT]

Looks like cloud cover is starting to increase over E/C KS but presently none of it appears to be convective in nature.

[Ed Mahmoud]

1700 balloon release from "LMN", which per map of where it is, appears to be in Oklahoma near I-35 just across from Kansas line. CINH still present, but no longer a cap of forged steel, and CAPE is high. Shear isn't particularly high.

[Ed Mahmoud]

I can't find a station "LMN". I'm wondering if a NOAA or university research crew released one in the field

[Ed Mahmoud]

Maybe that little puff of cu near the dry line popping up near Durant, OK is the beginning of something big.




Or maybe not.

[Bunkertor]

What do you think ?

Will they

-reduce
-expand the MDT area
-cancel and go to slgt

the 2000Z ?

[Ed Mahmoud]

What do you think ?

Will they

-reduce
-expand the MDT area
-cancel and go to slgt

the 2000Z ?

We'll know very soon.


NWS OUN AFD selected quote:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
230 PM CDT THU MAY 1 2008

.DISCUSSION...
THE LARGER SCALE PERSPECTIVE FOR TONIGHT`S WEATHER HAS NOT CHANGED
MUCH FROM EARLIER. THE MOST WESTWARD OF TWO SMALL MID/UPPER LOWS
OVER THE CENTRAL ROCKIES IS CURRENTLY PIVOTING THROUGH THE BASE OF A
BROADER SCALE TROUGH OVER THE FOUR CORNERS REGION WHICH IS
MAINTAINING AN AXIS OF LARGER PRESSURE FALLS OVER THE OKLAHOMA
PANHANDLE. AN ASSOCIATED COLD FRONTAL BOUNDARY NEAR A LINE FROM
MEDFORD TO SEILING HAS STALLED WHILE THE DRYLINE HAS BECOME SLIGHTLY
MORE DISCERNIBLE FROM PERRY...TO EL RENO...AND WAURIKA. A 20Z
BALLOON FROM KOUN WILL BE RELEASED SHORTLY. IN THE MEANTIME...
SATELLITE AND PROFILER/METARS TRENDS CONTINUE TO INDICATE SHALLOW
MOISTURE AND A MODEST CAP.

ISOLATED CONVECTION REMAINS UNLIKELY BUT POSSIBLE ANYWHERE NEAR THE
DRYLINE THROUGH MID EVENING...BY WHICH TIME THE DRYLINE SHOULD HAVE
RETREATED IN RESPONSE TO THE APPROACHING UPPER LOW. MEANWHILE...THE
STALLED FRONT OVER NORTHERN OKLAHOMA SHOULD RESUME A SOUTHWARD
MOVEMENT TOWARD THE DRYLINE AND INTO A DEEPENING MOIST WARM SECTOR.
OUR GREATEST CONCERN FOR SEVERE THUNDERSTORMS IS THIS EVENING AS THE
DRYLINE RETREATS TOWARD THE REORGANIZING COLD FRONT OVER NORTHWEST
OR NORTH CENTRAL OKLAHOMA...WHICH IS WHEN INSTABILITY WILL
HIGHEST...CONVECTIVE INHIBITION LOWEST...AND VERTICAL WIND PROFILES
MOST SUPPORTIVE OF SUPERCELLS.

[KWT]

I suspect they will likely hold the mod and probably not change anything because there doesn't seem to be any real change to what the models were progging.

there is some small convective cumulus starting to show up but still a little away from the big convective cells yet I suspect given the cap.

[Bunkertor]

Ha ! Hold. Yes, i forgot that possibility due to being in a hurry to get the poll up in time.

I´ll be on vacation tomorrow, because i have to attend to a marriage.

So maybe i will be up all night long.

[KWT]

The problem with living in the UK is that all the action tends to occur in the early morning hours over here so I may not last to see the real explosive supercells but who knows!

Interesting to see they are putting up a balloon, should have the results soon enough!

[Bunkertor]

This is the dryline, right ?

[Ed Mahmoud]

Looks like some kind of boundary. Which radar is it?

[Bunkertor]

Looks like some kind of boundary. Which radar is it?

Thats the normal NWS radar for OUN

http://radar.weather.gov/radar.php?rid= ... 11&loop=no