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Severe Weather Outbreak April 10-12th Disc./Obs.


WilkesboroDude

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have you seen the NAM hodographs? some of them look pretty impressive from SC to NC. lots of low level shear, we could be surprised tomorrow evening.

 

I actually just took a glance at them. Pretty good looking sounding here from KSPA..

 

SKT_NAM__KSPA.png

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Yeah we lost the 45% area. Can never trust these outlooks. I was excited to see some severe storm. Now my forecast just mentions plain storms and a decreased Pop.

 

Lol what did you expect? Waycross was barely in the 30% area to begin with... :facepalm:

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5% tornado...was thinking closer to 2%.

day1probotlk_1200_torn.gif

If you took a look at any of the hodographs from around Raleigh west and all over SC they were conducive of supercells and tornado development...lots of low level shear in a lot of places like I posted earlier. Can't just look at CAPE for the SE, lots of other players and the atmosphere works different here than in Arkansas. It's likely this thing won't slow down though, the atmosphere will be primed by daytime heating so we're looking at a small tornado window but the chance is there and not just for western NC. My area looked pretty good on the NAM yesterday...south of Raleigh. I'm looking forward to going outside and looking up to see how fast these clouds are moving tomorrow night, a lot of the hodographs had 40-50kt winds just above the service. The thing that sucks is that it's going to be a night time event...

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5% tornado...was thinking closer to 2%.

 

2.5 times greater than negligible is still basically negligible.  What does it matter?  These probabilities are already so low anyway.  (Not that they ever issue super high probabilities for tornadoes anyway.)  I'm not sure how one is capable of differentiating between 2% and 5%.  The vast majority of the land area under these warnings for any particular system will never be affected by a tornado.  Of course, if you're in the small minority that is affected, your perspective is quite different.

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2.5 times greater than negligible is still basically negligible.  What does it matter?  These probabilities are already so low anyway.  (Not that they ever issue super high probabilities for tornadoes anyway.)  I'm not sure how one is capable of differentiating between 2% and 5%.  The vast majority of the land area under these warnings for any particular system will never be affected by a tornado.  Of course, if you're in the small minority that is affected, your perspective is quite different.

Yeah, even 4/27/11 only had a hatched 45% and that was pretty much the ideal TOR setup on the models.

 

5% from SPC is enough to at least make sure you're paying attention when the storms are rolling in, and anything higher is "hey time to let the schools out early" territory.

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The thing that might limit the tornado threat is the slight backing of the winds above ~800/750mb. It's ever so slight, but might be enough to keep tornadoes from becoming too strong. Still, low level shear is more than enough to spin up a quick tornado IF we get warm enough. I wouldn't be surprised to see a few thunderstorms bubble up near ATL and areas seeing a fair amount of sunshine this morning. Also, BMX mentioned a few of the Hi-Res models developing a low in MS and riding along I-20. That has been hinted at by some models the past few days, so we'll see if that comes to fruition. If that low does develop, then shear profiles will become more conducive for tornadoes.

 

Snippet of BMX's morning discussion:

SO...INSTABILITIES SURE DON`T LOOK TO BE A PROBLEM TODAY...IF THEY
ARE IN FACT REALIZED. LOOKING NEXT INTO THE WIND PROFILES...FORECAST
SOUNDINGS ARE STILL ADVERTISING MORE OF A LINEAR MODE OF CONVECTION
AT LEAST TO START OUT THE DAY ACROSS OUR WESTERN COUNTIES AND
NORTHWESTERN COUNTIES. THE EXPECTED SQUALL LINE SHOULD BE ENTERING
OUR WESTERN AND NORTHWESTERN COUNTIES ROUGHLY FROM 9AM TO 12PM BASED
ON THE LATEST TRENDS. THINGS THEN BECOME TRICKY IN TERMS OF TIMING
OF SEVERE WEATHER AND THE MODES OF CONVECTION INTO THE AFTERNOON
HOURS. AS THE SHORTWAVE GETS ITS ACT TOGETHER TO OUR WEST...THE
TROUGH AXIS IS EXPECTED TO BECOME NEGATIVELY TILTED. IN
ADDITION...HI-RES MODELS ARE PICKING UP ON A LOW PRESSURE DEVELOPING
ALONG THE COLD FRONT NEAR MERIDIAN MISSISSIPPI AND TRACKING
NORTHEAST ALONG THE INTERSTATE 20 CORRIDOR. IF THIS SOLUTION DOES IN
FACT VERIFY...WE WILL BE LOOKING AT INCREASED SHEAR PROFILES...AND
WITH THE VERY UNSTABLE AIRMASS AND JET STRUCTURE IN PLACE...
SUPERCELL
DEVELOPMENT WILL MOST CERTAINLY BE IN THE CARDS OUT AHEAD OF THE
SQUALL LINE. CURRENT THINKING IS THAT SUPERCELL DEVELOPMENT WILL BE
THE MOST FAVORABLE ALONG AND SOUTHEAST OF A LINE FROM DEMOPOLIS...TO
CALERA...TO ANNISTON LINE. OF COURSE...THIS WILL ALL DEPEND ON THE
MESOSCALE...WHICH WILL HAVE TO BE CLOSELY WATCHED THROUGH THE DAY
TODAY AND ESPECIALLY THIS AFTERNOON AND EVENING.

 

 

As Dacula mentioned, this thing has slowed down considerably! The northern part of the line is barely moving, while the southern end, the part over southern LA, is picking up speed. That's where the stronger storms are located and will likely become the worst part of the storm, at least through the short-term.

 

Another thing to consider is the possibility of stronger thunderstorms near the Gulf cutting off the moisture feed north. I've seen it a few times in my time here and is just something to keep an eye on throughout the day.

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Guys just bumping in from up North, they kept us in below 15 percent chance of severe and ruled out any type of watch and ended up with a ton of wind damage reports and lots and lots of trees down. So, as good as the SPC is just keep an eye on it, I didn't think we'd be having family over for power outages yesterday and bam. 

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2.5 times greater than negligible is still basically negligible.  What does it matter?  These probabilities are already so low anyway.  (Not that they ever issue super high probabilities for tornadoes anyway.)  I'm not sure how one is capable of differentiating between 2% and 5%.  The vast majority of the land area under these warnings for any particular system will never be affected by a tornado.  Of course, if you're in the small minority that is affected, your perspective is quite different.

 

Yeah, even 4/27/11 only had a hatched 45% and that was pretty much the ideal TOR setup on the models.

 

5% from SPC is enough to at least make sure you're paying attention when the storms are rolling in, and anything higher is "hey time to let the schools out early" territory.

 

There was a tornado last year with 2% over NC and some of the wind profiles are definitely conducive of some pretty decent rotation...will it reach the ground? probably not, but at least there is a chance. It's better than seeing "Less than 2% all areas" on the map and just getting straight line winds. Tonight should be interesting.

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The broad 5% is about all they can do for now. Expect a small 10% in later updates when surface features become better established. Upper level winds are going to be somewhat unidirectional, or even veer-back. Potent short-wave ejecting out of Texas, but it's almost closed. I'm afraid the upper air sampling, showing an open wave on upper charts, was not great in Mexico. Vapor shows closed.

 

Lack of an open wave takes major outbreak off the table. One would look to locally higher low level helicity. Some of the leading cells should become severe though. I'm watching two areas. The Gulf Front, defined as 68+ dewpoints, will be a focus. Dews on the GA/SC coast are impressive but upper shear is less. Low level shear would be great if the WRF/NAM is right about the surge in southeast sfc winds.

 

North Alabama, north Georgia, and southeast Tennessee will see isolated cells ahead of the line, but nah I don't see tornadoes. Stubborn dewpoint min. Go to the coastal fronts; either Gulf Coast or the quasi-coastal front near the GA/SC coasts. Even the coastal fronts are a low probability play, but the best I can see. I'll be relaxing at home watching radar after work. :popcorn:

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Upgraded map by SPC as of 15 minutes ago...

 

downplayed the tor threat, the timing should downplay it even more.

 

day1probotlk_1630_torn.gif

   FROM SPC:   AT THIS TIME...THE MORE PROBABLE SCENARIO APPEARS TO BE FOR STORMS   ALONG THE FRONT TO STRENGTHEN GRADUALLY INTO THE AFTERNOON...WITH A   SLOW INCREASE IN THE RISK FOR DAMAGING GUSTS WITH EMBEDDED BOWING   SEGMENTS FROM TN SWD INTO AL.  VERTICAL SHEAR WILL ALSO INCREASE   FROM W-E THIS AFTERNOON...SUCH THAT PRE-FRONTAL CONVECTION COULD   EVOLVE INTO A COUPLE OF SUPERCELLS ACROSS AL...WHILE VERTICAL SHEAR   WILL BE MORE MARGINAL FARTHER E INTO GA/FL FOR ANY DIURNAL   CONVECTION THAT MANAGES TO DEVELOP.  GIVEN THE PREDOMINANTLY LINEAR   MODE WITH STORMS ALONG THE FRONT...DAMAGING GUSTS WILL BE THE MAIN   SEVERE THREAT.  THE TORNADO RISK IS A BIT MORE UNCERTAIN AND HINGES   ON MORE DISCRETE DEVELOPMENT AHEAD OF THE FRONT...THOUGH EMBEDDED   CIRCULATIONS IN THE LINE COULD POSE A RISK FOR A COUPLE OF   TORNADOES.

However, from NWS RAH as of 11:05AM:

 

NOON AND SUPPORT CONVECTIVE DEVELOPMENT IN THE
CAROLINAS OVERNIGHT. SCATTERED CONVECTION THAT IS EXPECTED TO
DEVELOP ACROSS THE FOOTHILLS AND WESTERN PIEDMONT THIS EVENING WILL
LIKELY BE OVERRUN BY THE LARGER AREA OF CONVECTION AFTER MIDNIGHT
AND MERGE INTO A COMPLEX AREA OF CONVECTION WITH MIXED MODES.

THE AIR MASS ACROSS CENTRAL NC IS EXPECTED TO BE MARGINALLY UNSTABLE
OVERNIGHT WITH NAM SBCAPE VALUES IN THE 300-900 J/KG RANGE WHILE GFS
VALUES ARE ABOUT HALF OF THAT. WHILE INSTABILITY IS LIMITED NAM/GFS
BUFR SOUNDINGS NOTE THAT THE SURFACE LAYER REMAINS AT LEAST
NEUTRALLY STABLE OVERNIGHT. THE STRONGEST LOW LEVEL FLOW AND SHEAR
ARRIVES WITH THE MAIN CONVECTIVE LINE AFTER MIDNIGHT SUGGESTING A
LOWER SEVERE THREAT WITH THE EARLY/MID EVENING CONVECTION IN THE
WESTERN PIEDMONT. A DEEP LAYER FLOW THAT IS ALIGNED MORE PARALLEL
WITH THE FORCING MECHANISM SUGGESTS A QLCS TYPE EVENT OVERNIGHT WITH
A PRIMARY THREAT OF DAMAGING WINDS. A SLIGHTLY BACKED SURFACE FLOW
OVERNIGHT RESULTING FROM DEEPENING LOW PRESSURE IN THE NORTHERN
APPALACHIANS COMBINED WITH A LARGE CYCLONICALLY CURVED HODOGRAPHS
HIGHLIGHTS AT LEAST A LIMITED POTENTIAL FOR A TORNADO ACROSS CENTRAL
NC...MAINLY IN THE 04-12Z TIMEFRAME.
AS NOTED IN THE PREVIOUS
DISCUSSION...THE LATEST CONVECTION-ALLOWING MODEL RUNS SUGGEST A
FRACTURING ORGANIZATION AND DECREASING COVERAGE IN THE CONVECTION
OVERNIGHT...SUGGESTING A GRADUALLY DECREASING RISK OF SEVERE WEATHER
LATE TONIGHT AS THE CONVECTION MOVES EAST. LOWS TONIGHT WILL RANGE
IN THE MID TO UPPER 60S.

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SEVERE WEATHER STATEMENT

NATIONAL WEATHER SERVICE JACKSON MS

1144 AM CDT THU APR 11 2013

 

MSC069-111730-

/O.CON.KJAN.TO.W.0046.000000T0000Z-130411T1730Z/

KEMPER MS-

1144 AM CDT THU APR 11 2013

 

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 1230 PM CDT FOR CENTRAL

KEMPER COUNTY...

 

AT 1144 AM CDT...A DAMAGING TORNADO HAS BEEN CONFIRMED.  THIS TORNADO

WAS LOCATED NEAR BLUFF SPRINGS MOVING NORTHEAST AT 50 MPH.

 

THE TORNADO WILL BE NEAR...

  RURAL NORTHERN KEMPER COUNTY AT NOON CDT

 

 

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URGENT - IMMEDIATE BROADCAST REQUESTED  

TORNADO WATCH NUMBER 96  

NWS STORM PREDICTION CENTER NORMAN OK  

1200 PM CDT THU APR 11 2013  

 

THE NWS STORM PREDICTION CENTER HAS ISSUED A  

TORNADO WATCH FOR PORTIONS OF  

 

WEST CENTRAL INTO NORTH CENTRAL ALABAMA  

SOUTHERN MIDDLE TENNESSEE  

 

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM NOON UNTIL 700  

PM CDT.  

 

TORNADOES...HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND  

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE  

AREAS.  

 

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 55 STATUTE  

MILES EAST AND WEST OF A LINE FROM 30 MILES EAST SOUTHEAST OF  

MERIDIAN MISSISSIPPI TO 25 MILES NORTH NORTHWEST OF HUNTSVILLE  

ALABAMA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE  

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6).  

 

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR  

TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH  

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR  

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS  

AND POSSIBLE WARNINGS.  

 

OTHER WATCH INFORMATION...CONTINUE...WW 95...  

 

DISCUSSION...PRE-FRONTAL SUPERCELL HAS FORMED IN E CENTRAL MS AND  

WILL CONTINUE TO MOVE NEWD INTO WRN AL AROUND THE TIME THE STORM  

MERGES WITH THE FRONTAL BAND OF CONVECTION IMMEDIATELY TO ITS W.  

SOME SURFACE HEATING IN A FEW CLOUD BREAKS AND INCREASING LOW-LEVEL  

MOISTURE WILL RESULT IN DESTABILIZATION AND THE LIKELIHOOD THAT  

STORMS IN THE LINE WILL STRENGTHEN THIS AFTERNOON WITH AN ATTENDANT  

RISK FOR DAMAGING WINDS. THE TORNADO THREAT WILL BE LARGELY  

DEPENDENT ON THE FORMATION OF MORE DISCRETE STORMS AHEAD OF THE  

LINE...THOUGH LOW-LEVEL SHEAR WILL BE SUFFICIENT FOR CIRCULATIONS  

WITHIN THE LINE.

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BULLETIN - EAS ACTIVATION REQUESTED

TORNADO WARNING

NATIONAL WEATHER SERVICE JACKSON MS

1156 AM CDT THU APR 11 2013

THE NATIONAL WEATHER SERVICE IN JACKSON HAS ISSUED A

* TORNADO WARNING FOR...

NOXUBEE COUNTY IN EAST CENTRAL MISSISSIPPI...

* UNTIL 100 PM CDT

* AT 1157 AM CDT...A CONFIRMED DAMAGING TORNADO WAS LOCATED 6 MILES

SOUTH OF GHOLSON MOVING NORTHEAST AT 50 MPH.

* THE TORNADO WILL BE NEAR...

MACON BY 1220 PM CDT...

BROOKSVILLE BY 1225 PM CDT...

DEERBROOK AND PRAIRIE POINT BY 1230 PM CDT...

BIGBEE VALLEY BY 1235 PM CDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS STORM HAS A HISTORY OF PRODUCING TORNADOES WITH INJURIES.


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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE JACKSON MS
1158 AM CDT THU APR 11 2013

..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..

1138 AM TORNADO 4 NW LIBERTY 32.70N 88.81W
04/11/2013 KEMPER MS BROADCAST MEDIA

DAMAGE WITH POSSIBLE INJURIES REPORTED ALONG HIGHWAY 493
NORTHWEST OF LIBERTY

 

 

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485 

WWUS54 KJAN 111703

SVSJAN

 

SEVERE WEATHER STATEMENT

NATIONAL WEATHER SERVICE JACKSON MS

1203 PM CDT THU APR 11 2013

 

MSC069-111730-

/O.CON.KJAN.TO.W.0046.000000T0000Z-130411T1730Z/

KEMPER MS-

1203 PM CDT THU APR 11 2013

 

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 1230 PM CDT FOR NORTH

CENTRAL KEMPER COUNTY...

 

...THIS IS A TORNADO EMERGENCY FOR LOCATIONS ALONG THE PATH OF THE

TORNADO...

 

AT 1203 PM CDT...METEOROLOGISTS AND TRAINED SPOTTERS WERE TRACKING A

LARGE...VIOLENT AND EXTREMELY DANGEROUS TORNADO.  THIS TORNADO WAS

LOCATED OVER NORTH CENTRAL KEMPER COUNTY MOVING NORTHEAST AT 45 MPH.
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