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October 13-14 Severe Threat


Kory

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I figured with the models pointing to a potent squall line and possible discrete convection, I figured this warranted a thread.  12z Euro and 15z SREF are showing some backing surface winds beginning 12z Monday in Eastern Arkansas shifting eastward throughout the day, along with significant winds at the 850 mbar and 700 mbar level blasting in from the SW.  Thermodynamics have ticked upwards, generally in the 1000-1500 J/KG range.  Dominant storm mode looks to be damaging winds, but tornadoes looks like a definitely possibility.  

 

Analogs are certainly nothing to ignore...with November 24, 2001 and November 21-23, 1992 being the top matches.  

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Well the 18z GFS just took a major dip south with the surface low.  I don't know about you guys, but I'm getting a hint of a pre-frontal trough on the GFS.  A slight convergence in the surface winds at the AR/MS border at 21z on Monday.  With decent hodographs and CAPE in front of the said feature I think MS will be a place to watch.

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I'm just gonna go ahead and expect 1-2 supercells out ahead of the squall line around the NE Al/NW Ga/SE Tn line. That seems to be the hot zone now for development. Is the timing for this still early Tues A.M. for east Tn?

I think any tornado threat will be further west, but that's something that's really determined by any mesoscale placements.  Don't know until the day of the event.  But the squall line looks to get to that area around 12z or 7am.  

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For you Tennessee Valley folks:  the 06z SPC outlook mentions a possible upgrade to moderate risk on Monday.  The 30% risk area is still large in this outlook, and they have introduced a hatching for significant severe wx over most of that 30% area. The slight risk areas of these two days (Sun and Mon) seem to be applicable to the Central/Western Subforum, Tennessee Valley, and Southeast Subforum.

 

SPC text: (read the full discussion if you want to)

----

  ...ERN TX THROUGH THE LOWER-MID MS VALLEYS...OH AND TN VALLEYS...   POTENTIAL EXISTS FOR A WIDESPREAD DAMAGING WIND EVENT AND A FEW   TORNADOES...ESPECIALLY OVER A PORTION OF THE LOWER MS VALLEY REGION   MONDAY INTO MONDAY EVENING. A POTENTIAL UPGRADE TO MODERATE RISK   MIGHT BE NEEDED IN LATER OUTLOOK UPDATES.

----

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Well the 18z GFS just took a major dip south with the surface low. I don't know about you guys, but I'm getting a hint of a pre-frontal trough on the GFS. A slight convergence in the surface winds at the AR/MS border at 21z on Monday. With decent hodographs and CAPE in front of the said feature I think MS will be a place to watch.

I agree with the location. Central to North Mississippi into West Tennessee is the hot spot if you ask me. I'm thinking we could see bands of discrete cells where convergence is occurring ahead of the main line.
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...MID-SOUTH/LOWER-MIDDLE MS VALLEY/TN VALLEY/OH VALLEY...
THE POTENTIAL EXISTS FOR A REGIONAL SEVERE WEATHER EVENT ON MONDAY

INCLUDING CORRIDORS OF DAMAGING WINDS AND SOME TORNADOES...INCLUDING

A FEW POTENTIALLY STRONG...PARTICULARLY ACROSS THE MID-SOUTH AND

LOWER/MIDDLE MS RIVER VALLEY TO TN VALLEY

. WHILE A HIGHER-END SLIGHT

RISK /ENHANCED SLIGHT EQUIVALENT/ WILL CURRENTLY BE

MAINTAINED...PORTIONS OF THE REGION MAY WARRANT A MODERATE RISK

UPGRADE IN DAY 1 OUTLOOKS.

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...MID-SOUTH/LOWER-MIDDLE MS VALLEY/TN VALLEY/OH VALLEY...
THE POTENTIAL EXISTS FOR A REGIONAL SEVERE WEATHER EVENT ON MONDAY

INCLUDING CORRIDORS OF DAMAGING WINDS AND SOME TORNADOES...INCLUDING

A FEW POTENTIALLY STRONG...PARTICULARLY ACROSS THE MID-SOUTH AND

LOWER/MIDDLE MS RIVER VALLEY TO TN VALLEY

. WHILE A HIGHER-END SLIGHT

RISK /ENHANCED SLIGHT EQUIVALENT/ WILL CURRENTLY BE

MAINTAINED...PORTIONS OF THE REGION MAY WARRANT A MODERATE RISK

UPGRADE IN DAY 1 OUTLOOKS.

 

 

 

You making it out to chase tomorrow?  Thinking I will head for the AL/MS border, maybe target 100 or so miles south of TN and drift W or E depending on mesoanalysis midday.

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You making it out to chase tomorrow?  Thinking I will head for the AL/MS border, maybe target 100 or so miles south of TN and drift W or E depending on mesoanalysis midday.

Good location.  I'd head a little more west, but that's something to determine tomorrow morning.  

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Here is the 4km NAM reflectivity for tomorrow at 03z, with a solid squall line through Mississippi and potentially some discrete supercells ahead of the line in Alabama. It just shows the potential for a large number of severe storms in the afternoon/nighttime.   I am also attaching the 60 hour rainfall total from the 4km NAM. This shows that there is some potential for 5" -6" in Tennessee

 

post-1182-0-60881900-1413139694_thumb.pn

 

post-1182-0-66439700-1413139711_thumb.gi

 

 

 

 

 

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Here is the 4km NAM reflectivity for tomorrow at 03z, with a solid squall line through Mississippi and potentially some discrete supercells ahead of the line in Alabama. It just shows the potential for a large number of severe storms in the afternoon/nighttime.   I am also attaching the 60 hour rainfall total from the 4km NAM. This shows that there is some potential for 5" -6" in Tennessee

 

attachicon.gifnam4km_ref_seus_13.png

 

attachicon.gif2014_10_12_12z_conusnest_12z_pcp60h_f60.gif

Welp, I didn't see your post before mine, but that is definitely what I was referring too in mine.

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Good location. I'd head a little more west, but that's something to determine tomorrow morning.

Yeah just finished my midterms on Friday. West is most likely the best play for something strong but I will stop somewhere around lunchtime or so to get a good wifi signal and check data, then adjust my route accordingly. Should be interesting, thanks for your input.

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Flooding appears to be a significant issue due to saturation of the ground in NE TN.  MRX has issued a special weather statement for the eastern TN Valley.  

SPECIAL WEATHER STATEMENTNATIONAL WEATHER SERVICE MORRISTOWN TN334 PM EDT SUN OCT 12 2014NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002-005-006-008-131000-CHEROKEE-CLAY-SCOTT TN-CAMPBELL-CLAIBORNE-HANCOCK-HAWKINS-SULLIVAN-JOHNSON-MORGAN-ANDERSON-UNION-GRAINGER-HAMBLEN-NORTHWEST COCKE-COCKE SMOKY MOUNTAINS-NORTHWEST GREENE-SOUTHEAST GREENE-WASHINGTON TN-UNICOI-NORTHWEST CARTER-SOUTHEAST CARTER-ROANE-LOUDON-KNOX-JEFFERSON-NW BLOUNT-BLOUNT SMOKY MOUNTAINS-NORTH SEVIER-SEVIER SMOKY MOUNTAINS-SEQUATCHIE-BLEDSOE-RHEA-MEIGS-MCMINN-NORTHWEST MONROE-SOUTHEAST MONROE-MARION-HAMILTON-BRADLEY-WEST POLK-EAST POLK-LEE-WISE-SCOTT-RUSSELL-WASHINGTON-INCLUDING THE CITIES OF...MURPHY...HAYESVILLE...ONEIDA...LA FOLLETTE...TAZEWELL...SNEEDVILLE...ROGERSVILLE...KINGSPORT...BRISTOL...MOUNTAIN CITY...WARTBURG...CLINTON...OAK RIDGE...MAYNARDVILLE...RUTLEDGE...MORRISTOWN...NEWPORT...COSBY...GREENEVILLE...CEDAR CREEK...JOHNSON CITY...ERWIN...ELIZABETHTON...ROAN MOUNTAIN...KINGSTON...LENOIR CITY...KNOXVILLE...DANDRIDGE...MARYVILLE...CADES COVE...SEVIERVILLE...GATLINBURG...DUNLAP...PIKEVILLE...DAYTON...DECATUR...ATHENS...MADISONVILLE...COKER CREEK...JASPER...CHATTANOOGA...CLEVELAND...BENTON...DUCKTOWN...JONESVILLE...WISE...NORTON...GATE CITY...LEBANON...ABINGDON334 PM EDT SUN OCT 12 2014...SEVERE THUNDERSTORMS...TORRENTIAL RAINS AND FLASH FLOODING AREPOSSIBLE TUESDAY......HIGH WIND WATCH IS IN EFFECT FOR THE MOUNTAINS AND ADJACENTFOOTHILLS FOR MONDAY NIGHT AND TUESDAY...A STRONG STORM SYSTEM AND ASSOCIATED COLD FRONT WILL MOVE ACROSSTHE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS FROM LATE MONDAYNIGHT THROUGH TUESDAY. THIS SYSTEM WILL TIGHTEN THE PRESSUREGRADIENT ACROSS THE REGION PRODUCING STRONG AND GUSTY WINDS OVERTHEMOUNTAINS AND ADJACENT FOOTHILLS MONDAY NIGHT AND TUESDAY. THE HIGHWINDS MAY DOWN TREES AND POWER LINES.THIS SYSTEM WILL PULL ANOTHER ROUND OF HEAVY RAINFALL BACK INTO THEAREA TUESDAY. SINCE THE GROUND IS ALREADY SATURATED FROM THE RECENTRAINFALL...THE ADDITIONAL HEAVY RAINS MAY PRODUCE FLASH FLOODING OFSTREAMS...STREET FLOODING...FLOODING OF LOW-LYING AREAS AND MUDSLIDES.AS THE COLD FRONT MOVES THROUGH TUESDAY...WIDESPREAD THUNDERSTORMSARE EXPECTED. DUE TO THE STRONG WINDS ALOFT...SOME OF THESE STORMSMAY PRODUCE DAMAGING WINDS WITH AN ISOLATED TORNADO. THE EXACTTIMING OF THE STORMS ARE STILL UNCERTAIN.PLEASE STAY TUNED TO YOUR NOAA WEATHER RADIO AND OTHER LOCAL MEDIAFOR FURTHER DETAILS OR UPDATES.
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The hatched 45% wind threat catches my eye.  The fact that we'll have a 55-65kt low level jet is enough to spur a very intense squall line possible of winds in excess of 70+ mph across portions of Arkansas, N. Louisiana, N. and Central Mississippi, and West Tennessee.  And of course, a few strong tornadoes are possible with a few discrete cells ahead of the line, hence the hatched area.  

 

day1probotlk_1200_wind.gif?1413198448465

 

Some mesoscale models are breaking up the squall line by the time it reaches East Mississippi/West Alabama, which may slightly enhance the tornado threat there.   

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URGENT - IMMEDIATE BROADCAST REQUESTED
   TORNADO WATCH NUMBER 534
   NWS STORM PREDICTION CENTER NORMAN OK
   710 AM CDT MON OCT 13 2014

   THE NWS STORM PREDICTION CENTER HAS ISSUED A

   * TORNADO WATCH FOR PORTIONS OF
     CENTRAL AND EASTERN ARKANSAS
     NORTHERN LOUISIANA
     MISSOURI BOOTHEEL
     WESTERN MISSISSIPPI
     WESTERN TENNESSEE
     SMALL PART OF EAST TEXAS

   * EFFECTIVE THIS MONDAY MORNING AND AFTERNOON FROM 710 AM UNTIL
     200 PM CDT.

   * PRIMARY THREATS INCLUDE...
     A FEW TORNADOES POSSIBLE
     SCATTERED DAMAGING WINDS AND ISOLATED SIGNIFICANT GUSTS TO 75
       MPH POSSIBLE

   THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 85 STATUTE
   MILES EAST AND WEST OF A LINE FROM 25 MILES WEST SOUTHWEST OF
   ALEXANDRIA LOUISIANA TO 30 MILES NORTHEAST OF WALNUT RIDGE
   ARKANSAS.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
   ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU4).

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