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April 26th-30th, 2014 Major Tornado Outbreak


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MESOSCALE DISCUSSION 0476
   NWS STORM PREDICTION CENTER NORMAN OK
   1226 PM CDT TUE APR 29 2014

   AREAS AFFECTED...FAR NRN SC...NC...FAR SRN VA

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

   VALID 291726Z - 291900Z

   PROBABILITY OF WATCH ISSUANCE...60 PERCENT

   SUMMARY...A SEVERE THREAT IS EXPECTED TO DEVELOP THIS AFTERNOON. AS
   CELLS INCREASE IN INTENSITY...A FEW TORNADOES MAY OCCUR WITH THE
   MORE DOMINANT ROTATING STORMS. THE STRONGER CELLS WILL ALSO BE
   CAPABLE OF PRODUCING HAIL AND DAMAGING WIND GUSTS. WW ISSUANCE MAY
   BECOME NECESSARY ACROSS NC LATER THIS AFTERNOON.

   DISCUSSION...THE LATEST SFC ANALYSIS SHOWS A SHARPLY-DEFINED WARM
   FRONT EXTENDING EWD ACROSS CNTRL AND ERN NC. THUNDERSTORMS ARE
   DEVELOPING NORTH OF THE BOUNDARY IN A WEAKLY UNSTABLE AIRMASS. THIS
   ACTIVITY COULD CONTAIN A HAIL THREAT. FURTHER TO THE SOUTH ACROSS
   SCNTRL NC AND NRN SC...MODERATE INSTABILITY IS IN PLACE WITH MLCAPE
   ESTIMATED IN THE 1000 TO 2000 J/KG RANGE. THE WRF-HRRR AND 12Z NAM
   ARE INITIATING SCATTERED CONVECTION OVER THE NEXT FEW HOURS ON THE
   NRN EDGE OF MODERATE INSTABILITY EXTENDING NWD TO NEAR AND JUST
   NORTH OF THE WARM FRONT. DUE TO CONTINUED DESTABILIZATION AND
   MODERATE DEEP LAYER SHEAR ASSOCIATED WITH A 50 TO 60 KT LOW TO
   MID-LEVEL JET...CELLS SHOULD BECOME ORGANIZED AS CELLS INCREASE IN
   COVERAGE THIS AFTERNOON. IN ADDITION...0-3 KM STORM RELATIVE
   HELICITIES AROUND 400 M2/S2 EVIDENT ON THE RALEIGH NC WSR-88D VWP
   SHOULD SUPPORT SUPERCELL DEVELOPMENT AND A POTENTIAL FOR TORNADOES.
   A WIND DAMAGE THREAT SHOULD ALSO DEVELOP AS LOW-LEVEL LAPSE RATES
   STEEPEN. ISOLATED LARGE HAIL MAY ALSO OCCUR WITH THE MORE INTENSE
   CORES.

   ..BROYLES/THOMPSON.. 04/29/2014
 

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You can see how the MCS over the Gulf of Mexico is robbing most of the southeast of the best moisture advection. CAPE is slowly recovering but should be nowhere near the 3000 J/kg amounts that were observed over a large portion of the southeast yesterday. Since the flow is still backed across most of MS and AL, even though many of these areas will have mostly clear skies with plenty of daytime heating, all of that southerly flow will be advecting a less favorable thermodynamic environment further southeast in southern AL and GA where the environment has been worked over and will be stuck in clouds for a large portion of the day. Thus, I wouldn't be surprised if CAPE recovery across Mississippi and Alabama has a hard time getting much above 1000 J/kg.

 

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You can see how the MCS over the Gulf of Mexico is robbing most of the southeast of the best moisture advection. CAPE is slowly recovering but should be nowhere near the 3000 J/kg amounts that were observed over a large portion of the southeast yesterday. Since the flow is still backed across most of MS and AL, even though many of these areas will have mostly clear skies with plenty of daytime heating, all of that southerly flow will be advecting a less favorable thermodynamic environment further southeast in southern AL and GA where the environment has been worked over and will be stuck in clouds for a large portion of the day. Thus, I wouldn't be surprised if CAPE recovery across Mississippi and Alabama has a hard time getting much above 1000 J/kg.

 

There should still be a sweet spot of sufficient recovery in the JAN-MEI-PIB-MCB box this afternoon. Instability/theta-e axis running up through southwest MS to JAN with already 3000 j/kg of SBCAPE poking up into MS.

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Has there been a preliminary tornado count from the last 2 days yet?

 

 

36 on Sunday, 88 on Monday, 1 so far today. Preliminary numbers of course. 125 so far.

 

 

Filtered reports have the total at 100. 33 Sunday, 67 Monday.

 

Tornado count =/= tornado reports

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You can see how the MCS over the Gulf of Mexico is robbing most of the southeast of the best moisture advection. CAPE is slowly recovering but should be nowhere near the 3000 J/kg amounts that were observed over a large portion of the southeast yesterday. Since the flow is still backed across most of MS and AL, even though many of these areas will have mostly clear skies with plenty of daytime heating, all of that southerly flow will be advecting a less favorable thermodynamic environment further southeast in southern AL and GA where the environment has been worked over and will be stuck in clouds for a large portion of the day. Thus, I wouldn't be surprised if CAPE recovery across Mississippi and Alabama has a hard time getting much above 1000 J/kg.

...Except for the fact that flow from 850mb upward is from the SW, advecting air from the much less afflicted LA coast over the moderate risk area.  Evidence of this return is already present across MS, with a strong moisture advection nose right up the middle of the state.

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What is better to use filtered or unfiltered?

 

Filtered is marginally better, since it will trim reports based on the same lat/lon or time of occurrence. However, that doesn't mean a continuous tornado being reported multiple times along its path will not be including many times. So we'll have to wait for official surveys to be completed for a final count.

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Filtered is marginally better, since it will trim reports based on the same lat/lon or time of occurrence. However, that doesn't mean a continuous tornado being reported multiple times along its path will not be including many times. So we'll have to wait for official surveys to be completed for a final count.

 

correct... I believe the tornado that went through the Mayflower, AR area sunday night had at least 8-10 reports along it.

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Filtered is marginally better, since it will trim reports based on the same lat/lon or time of occurrence. However, that doesn't mean a continuous tornado being reported multiple times along its path will not be including many times. So we'll have to wait for official surveys to be completed for a final count.

 

Thank you! If a tornado cycles and is reported several times, does it still count as multiple tornadoes or just one the whole time that super-cell produces a tornado?

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...Except for the fact that flow from 850mb upward is from the SW, advecting air from the much less afflicted LA coast over the moderate risk area.  Evidence of this return is already present across MS, with a strong moisture advection nose right up the middle of the state.

 

Surface theta-e climbing nicely across MS to go with the injection of steeper lapse rates aloft too.

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Thank you! If a tornado cycles and is reported several times, does it still count as multiple tornadoes or just one the whole time that super-cell produces a tornado?

 

Depends on if there is evidence of a continuous damage path. Typically a true occlusion and re-cycling will have separate damage paths, but sometimes there is no discernible break in path.

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Definetly priming up again, clearing out quickly over MS and AL. Not seeing any good initiation quite yet, but there is some stuff popping up over northern LA currently. Birmingham area might have to be on guard again if these storms continue taking the same northeast track they did last night.

 

Meanwhile up here in NW OH, clear skies and very juicy outside. SBCape 1500-2000 j/kg, MLCape 1000 j/kg, and 50-60kt of shear at the 6km height. Thinking mostly surface-based stuff here

 

Thoughts?

 

Looking like winds and especially hail today to be the threat

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...Except for the fact that flow from 850mb upward is from the SW, advecting air from the much less afflicted LA coast over the moderate risk area.  Evidence of this return is already present across MS, with a strong moisture advection nose right up the middle of the state.

 

hrwl8.png

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