2014 Mid-Atlantic Severe Discussion Thread

[Eskimo Joe]

Perhaps isolated severe but this should henrun of the mill summer thunderstorms.

[yoda]

BULLETIN - EAS ACTIVATION REQUESTED  

SEVERE THUNDERSTORM WARNING  

NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC  

145 PM EDT TUE MAY 27 2014  

 

THE NATIONAL WEATHER SERVICE IN STERLING VIRGINIA HAS ISSUED A  

 

* SEVERE THUNDERSTORM WARNING FOR...  

SOUTHERN ROCKINGHAM COUNTY IN WESTERN VIRGINIA...  

NORTHERN CITY OF STAUNTON IN WESTERN VIRGINIA...  

EASTERN AUGUSTA COUNTY IN WESTERN VIRGINIA...  

 

* UNTIL 230 PM EDT  

 

* AT 143 PM EDT...A SEVERE THUNDERSTORM WAS DETECTED NEAR STAUNTON...  

AND WAS MOVING EAST AT 25 MPH. THIS STORM IS CAPABLE OF PRODUCING  

HAIL UP TO THE SIZE OF QUARTERS AND DAMAGING WINDS IN EXCESS OF 60  

MPH.  

[yoda]

Also -- http://www.spc.noaa.gov/products/md/md0726.html

 

Hooray meh pulse warnings and meh watch?

[yoda]

Hey, a meh watch!

URGENT - IMMEDIATE BROADCAST REQUESTED  SEVERE THUNDERSTORM WATCH NUMBER 190  NWS STORM PREDICTION CENTER NORMAN OK  215 PM EDT TUE MAY 27 2014    THE NWS STORM PREDICTION CENTER HAS ISSUED A    * SEVERE THUNDERSTORM WATCH FOR PORTIONS OF     DISTRICT OF COLUMBIA    MARYLAND    SOUTHERN NEW YORK    CENTRAL AND EASTERN PENNSYLVANIA    NORTHERN AND CENTRAL VIRGINIA    EASTERN WEST VIRGINIA    COASTAL WATERS    * EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 215 PM UNTIL    900 PM EDT.    * PRIMARY THREATS INCLUDE...    SCATTERED DAMAGING WIND GUSTS TO 70 MPH POSSIBLE    ISOLATED LARGE HAIL EVENTS TO 1.5 INCHES IN DIAMETER POSSIBLE    THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 70  STATUTE MILES EAST AND WEST OF A LINE FROM 30 MILES EAST  NORTHEAST OF ITHACA NEW YORK TO 55 MILES EAST OF STAUNTON  VIRGINIA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE  ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).    PRECAUTIONARY/PREPAREDNESS ACTIONS...    REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE  FAVORABLE FOR 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. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY  DO PRODUCE TORNADOES.    

 
 
DISCUSSION...TSTMS FORMING OVER THE HIGHER TERRAIN OF CNTRL/SW PA  
AND PARTS OF WV EXPECTED TO MOVE/DEVELOP ESE WITH MODERATE LARGELY  
UNIDIRECTIONAL WNWLY UPR FLOW. DIURNAL DEVELOPMENT APPEARS TO HAVE  
BEEN AIDED BY INFLOW OF FAIRLY RICH LOW-LVL MOISTURE FROM THE OH  
VLY...AND BY A WEAK DISTURBANCE NOW OVER NW PA /REF MCD 726/. WITH  
THE LIKELIHOOD FOR UPSCALE GROWTH INTO ONE OR MORE BANDS...AND GIVEN  
THE DEGREE OF BUOYANCY /MLCAPE TO 2000 J PER KG/...SETUP MAY YIELD  
SCTD INSTANCES OF SVR HAIL/LOCALLY DMGG WIND. 

[high risk]

blue box now out for the local area.    seems somewhat marginal - decent cape but very modest shear.

[yoda]

blue box now out for the local area.    seems somewhat marginal - decent cape but very modest shear.

 

20kt shear is terrible... pulse warnings ftw

[high risk]

20kt shear is terrible... pulse warnings ftw

 

    no disagreement on the shear.    I chose to describe it as "modest";  you were more blunt and called it "terrible".        

 

    even worse, the NAM forecasts the shear to slightly decrease later in the day.   The best I can say is that the storms to our northwest at least look somewhat organized.   

[T. August]

Now in slight risk...

 

http://www.spc.noaa.gov/products/outlook/day1otlk.html

[mappy]

Nice thunder and lightning here for last 30 min. Sweet shelf cloud west towards Westminster

[WxUSAF]

Nice thunder and lightning here for last 30 min. Sweet shelf cloud west towards Westminster

Had a shelf cloud pass here as well.

[usedtobe]

Got thunder and rain but no strong winds. 

[hosj III]

Lots of loud thunder and lightning between 6 and 7:30 with several nearby cracks. 1-1.5" rain and winds I'd ballpark at 35-45 MPH. Def not severe, but interesting storm regardless.

[Eskimo Joe]

I think there was a microburst in Germantown / Gaithersburg yesterday.  We had approximately 35,000 people in the dark last night and numerous trees down in the vicinity of MD 355 & Plummer Drive in Germantown.  The area in question is only about 1 - 2 miles.  

[Ian]

Tuesday looks juicy

 

[wxmeddler]

Tuesday looks juicy

and pulsy. Uniform shear in speed and direction.

[mattie g]

Tuesday looks juicy

 

gfsNE_sfc_dewp_105.gif

 

 

Excited for more "Mid-Atlantic severe?"

[Ian]

and pulsy. Uniform shear in speed and direction.

pretty standard here tho can cause a crashing line like last week into good cape etc. gfs probably overdone with 75 dews tho lol?

 

Excited for more "Mid-Atlantic severe?"

for now hope for well timed lightning i guess.

[wxmeddler]

Excited for more "Mid-Atlantic severe?"

Bring it on.

 

pretty standard here tho can cause a crashing line like last week into good cape etc. gfs probably overdone with 75 dews tho lol?

 

True, although little more speed shear would help to get that ball rolling. Still 5 days away.. 75 Td seems a bit ridiculous.

[StudentOfClimatology]

Re: Dewpoints, I'm pretty sure DCA hit 80 last summer?

I'm not betting against high dews with all the recent rainfall/resulting transpiration. The woods behind my townhouse are as thick as I've ever seen them.

[mattie g]

pretty standard here tho can cause a crashing line like last week into good cape etc. gfs probably overdone with 75 dews tho lol?

for now hope for well timed lightning i guess.

I wouldn't mind a decent storm or two if we get a little warm next week.

I was in Hilton Head the last 10 days and just missed out on some big pulsers that were just inland and couldn't quite get to the coast. Great weather on the island though.

Pretty cool wall cloud with one of the storms. I had a perfect vantage point looking at this thing over the creek/sound. I saw this thing as it blew up - I was out kayak fishing and didn't waste any time getting back to the dock. Too bad the thing never quite got to me, so it was kind of a wasted fishing day.

[Disc]

D5 sounds pretty interesting.. Far western MD and E WV highlighted.

 

 WED /DAY 5/...THE SHORTWAVE TROUGH WILL CONTINUE EWD THROUGH THE OH
   VALLEY WHERE AN E-W FRONT WILL BE IN PLACE WITH A MOIST...UNSTABLE
   WARM SECTOR SOUTH OF THIS FEATURE ACROSS MUCH OF THE OH VALLEY. BELT
   OF STRONGER MID-UPPER FLOW WILL ACCOMPANY THE IMPULSE...AND STORMS
   WILL LIKELY REDEVELOP DURING THE DAY IN ADDITION TO POSSIBLE ONGOING
   MCS TO CONTINUE. VERTICAL SHEAR FROM 35-40 KT AND A FAVORABLE
   THERMODYNAMIC ENVIRONMENT WILL SUPPORT POTENTIAL FOR BOTH SUPERCELLS
   AND ORGANIZED MCS EVENTS WITH LARGE HAIL ALONG WITH POTENTIAL FOR
   WIDESPREAD DAMAGING WIND.
 

 

[yoda]

Day 5 to 7 aka Wed to Fri next week looks intriguing based off SPC disco and LWX disco

 

Snippet from this afternoon's disco:

 

 

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
WARM...HUMID AND UNSTABLE CONDITIONS WILL PERSIST THROUGH MUCH /IF
NOT ALL/ OF THE EXTENDED PERIOD. A LARGE AREA OF SUBTROPICAL HIGH
PRESSURE WILL SET UP SHOP OFF THE EAST COAST OF THE UNITED
STATES...AND A FRONT THAT APPROACHES FROM THE WEST WILL RUN INTO
THIS RIDGE AND STALL NEAR THE AREA TUESDAY NIGHT.

WIND SHEAR INCREASES BY WEDNESDAY NIGHT TO NEAR 40 KTS /0-6 KM BULK
SHEAR/...WHILE AT THE SAME TIME WAVES OF LOW PRESSURE KINK THE FRONT
OVER THE AREA. THIS TYPE OF ENVIRONMENT IS CONDUCIVE FOR COMPLEXES
OF THUNDERSTORMS TO TREK EAST INTO THE AREA FROM THE OHIO VALLEY.
COVERAGE/SEVERITY WILL DEPEND ON HOW MUCH BUOYANCY IS REALIZED AS
THIS WILL DETERMINE WHETHER OR NOT ANY COMPLEX THAT DEVELOPS
UPSTREAM WILL BE ABLE TO MAKE IT ACROSS THE MOUNTAINS. ALSO...STORMS
WILL TEND TO RIDE ALONG THE FRONTAL ZONE...SO WHERE EXACTLY THE
FRONT SETS UP WILL DETERMINE THE AREAS MOST LIKELY TO SEE
CONVECTION.

NOT MUCH WILL CHANGE IN THE OVERALL SYNOPTIC PATTERN THROUGH THE END
OF THE WEEK. AS SUCH...EXPECT A CONTINUATION OF WARM AND HUMID
CONDITIONS WITH EPISODES OF SHOWERS AND THUNDERSTORMS.

[yoda]

Wednesday into Thursday?  Yes?  No?  MCS complex?  Derecho?  Meh severe?

 

LWX HWO from this morning makes mention of threat:

 

 

SEVERE THUNDERSTORMS ARE POSSIBLE ACROSS THE AREA LATE WEDNESDAYNIGHT INTO THURSDAY. THE MAIN THREAT IS DAMAGING WINDS.

[Disc]

RNK also has a HWO mentioning the same risks. Looks like this is one of our better chances of severe so far this year.

 

 A SERIES OF UPPER-LEVEL DISTURBANCES WILL BRING REPEATED CHANCES
FOR THUNDERSTORMS TO THE REGION DURING THE PERIOD. AT THIS
TIME...THE BEST CHANCES FOR THUNDERSTORMS APPEAR TO BE
TUESDAY AFTERNOON...THURSDAY AFTERNOON...AND SUNDAY. STRONG TO
SEVERE THUNDERSTORMS WILL BE POSSIBLE THURSDAY...WITH LARGE HAIL
AND DAMAGING WINDS BEING THE MAIN THREAT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THURSDAY.
 

 

[yoda]

Decent 12z sounding at DCA Thur morning according to my eyes (which probably means its wrong lol)... this is as far as Earl Barker will let me go:

 

 

 

 

 

 

[high risk]

Wednesday night or early afternoon Thursday have potential, depending on your model of choice.   The more progressive GFS swing the front through very early Thursday, but it suggests that the big MCS in the Ohio Valley Wednesday evening stays somewhat intact as it marches to the east coast.    The NAM is slower, so the MCS basically outruns the dynamics and weakens as it comes east.   But with the NAM, the sfc low deepens to our northwest, and frontal passage doesn't occur until early to mid afternoon.   This allows most of the area to have 3000 j/kg of SB cape by 18z along with a decent wind field, and you could easily get new development along the front at peak heating.     At the least, a squall line could impact the east side of DC.

[yoda]

Wednesday night or early afternoon Thursday have potential, depending on your model of choice.   The more progressive GFS swing the front through very early Thursday, but it suggests that the big MCS in the Ohio Valley Wednesday evening stays somewhat intact as it marches to the east coast.    The NAM is slower, so the MCS basically outruns the dynamics and weakens as it comes east.   But with the NAM, the sfc low deepens to our northwest, and frontal passage doesn't occur until early to mid afternoon.   This allows most of the area to have 3000 j/kg of SB cape by 18z along with a decent wind field, and you could easily get new development along the front at peak heating.     At the least, a squall line could impact the east side of DC.

 

Thanks for your response good sir.  With the GFS, is the MCS still severe at all?  Or has it outrun its dynamics by the time it gets to the LWX CWA?  If I am looking at the 12z GFS sounding at KIAD at 06z THUR correctly, SRH is through the roof and SWEAT index is decent, but with positive LI and basically zero SBCAPE or MLCAPE, all storms, if any, would be elevated, no?

[high risk]

Thanks for your response good sir.  With the GFS, is the MCS still severe at all?  Or has it outrun its dynamics by the time it gets to the LWX CWA?  If I am looking at the 12z GFS sounding at KIAD at 06z THUR correctly, SRH is through the roof and SWEAT index is decent, but with positive LI and basically zero SBCAPE or MLCAPE, all storms, if any, would be elevated, no?

 

        quite possible.   The GFS Dulles sounding at 6z is after the rain has arrived, so it's possible that there is more sfc-based instability available in the "uncontaminated" environment.    But I think we all know that getting decent sfc-based cape here late at night is tough to do.

[yoda]

quite possible. The GFS Dulles sounding at 6z is after the rain has arrived, so it's possible that there is more sfc-based instability available in the "uncontaminated" environment. But I think we all know that getting decent sfc-based cape here late at night is tough to do.

Def agree... no sign of an EML or remnants of one?

[high risk]

Def agree... no sign of an EML or remnants of one?

 

     no.   EMLs are hard to get east of the mountains, especially when there is a lot of upstream convection.     All of the stuff in the midwest the next few days should overturn things pretty handily, so an EML reaching the eastern states is unlikely.