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2013 Mt. Holly CWA Convection Thread


SouthernNJ

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If there wasn't going to be so much crapvection, I'd be tempted to head out to the area between York and Westminster, MD. I just noticed 18z NAM was spitting out some not-too-shabby hodos.

Westminster, MD at 21z:

6-26-13hodo1.png

York, PA at 00z:

6-26-13hodo2.png

That's pretty impressive. Like you said, pretty questionable in regards to debris

Edit* neW nam kinda shifts the best backing of the winds towards state college

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Edit* neW nam kinda shifts the best backing of the winds towards state college

 

SPC WRF agrees that the best shot at rotating storms is central PA.  It builds a N-S line through central PA by 22z but then collapses it just outside of the city at 0z.  Seems a bit later than the NAM though.  The NAM has been indicating precip as early as 18z if I recall right.

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day1otlk_20130627_1200_prt.gif

 

day1probotlk_20130627_1200_torn_prt.gif

 

day1probotlk_20130627_1200_wind_prt.gif

 

day1probotlk_20130627_1200_hail_prt.gif

...MID ATLANTIC THROUGH A PORTION OF THE NERN STATES...

   SEVERE THREAT IN THIS REGION IS SOMEWHAT UNCERTAIN. HOWEVER...LOW
   END SEVERE PROBABILITIES HAVE BEEN MAINTAINED. VERTICAL SHEAR WILL
   REMAIN MODEST...BUT FLOW ALOFT WILL UNDERGO SOME INCREASE AHEAD OF
   THE PROGRESSIVE SHORTWAVE TROUGH. DIABATIC WARMING WILL SUPPORT SOME
   DESTABILIZATION...BUT INSTABILITY WILL PROBABLY REMAIN SOMEWHAT
   MARGINAL DUE TO WEAK LAPSE RATES. STORMS WILL LIKELY REDEVELOP OVER
   THE HIGHER TERRAIN OF THE APPALACHIANS AND WITHIN CONVERGENCE ZONE
   ALONG LEE TROUGH AND SPREAD EWD. IF SUFFICIENT DESTABILIZATION OF
   THE BOUNDARY LAYER OCCURS...THE STRONGER STORMS MAY POSE A THREAT
   FOR MAINLY ISOLATED STRONG TO DAMAGING WIND GUSTS.

   ..DIAL/LEITMAN.. 06/27/2013
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^^^they don't sound too encouraged. Expect the norm, isolated severe, scattered heavy showers.

 

Coverage is probably more widespread due to the disturbance coming into Western PA this AM.  Today probably shapes up more as a heavy rain threat with some downbursts in the strongest of storms.

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The 4-incher had even more, 1.61".  Must've been too fast for the tipper to keep up.  The other reliable CoCoRaHS station had even more, 1.74.

 

 

There were some radar estimates of 1.5-2.5 inches over a one hour period in that area last night.

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I have a question whats more important when it comes to storms Surface based cape or Cape-100mb mixed layer? I always notice there is a difference. For example currently the surface based cape is 2000 but the 100mb mixed layer is aroud 750. Just curious what the difference is between the two.

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I have a question whats more important when it comes to storms Surface based cape or Cape-100mb mixed layer? I always notice there is a difference. For example currently the surface based cape is 2000 but the 100mb mixed layer is aroud 750. Just curious what the difference is between the two.

From my understanding, if you want severe, surface based cape gets you surface based storms, and not elevated ones. ML cape does help support hail growth and sustain updrafts. But usually, it's always <sb cape.

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I'd call that an interesting 1630 update.

 

Shaved 15% hail back south but introduced a new 15% contour for the Lehigh Valley on north.

 

Put us all in a 30% wind.

 

And upgraded Kansas to MDT with a 45% hatched for wind.

 

day1otlk_20130627_1630_prt.gif

 

day1probotlk_20130627_1630_torn_prt.gif

 

day1probotlk_20130627_1630_wind_prt.gif

 

day1probotlk_20130627_1630_hail_prt.gif

 

Discussion is pretty milquetoast though:

...ERN GULF STATES AND APPALACHIANS TO ATLANTIC SEABOARD...
   DEEP LAYER SHEAR ACROSS MUCH OF THE REGION IS EXPECTED TO REMAIN
   WEAK THROUGH THE PERIOD.  HOWEVER...FORCING ASSOCIATED WITH THE MAIN
   IMPULSE TURNING EAST OF THE NORTH CENTRAL APPALACHIANS...COUPLED
   WITH AN ASSOCIATED BELT OF MODEST LOWER/MID-LEVEL FLOW...COULD
   ENHANCE CONVECTIVE DEVELOPMENT LATE THIS AFTERNOON ACROSS PARTS OF
   EASTERN VIRGINIA/MARYLAND AND THE DELMARVA PENINSULA INTO NORTHERN
   MID ATLANTIC COASTAL AREAS.  A LINE OR CLUSTER OF STORMS APPEARS
   POSSIBLE...WITH THE RISK FOR POTENTIALLY DAMAGING WIND GUSTS.  

   OTHER SCATTERED STRONG/SEVERE STORM DEVELOPMENT STILL APPEARS
   POSSIBLE IN THE PRESENCE OF MODERATE INSTABILITY...NORTHWARD INTO
   UPSTATE NEW YORK...AND SOUTHWARD...TO THE SOUTH AND EAST OF THE
   SOUTHERN APPALACHIANS.  IT IS POSSIBLE THAT THE CONVECTIVELY
   ENHANCED PERTURBATION COULD CONTRIBUTE TO ANOTHER CLUSTER OVER
   STORMS TODAY ACROSS PARTS OF ALABAMA AND GEORGIA...WHICH COULD
   PERHAPS DEVELOP SOUTHWARD INTO NORTHERN FLORIDA.

   ..KERR/GRAMS.. 06/27/2013
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Just curious, but does anyone have a nice checklist for indices.  I'm putting something together for Camden County Skywarn.  If anyone has something really nice, let me know..

 

Looks like a new watch will be going up this afternoon, say from 2 to 10pm. 

 

http://www.spc.noaa.gov/products/md/md1266.html

 

Looks a good case where these storms will cause a lot of lightning and damaging winds.. But that heavy rain will be another major factor this afternoon and evening.

 

I'll say one thing about last night, saw a lightning display on par with what you see in July with thunderstorms. I mean lots of cloud to ground lightning strikes.  Even losing power for a few seconds. 

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Good chance of another Severe Thunderstorm Watch:

 

 

Mesoscale Discussion 1266 < Previous MD mcd1266.gif
   MESOSCALE DISCUSSION 1266   NWS STORM PREDICTION CENTER NORMAN OK   1204 PM CDT THU JUN 27 2013   AREAS AFFECTED...UPPER MID-ATLANTIC...NORTHEAST   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE    VALID 271704Z - 271900Z   PROBABILITY OF WATCH ISSUANCE...60 PERCENT   SUMMARY...TSTM COVERAGE AND INTENSITY WILL INCREASE IN ASSOCIATION   WITH AN MCV SHIFTING NEWD FROM NRN VA. STRENGTHENING DEEP-LAYER   SHEAR ALONG WITH CONTINUED DOWNSTREAM DESTABILIZATION SHOULD BE   SUFFICIENT FOR AT LEAST ISOLATED SEVERE TSTMS WITH A PRIMARY RISK OF   DAMAGING WINDS AND SOME HAIL.   DISCUSSION...16Z SURFACE ANALYSIS PLACED A 1006 MB CYCLONE NEAR THE   MD PANHANDLE WITH AN MCV EVIDENT IN VISIBLE SATELLITE IMAGERY ACROSS   NRN VA AHEAD OF THE BROADER MID-LEVEL TROUGH CROSSING THE CNTRL   APPALACHIANS. SURFACE TEMPERATURES HAVE HEATED WELL INTO THE 80S   DOWNSTREAM OF THE THICKER CLOUD DECKS ASSOCIATED WITH THE MCV AND   ALONG THE APPALACHIANS. A NARROW BELT OF MODERATELY STRONG MID-LEVEL   SWLYS /AROUND 30-35 KT/ WAS SAMPLED IN CCX/BGM VWP DATA AND THIS   ENHANCEMENT SHOULD SHIFT EWD THROUGH THE AFTERNOON.   MEANWHILE...STRONGER LOW-LEVEL FLOW SAMPLED IN AKQ VWP DATA SHOULD   DEVELOP NEWD ALONG THE COASTAL PLAIN. SETUP MAY YIELD SEVERAL   CLUSTERS WITH DAMAGING WINDS AND MARGINALLY SEVERE HAIL AS THE MAIN   HAZARDS...WITH PERHAPS A BRIEF TORNADO OR TWO POSSIBLE WITH   TRANSIENT SUPERCELL STRUCTURES NEAR THE ATLANTIC COAST.   ..GRAMS/KERR.. 06/27/2013
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Wow - it's a Tornado Watch.

 

http://www.spc.ncep.noaa.gov/products/watch/ww0377.html

WOUS64 KWNS 271754
     WOU7
     
     BULLETIN - IMMEDIATE BROADCAST REQUESTED
     TORNADO WATCH OUTLINE UPDATE FOR WT 377
     NWS STORM PREDICTION CENTER NORMAN OK
     200 PM EDT THU JUN 27 2013
     
     TORNADO WATCH 377 IS IN EFFECT UNTIL 1000 PM EDT FOR THE
      FOLLOWING LOCATIONS
     
     DCC001-280200-
     /O.NEW.KWNS.TO.A.0377.130627T1800Z-130628T0200Z/
     
     DC 
     .    DISTRICT OF COLUMBIA COUNTIES INCLUDED ARE
     
     DISTRICT OF COLUMBIA 
     
     
     DEC001-003-005-280200-
     /O.NEW.KWNS.TO.A.0377.130627T1800Z-130628T0200Z/
     
     DE 
     .    DELAWARE COUNTIES INCLUDED ARE
     
     KENT                 NEW CASTLE          SUSSEX              
     
     
     MDC003-005-009-011-013-015-017-021-025-027-029-031-033-035-037-
     041-043-510-280200-
     /O.NEW.KWNS.TO.A.0377.130627T1800Z-130628T0200Z/
     
     MD 
     .    MARYLAND COUNTIES INCLUDED ARE
     
     ANNE ARUNDEL         BALTIMORE           CALVERT             
     CAROLINE             CARROLL             CECIL               
     CHARLES              FREDERICK           HARFORD             
     HOWARD               KENT                MONTGOMERY          
     PRINCE GEORGES       QUEEN ANNE'S        ST. MARYS           
     TALBOT               WASHINGTON          
     
     
     MARYLAND INDEPENDENT CITIES INCLUDED ARE
     
     BALTIMORE CITY       
     
     
     NJC001-005-007-009-011-015-019-021-023-025-027-029-033-035-037-
     041-280200-
     /O.NEW.KWNS.TO.A.0377.130627T1800Z-130628T0200Z/
     
     NJ 
     .    NEW JERSEY COUNTIES INCLUDED ARE
     
     ATLANTIC             BURLINGTON          CAMDEN              
     CAPE MAY             CUMBERLAND          GLOUCESTER          
     HUNTERDON            MERCER              MIDDLESEX           
     MONMOUTH             MORRIS              OCEAN               
     SALEM                SOMERSET            SUSSEX              
     WARREN               
     
     
     PAC001-011-017-025-029-037-041-043-045-055-057-061-067-071-075-
     077-087-089-091-093-095-097-099-101-107-109-119-133-280200-
     /O.NEW.KWNS.TO.A.0377.130627T1800Z-130628T0200Z/
     
     PA 
     .    PENNSYLVANIA COUNTIES INCLUDED ARE
     
     ADAMS                BERKS               BUCKS               
     CARBON               CHESTER             COLUMBIA            
     CUMBERLAND           DAUPHIN             DELAWARE            
     FRANKLIN             FULTON              HUNTINGDON          
     JUNIATA              LANCASTER           LEBANON             
     LEHIGH               MIFFLIN             MONROE              
     MONTGOMERY           MONTOUR             NORTHAMPTON         
     NORTHUMBERLAND       PERRY               PHILADELPHIA        
     SCHUYLKILL           SNYDER              UNION               
     YORK                 
     
     
     VAC013-059-107-600-280200-
     /O.NEW.KWNS.TO.A.0377.130627T1800Z-130628T0200Z/
     
     VA 
     .    VIRGINIA COUNTIES INCLUDED ARE
     
     ARLINGTON            FAIRFAX             LOUDOUN             
     
     
     VIRGINIA INDEPENDENT CITIES INCLUDED ARE
     
     FAIRFAX              
     
     
     ANZ430-431-530-531-532-533-534-535-536-537-538-539-540-541-542-
     280200-
     /O.NEW.KWNS.TO.A.0377.130627T1800Z-130628T0200Z/
     
     CW 
     
     .    ADJACENT COASTAL WATERS INCLUDED ARE
     
     DELAWARE BAY WATERS NORTH OF EAST POINT NJ TO SLAUGHTER BEACH DE 
     
     DELAWARE BAY WATERS SOUTH OF EAST POINT NJ TO SLAUGHTER BEACH DE 
     
     CHESAPEAKE BAY NORTH OF POOLES ISLAND MD 
     
     CHESAPEAKE BAY FROM POOLES ISLAND TO SANDY POINT MD 
     
     CHESAPEAKE BAY FROM SANDY POINT TO NORTH BEACH MD 
     
     CHESAPEAKE BAY FROM NORTH BEACH TO DRUM POINT MD 
     
     CHESAPEAKE BAY FROM DRUM POINT MD TO SMITH POINT VA 
     
     TIDAL POTOMAC FROM KEY BRIDGE TO INDIAN HEAD MD 
     
     TIDAL POTOMAC FROM INDIAN HEAD TO COBB ISLAND MD 
     
     TIDAL POTOMAC FROM COBB ISLAND MD TO SMITH POINT VA 
     
     PATAPSCO RIVER INCLUDING BALTIMORE HARBOR 
     
     CHESTER RIVER TO QUEENSTOWN MD 
     
     EASTERN BAY 
     
     CHOPTANK RIVER TO CAMBRIDGE MD AND THE LITTLE CHOPTANK RIVER 
     
     PATUXENT RIVER TO BROOMES ISLAND MD 
     
     ATTN...WFO...LWX...PHI...CTP...
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Tornadoes


Probability of 2 or more tornadoes

Mod (30%)

Probability of 1 or more strong (F2-F5) tornadoes

Low (20%)

Wind


Probability of 10 or more severe wind events

Mod (50%)

Probability of 1 or more wind events > 65 knots

Low (10%)

Hail


Probability of 10 or more severe hail events

Low (20%)

Probability of 1 or more hailstones > 2 inches

Low (10%)

Combined Severe Hail/Wind


Probability of 6 or more combined severe hail/wind events

High (80%)

For each watch, probabilities for particular events inside the watch (listed above in each table)

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