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Convection & Thunderstorm Discussion May 21-24


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Any sun or clearing should help destabalize. There is a pocket of 40kt+ of shear over northern and eastern PA which should continue to swing this way. SBCAPE is now in excess of 1500 J/KG over northern NJ and surroundiung areas. This could be quite a day for severe weather, supercell composite of 2 showing up near Philly

 

scp.gif?1369319044547

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The 12z OKX sounding has forecast SBCAPE and LI 1432 J/kg and -5. With 0-6km shear at 30kt. That more that I expected out there, at this time.

 

The 12z HRRR has convection forming NNJ and LHV between 15z and 18z. So I think severe t-storm watch could be issued for areas N&W by early afternoon:

 

Edit: There's already some showers forming Western NJ that will may hamper our instability:

 

2zqsexc.jpg

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I wonder if today could be one of those surprise severe days, our worst usually happens when it's not obvious.

Also could we be seeing a prolonged and major heat wave starting later next week?

I don't think it would really be a surprise. Thunderstorms have been in the forecast for days with isolated severe

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Any sun or clearing should help destabalize. There is a pocket of 40kt+ of shear over northern and eastern PA which should continue to swing this way. SBCAPE is now in excess of 1500 J/KG over northern NJ and surroundiung areas. This could be quite a day for severe weather, supercell composite of 2 showing up near Philly

 

scp.gif?1369319044547

Vis loop has a bunch of junk out there. Looks to be hanging tough south and  s/w of the metro area.

 

http://www.meteo.psu.edu/~fxg1/SAT_PA/anim8vis.html

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They seem to be increasing in coverage and intensity especially over Somerset county.

 

Maybe they will go severe with the instability already in place. SPC seems that think that too:

 

 

 

11qpnnq.jpg

MESOSCALE DISCUSSION 0779

NWS STORM PREDICTION CENTER NORMAN OK

1023 AM CDT THU MAY 23 2013

AREAS AFFECTED...PARTS OF THE UPPER MID-ATLANTIC/SRN NEW ENGLAND

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 231523Z - 231800Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...MONITORING FOR AN INCREASING DAMAGING WIND/MARGINAL SEVERE

HAIL HAZARD WITH INITIAL CONVECTIVE DEVELOPMENT OCCURRING ACROSS FAR

ERN PA/NRN NJ. A WW ISSUANCE MAY BECOME NECESSARY WHERE GREATER

CLUSTER/LINEAR ORGANIZATION IS APPARENT.

DISCUSSION...AN INCREASE IN CONVECTIVE DEVELOPMENT HAS BEEN NOTED IN

RADAR IMAGERY FROM NEAR THE ABE/TTN TO 20 NW EWR AREA AS CONVECTIVE

TEMPERATURES OFF THE 12Z APG/WAL RAOBS HAVE BEEN BREACHED WITH

MIDDLE TO UPPER 70S IN 15Z METARS. AMIDST A PLUME OF MIDDLE TO UPPER

60S SURFACE DEW POINTS...MLCAPE HAS ALREADY REACHED 500-1000 J/KG.

MODERATELY STRONG UNIDIRECTIONAL SWLY WIND PROFILES WITHIN THE RIGHT

ENTRANCE REGION OF A FAST UPPER-LEVEL JET SHOULD PROMOTE ADDITIONAL

CONVECTION WHICH MAY ORGANIZE INTO CLUSTERS AND SHORT-LINE SEGMENTS

PRIMARILY PRODUCING SPORADIC DAMAGING WINDS AND MARGINALLY SEVERE

HAIL.

..GRAMS/KERR.. 05/23/2013

ATTN...WFO...GYX...BOX...BTV...OKX...ALY...PHI...BGM...

--------------------

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Some clearing is still trying to push north through Central NJ to the south of this weak convection. I think we'll need that to push north before we can start talking about any legit severe threat. The stuff over NJ now is probably unlikely to turn strong or severe given the current environment.

 

But it looks like most of it is starting to move north and west of NYC. If we can open the door for a little more thermodynamic support, we could be in business this afternoon.

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Some clearing is still trying to push north through Central NJ to the south of this weak convection. I think we'll need that to push north before we can start talking about any legit severe threat. The stuff over NJ now is probably unlikely to turn strong or severe given the current environment.

 

But it looks like most of it is starting to move north and west of NYC. If we can open the door for a little more thermodynamic support, we could be in business this afternoon.

 

I think this too. The 13z HRRR has this moving out into Hudson Valley and more convection developing further SW, the later this afternoon.

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I think this too. The 13z HRRR has this moving out into Hudson Valley and more convection developing further SW, the later this afternoon.

One problem could be the firehose type deal coming from the southeast and associated clouds. That could muck up the warm sector and the lift could start triggering what i would like to call crapvection. We'll see.

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One problem could be the firehose type deal coming from the southeast and associated clouds. That could muck up the warm sector and the lift could start triggering what i would like to call crapvection. We'll see.

 

I see that happening too. CU is already popping up and streaking over lower half of NJ. I wish we had more cap:

 

LongIsland.vis.gif

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Very low CIN values for a classic severe threat. The atmosphere is so buoyant that showers and thunderstorms are already ongoing at this hour, and that is usually a tell tale sign that this will be primarily a hvy rain / isolated severe type day. Generally we like to see at least a weak to moderate CAP to prevent morning/midday contamination by scattered convection. Bulk shear is modest as are low level lapse rates. Instability parameters aren't impressive, and more sunshine would help destabilize things further. However, as it stands, it looks like more widespread convection by evening but generally isolated severe.

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Just got clipped by a storm. Had moderate to heavy rain for about 10 minutes before letting up. Before it started to rain, there were two close lightning strikes, one of which simply sounded like a loud 'pop' with no rumbling at all. After that, there was no thunder at all. Currently the sun is out.

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They just upgraded to a warning, they did an EAS activation and the whole 9 yards

 

FLASH FLOOD WARNING
NJC003-031-NYC079-087-119-231830-
/O.NEW.KOKX.FF.W.0003.130523T1700Z-130523T1830Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE NEW YORK NY
100 PM EDT THU MAY 23 2013

THE NATIONAL WEATHER SERVICE IN UPTON NY HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  PASSAIC COUNTY IN NORTHEAST NEW JERSEY...
  WESTCHESTER COUNTY IN SOUTHEAST NEW YORK...
  BERGEN COUNTY IN NORTHEAST NEW JERSEY...
  ROCKLAND COUNTY IN SOUTHEAST NEW YORK...
  PUTNAM COUNTY IN SOUTHEAST NEW YORK...

* UNTIL 230 PM EDT...

* AT 1257 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
  FLASH FLOODING FROM THUNDERSTORMS ALONG A LINE EXTENDING FROM
  YORKTOWN HEIGHTS TO HAWTHORNE...OR ALONG A LINE EXTENDING FROM
  PEEKSKILL TO PARAMUS...MOVING NORTHEAST AT 10 MPH.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

EXCESSIVE RUNOFF FROM HEAVY RAINFALL WILL CAUSE FLOODING OF SMALL
CREEKS AND STREAMS...URBAN AREAS...HIGHWAYS...STREETS AND UNDERPASSES
AS WELL AS OTHER DRAINAGE AREAS AND LOW LYING SPOTS.

DO NOT UNDERESTIMATE THE POWER OF FLOOD WATERS. ONLY A FEW INCHES OF
RAPIDLY FLOWING WATER CAN QUICKLY CARRY AWAY YOUR VEHICLE.

TO REPORT FLOODING...HAVE THE NEAREST LAW ENFORCEMENT AGENCY RELAY
YOUR REPORT TO THE NATIONAL WEATHER SERVICE FORECAST OFFICE IN UPTON
NY.

&&

LAT...LON 4125 7409 4134 7397 4140 7396 4147 7390
      4123 7361 4082 7413 4086 7420 4100 7430

$$

JMC

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I for one never believed the NAM, for a model that is supposed to be good for convection, they had this area only getting 0.50"+ over the next 3 days. We're already over that. The 12z NAM more than trippled amounts.

 

NAM had 1.37" of rain for NYC through Sunday morning.

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