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2013 Mt. Holly CWA Convection Thread


SouthernNJ

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New STW to our west..

Those probs are awfully low given the parameters and moderate risk

 

Tornadoes

 

Probability of 2 or more tornadoes

Low (20%)

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

Low (10%)

Wind

 

Probability of 10 or more severe wind events

Low (20%)

Probability of 1 or more wind events > 65 knots

Low (10%)

Hail

 

Probability of 10 or more severe hail events

Mod (30%)

Probability of 1 or more hailstones > 2 inches

Mod (30%)

Combined Severe Hail/Wind

 

Probability of 6 or more combined severe hail/wind events

High (70%)

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I am becoming interested in E-C, SE PA into the Delaware Valley / C&S NJ for later this afternoon. Excellent differential cyclonic vorticity advection and deep layer shear with BL recovery likely. The only thing I would say is watch the surface winds as the low moves erratically south/east. The warm sector will likely become largely unidirectional but any backing locally would significantly enlarge hodographs near strongest pressure falls/warm front.

Still feeling that way even though the spc dropped us from 45% to "lol" ?

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So...we are clearing quite nicely but now less chance of severe?  Also...seems like some of the high res models fire things up again later...what are we suddenly lacking?

 

Probabilistically, yeah our chances went down when the MCS came plowing through us this morning. The low to mid levels need to recover which have been significantly cooled/moistened. Having said that, a developing thermal ridge up into S-C PA is being detected with levels drying out somewhat. There is MLCAPE developing here but it needs to get a lot stronger with the level of deep layer shear in place. If we properly destabilize, you'll see the probabilities come back up.

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This is a very odd setup. I just bolted out of Philly, but I'm not sure I want to rush all the way down to VA only to have an 8 hour ride home tonight. I still think there's still somewhat of a threat from BWI to PHL and the major flip flop by SPC is, I just don't know. Like HM eluded to, there's gotta be potential ahead of the low as it dives SE thru PA. That seemed be the best overlap region of some instability and greatly increased shear and helicity.

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Probabilistically, yeah our chances went down when the MCS came plowing through us this morning. The low to mid levels need to recover which have been significantly cooled/moistened. Having said that, a developing thermal ridge up into S-C PA is being detected with levels drying out somewhat. There is MLCAPE developing here but it needs to get a lot stronger with the level of deep layer shear in place. If we properly destabilize, you'll see the probabilities come back up.

 

Thanks for the explanation....I was expecting perhaps trimming back the moderate, but not with a chainsaw...also I thought the prevailing wisdom was that the type of clearing we are seeing would tend more towards a robust threat for a round two for this area..plus we were expected to get either a still healthy MCS if not signifcant leftovers when the previous moderate outlooks were issued....not to mention 45 down to 5?  continuity, we don't need no steenking forecast continuity!

 

Meh...this is why I've never been a severe-centric weather weenie....sometimes it seems more scorcery than science to me.

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Recovering from a sizable MCS like this isn't easy and you need some pretty good thermal advection and diabatic heating. Given the placement of the mid level lows and temps over PA, there is actually positive buoyancy in the soundings. Until the SPC knows if the CAPE can recover sufficiently with the kind of shear we have in place, you won't see their focus on our area/probs will stay low.

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Thanks for the explanation....I was expecting perhaps trimming back the moderate, but not with a chainsaw...also I thought the prevailing wisdom was that the type of clearing we are seeing would tend more towards a robust threat for a round two for this area..plus we were expected to get either a still healthy MCS if not signifcant leftovers when the previous moderate outlooks were issued....not to mention 45 down to 5?  continuity, we don't need no steenking forecast continuity!

 

Meh...this is why I've never been a severe-centric weather weenie....sometimes it seems more scorcery than science to me.

 

This is why long-range severe weather forecasts for  "derechos" is generally a bad idea (if you are going to get "cute" I would at least wait for a medium range signal a bit more notorious than this one. EML trajectories were not classic for our area in this case). It is not quite as bad but almost as bad as telling people a certain EF tornado is on the way before a damage assessment. Our entire threat was always contingent on what happens in the Midwest in the day and night before. While there was some hint on the modeling, none of them fully captured the extent of this MCS plowing straight through.

 

Having said all of this and despite the new 1630z, I am still interested in PA.

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CTP basically saying the same thing...."um maybe?!?!"

 

NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE LINE OF STRONG STORMS THAT BROUGHT THE HEAVY RAIN AND HIGH
WINDS EARLY TODAY HAS MOVED TO THE NJ COAST. THE SURFACE AND
UPPER LOW THAT TRIGGERED THE LINE ARE STILL MEANDERING THROUGH THE
REGION WITH VERY WARM AND HUMID AIR STILL IN PLACE. THE BIG
QUESTION IS IF WE CAN SEE THE ATMOSPHERE RECOVER IN TIME FOR NEW
CONVECTION TO BECOME AN ISSUE...MAINLY OVER SOUTHERN AREAS AS THE
SFC LOW SLIDES EAST OR SOUTHEAST. MESO MODELS ARE SHOWING THE BEST
CHANCE OF THE CONVECTION REMAINING JUST SOUTH OF THE BORDER...BUT
A FAIR AMOUNT OF SHOWER ACTIVITY LINGERING OR REDEVELOPING OVER
THE REGION. CONCERN IS THE BINOVC/CLEARING THAT IS DEVELOPING OVER
THE LOWER SUSQ COULD RAISE THE THREAT. THE RAP SHOWS CAPES
REBOUNDING IN THAT AREA AS WELL. THIS WILL BE THE AREA OF MOST
CONCERN IN THE CWA FOR THE NEXT SEVERAL HOURS.

HAVE DROPPED THE FLOOD WATCH FOR ALL BUT THE SERN 3 COUNTIES
SINCE IT LOOKS LIKE THE THREAT FOR HEAVIEST RAIN WILL REMAIN SOUTH
OF OUR BORDER. IF IT BUILDS BACK TO THE NORTH AT ALL...THOSE
COUNTIES WOULD BE MOST UNDER THE GUN.

 

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Sun is breaking out in Southern Ocean County for the time being :)

 

Will those lower 70s dewpoints from Delaware be able to arrive before the SLP does? The visible loop is pretty but I know our problem runs "deeper" than that...okay that pun was lame.

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Will those lower 70s dewpoints from Delaware be able to arrive before the SLP does? The visible loop is pretty but I know our problem runs "deeper" than that...okay that pun was lame.

 

those dissipating mid-level clouds does not mean we have solid mid-level atmosphere back in place ehh. I guess many said all along that it would all come down to how the midwest severe evolved overnight. And for the love of god, can the media put the freaking derecho talk to rest now!? 

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those dissipating mid-level clouds does not mean we have solid mid-level atmosphere back in place ehh. I guess many said all along that it would all come down to how the midwest severe evolved overnight. And for the love of god, can the media put the freaking derecho talk to rest now!? 

i heard it 3x on local tv yesterday/this am

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those dissipating mid-level clouds does not mean we have solid mid-level atmosphere back in place ehh. I guess many said all along that it would all come down to how the midwest severe evolved overnight. And for the love of god, can the media put the freaking derecho talk to rest now!? 

 

The problems are deep for sure. We have now moistened the 800-600mb level but there is some drier mid level air with the lows themselves that will try to spread in over E PA. The low-level moisture source is not ample/widespread but broken (certain areas that mixed out and did not) with localized pooling near boundaries. Lowering the severe risks was a good move by the SPC. Still, the right set of things could come together for E-C / SE PA into the Delaware Valley as the low drops east/south.  

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