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June 19th Thunderstorm Discussions & Observations


bluewave

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Hot off the press from Mount Holly

Quote

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

A convectively active afternoon is expected across at least the
western half of our area, which then shifts east this evening. A
cold front will be approaching later today, however ongoing
showers/thunder well to our west should strengthen eastward through
the afternoon as it encounters a more unstable air mass. Some
isolated convection could develop well ahead of this. In addition, a
pre-frontal trough may help to organize a separate band of
convection with storms probably tending to congeal into a single
line as we get closer to the early evening.

The air mass in place is rather warm and moist with PW values
already near 2 inches. This is already resulting in quite a bit of
instability with a mesoscale analysis indicating MLCAPE in the 1000-
2000 J/KG range. Some lower cloud bases have quickly developed
within this very warm and moist environment, however as mixing
increases these should rise some. The deep southwesterly flow will
mostly favor a linear convective mode, however as the convective
line grows upscale (some increase in the shear as a low-level jet
strengthens) later today there could be some embedded cells with
some updraft rotation. Given the mostly unidirectional flow though,
straight-line damaging wind gusts is the main threat. The mid level
lapse rates do not appear to be all that steep, therefore while some
hail is possible this may temper this potential. The 12z Sterling,
VA RAOB shows a bit of dry air just above 500 MB, and this could
aide in downdraft strength. The overall high moisture content of the
air mass though may result in water-loaded downdrafts which can
enhance the surface winds, especially with any segments that bow
out. The tropical air mass should also be conducive for convective
to produce frequent lightning.

As mentioned earlier the PW values will be around 2 inches. This
will result in areas of very heavy rain as convection should be
efficient rainfall products. While the storm motions should be
fairly quick, a linear mode and possible backbuilding of updrafts
may result in the potential for local flash flooding. Therefore, the
Flash Flood Watch remains as is.

 

 

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2 minutes ago, friedmators said:

I really can't remember the last truly severe storm in Edison.  Is there a database of verified severe conditions based on locale?

It's funny that nobody around here thinks we ever get severe weather. My last severe storm was very late on May 31st of this year when it hailed up to the size of ping pong balls for five minutes.

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Just now, NJwx85 said:

It's funny that nobody around here thinks we ever get severe weather. My last severe storm was very late on May 31st of this year when it hailed up to the size of ping pong balls for five minutes.

I havent seen hail in years here at home.  I actually thought hail AND wind was a requirement but its either.  Still haven't had one here in a while.

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Just now, friedmators said:

I havent seen hail in years here at home.  I actually thought hail AND wind was a requirement but its either.  Still haven't had one here in a while.

I've had hail twice here in plainfield. One was at the tail end of the March 2010 noreaster. Severe I saw last July and before that probably June 2009 where wind criteria was met. So once every 5 years is pretty pitiful

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5 minutes ago, NJwx85 said:

It's funny that nobody around here thinks we ever get severe weather. My last severe storm was very late on May 31st of this year when it hailed up to the size of ping pong balls for five minutes.

it's all about expectations.   Too much hype most times and even in the best setups, most will come up empty....

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Just now, Brian5671 said:

it's all about expectations.   Too much hype most times and even in the best setups, most will come up empty....

The night I had the severe hail we had very steep mid and low level lapse rates which certainly was unusual for this area. I believe someone on here posted that they were driving down the Thurway in Suffern and saw hail as large as golf balls. That's not more than a mile or two away from where I live.

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My only hail so far this decade could have easily been mistaken for sleet in terms of size. That said, with the May 31 event producing golf balls and a tornado 20 minutes away from me, it's hard to say severe doesn't happen here. You just need a little patience in this part of the country.

As for today, still quite sunny imby and numerous small cells are popping off to the west.

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MD 1090 graphic

Mesoscale Discussion 1090
   NWS Storm Prediction Center Norman OK
   0945 AM CDT Mon Jun 19 2017

   Areas affected...Parts of the northern Mid Atlantic Coast region
   into New England

   Concerning...Severe potential...Watch likely 

   Valid 191445Z - 191715Z

   Probability of Watch Issuance...95 percent

   SUMMARY...Increasing thunderstorm activity is expected into and
   through the 1-4 PM EDT time frame, accompanied by a risk for
   potentially damaging wind gusts.  At least a couple of severe
   weather watches appear likely within the next hour or two.

   DISCUSSION...Ahead of lingering pre-frontal convection, insolation
   within a seasonably high moisture content boundary layer (surface
   dew points near/above 70F) is contributing to moderately large CAPE
   and weakening inhibition.  This is occurring from the lee of the
   Allegheny Mountains through much of the Hudson/Champlain Valleys
   into the mountains of northern New England, where lower/mid
   tropospheric flow is already cyclonic and modest in strength. 
   Although large-scale upstream troughing is only very slowly
   progressing eastward, weak mid-level height falls associated with
   subtle embedded perturbations may aid storm development into the
   17-20Z time frame.  

   The initiation of thunderstorms already appears underway across the
   Poconos, Catskills into and northeast of the Berkshires, and a
   gradual increase in coverage/intensification seems probable into
   early afternoon.  Eventually, in the presence of soundings that
   appear characterized by high precipitable water and 30-40 kt south
   to southwesterly lower/mid tropospheric flow, heavy precipitation
   loading and downward momentum transfer may contribute to increasing
   potential for downbursts.  Consolidating and strengthening cold
   pools may also contribute to organizing convection accompanied by
   strong, potentially damaging wind gusts.
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The last wide spread severe event in this region was the Labor Day 98 derecho. We talk about every severe season. I think the best chance of severe today would be with any discrete cells out ahead of the main line. The main line will probably be your typical underwhelming 30mph gust type of squall line. I'm just hoping to see a nice shelf here at beach and maybe a scud or two

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WW0354 Radar

 SEL4

   URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 354
   NWS Storm Prediction Center Norman OK
   1115 AM EDT Mon Jun 19 2017

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     Connecticut
     Western and Central Massachusetts
     Northern New Jersey
     Eastern New York
     Eastern Pennsylvania
     Southern Vermont
     Coastal Waters

   * Effective this Monday morning and evening from 1115 AM until
     800 PM EDT.

   * Primary threats include...
     Scattered damaging wind gusts to 70 mph likely
     Scattered large hail events to 1.5 inches in diameter possible
     A tornado or two possible

   SUMMARY...Scattered thunderstorms are expected to intensify across
   the watch area through the afternoon, with the strongest cells
   capable of damaging wind gusts and some hail.

   The severe thunderstorm watch area is approximately along and 75
   statute miles east and west of a line from 45 miles southeast of
   Harrisburg PA to 35 miles northwest of Keene NH. For a complete
   depiction of the watch see the associated watch outline update
   (WOUS64 KWNS WOU4).

   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.

   &&

   AVIATION...A few severe thunderstorms with hail surface and aloft to
   1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
   few cumulonimbi with maximum tops to 500. Mean storm motion vector
   25035.
 

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