Potential For ISOLATED severe weather in the NE tomorrow

[USAwx1]

There is the potential for SOME severe weather in the northeast tomorrow afternoon and evening. just DON’T get too excited though.

By 21z TUE, strong closed 500mb low should be located over MI w/ the SFC and 850mb low centers running into SRN Ontario.

45 KT mid level flow associated with the 500mb low will push NWD into WRN PA and NY during the late afternoon and evening hours which should contribute to 35-40 KT of deep-layer vertical shear in the lowest 6km which can be supported by relatively long hodographs at sites across the region. Meanwhile, BACKING of the low-level flow will occur INVOF the warm front over PA and NY w/ SE winds at the SFC becoming S to SW at and above 850H leading to a favorable environment for rotating supercells—supported by a rather potent 30-35KT LLJ around 900H (as noted on ETA BUFKIT soundings at IPT).

With that said, there will be PLENTY of cloud cover over the region preventing strong surface heating, and ultimately holding SB CAPE values to at or below 1000J/kg. Furthermore, mid level temps will be WARM (w/ 500H temps of only -6 to -7 DEG C) holding Lapse rates in check.

Conclusively, while Shear/wind profiles are IMPRESSIVE instability will be limited and cloud cover plentiful, thus preventing any major large-scale severe weather outbreak. However SOME thunderstorms which do develop MAY become severe w/ possible rotation.

[weatherfan]

There are severe storms right now over Del and NJ that possabley may be severe.As radar is showing some rotation inbembed in one of the cells in the small line.A bit surpise there is no warning on that small complax right now.


P.S looks like the storm has weakend but earlyer was showing some possable rotation.

[BL03]

Code: Select all

SEVERE THUNDERSTORM WARNING

PAC091-271900-

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
225 PM EDT TUE JUL 27 2004

THE NATIONAL WEATHER SERVICE IN MOUNT HOLLY NJ HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
SOUTHEASTERN MONTGOMERY COUNTY IN SOUTHEAST PENNSYLVANIA.

* UNTIL 300 PM EDT

* AT 221 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORM.  THIS STORM WAS LOCATED NEAR PLYMOUTH
MEETING...OR ABOUT 9 MILES WEST OF PHILADELPHIA...AND MOVING
NORTHEAST AT 15 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
PLYMOUTH MEETING BY 230 PM EDT...
AMBLER BY 245 PM EDT...
7 MILES SOUTHEAST OF LANSDALE BY 255 PM EDT...

IN ADDITION TO DAMAGING WINDS...FREQUENT CLOUD TO GROUND LIGHTNING
AND TORRENTIAL RAINS ARE LIKELY WITH THIS STORM. MOVE INDOORS
IMMEDIATELY! LIGHTNING IS ONE OF NATURES NUMBER ONE KILLERS.
REMEMBER...IF YOU CAN HEAR THUNDER...YOU ARE CLOSE ENOUGH TO BE
STRUCK BY LIGHTNING.

LAT...LON 4011 7542 4001 7530 4017 7511 4027 7527

$$

JRP







[USAwx1]

I'm MOST concerned about the Delmarva region, Southeast PA (from the Lower Susquehanna Valley eastward into the PHL area), central and SRN Jersey.

This is where SB CAPE is on the order of 1000-3000 J/kg, the low-level flow is backing considerably from the Surface to 850H and the stronger 6Km vertical shear (of 30-35 KT) intersects the northern portions of the instability axis.

Plus, Boundary layer moisture is very impressive w/ SFC Td's up to 74-76F.

Albeit, lower tropospheric instability is ALOT stronger then I thought they would be yesterday when I posted this topic and that could make a WORLD of difference. I was anticipating the best CAPE in the lowest 300mb to be elevated.

[USAwx1]

Got some rotation detected in a Cell crossing the Chesapeake bay into Dorchester county MD. No TVS/ETVS signatures yet.

[USAwx1]

12z RUC soundings at ILG and ABE still show impressive 35-40 KT deep-layer shear and relatively long hodographs even in the lower levels--Along with an increasing LLJ around 900H toward evening.

[weatherfan]

As HM said how many set ups can there be that are a like what we have been seeing this summer like this lol.This is atleast the 3red time we have seen this sort of set up.Where the warm front was in Md PA border.And storms just get enough of the feed of the warm front to get some roatation in them.Not unheard of for july but diffentey unuseal in the amount of times this pattern has repeated it self this summer.Almost been a spring time pattern in july this year.

[USAwx1]

As HM said how many set ups can there be that are a like what we have been seeing this summer like this lol.This is atleast the 3red time we have seen this sort of set up.Where the warm front was in Md PA border.And storms just get enough of the feed of the warm front to get some roatation in them.Not unheard of for july but diffentey unuseal in the amount of times this pattern has repeated it self this summer.Almost been a spring time pattern in july this year.

Thats what i was concerned about yesterday WRT to rotation in thunderstorms which are able to tap the low level directional shear INVOF the warmfront. This is ALSO an area where the Instability axis S of the front interacts w/ the 35-40 KT of deep layer shear--and the reason why I'm especially concerned about the delmarva regions and even more so SE PA. That is where the Low level Flow close to the SFC is SE backing sharply around to SW at about 850mb.

When it comes to CLIMO, sure this is NOT unheard of but not exactly common either.

I'm looking into years which had the same set-ups frequently during the summer as to what (if any) possible correlation there is w/ the following fall and winter patterns.

[donsutherland1]

Good call, USAwx1. Your concerns were well-founded.

Parts of the NYC area received torrential downpours and heavy thunderstorms a short while ago. NJ had some severe weather.

[USAwx1]

Good call, USAwx1. Your concerns were well-founded.

Parts of the NYC area received torrential downpours and heavy thunderstorms a short while ago. NJ had some severe weather.

Thanks. As Tom noted in his thread, there were reports of tornadoes this afternoon across the region which I had thought was under the gun. Still think this region could have used an outlook upgrade to categorical Slight risk.

Otherwise, How about that 5-6" core in Berks county. That was pretty impressive, and will probably continue to increase.

[Stephanie]

You sure did call it USA! It will be interesting to see what your research comes up with regarding a correlation between this summer's pattern and the fall and winter.

WE're gettin torrential rains down here in AC AGAIN.

[USAwx1]

You sure did call it USA! It will be interesting to see what your research comes up with regarding a correlation between this summer's pattern and the fall and winter.

WE're gettin torrential rains down here in AC AGAIN.

We may still have a few more of these episodes before the end of the summer, or even in early fall (like last year). So I'll wait until OCT before I really look hard at it.