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Severe weather thread number ...I think X ?


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The NAM soundings are very impressive even down to this area, but it is certainty interesting to see it insisting on storms struggling to get south of the NY/NJ border. You can see on the 500mb height panel that the vorticity shoots eastward after this frame and the storms do so as well. The NAM keys in on more convective development Friday afternoon with the height falls around 18z.

Yeah it also kind of holds off on those stronger height falls until Friday...something else to consider here.

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Northeastern PA/Central NY has a lot going for it in this run, given that the NAM does initiate convection in the area and it's looking at running the convection smack into the areas of highest parameters...

6/23/44 was another big one around the Apps, FWIW.

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One of the greatest derechos in US history happened the day before the May 31st 1998 tornado outbreak. The night of May 30-31st had a derecho with gusts to 130 mph plow through Wisconsin and Michigan...definitely comparible in intensity of July 15, 1995.

What's your take on what will happen in our areas?

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DAY 2 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1253 AM CDT WED JUL 25 2012

VALID 261200Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM NEW ENGLAND TO SRN MO/NRN

AR...

..NEW ENGLAND/OH VALLEY/MID MS VALLEY TO SRN PLAINS

LATEST MODEL GUIDANCE IN PRINCIPAL AGREE THAT AN EARLY DAY MID LEVEL

SPEED MAX ON THE ORDER OF 50-60KT WILL TRANSLATE ACROSS UPSTATE NY

INTO NEW ENGLAND AND SHOULD PROVE PARTLY RESPONSIBLE FOR A CORRIDOR

OF ELEVATED THUNDERSTORMS AHEAD OF ATTENDANT SFC LOW. GFS IS

CONSIDERABLY STRONGER WITH LOW LEVEL WARM ADVECTION/SFC LOW AS IT

SPREADS INTO NEW ENGLAND AND ALLOWS FOR A MORE NWD EXTENSION OF

TSTMS INTO PORTIONS OF SRN ME THAN THE NAM. THIS EARLY ACTIVITY MAY

PRODUCE SOME HAIL BUT THE PRIMARY SEVERE THREAT THURSDAY WILL OCCUR

ALONG/AHEAD OF TRAILING COLD FRONT SWWD ACROSS THE OH VALLEY.

STRONG BOUNDARY LAYER HEATING IS EXPECTED AHEAD OF COLD FRONT ACROSS

THE OH VALLEY AND LATEST NAM SOUNDINGS SUGGEST SFC TEMPERATURES MAY

SOAR WELL INTO THE UPPER 90S BY 18Z ACROSS THE OH VALLEY...LIKELY AS

FAR NE AS WRN PA WITH NEAR 90 POSSIBLE INTO PARTS OF WRN NY.

NEEDLESS TO SAY CONVECTIVE TEMPERATURES WILL EASILY BE ATTAINED WITH

THIS INTENSE HEATING AND COMBINED WITH FRONTAL CONVERGENCE THERE IS

LITTLE DOUBT THAT SCATTERED-NUMEROUS THUNDERSTORMS WILL EVOLVE ALONG

THE ADVANCING BOUNDARY. ADDITIONALLY...500 MB FLOW ON THE ORDER OF

40-50KT WILL EXTEND ACROSS THIS DEVELOPING ACTIVITY AND ORGANIZED

SEVERE THUNDERSTORMS ARE EXPECTED TO DEVELOP BY EARLY AFTERNOON.

FORECAST SOUNDINGS SUGGEST VERY STEEP LAPSE RATES WILL BE IN PLACE

AS CONVECTION MATURES. AS A RESULT THERE IS INCREASING CONCERN THAT

DAMAGING WINDS MAY BE COMMON WITH WARM SECTOR CONVECTION. GIVEN THE

POTENTIAL FOR WIDESPREAD ORGANIZED SEVERE STORMS AN AREA FROM SRN OH

ACROSS MUCH OF WRN/NRN PA INTO CNTRL NY MAY BE UPGRADED TO A

MODERATE CATEGORICAL RISK IN LATER OUTLOOKS.

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I honestly don't think there is a big tornado threat.

I think there is a tornado threat tomorrow although not sure if I would say "big" tornado threat. Just south of the warm front where llvl winds stay backed and helicity is higher there looks to be solid potential.

There certainly are still issues though, especially with regards to timing...here at least. The strongest instability doesn't move in until close to 0z and by that time the strongest of the shear has moved off, however, we're still dealing with solid shear with a good directional component to the winds.

Can't wait to see 12z/18z data when I get out of work today.

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I found it a bit strange that there was no mention of tornadoes in the D2, although I did expect a 30% (wasn't expecting the MDT mention this early, to be honest).

I honestly don't think there is a big tornado threat.

I would agree with both of these statements. But these morning MCS ahead of a warm frontal surge can be very interesting, and catch people off guard. The EF2 in brooklyn back in August 2007 was of this variety, occurring at sunrise.

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Kind of a noisy picture tomorrow. That morning complex may mess around with things. Friday looked interesting.

After reviewing this morning's data, I feel pretty strongly that some type of complex (I wouldn't call it an MCS and I wouldn't call it a lonely supercell either) will move eastwardly through SE NY / W CT / NE PA and far N NJ tomorrow evening. I think the atmosphere would support the potential for a significant supercell / tornado in this region.

Wherever the MCS goes through, yes it will feel like an eternity getting the atmosphere to recover. However, I think a differential heating boundary will develop 15-18z / positive frontogenesis (warming from solar heating on SW side of complex and cooling / clouds NE side) and a notable warm front will develop. This will be the "tracks" for the complex later in the afternoon.

S NY / W CT / extreme N NJ seems to be where the models are threatening this potential, including the NYC metro area.

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After reviewing this morning's data, I feel pretty strongly that some type of complex (I wouldn't call it an MCS and I wouldn't call it a lonely supercell either) will move eastwardly through SE NY / W CT / NE PA and far N NJ tomorrow evening. I think the atmosphere would support the potential for a significant supercell / tornado in this region.

Wherever the MCS goes through, yes it will feel like an eternity getting the atmosphere to recover. However, I think a differential heating boundary will develop 15-18z / positive frontogenesis (warming from solar heating on SW side of complex and cooling / clouds NE side) and a notable warm front will develop. This will be the "tracks" for the complex later in the afternoon.

S NY / W CT / extreme N NJ seems to be where the models are threatening this potential, including the NYC metro area.

Yeah further sw in those areas was where it looked best in my quick glance of things. Could be a hell of a rain event too.

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After reviewing this morning's data, I feel pretty strongly that some type of complex (I wouldn't call it an MCS and I wouldn't call it a lonely supercell either) will move eastwardly through SE NY / W CT / NE PA and far N NJ tomorrow evening. I think the atmosphere would support the potential for a significant supercell / tornado in this region.

Wherever the MCS goes through, yes it will feel like an eternity getting the atmosphere to recover. However, I think a differential heating boundary will develop 15-18z / positive frontogenesis (warming from solar heating on SW side of complex and cooling / clouds NE side) and a notable warm front will develop. This will be the "tracks" for the complex later in the afternoon.

S NY / W CT / extreme N NJ seems to be where the models are threatening this potential, including the NYC metro area.

Where do you think the overnight/early morning complex will ride thru?

Secondarily..where do you think that diffuse warm frontal boundary sets up tomorrow?

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Yeah further sw in those areas was where it looked best in my quick glance of things. Could be a hell of a rain event too.

Agree. It could definitely be on the SW edge and it has all to do with the morning complex and evolution of the approaching SLP. The 6z NAM (and to some degree the globals) seemed to develop this warm front in the wake of the MCS and almost form a triple point in SE NY / W CT during the evening. The 6z GFS was much quicker with the whole ordeal.

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Where do you think the overnight/early morning complex will ride thru?

Secondarily..where do you think that diffuse warm frontal boundary sets up tomorrow?

The morning rainfall looks to move over N-C CT / MA and E NY, staying north of the NYC area. I have no idea where this diffuse boundary will setup, especially with the strong WAA throughout the day. It could end up somewhere in the Hudson Valley / W CT.

The limiting factors for tornadoes will be the degree of turning and raising LCL heights in the warm sector. So, the best tornado threat (probably with this possible cluster I am talking about) will be near this boundary and in an area that doesn't see the best destabilization but sufficient.

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After reviewing this morning's data, I feel pretty strongly that some type of complex (I wouldn't call it an MCS and I wouldn't call it a lonely supercell either) will move eastwardly through SE NY / W CT / NE PA and far N NJ tomorrow evening. I think the atmosphere would support the potential for a significant supercell / tornado in this region.

Wherever the MCS goes through, yes it will feel like an eternity getting the atmosphere to recover. However, I think a differential heating boundary will develop 15-18z / positive frontogenesis (warming from solar heating on SW side of complex and cooling / clouds NE side) and a notable warm front will develop. This will be the "tracks" for the complex later in the afternoon.

S NY / W CT / extreme N NJ seems to be where the models are threatening this potential, including the NYC metro area.

Interesting breakdown, the 6z nam looks very similar to the evolution you describe here. It will be interesting to see how backed the surface winds are by the late afternoon, though even sw - ssw winds suggest some nice directional shear in this setup. The srefs also seems to suggest quite a fine line between a nice setup and a lacking one to the southwest within the most unstable atmosphere

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The morning rainfall looks to move over N-C CT / MA and E NY, staying north of the NYC area. I have no idea where this diffuse boundary will setup, especially with the strong WAA throughout the day. It could end up somewhere in the Hudson Valley / W CT.

The limiting factors for tornadoes will be the degree of turning and raising LCL heights in the warm sector. So, the best tornado threat (probably with this possible cluster I am talking about) will be near this boundary and in an area that doesn't see the best destabilization but sufficient.

That's how the long track NH tornado formed. Not much instability but low LCLs and dews near 74 or so.

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