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JULY 2012 Severe Weather /Convection Discussion


NEG NAO

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I would like to add that the MCS that came through south Jersey and the Mid-Atlantic a few weeks ago which caused the derecho came through my area around midnight, in other words well after dark. The entire area had been baking in the sun all day and at that hour SBCAPE values were still very high. In other words, don't be discouraged just because we might have to wait until after sunset. In some aspects it may allow us to reach our maximum amount of destabilization.

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Seems like there are 2 triggers. The 1st one is for well north of the area but then the MCS rolls through here tomorrow evening and brings NYC and north into the game.

Well, technically there are two "events" but I wouldn't call them triggers. The first one is a (likely somewhat elevated) MCS that moves through Central New England early tomorrow morning along the warm front. I wouldn't be surprised to see some severe reports with this but it will likely decay by 18z-21z. The second is more cold front/height fall triggered back to our west over the OV...and we're sitting pretty along a mid level height gradient and baroclinic zone. With the surface low to our north over Albany and the mid level trough back to our west, we'll be underneath a plume of favorable 0-6km shear as well as low level shear and helicity...which is why you're seeing some high tornado probability numbers especially to our north and west on the NAM and SREF. But for our area, if we can develop an MCS that can ride the gradient, it should guide it directly through SE NY/N NJ including the NYC area...with the NAM indicating 3000 joules of cape over parts of NJ at 00z Thursday and 40 kts of effective shear..it shouldn't have trouble maintaining the potential for widespread damaging winds.

Edit: just saw Jake already responded with a similar idea.

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pretty scary looking numbers. Hope people are becoming aware of the raw potential here. Watching the early news today before my morning tee time, didn't really get the impression the severe potential was being hit too hard. Hopefully that changes tonight and tomorrow morning.
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The entire metro area is still very much in the game for severe weather, as far south as PHL. Thermodynamic parameters are impressive with 2500+ CAPE, bulk effective shear of 30-40kts across NJ/NYC, and helicity values up near 3 for late Thursday afternoon.

Still think highest supercell risk is NE PA/S NY and western New England.

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Wow, some of the data from the NAM seems to support a tornado threat around 3z as well? That kinda makes sense considering the H5 setup looks a little better.

Still though it's increasingly likely that we may see supercells and perhaps tornadoes to our north. I wouldn't worry about instability being a tad lower or whatever...it still looks just fine to me and I would sacrifice a bit of CAPE for more shear, low level helicity, and lower LCL heights. We have plenty of CAPE to work with and 2500J/KG should get the job done.

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As they should more than 24 hours out...though they might have mentioned that some of the storms could be severe as they usually do

That is exactly what I was getting at. I wouldn't have said typical summer storms though. I would have said strong storms with the potential for gusty winds. I don't think a bit of strong wording is out of the question. The thing is, the main weather guy (Mr. G) is on vacation this week so I wonder what they are using.

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LCL heights are a little high for the NYC area to see anything tornadic until after 00Z, but as of 9PM on Thursday they fall to ~1300 m with CAPE in excess of 3000 J/kg, 0-3 km SRH values around 300 m2/s2, a SWEAT of 352 and an EHI of 5.75. Bulk Richardson numbers also fall to around 40 in this time frame. 7-10PM looks to be the greatest threat in the immediate NYC metro area if anything surface-based can get going and advect into the area.

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LCL heights are a little high for the NYC area to see anything tornadic until after 00Z, but as of 9PM on Thursday they fall to ~1300 m with CAPE in excess of 3000 J/kg, 0-3 km SRH values around 300 m2/s2, a SWEAT of 352 and an EHI of 5.75. Bulk Richardson numbers also fall to around 40 in this time frame. 7-10PM looks to be the greatest threat in the immediate NYC metro area if anything surface-based can get going and advect into the area.

I was just going to post about the LCL's...That's another parameter where heading a little further northeast, perhaps sacrificing a little CAPE as Doug put it, can improve things...Its a fine boundary of elements that i'm sure we won't know exactly where it lines up until the hour of

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Big if here, but if a sustained supercell could get itself going and turn right of the mean wind (from about 250° to 280°) around 9PM it'd increase our 0-1 km SRH values to over 160 m2/s2 and our 0-3 km SRH values to in excess of 300 m2/s2. (Can anyone tell I just learned how to modify the hodograph in BUFKIT? :lol:). That'd be exciting. If only 500 hPa winds were a bit stronger...

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Ag3 is the man...but he made me think we are getting nothing.....does this look like late afternoon sun event?

Made the mistake of not pointing out I was talking about the morning stuff.

The evening/MCS stuff looks great as the great posters for convection have pointed out.

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Made the mistake of not pointing out I was talking about the morning stuff.

The evening/MCS stuff looks great as the great posters for convection have pointed out.

Thanks bud...right now the middlesex crew will be smoking anvils again...seems about right

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Thanks bud...right now the middlesex crew will be smoking anvils again...seems about right

Yeah I'm a bit concerned we're too far SE of the height falls/associated forcing to see big time convection but we're still very much in the game. I'm not crazy about events that take until after 7pm to get into our area as they usually die out. However, this particular event will feature more conducive dynamics thurs eve than during the afternoon, so hopefully we can maintain that convection into CNJ.

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Big if here, but if a sustained supercell could get itself going and turn right of the mean wind (from about 250° to 280°) around 9PM it'd increase our 0-1 km SRH values to over 160 m2/s2 and our 0-3 km SRH values to in excess of 300 m2/s2. (Can anyone tell I just learned how to modify the hodograph in BUFKIT? :lol:). That'd be exciting. If only 500 hPa winds were a bit stronger...

on the hodograph, drag the orange storm motion vector downward for a right turner. You have to click on the intersection of the orange storm motion vector and the 2 blue vectors that are calculating the area of the wind graph for helicity.

edit: I misread your post. I thought you were asking how to lol.

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on the hodograph, drag the orange storm motion vector downward for a right turner. You have to click on the intersection of the orange storm motion vector and the 2 blue vectors that are calculating the area of the wind graph for helicity.

edit: I misread your post. I thought you were asking how to lol.

:lol: No worries.

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This might be a dumb question but I see Upton is forecasting my area to have a South wind in the afternoon Thursday wouldn't this hurt my chances of seeing severe weather cause the marine layer will stabilize us???,

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This might be a dumb question but I see Upton is forecasting my area to have a South wind in the afternoon Thursday wouldn't this hurt my chances of seeing severe weather cause the marine layer will stabilize us???,

Depends on where you are located...

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Sorry im located in western Nassau county on the island more specific Im located by mineola just South of the northern state pkwy so im not the South shore witch is good I guess but im still on the island witch is bad Im gathering by other post

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...SYNOPSIS...

VIGOROUS SHORT WAVE TROUGH OVER THE SRN CANADIAN PRAIRIES WILL MOVE

SEWD AND REACH THE UPPER GREAT LAKES BY EARLY FRI...WITH A

MODERATELY FAST ZONAL FLOW REGIME EXISTING DOWNSTREAM ACROSS THE

NERN CONUS. AT THE SURFACE...A WARM FRONT WILL ADVANCE NEWD IN THE

NORTHEAST AND SHOULD REMAIN QUASI-STATIONARY ACROSS THE CNTRL GREAT

LAKES. A SERIES OF WEAK CYCLONES SHOULD BE PREVALENT ALONG THIS

BOUNDARY...WHICH WILL INTERSECT A SLOW-MOVING COLD FRONT MOVING SEWD

FROM THE MID-MS VALLEY TO THE SRN PLAINS. IN THE WEST...MID-LEVEL

RIDGING WILL BUILD FROM THE SOUTHWEST ACROSS THE INTERMOUNTAIN WEST.

...MID-MS/OH VALLEYS TO THE NORTHEAST/SRN NEW ENGLAND...

CONFIDENCE CONTINUES TO GROW WITH POTENTIAL FOR SCATTERED TO

NUMEROUS ORGANIZED SEVERE TSTMS...PARTICULARLY FROM THE MIDWEST TO

THE NORTHEAST. AN MCS SHOULD BE ONGOING ACROSS PARTS OF THE LOWER

GREAT LAKES...SUPPORTED BY AN INITIAL MID-LEVEL SPEED MAX AND ROBUST

LOW-LEVEL WAA ADVECTION. THIS SHOULD RETARD THE NERN ADVANCEMENT OF

THE WARM FRONT AND SUBSEQUENT EVOLUTION OF THIS ACTIVITY DOES BREED

UNCERTAINTY OVER WHERE THE FRONT WILL ULTIMATELY ANCHOR.

AN EXPANSIVE UNCAPPED WARM SECTOR CHARACTERIZED BY 90S/60S SURFACE

TEMPERATURES/DEW POINTS WILL CONTRIBUTE TO MODERATE TO STRONG

BUOYANCY THU AFTERNOON WITH MLCAPE OF 2000-4000 J/KG. A LARGE SWATH

OF 30-50 KT 700-500 MB WLYS WILL OVERLAP THIS INSTABILITY...AND WITH

WEAK MID-LEVEL HEIGHT FALLS COMBINING WITH FRONTAL

CONVERGENCE...THIS SETUP WILL YIELD SCATTERED TO NUMEROUS TSTMS

FORMING ALONG AND AHEAD OF THE COLD FRONT. THE UNIDIRECTIONAL WIND

PROFILES AND STEEP LOW-LEVEL LAPSE RATES SHOULD SUPPORT UPSCALE

GROWTH INTO SEVERAL CLUSTERS WITH BOWING SEGMENTS AND EMBEDDED

SUPERCELL STRUCTURES. DAMAGING WINDS /POTENTIALLY WIDESPREAD AND

SIGNIFICANT/ WILL BE THE PRIMARY THREAT.

A RELATIVELY NARROW CORRIDOR OF ENHANCED TORNADO RISK SHOULD DEVELOP

ALONG THE WARM FRONTAL ZONE WHERE EFFECTIVE SRH AND STRONGEST

DEEP-LAYER SHEAR WILL BE MAXIMIZED. ALTHOUGH PINPOINTING THIS

CORRIDOR IS DIFFICULT GIVEN LIKELIHOOD OF PRECEDING OVERNIGHT

CONVECTION...IT APPEARS MOST PROBABLE FROM PARTS OF NY INTO SRN NEW

ENGLAND. SOME CONVECTION-ALLOWING GUIDANCE SUGGESTS THAT DISCRETE

CONVECTION MAY FORM WITHIN A PERSISTING WAA REGIME THU AFTERNOON.

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