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Sept 11-12 Wednesday, Thursday Storm Threat


free_man

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My God...if they are able to develop discrete cells tomorrow across central/upstate NY and VT there could be a strong tornado tomorrow.

 

I agree with Kevin, Thursday is the day for us down here.  We may not have the EML, but lapse rates still look more than sufficient and shear is quite strong.  

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We really won't know the lapse rate situation for us until Tuesday night or Wednesday.  It seems unlikely we will still have an EML present, however, we could still have mlvl lapse rates on order of 6.5-7 C/KM but this will really depend on contamination and if there are any showers around.  The GFS does have some morning crap around which weakens lapse rates.

 

EML or not though on Thursday, these are some pretty strong dynamics with intense forcing so if we even manage 1500 Cape or so that should lead to pockets of isolated severe weather

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Just wow for tomorrow. The 12z NAM continues to look very impressive for upstate NY and into NNE. Same for 9z SREF.

May not be appropriate to use the "D" word, but the NAM shows one heck of a squall line. SREF has 70% probabilities for a Derecho Composite Value of >5. Extreme instability, strong wind speeds and shear and having that EML is a big piece to the puzzle. Timing, cloud-cover and overcoming any CIN will be critical.

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Just wow for tomorrow. The 12z NAM continues to look very impressive for upstate NY and into NNE. Same for 9z SREF.

May not be appropriate to use the "D" word, but the NAM shows one heck of a squall line. SREF has 70% probabilities for a Derecho Composite Value of >5. Extreme instability, strong wind speeds and shear and having that EML is a big piece to the puzzle. Timing, cloud-cover and overcoming any CIN will be critical.

Judging by some of the parameters mentioned here, I doubt there will be any trouble smashing the cinh too.

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Judging by some of the parameters mentioned here, I doubt there will be any trouble smashing the cinh too.

The NAM actually holds the squall line intact down to the Albany area early tomorrow afternoon before it collapses. Will be interesting to see how the rest of the 12z guidance handles/trends.

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Just wow for tomorrow. The 12z NAM continues to look very impressive for upstate NY and into NNE. Same for 9z SREF.

May not be appropriate to use the "D" word, but the NAM shows one heck of a squall line. SREF has 70% probabilities for a Derecho Composite Value of >5. Extreme instability, strong wind speeds and shear and having that EML is a big piece to the puzzle. Timing, cloud-cover and overcoming any CIN will be critical.

Indeed it does. Depending on convective mode sig tornadoes aren't out of the question initially before things consolidate into an MCS. On the leading edge of the EML plume I could see places like the Berkshires through the Monadnocks getting some good storms Tuesday night.

With ridge overhead on Wednesday and 700mb temps >10C we should be capped but we're going to be extremely unstable with the core of the EML overhead. NNE could rock again Wednesday. 

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Indeed it does. Depending on convective mode sig tornadoes aren't out of the question initially before things consolidate into an MCS. On the leading edge of the EML plume I could see places like the Berkshires through the Monadnocks getting some good storms Tuesday night.

With ridge overhead on Wednesday and 700mb temps >10C we should be capped but we're going to be extremely unstable with the core of the EML overhead. NNE could rock again Wednesday. 

No love for us in CT/RI and Eastern MA?

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Indeed it does. Depending on convective mode sig tornadoes aren't out of the question initially before things consolidate into an MCS. On the leading edge of the EML plume I could see places like the Berkshires through the Monadnocks getting some good storms Tuesday night.

With ridge overhead on Wednesday and 700mb temps >10C we should be capped but we're going to be extremely unstable with the core of the EML overhead. NNE could rock again Wednesday. 

Wednesday has some fat CAPE and nice lapse rates in SNE, but as mentioned, the capping and CIN will be difficult to overcome. Not much of a trigger. It's too bad...12z NAM has a 850-500mb lapse rate of 7.1C/km with 3264J of MLCAPE at BDL 18z Wed.

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Actually, having such strong capping Wednesday is a good thing really.  Besides the incredible Cape profiles, there really isn't much shear on Wednesday...although fat cape profiles with a ton of cape and little shear can be awesome but the less in the way of activity around Wednesday, the lesser chance of cloud debris or any muck weakening lapse rates Thursday.  

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If any discrete action gets going tomorrow...just wow.  Also have to watch Wednesday across VT/NH and western ME for any discrete that can get going.  The environment both days will be prime for strong tornadoes.  

 

Agreed, especially Wednesday IMO.  That's my ideal type severe day in New England...  It's like fishing for Tuna instead of bluegills.  Probably come back empty handed, but if not, wow.

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NWS BTV from overnight:

WITH OUR REGION
IN THE WARM SECTOR WITH POTENTIAL FOR SOME PARTLY SUNNY CONDITIONS
DEVELOPING. THIS SHOULD HELP DESTABILIZE THE AIR MASS WITH SBCAPE
VALUES 1500-2500 J/KG FROM THE GREEN MTS WWD ACROSS THE CHAMPLAIN
VLY AND NRN NY. LESSER INSTABILITY EXPECTED ACROSS FAR NERN VT.
THE INSTABILITY WILL BE BOLSTERED BY AN ELEVATED MIXED LAYER
PLUME WITH 700-500MB LAPSE RATES LIKELY AROUND 7C/KM ALOFT. THIS
VERY DYNAMIC PATTERN WILL BE HIGHLIGHTED BY RIBBON OF STRONG WLY
DEEP-LAYER SHEAR IN PLACE (SFC-6KM SHEAR AROUND 40 KTS). SOME OF
THE LOW-LEVEL SHEAR PROFILES ARE OFF THE CHART WITH 00Z NAM
SHOWING 850MB WINDS OF 63KTS AT KMSS AND SFC-1KM HELICITY VALUES
OF 500+ M2/S2 AT 18Z TUESDAY. THE 00Z GFS IS A BIT WEAKER WITH
40-45 KT WINDS AT 850MB AND SFC-1KM SRH AROUND 375 M2/S2.
HODOGRAPHS ARE STRONGLY CURVED AREAWIDE IN BOTH MODEL SOLNS. ONLY
QUESTION WILL BE A FORCING MECHANISM FOR CONVECTIVE
DEVELOPMENT...AS THERE DOESN/T APPEAR TO BE WELL-DEFINED FEATURE
IN PREVAILING WLY FLOW AND MID- LEVEL HEIGHTS ARE NEUTRAL.
CONDITIONAL PROBABILITY OF SEVERE IS VERY HIGH...AND ANY SUBTLE
SHORTWAVE OR OROGRAPHIC FORCING WOULD LIKELY LEAD TO POTENTIAL
ISOLATED SUPERCELLS.

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NWS BTV from overnight:

WITH OUR REGION

IN THE WARM SECTOR WITH POTENTIAL FOR SOME PARTLY SUNNY CONDITIONS

DEVELOPING. THIS SHOULD HELP DESTABILIZE THE AIR MASS WITH SBCAPE

VALUES 1500-2500 J/KG FROM THE GREEN MTS WWD ACROSS THE CHAMPLAIN

VLY AND NRN NY. LESSER INSTABILITY EXPECTED ACROSS FAR NERN VT.

THE INSTABILITY WILL BE BOLSTERED BY AN ELEVATED MIXED LAYER

PLUME WITH 700-500MB LAPSE RATES LIKELY AROUND 7C/KM ALOFT. THIS

VERY DYNAMIC PATTERN WILL BE HIGHLIGHTED BY RIBBON OF STRONG WLY

DEEP-LAYER SHEAR IN PLACE (SFC-6KM SHEAR AROUND 40 KTS). SOME OF

THE LOW-LEVEL SHEAR PROFILES ARE OFF THE CHART WITH 00Z NAM

SHOWING 850MB WINDS OF 63KTS AT KMSS AND SFC-1KM HELICITY VALUES

OF 500+ M2/S2 AT 18Z TUESDAY. THE 00Z GFS IS A BIT WEAKER WITH

40-45 KT WINDS AT 850MB AND SFC-1KM SRH AROUND 375 M2/S2.

HODOGRAPHS ARE STRONGLY CURVED AREAWIDE IN BOTH MODEL SOLNS. ONLY

QUESTION WILL BE A FORCING MECHANISM FOR CONVECTIVE

DEVELOPMENT...AS THERE DOESN/T APPEAR TO BE WELL-DEFINED FEATURE

IN PREVAILING WLY FLOW AND MID- LEVEL HEIGHTS ARE NEUTRAL.

CONDITIONAL PROBABILITY OF SEVERE IS VERY HIGH...AND ANY SUBTLE

SHORTWAVE OR OROGRAPHIC FORCING WOULD LIKELY LEAD TO POTENTIAL

ISOLATED SUPERCELLS.

 

The whole discussion is awesome.  Banacos would know something about this lol

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