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Thanksgiving Eve SECS/MECS Discussion II

gkrangers

By gkrangers,
in New York City Metro

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NEG NAO

NEG NAO

Posted
Posted

RGEM is more reliable than the NAM by a considerable margin. As the day progresses the RGEM will become the go to model until the HRRR and RAP get into their wheelhouse. 

After this evening it is NOWCASTING Time . Look how many times the HRRR as an example was wrong as we got very close to the start of the events during the summer months - best bet is start looking at up to date temp information at all levels and radars from all around the region once we get past midnight tonight - no model is going to accurately pinpoint rain/snow/sleet lines when a few miles either way is critical for millions of people.........

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mob1

mob1

Posted
Posted

Not having any sun out right now might help also

Not for DP's, you want to see clear skies for at least a good part of the night. Again, this is only because of how marginal it is, if we had a very significant warm push at the mid levels, this would all be moot.
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christhesnowman

christhesnowman

Posted
Posted

I think there might be some wide variations in totals across the city and maybe even northern Nassau. JFK I could see walking away with a slushy 1-2" and Yonkers with 6". 

agree, I guess when I refer to city I mean manhattan,  im with you I think jfk will see next to nothing, as u head into the heights and yonkers could go 3-6, far northwest nj could be jackpot here at 12 plus mt holly may need to bump it up a bit

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NEG NAO

NEG NAO

Posted
Posted

Not for DP's, you want to see clear skies for at least a good part of the night. Again, this is only because of how marginal it is, if we had a very significant warm push at the mid levels, this would all be moot.

check out the plummeting DP's at Newark this morning

 

http://www.wunderground.com/history/airport/KEWR/2014/11/25/DailyHistory.html?req_city=NA&req_state=NA&req_statename=NA

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SnowGoose69

SnowGoose69

Posted
Posted

12Z RGEM since this is a highly regarded model and coming into its best range..

 

http://models.weatherbell.com/cmc/20141125...acc_neng_17.png

 

The only thing suspicious on the RGEM, and there may be an explanation if the 700 low is crossing the area in that window (I did not have time to look) was that it showed the R/S line backing NW 18-21Z after it collapsed from 15-18z....if the mid level low isnt moving over the area from 18-21 thats probably an erroneous signal

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PB GFI

PB GFI

Posted
Posted

MT HOLLY .

 

SNOW WATER RATIOS PER INTERNAL COLLABORATION 6 TO 1 I-95 MAYBE
8 TO 1 KRDG TO KABE AND
10 OR 12 TO 1 FOR THE POCONOS.

FROM THE MID SHIFT BELOW...

MODEL GUIDANCE HAS COME INTO MUCH BETTER AGREEMENT OVERALL ON THE
EVOLUTION OF A STORM WHICH WILL DEVELOP OFF THE SERN CONUS CST ON
WED THEN TRACK NEWD DURG THE DAY ON WED. HOWEVER, WHILE THERE IS
GOOD AGREEMENT ON THE SYNOPTIC FEATURES, THERE REMAINS SOME
DISAGREEMENT ON THE THERMAL PROFILES AND SOME THE FINER DETAILS,
WHICH COULD PROVE IMPORTANT AS THE EVENT PLAYS OUT.

IT CONTINUES TO APPEAR AS THE AREAS N AND W OF PHILADELPHIA HAVE
THE BEST SHOT OF SEEING SUBSTANTIAL ELEVATION RELATED SNOW, WHICH
WILL IMPACT TRAVEL SIGNIFICANTLY. SRN AND ERN AREAS SE OF THE I95
CORRIDOR WILL LIKELY STAY ALL OR MOSTLY RAIN, SOME OF WHICH COULD
BE HEAVY AT TIMES. THE POTENTIAL FOR SOME PONDING OF RAIN ON
ROADWAYS AND POOR DRAINAGE AREAS IS POSSIBLE IN THESE LOCATIONS.

ADDITIONALLY, IT WAS QUITE WARM ON MONDAY AND WILL BE FAIRLY WARM
TODAY SO THE GROUND HAS IS WARM WHICH MAY NEGATE SOME ACCUMS,
ESPECIALLY AT THE ONSET ON ROADWAYS ETC, UNLESS THE SNOW COMES
DOWN HEAVY.

SO, ULTIMATELY IT REMAINS TO BE SEEN WHAT WILL WIN OUT IN THIS
AREA. THERE IS ALSO THE POTENTIAL FROM THE I-95 CORRIDOR N AND W
FOR SOME MESOSCALE BANDING WHICH COULD INCREASE ANY SNOWFALL
RATES, BUT THIS IS OFTEN DIFFICULT TO PREDICT MORE THAN A FEW
HOURS IN ADVANCE, AND AMOUNTS CAN VARY WIDELY BETWEEN THOSE AREAS
UNDER A BAND AND THOSE WHICH ARE NOT.

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NEG NAO

NEG NAO

Posted
Posted

MT HOLLY .

 

SNOW WATER RATIOS PER INTERNAL COLLABORATION 6 TO 1 I-95 MAYBE

8 TO 1 KRDG TO KABE AND

10 OR 12 TO 1 FOR THE POCONOS.

FROM THE MID SHIFT BELOW...

MODEL GUIDANCE HAS COME INTO MUCH BETTER AGREEMENT OVERALL ON THE

EVOLUTION OF A STORM WHICH WILL DEVELOP OFF THE SERN CONUS CST ON

WED THEN TRACK NEWD DURG THE DAY ON WED. HOWEVER, WHILE THERE IS

GOOD AGREEMENT ON THE SYNOPTIC FEATURES, THERE REMAINS SOME

DISAGREEMENT ON THE THERMAL PROFILES AND SOME THE FINER DETAILS,

WHICH COULD PROVE IMPORTANT AS THE EVENT PLAYS OUT.

IT CONTINUES TO APPEAR AS THE AREAS N AND W OF PHILADELPHIA HAVE

THE BEST SHOT OF SEEING SUBSTANTIAL ELEVATION RELATED SNOW, WHICH

WILL IMPACT TRAVEL SIGNIFICANTLY. SRN AND ERN AREAS SE OF THE I95

CORRIDOR WILL LIKELY STAY ALL OR MOSTLY RAIN, SOME OF WHICH COULD

BE HEAVY AT TIMES. THE POTENTIAL FOR SOME PONDING OF RAIN ON

ROADWAYS AND POOR DRAINAGE AREAS IS POSSIBLE IN THESE LOCATIONS.

ADDITIONALLY, IT WAS QUITE WARM ON MONDAY AND WILL BE FAIRLY WARM

TODAY SO THE GROUND HAS IS WARM WHICH MAY NEGATE SOME ACCUMS,

ESPECIALLY AT THE ONSET ON ROADWAYS ETC, UNLESS THE SNOW COMES

DOWN HEAVY.

SO, ULTIMATELY IT REMAINS TO BE SEEN WHAT WILL WIN OUT IN THIS

AREA. THERE IS ALSO THE POTENTIAL FROM THE I-95 CORRIDOR N AND W

FOR SOME MESOSCALE BANDING WHICH COULD INCREASE ANY SNOWFALL

RATES, BUT THIS IS OFTEN DIFFICULT TO PREDICT MORE THAN A FEW

HOURS IN ADVANCE, AND AMOUNTS CAN VARY WIDELY BETWEEN THOSE AREAS

UNDER A BAND AND THOSE WHICH ARE NOT.

excellent write-up - lets see if any of the shorter range models such as the HRRR start showing any mesocale banding - HRR had difficulties with severe weather  - T-Storms in the summer

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NJwinter23

NJwinter23

Posted
Posted

here is the 40km NAM soundings for JFK http://68.226.77.253/text/NAM212/NAM212_Kjfk.txt

 

The thing is, if the warming happens ABOVE 700MB, unless those layers are saturated it wont matter because the precip will be made BELOW that level. Snow is usually produced at 700MB...interesting situation, I dont believe I remember a sounding where the warming was above 700MB and the rest of the column was below 0C.

 

The snow growth zone is highlighted pretty well on bufkit for KEWR here. In this storm it is unusually high up in the 400-500mb range. Most importantly, notice the omegas are well below this layer as well on the nam...The GFS is quite similar... i cant justify as a forecast of more than 2-4 at Newark, and 1-3 in NYC proper

 

post-402-0-58085700-1416933586_thumb.png

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heavy_wx

heavy_wx

Posted
Posted

SO, ULTIMATELY IT REMAINS TO BE SEEN WHAT WILL WIN OUT IN THIS

AREA. THERE IS ALSO THE POTENTIAL FROM THE I-95 CORRIDOR N AND W

FOR SOME MESOSCALE BANDING WHICH COULD INCREASE ANY SNOWFALL

RATES, BUT THIS IS OFTEN DIFFICULT TO PREDICT MORE THAN A FEW

HOURS IN ADVANCE, AND AMOUNTS CAN VARY WIDELY BETWEEN THOSE AREAS

UNDER A BAND AND THOSE WHICH ARE NOT.

 

The 12z GFS had some decent frontogenesis associated with the ageostrophic circulation in the right entrance region of the upper level jet streak. For the NYC metro (with lift on the "warm" side of the circulation), the frontogenetic forcing was most significant around 700 mb and between 12 and 18z Wed. You can also see below that EPV is slightly negative into LI so perhaps some CSI or more likely, conditional instability is present as well. That supports the banding idea within precip generally enhanced by the mesoscale frontogenesis.

 

FRNT700gfs212F30.png

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heavy_wx

heavy_wx

Posted
Posted

The snow growth zone is highlighted pretty well on bufkit for KEWR here. In this storm it is unusually high up in the 400-500mb range. Most importantly, notice the omegas are well below this layer as well on the nam...The GFS is quite similar... i cant justify as a forecast of more than 2-4 at Newark, and 1-3 in NYC proper

 

Just to clarify, I believe that is the dendritic snow growth zone (-12C to -18C); other crystal types like needles/columns will grow in the warmer layer depicted by the models with most negative omega. But yeah, dendrites will grow faster, aggregate more efficiently and produce higher snow ratios than other types of crystals.

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NJwinter23

NJwinter23

Posted
Posted

Just to clarify, I believe that is the dendritic snow growth zone (-12C to -18C); other crystal types like needles/columns will grow in the warmer layer depicted by the models with most negative omega. But yeah, dendrites will grow faster, aggregate more efficiently and produce higher snow ratios than other types of crystals.

 

Yes that is correct. You would want to see the omegas in that layer though if we were gonna find a way to get bombed with a marginal boundary layer...ratios should be pretty terrible in this one as you implied

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Stormlover74

Stormlover74

Posted
Posted

good move by Upton on holding off on issuing a warning for the immediate metro as there is still the possibility the watch here never makes it to a warning in certain areas because of borderline temps.....

http://kamala.cod.edu/nj/latest.wwus41.KOKX.html

My guess is city and urban nj get advisories. Perhaps warnings for Western union/Essex and the rest of Passaic/Bergen

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