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Potential Major East Coast Storm on Saturday Part 2


IsentropicLift

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LOL at these new ads on here when you're on a phone, I just found myself wondering why someone attached a photo of a chick in prison gear to their post

She told the forum it wouldn't snow.

 

It will be interesting to see whether the GFS is correct in scaling back the amount of precipitation after the ECMWF had increased it.

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18z Rgem took away the majority of the rain for NYC.

Only 6mm of precip now as rain.

11mm as snow

4mm as ice

 

Always be careful with off hour RGEM runs, they tend to do odd things sometimes although this one did not so much.  It changes the front end over to ice faster but has more snow on the back end.

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Yep, we've been through this situation many times in Middlesex/Union/SI.  My guess is this is a reflection of how complex the system is and slight differences in opinions between the offices and lack of time to reach consensus at the "boundary conditions" lol - one office will be right and one won't, since the discontinuity, as shown, is an impossible outcome (unless there were perfect banding that stopped right at the borders of these counties).  

 

"Opinion" being the keyword, because not only does actual data play a big part in putting together a forecast but the forecasters opinion does as well, albeit a smaller role.

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does this automatically update.. 

 

Yes... it updates hourly starting around 20 minutes past the hour. That's probably why you see the images "jump" when its in the middle an update cycle which takes about 15 minutes to produce all the images.

 

http://www.atmos.albany.edu/student/ppapin/lb13_img/hrrr/hrrr_ncep_2d_alb.php

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not such great collaboration, as often happens along I-95 between Middlesex County in the Mt. Holly CWA and Union/SI in the Upton CWA.  1-2" for my area in northern Middlesex, adjacent to 3-4" amounts immediately to our north and east and you'd figure we'd get at least what SI gets, given that we're further inland at the same latitude.  The do have 0.10-0.25" of freezing rain falling in our area, though, which would surprise me.  

 

http://www.weather.gov/phi/winter

 

 

StormTotalSnowRange.png

 

StormTotalIceWebFcst.png

 

Just watched the NYC TV forecasts and they're even further apart than the NWS offices.  Just comparing NYC metro forecasts (NYC proper, i.e., the 5 boroughs, NENJ adjacent to NYC within ~5 miles of the Hudson/Arthur Kill, and western Nassau), Channel 7 had 1-3" forecast, Channel 2 had 0-2" forecast, and Channel 4 had 2-5" forecast, while TWC has 3-5" forecast.  I guess the bottom line is this variability simply reflects how complex and difficult this forecast is. 

 

Talk about discrepancies, although I'd rather have that than having them all hugging the same model.  Would be cool if they included a little graphic highlighting their forecast basis, like the NWS does in the AFD.  

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This is now 2 major fails by the new GFS OP inside it's first 10 days . This upgraded model has the same S E bias that it's been notorious for . The fact that this models glaring weakness was not addressed in its upgrade is a sad reminder that there are some who really believe it didn't exist.

0 for 2 and another 3 day OTS forecast gets put on file.

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This is now 2 major fails by the new GFS OP inside it's first 10 days . This upgraded model has the same S E bias that it's been notorious for . The fact that this models glaring weakness was not addressed in its upgrade is a sad reminder that there are some who really believe it didn't exist.

0 for 2 and another 3 day OTS forecast gets put on file.

 

You only need to be accurate under 48 hours for a weather forecast. Most people only are concerned with this is my understanding.

GFS had the storm. Question is on the precip totals at this point.

I am little concerned when lookiing at the radar, GFS may be a little light on the precip.

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Having reviewed some of the latest data...and factoring in climatological normals...the projected track of the cyclone...and a few other items...I think many parts of Long Island are looking at a total snowfall in the 5 to 10 inch range...with about 3 to 6 inches before any changeover...and another 2 to 4 inches during the afternoon hours...assuming a change back to accumulating snow.  It is late January...a very favorable time of the year...the water is cold...the track is fairly favorable...not too much warm air is going to be advected onshore or even aloft...I don't see it getting too much warmer than maybe 1 C at 850 mb...and that is within the normal error range of most of these models.  TWT. 

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Having reviewed some of the latest data...and factoring in climatological normals...the projected track of the cyclone...and a few other items...I think many parts of Long Island are looking at a total snowfall in the 5 to 10 inch range...with about 3 to 6 inches before any changeover...and another 2 to 4 inches during the afternoon hours...assuming a change back to accumulating snow.  It is late January...a very favorable time of the year...the water is cold...the track is fairly favorable...not too much warm air is going to be advected onshore or even aloft...I don't see it getting too much warmer than maybe 1 C at 850 mb...and that is within the normal error range of most of these models.  TWT. 

 

What are your thoughts in my local area.( not that it can vary that much from the current forecast)

your call will catch alot of people off guard on the island.

 

Best.

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Having reviewed some of the latest data...and factoring in climatological normals...the projected track of the cyclone...and a few other items...I think many parts of Long Island are looking at a total snowfall in the 5 to 10 inch range...with about 3 to 6 inches before any changeover...and another 2 to 4 inches during the afternoon hours...assuming a change back to accumulating snow.  It is late January...a very favorable time of the year...the water is cold...the track is fairly favorable...not too much warm air is going to be advected onshore or even aloft...I don't see it getting too much warmer than maybe 1 C at 850 mb...and that is within the normal error range of most of these models.  TWT. 

Not too shabby without a high to the north of us. I've got a hunch this storm might surprise some of us. :stun:

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Having reviewed some of the latest data...and factoring in climatological normals...the projected track of the cyclone...and a few other items...I think many parts of Long Island are looking at a total snowfall in the 5 to 10 inch range...with about 3 to 6 inches before any changeover...and another 2 to 4 inches during the afternoon hours...assuming a change back to accumulating snow.  It is late January...a very favorable time of the year...the water is cold...the track is fairly favorable...not too much warm air is going to be advected onshore or even aloft...I don't see it getting too much warmer than maybe 1 C at 850 mb...and that is within the normal error range of most of these models.  TWT. 

I really hope you're right. The precip right now looks quite robust. Is it ahead of schedule?

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Updated at about 7pm though I think it's basically same sine 4pm...NEAR TERM /UNTIL MIDNIGHT TONIGHT/...

-- Changed Discussion --

FORECAST ON TRACK. MINOR UPDATES TO HOURLY T/TD/WINDS. MID AND

HIGH CLOUDS MOVING IN THIS EVENING FROM THE SW. LOWS WILL LIKELY

BE MET AT MOST LOCATIONS THIS EVENING.

-- End Changed Discussion --

&&

.SHORT TERM /MIDNIGHT TONIGHT THROUGH SATURDAY NIGHT/...

-- Changed Discussion --

THE MAIN FOCUS DURING THIS PERIOD WILL BE ON A QUICK MOVING BUT

RAPIDLY INTENSIFYING LOW PRESSURE SYSTEM AFFECTING THE REGION LATE

TONIGHT INTO SATURDAY EVENING.

MODELS IN GOOD AGREEMENT WITH SOUTHERN STREAM SHORTWAVE ENERGY OVER

TEXAS THIS AFTERNOON SLIDING TO THE EAST COAST THROUGH SAT

AFTERNOON...WHILE INTERACTING WITH A NORTHERN STREAM SHORTWAVE. THE

TREND HAS BEEN MORE PROGRESSIVE WITH THE INTENSIFYING

SHORTWAVE...WITH FULL PHASING AND CLOSED UPPER LOW DEVELOPMENT NE OF

THE REGION. SIMILARLY MODELS IN GOOD AGREEMENT WITH LOW PRESSURE

ALONG THE GULF COAST THIS AFTERNOON QUICKLY TRACKING NE TONIGHT

TOWARDS THE MID-ATLANTIC...AND NOW INSIDE OF THE 40/70 LAT/LON

BENCHMARK BY SATURDAY EVENING. ALL OF THE ABOVE POINTS TO AN INTENSE

BUT QUICK MOVING SYSTEM...WITH A FASTER...MORE WESTWARD TRACK...AND

SLIGHTLY WETTER THAN 24 HOURS AGO.

WITH NO HIGH TO THE NORTH OF THE REGION...A MARGINALLY COLD AIRMASS

WILL BE IN PLACE. THERMAL PROFILES AND EXPECTED EVAPORATIONAL

COOLING POINTS TOWARDS CONDITIONS COLD ENOUGH FOR PRECIP TO START AS

SNOW FOR ALL AREAS...MAINLY AFTER MIDNIGHT. SNOW SHOULD BECOME

MODERATE TO HEAVY FROM SW TO NE BTWN 4-7AM WITH STRONG WAA/MOISTURE

ADVECTION ALOFT AND STRONG LIFT FROM A COUPLE JET STRUCTURE WITH

STRONG FRONTOGENETIC FORCING. 1+ INCH SNOWFALL RATES POSSIBLE

SATURDAY MORNING.

AS INTENSIFYING LOW PRESSURE APPROACHES...AN E/SE LLJ JET BEGINS

TO ADVECT +1-4C 850-900MB AIR FROM S TO N FOR ALL BUT FAR NW

PORTIONS OF THE REGION BETWEEN 10Z AND 14Z. THIS SHOULD TRANSITION

PRECIP TO SLEET/FREEZING RAIN/RAIN FROM S TO N...BTWN 6AM AND 8AM

FOR NY/NJ METRO AND COASTAL AREAS...AND MID MORNING TO MIDDAY

WORKING INTO MUCH OF INTERIOR. INDICATIONS ARE THAT FOR THE NY/NJ

METRO AND COASTAL PLAIN...THAT ENOUGH WARM AIR GETS IN ALOFT FOR A

CHANGE TO MAINLY LIQUID PRECIP (RAIN/FREEZING RAIN) FROM MID

MORNING INTO EARLY AFTERNOON. A BIT FARTHER N AND W...THIS WILL

LIKELY BE A MIX OF SLEET...SNOW...AND FREEZING RAIN. WHILE

INTERIOR PORTIONS OF NE NJ...LOWER HUDSON VALLEY...AND SW CT WILL

LIKELY BE MAINLY SNOW THROUGH THE EVENT.

THERMAL PROFILES ARE ONE ISSUE...BUT THE OTHER ISSUE IS BANDING

PLACEMENT AND QPF. BASED ON WESTWARD ENSEMBLE OPER MODEL

TREND...HAVE INCREASED QPF BY ABOUT 1/4 INCH ACROSS THE BOARD FROM

PREVIOUS FORECAST. THE SWEET SPOT FOR DEFORMATION BANDING

POTENTIAL AND COLDER THERMAL PROFILE SAT AFTERNOON APPEARS TO BE

ACROSS INTERIOR SW CT AND NORTHEASTERN HUDSON VALLEY ZONES...WITH

THE HIGHEST SIGNIFICANT SNOWFALL THREAT.

IN TERMS OF SNOW AMOUNTS...THE TOUGH PART OF THIS FORECAST IS

THAT WE COULD BE LOOKING AT 1+ INCH SNOWFALL RATES AS WE ARE ARE

TRANSITIONING SATURDAY MORNING...SO A 1-2 HR TIMING DIFFERENCE IN

CHANGEOVER COULD BE A 1 TO 3 INCH DIFFERENCE IN SNOWFALL. FOR THE

NYC/NJ METRO AND COAST MOST OF THE SNOW ACCUM SHOULD BE LATE

TONIGHT INTO EARLY SAT MORNING. A GENERAL 2 TO 5 INCH RANGE STILL

LOOKS REASONABLE THERE...WITH HIGHER AMOUNTS ACROSS NE NJ...LOWER

HUDSON VALLEY...AND SW CT. AGAIN WITH BEST BANDING POTENTIAL AND

WESTWARD MODEL DRIFT ACROSS INTERIOR PORTIONS OF THE SW CT ZONES

AND PUTNAM COUNTY...5 TO 8 INCHES EXPECTED THERE...AND A WARNING

HAS BEEN ISSUED.

IN TERM OF FREEZING RAIN THREAT...ISALLOBARIC RESPONSE FROM THE

RAPIDLY INTENSIFYING LOW SHOULD KEEP WINDS MORE NORTHERLY THROUGH

THE PEAK OF THE STORM. THIS TYPICALLY PROMOTES COLD AIR DRAINAGE

DOWN THE HUDSON AND CT RIVER VALLEYS...WHICH SHOULD HOLD SURFACE

TEMPS NEAR FREEZING OR JUST BELOW FOR NY/NJ METRO...NORTH SHORE

OF LI...AND COASTAL SW/SC CT THROUGH THE MID TO LATE MORNING(AFTER

CHANGEOVER). SO POTENTIAL OF UP TO TENTH OF AN INCH OF ICE

ACCRETION AWAY FROM SOUTH COASTAL LI/NYC IN THE MORNING. HEAVIEST

ICE ACCRETION LIKELY ACROSS SOUTHERN CT...WITH WARMER AIR WORKING

IN ALOFT BUT SURFACE TEMPS REMAINING NEAR OR SLIGHTLY BELOW

FREEZING. POTENTIAL FOR UP TO 1/4 INCH OF ICE HERE.

IN TERMS OF WINDS...NORTHERLY WINDS INCREASE SAT

AFTERNOON...PEAKING IN THE AFTERNOON AND EVENING. GENERALLY 10 TO

20 MPH WITH GUSTS IN THE 30S. A PEAK GUST TO 40 MPH IS POSSIBLE

ACROSS EASTERN LI/SE CT.

ACROSS LI AND COASTAL CT...HEAVY RAIN SAT MORN/EARLY AFT AND EARLIER

SNOW MAY RESULT IN SOME MINOR URBAN FLOODING ISSUES. ESPECIALLY

ALONG THE COAST DURING TIMES OF HIGH TIDE LATE MORNING INTO EARLY

AFTERNOON.

THERMAL PROFILES APPEARS TO COOL ENOUGH BY MID TO LATE AFTERNOON

FOR A CHANGE BACK TO SLEET THEN SNOW DOWN TO COAST...BUT QUESTION

WILL BE HOW MUCH PRECIP IS LEFT. UNCERTAINTY EXISTS ON HOW FAR

SOUTH BANDING POTENTIAL EXISTS...AND WILL NOT LIKELY BECOME CLEAR

UNTIL SAT AFTERNOON. WITH PROGRESSIVE TREND OF THE UPPER TROUGH

EXPECTING ADDITIONAL ACCUM FOR THE METRO/COAST TO BE LIGHT

(COATING TO 3 INCHES) MID-LATE SAT AFT INTO EARLY SAT EVE FOR

NY/NJ METRO AND COAST AS COLDER AIR WORKS IN. AS MENTIONED

BEFORE...THE SWEET SPOT FOR DEFORMATION BANDING SAT AFTERNOON

STILL APPEARS TO BE ACROSS INTERIOR SOUTHERN CONNECTICUT ZONES.

ANY SNOW COMES TO AND END LATE SAT AFTERNOON/EARLY SAT

EVENING...WITH BREEZY AND NEAR SEASONABLE TEMPS SAT NIGHT.

-- End Changed Discussion --

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What are your thoughts in my local area.( not that it can vary that much from the current forecast)

your call will catch alot of people off guard on the island.

 

Best.

 

Probably 6 to 12 inches over western Passaic / eastern Sussex Counties...certainly no changeover to liquid...maybe a brief period of sleet at the height of the storm.

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Pamela ...what's your thoughts .for Nyc and 5 boroughs ?

 

Probably 4 to 8 inches...least in Staten Island...where the warming aloft will intrude first...and that afternoon band appears to be focused a bit to the east...so they have two things going against them. 

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