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Jan 23/24 Major Coastal Storm Discussion


Zelocita Weather

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Can any of the "Pros that blow him clear out of the water" comment on his take that Nor'easters typically slide north a little?I'm curious to hear more as to the truth of his comment and/or why the models are trending so hard east.

 

It trends east because of the confluence to the north. Why would it run into a brick wall of cold, dry air when it could skirt to the east in the warmer oceans?

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Posting Upton's coastal flood discussion. Right around 5 feet of surge is where real problems can start to happen. If it gets to that point hopefully its around low tide like they mention:

 

.TIDES/COASTAL FLOODING...
A POWERFUL NOR`EASTER WILL LIKELY RESULT IN MULTIPLE EPISODES OF
COASTAL FLOODING AROUND THE TIMES OF HIGH TIDE SAT INTO SUN.

THE TIDES OF PRIMARY CONCERN CONTINUE TO BE SAT MORNING AND
PARTICULARLY SAT EVE/NIGHT...WITH POTENTIAL GALE TO STORM FORCE
NE WINDS PILING WATER ALONG THE COAST.

POSITIVE TIDAL DEPARTURES OF 1 1/2 TO 2 FT ARE NEEDED FOR MINOR
COASTAL FLOODING AND 2 1/4 TO 3 FT FOR MODERATE COASTAL FLOODING
WITH THE SAT MORNING HIGH TIDE. PREFERENCE IS TO TAKE AN AVERAGE OF
BIAS CORRECTED ESTOFS/ETSS AND STEVENS SURGE GUIDANCE...WEIGHTED
TOWARDS THE HIGHER ESTOFS. ETSS AND STEVENS GUIDANCES APPEAR TO BE
TOO LOW BASED ON 040-050 NE WINDS RAMPING UP TO GALE THROUGH THE
TIME OF HIGH TIDE. BASED ON THESE EARLY NUMBERS WIDESPREAD MINOR TO
LOCALIZED MODERATE COASTAL FLOODING WOULD BE THE MOST LIKELY
SCENARIO...WITH BETWEEN 1 1/2 TO 3 FT OF SURGE.

FOR THE SAT EVENING HIGH TIDE...POSITIVE TIDAL DEPARTURES OF 2 TO 2
1/2 FT ARE NEEDED FOR MINOR COASTAL FLOODING...AND 3 TO 4 FT FOR
MODERATE COASTAL FLOODING. MODEL GUIDANCE FAIRLY CONSISTENT AND
COLLABORATED ON NE GALE TO STORM FORCE WINDS UNTIL THE TIME OF HIGH
TIDE WITH WINDS/SURGE POSSIBLY PEAKING DURING LOW TIDE SAT AFTERNOON
AT 3 TO 5 FT. THE QUESTION IS HOW MUCH THE WINDS BEGIN TO BACK AS WE
APPROACH THE TIME OF HIGH TIDE AND HOW MUCH THE SURGE FALLS. THE
TENDENCY IS FOR MODELS TO UNDERESTIMATE THE NORTHWARD BACKING OF
WINDS DURING INTENSE NOR`EASTERS TRACKING TO THE SE OF LI...WHICH
IN TURN ACTS TO REDUCE SURGE ALONG THE TRI-STATE AREA. ONCE AGAIN
AT THIS POINT...PREFERENCE IS TO TAKE AN AVERAGE OF BIAS CORRECTED
ESTOFS/ETSS AND STEVENS SURGE GUIDANCE...WEIGHTED TOWARDS THE
HIGHER ESTOFS. BASED ON THESE EARLY NUMBERS...POTENTIAL CONTINUES
FOR WIDESPREAD MODERATE COASTAL FLOODING...WITH BETWEEN 2 1/2 TO 4
1/4 FT OF SURGE AT HIGH TIDE. THIS SURGE RANGE MATCHES FAIRLY
WELL WITH SIMILAR COASTAL STORM ANALOGS...AND THE RANGE SHOULD BE
ABLE TO BE NARROWED AS MODELS COME INTO BETTER AGREEMENT WITH
STORM EVOLUTION.

THE MOST VULNERABLE AREAS TO MODERATE COASTAL FLOODING WILL BE
ALONG WESTERN/CENTRAL HALF OF LI SOUND...SOUTHERN BAYS OF WESTERN
LI AND NYC...AND THE TRADITIONALLY VULNERABLE PORTIONS OF NY
HARBOR...NEWARK BAYS...AND LOWER REACHES OF HACKENSACK AND
PASSAIC. NOTE...LOCALIZED MAJOR FLOODING IS POSSIBLE ALONG THE
SOUTH SHORE BACK BAYS OF LI...WHERE ONLY 3 1/2 FT OR SURGE IS
NEEDED FOR MAJOR FLOOD IMPACTS IN THE MOST VULNERABLE LOCALES.
ELSEWHERE IT WOULD TAKE 5 TO 6 FT OF SURGE TO REACH MAJOR FLOODING
LEVELS...WHICH IS NOT EXPECTED.

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Remember we are getting into the range that the GFS tends to be more accurate than the ECMWF. It nailed Juno during this time frame and it also picked up the chance of light snow last weekend before the NAM and ECMWF.

The GFS run today looked the most normal of its last 3-4 by far. It didn't do bizarre things with the precip shield and had less craziness on temps in the mid levels. The GFS was better with Juno because it was more a northern stream system, this one isn't so I don't know. The Euro though hasn't impressed me this winter so I'm less inclined to trust it than I once was

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Posting Upton's coastal flood discussion. Right around 5 feet of surge is where real problems can start to happen. If it gets to that point hopefully its around low tide like they mention:

 

.TIDES/COASTAL FLOODING...

A POWERFUL NOR`EASTER WILL LIKELY RESULT IN MULTIPLE EPISODES OF

COASTAL FLOODING AROUND THE TIMES OF HIGH TIDE SAT INTO SUN.

THE TIDES OF PRIMARY CONCERN CONTINUE TO BE SAT MORNING AND

PARTICULARLY SAT EVE/NIGHT...WITH POTENTIAL GALE TO STORM FORCE

NE WINDS PILING WATER ALONG THE COAST.

POSITIVE TIDAL DEPARTURES OF 1 1/2 TO 2 FT ARE NEEDED FOR MINOR

COASTAL FLOODING AND 2 1/4 TO 3 FT FOR MODERATE COASTAL FLOODING

WITH THE SAT MORNING HIGH TIDE. PREFERENCE IS TO TAKE AN AVERAGE OF

BIAS CORRECTED ESTOFS/ETSS AND STEVENS SURGE GUIDANCE...WEIGHTED

TOWARDS THE HIGHER ESTOFS. ETSS AND STEVENS GUIDANCES APPEAR TO BE

TOO LOW BASED ON 040-050 NE WINDS RAMPING UP TO GALE THROUGH THE

TIME OF HIGH TIDE. BASED ON THESE EARLY NUMBERS WIDESPREAD MINOR TO

LOCALIZED MODERATE COASTAL FLOODING WOULD BE THE MOST LIKELY

SCENARIO...WITH BETWEEN 1 1/2 TO 3 FT OF SURGE.

FOR THE SAT EVENING HIGH TIDE...POSITIVE TIDAL DEPARTURES OF 2 TO 2

1/2 FT ARE NEEDED FOR MINOR COASTAL FLOODING...AND 3 TO 4 FT FOR

MODERATE COASTAL FLOODING. MODEL GUIDANCE FAIRLY CONSISTENT AND

COLLABORATED ON NE GALE TO STORM FORCE WINDS UNTIL THE TIME OF HIGH

TIDE WITH WINDS/SURGE POSSIBLY PEAKING DURING LOW TIDE SAT AFTERNOON

AT 3 TO 5 FT. THE QUESTION IS HOW MUCH THE WINDS BEGIN TO BACK AS WE

APPROACH THE TIME OF HIGH TIDE AND HOW MUCH THE SURGE FALLS. THE

TENDENCY IS FOR MODELS TO UNDERESTIMATE THE NORTHWARD BACKING OF

WINDS DURING INTENSE NOR`EASTERS TRACKING TO THE SE OF LI...WHICH

IN TURN ACTS TO REDUCE SURGE ALONG THE TRI-STATE AREA. ONCE AGAIN

AT THIS POINT...PREFERENCE IS TO TAKE AN AVERAGE OF BIAS CORRECTED

ESTOFS/ETSS AND STEVENS SURGE GUIDANCE...WEIGHTED TOWARDS THE

HIGHER ESTOFS. BASED ON THESE EARLY NUMBERS...POTENTIAL CONTINUES

FOR WIDESPREAD MODERATE COASTAL FLOODING...WITH BETWEEN 2 1/2 TO 4

1/4 FT OF SURGE AT HIGH TIDE. THIS SURGE RANGE MATCHES FAIRLY

WELL WITH SIMILAR COASTAL STORM ANALOGS...AND THE RANGE SHOULD BE

ABLE TO BE NARROWED AS MODELS COME INTO BETTER AGREEMENT WITH

STORM EVOLUTION.

THE MOST VULNERABLE AREAS TO MODERATE COASTAL FLOODING WILL BE

ALONG WESTERN/CENTRAL HALF OF LI SOUND...SOUTHERN BAYS OF WESTERN

LI AND NYC...AND THE TRADITIONALLY VULNERABLE PORTIONS OF NY

HARBOR...NEWARK BAYS...AND LOWER REACHES OF HACKENSACK AND

PASSAIC. NOTE...LOCALIZED MAJOR FLOODING IS POSSIBLE ALONG THE

SOUTH SHORE BACK BAYS OF LI...WHERE ONLY 3 1/2 FT OR SURGE IS

NEEDED FOR MAJOR FLOOD IMPACTS IN THE MOST VULNERABLE LOCALES.

ELSEWHERE IT WOULD TAKE 5 TO 6 FT OF SURGE TO REACH MAJOR FLOODING

LEVELS...WHICH IS NOT EXPECTED.

 

As Bryan Norcross explained so well after Sandy, the NWS and others continue to do a horrible job communicating coastal flooding data and risks in a way that the general public can understand.  Even in this disco, they switch between "positive departures" and "surge" without defining exactly what they mean.  Also, any time they talk about coastal flooding, now, they ought to include the much greater departures seen for Sandy, so that people know the flooding that might come, even if "major" is nowhere near Sandy levels, which were generally 3-4 feet greater than Irene or March 1962 or other great storms in the past (or this one, even in the worst case).  

 

http://www.wunderground.com/blog/bnorcross/unraveling-the-sandy-stormsurge-forecast 

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