Marine Interpretation Message
Issued by NWS

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000
AGNT40 KWNM 291927
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
320 PM EDT FRI 29 APR 2016

.FORECAST DISCUSSION: MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT
.WEATHER FOR THE NORTH ATLANTIC OCEAN W OF 50W FROM 30N TO 50N.

A 1315Z RAPIDSCAT OVERPASS INDICATED SURFACE LOW CENTERED NEAR
37N73W WHICH WAS CONSISTENT WITH 12Z MODELS. IT ALSO RETURNED
GALES OVER THE GULF STREAM N OF THE LOW CENTER. WITH RAPIDSCAT
RETRIEVALS CONSISTENTLY HIGHER THAN ASCAT AM NOT YET BUYING INTO
THE GALES. HOWEVER AS LOW CONSOLIDATES SOMEWHAT TONIGHT INTO
EARLY SAT PLAN TO ADD SOME GALES OVER OUTER ANZ920 AND AZN910
ZONES ALONG GULF STREAM. WITH THE TYPICALLY UNDERDONE 12Z ECMWF
SURFACE WINDS INDICATING 30 KT OVER THE GULF STREAM WE HAVE
SLIGHTLY ABOVE AVERAGE FORECAST CONFIDENCE WITH THESE GALES. 12Z
MODELS ARE IN GOOD AGREEMENT OVER THE NEXT FEW DAYS THAT THE LOW
WILL SLIP E OF THE MID ATLC OFFSHORE WATERS SAT MORNING AS HIGH
PRES EXPANDS S AND SE FROM NEW ENGLAND SAT INTO SUN. MODELS THEN
ALL SHOW WARM FRONT LIFTING N THROUGH NT2 WATERS SAT NIGHT AND
SUN. IN RESPONSE TO A RELATIVELY FLAT UPPER SHORTWAVE
APPROACHING SOUTHERN NEW ENGLAND...A DEVELOPING SURFACE LOW
SHOULD EMERGE OFF THE NORTHERN MID ATLC COAST LATE SUN NIGHT AND
EARLY MON. WHEN COMPARED TO ITS PREVIOUS RUNS THE 12Z GFS
TRENDED FURTHER N WITH THE TRACK OF THIS LOW AND NOW IS IN
BETTER AGREEMENT WITH THE ECMWF/UKMET MON AND MON NIGHT. 12Z
MODELS ALL AGREE THAT THIS COULD BE ANOTHER MARGINAL GALE EVENT
FOR NORTHERN MID ATLC AND SOUTHERN NEW ENGLAND WATERS. AGAIN
WITH TYPICALLY UNDERDONE ECMWF AND UKMET WINDS UP TO 30
KT...WILL GO AHEAD AND ADD SOME GALES OVER OUTER ZONES MID ATLC
ZONES N OF BALTIMORE CANYON AND GEORGES BANK MON INTO MON NIGHT
WITH NEAR AVERAGE FORECAST CONFIDENCE.

BY TUE/WED MODELS AGREE THAT AMPLIFIED UPPER TROUGH WILL DEVELOP
OVER THE EASTERN US BUT OFFER SIGNIFICANT DIFFERENCES WITH UPPER
SHORTWAVE DETAILS. OF 12Z DETERMINISTIC MODELS GFS/GFSX/GLOBAL
GEM ARE GENERALLY STRONGER WITH SURFACE LOWS THAN UKMET/ECMWF.
LATEST GEFS AND ECMWF EPS MEANS ALSO SUGGESTING THAT GFS/GFSX/
GLOBAL GEM ARE TOO PROGRESSIVE AT MIDWEEK. FOR WED THROUGH THU
NIGHT WILL POPULATE WITH BLEND OF WEAKER LESS PROGRESSIVE 00Z
ECMWF AND 12Z ECMWF WHICH IS IN LINE WITH LATEST WPC MEDIUM
RANGE GUIDANCE. AT DAYS 4 THROUGH 6 FORECAST CONFIDENCE IS LOW.


SEAS...BOTH THE 12Z MULTIGRID WAVEWATCH III AND THE 12Z ECMWF
WAM WERE WELL INITIALIZED WITH THE W ATLC WAVE HEIGHTS THIS
MORNING. THESE MODELS ARE IN VERY GOOD AGREEMENT THROUGH SUN
NIGHT. THEN WITH GFS STRONGER THAN ECMWF WITH THE WINDS MON/MON
NIGHT...THE WAVEWATCH III IN TURN IS ABOUT 3 TO 5 FT HIGHER WITH
WAVE HEIGHTS NORTHERN NT2 AND GEORGES BANK AT THAT TIME. USED A
50/50 BLEND OF THE ABOVE GUIDANCE THROUGH TUE NIGHT BEFORE
SWITCHING TO A 50/50 BLEND OF THE 00Z AND 12Z ECMWF WAM WED
THROUGH THU NIGHT.

.EXTRATROPICAL STORM SURGE GUIDANCE...N/A.

.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
.ANZ900...GEORGES BANK EAST OF 68W...
     GALE POSSIBLE MON.

.NT2 MID ATLC WATERS...
.ANZ920...BALTIMORE CANYON TO THE GREAT SOUTH CHANNEL...
     GALE TONIGHT INTO SAT.
     GALE POSSIBLE MON.
.ANZ905...THE GREAT SOUTH CHANNEL TO THE HAGUE LINE...
     GALE POSSIBLE MON.
.ANZ910...EAST OF THE GREAT SOUTH CHANNEL AND SOUTH OF 39N...
     GALE TONIGHT INTO SAT.
     GALE POSSIBLE MON INTO MON NIGHT.

$$

.FORECASTER CLARK. OCEAN PREDICTION CENTER.


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