Marine Interpretation Message
Issued by NWS

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000
AGNT40 KWNM 301951
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
345 PM EDT SAT 30 APR 2016

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

12Z RAPIDSCAT OVERPASS DID RETURN SOME GALES OUTER MID ATLC
ZONES N OF BALTIMORE CANYON. HOWERVER THE 15Z ASCAT OVERPASS
THEN CONFIRMED THAT THE NE GALES HAD SHIFTED JUST S AND SE OF
OUTER MID ATLC ZONES ANZ920 AND ANZ910. 12Z MODELS ARE IN GOOD
AGREEMENT OVER THE NEXT COUPLE DAYS THAT WINDS WILL CONTINUE TO
DIMINISH THROUGH TONIGHT AS A HIGH PRES RIDGE SLOWLY MOVES E
ACROSS THE NEW ENGLAND AND MID ATLC OFFSHORE WATERS TONIGHT AND
SUN. THEN LATER SUN INTO SUN NIGHT MODELS ALL INDICATE THAT THE
STALLED FRONT OVER THE SOUTHERN MID ATLC WATERS WILL LIFT N AS A
WARM FRONT WITH LOW PRES DEVELOPING ALONG THE FRONT NEAR THE
NORTHERN MID ATLC COAST EARLY MON. OVER THE LAST 24 HOURS MODELS
HAVE ALL TRENDED N WITH TRACK OF THIS SURFACE LOW. 12Z
GFS/ECMWF/ UKMET ALL MOVE THE SURFACE LOW NE NEAR THE MAINE
COAST LATE MON INTO EARLY MON NIGHT. 12Z GFS AND 12Z ECMWF ARE
WEAKER THAN PREVIOUS RUNS WITH SW WINDS OVER NORTHERN MID ATLC
WATERS. HOWEVER WITH THE TYPICALLY UNDERDONE ECMWF AND UKMET
SURFACE WINDS STILL UP TO 30 KT OVER THE GULF STREAM WILL RETAIN
THE MARGINAL GALES LATE MON/MON NIGHT WITH NEAR AVERAGE FORECAST
CONFIDENCE. WITH THE MORE NORTHERN TRACK MODELS HAVE ALSO COME
INTO AGREEMENT THAT GALES COULD DEVELOP OVER THE GULF OF MAINE N
ANE NE OF THE WARM FRONT MON. GIVEN NEARLY UNANIMOUS MODEL
SUPPORT WILL ADD GALES TO GULF OF MAINE LATE MON.

BY MON NIGHT AND TUE AS THE COLD FRONT APPROACHES THE VA
TIDEWATER AREA GFS AND ECMWF NOW INDICATE THAT MULTIPLE SURFACE
LOWS WILL DEVELOP AND MOVE NE ACROSS WATERS ALONG THE FRONT.
BOTH 12Z RUNS HAVE TRENDED STRONGER WITH SW WINDS SE OF THE
FRONT. HOWEVER 12Z GFS APPEARS OVERDONE IN ADVERTISING GALE
FORCE WINDS. WILL CAP WINDS AT 30 KT BUT WILL HAVE TO WATCH
MODEL TRENDS AS THERE IS SOME POTENTIAL FOR WINDS TO REACH GALE
OVER OUTER NT2 WATERS NEAR THE GULF STREAM. MODELS THEN DIVERGE
SIGNIFICANTLY BY MIDWEEK. ALTHOUGH MODELS GENERALLY AGREE THAT
AN AMPLIFIED UPPER TROUGH/CLOSED LOW WILL MOVE INTO THE EASTERN
US THERE ARE SIGNIFICANT DIFFERENCES WITH THE EVOLUTION OF THE
ASSOCIATED SURFACE LOW DEVELOPMENT(S) NEAR THE COAST WED/THU.
OVER PAST FEW DAYS MODELS HAVE SHOWN LITTLE RUN TO RUN
CONSISTENCY AND HAVE LITTLE TO NO FORECAST CONFIDENCE IN ANY ONE
DETERMINISTIC MODEL SOLUTION. TO KEEP SOME CONTINUITY WITH BOTH
PREVIOUS OPC GRIDS AND WITH WPC MEDIUM RANGE WILL USE A 50/50
BLEND OF THE 00Z ECMWF AND 12Z ECMWF WED NIGHT THROUGH FRI
NIGHT. WILL AGAIN REITERATE THAT HAVE VERY LOW CONFIDENCE AT
DAYS 4 THROUGH 6.

.SEAS...WAVE HEIGHTS OVER INNER WATERS S OF NEW ENGLAND EXENDING
S TO NEAR CAPE HATTERAS ARE 1 TO 2 FT CONTINUE ABOUT 1 TO 2 FT
HIGHER THAN THE 12Z WAVEWATCH III AND 12Z ECMWF WAM. AFTER THESE
INITIAL ADJUSTMENTS USED THE 12Z WW3 THROUGH MON NIGHT. THEN
BASED ON MODEL PREFERENCE IN THE MEDIUM RANGE USED 12Z ECMWF WAM
TUE THROUGH WED...THEN A 50/50 BLEND OF 00Z AND 12Z ECMWF WAM
WED NIGHT THROUGH FRI NIGHT.

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

.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
.ANZ800...GULF OF MAINE...
     GALE MON.
     GALE POSSIBLE MON NIGHT.

.NT2 MID ATLC WATERS...
.ANZ920...BALTIMORE CANYON TO THE GREAT SOUTH CHANNEL...
     GALE MON.
.ANZ905...THE GREAT SOUTH CHANNEL TO THE HAGUE LINE...
     GALE MON.
     GALE POSSIBLE MON NIGHT.

$$

.FORECASTER CLARK. OCEAN PREDICTION CENTER.


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