Marine Interpretation Message
Issued by NWS

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000 AGNT40 KWNM 150123 MIMATN MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN NWS OCEAN PREDICTION CENTER WASHINGTON DC 930 PM EDT SUN 14 SEP 2014 .FORECAST DISCUSSION: MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT .WEATHER FOR THE NORTH ATLANTIC OCEAN W OF 50W FROM 30N TO 50N. DIAMOND SHOALS BUOY 41025 CONTINUES REPORTING WINDS UP TO 20 KT THIS EVENING W OF STNRY FRONT. LAST HI RES ASCAT OVERPASS WAS FROM 1540Z AND INDICATED N TO NE 20 KT EXTENDING TO JUST S OF CAPE FEAR. LATEST MDLS ARE SLIGHTLY UNDERDONE INITIALLY HERE BUT ELSEWHERE ARE REASONABLE OVER W ATLC. OPC MDL PREFERENCE CONTINUES WITH 12Z ECMWF TUE THRU FRI AS IT OFFERS COMPROMISE WITH STRENGTH OF FRONTAL WAVES TO DVLP OFFSHORE. AS STRONG HIGH PRES BUILDS TO NEW ENGL COAST FRI AND FRI NGT ECMWF AND GFS ARE IN REASONABLE AGREEMENT WITH STRENGTHENING OFFSHORE PRES GRADIENT. OVERALL WILL NOT BE SIGNIFICANT CHANGES FROM PREVIOUS NT1/NT2 FORECASTS. BOTH 18Z MWW3 AND 12Z ECMWF WAVE MDL SIG WV HGTS HAVE BEEN IN GOOD AGREEMENT WITH LATEST W ATLC SIG WV HGT OBS THRU THE EVENING. HOWERVER MWW3 APPEARS TO HAVE MUCH BETTER HANDLE WITH SWELL ASSOCICATED WITH HURCN EDOUARD OVER NEXT FEW DAYS. ---------------------------------------------------------------- ...PREVIOUS DISCUSSION... OVER THE SHORT TERM...THE NEW 12Z MDLS REMAIN REL CONSISTENT AND PRESENT NO SIG FCST PROBLEMS. THE MDLS ALL FCST A HIGH PRES RIDGE TO BUILD IN FM THE NW TONITE...THEN DRIFT SLOWLY OFSHR MON/MON NITE CAUSING GNRLY WEAK GRADIENTS (MAINLY 10-15 KT...OR LESS) THRUT THE CSTL/OFSHR WTRS. THEN ON TUE/TUE NITE THE 12Z MDLS SHARE SMLR FCST TIMING FOR A WEAK COLD FRONT TO PUSH OFSHR ACRS THE NT1 AND NRN/CNTRL NT2 WTRS. WHERE THE MDLS DO DISAGREE IS WHETHER OR NOT A FRONTAL WAVE WL DVLP AS THE FRONT MOVES OFSHR. THE 12Z UKMET DOES NOT FCST A CLEAR CUT FRONTAL WAVE AT ALL. THE 12Z NAM/GFS/GEM/ECMWF ALL DO FCST A WAVE TO DVLP BUT WITH SLIGHTLY DIFFERENT TIMING/STRENGTH. THE 12Z NAM/GFS/GEM/ECMWF THO DO FCST SMLR ASCD GRADIENTS (WITH MAX ASCD WINDS GNRLY IN THE 15-20 KT RANGE) WITH THIS FROPA. THEREFORE PLAN ON POPULATING OUR SHORT TERM WIND GRIDS WITH THE 12Z GFS 10M BL WINDS FOR TONITE THRU MON NITE...THEN MAINLY DUE TO ITS BETTER FCST CONSISTENCY WITH ITS FRONTAL WAVE WL TRANSITION TO THE 12Z ECMWF BL WINDS FOR TUE/TUE NITE WITH SM FURTHER EDITS THEN MADE MAINLY IN DEFERENCE TO THE 12Z ECMWF. SO THE END RESULT WL BE THAT ONLY MINOR SHORT TERM CHNGS WL BE MADE TO THE PREV OFSHR FCST PACKAGE. IN THE LONG RANGE...ON WED INTO FRI THE 12Z MDLS AGREE THAT THE COLD FRONT WL DRIFT SLOWLY SE ACRS THE SRN NT2 WTRS...BUT THE MDLS CONT TO DIFFER IN REGARDS TO THEIR FCST TIMING/STRENGTH OF ANY ASCD FRONTAL WAVES. AS A COMPROMISE BTWN THE STRONGER 12Z GEM/UKMET AND WEAKER 12Z GFS SOLUTIONS WITH A LOW FCST CONFIDENCE WULD FAVOR THE 12Z ECMWF SOLUTION AS A COMPROMISE. WHERE THE MDLS DO THO GNRLY AGREE IS THAT AS STRONG HIGH PRES IS FCST TO BUILD IN FM THE N THAT A MOD STRONG (PRIMARILY UP TO 25 OR 30 KT AT MOST) ENELY GRADIENT WL DVLP ACRS THE NT2 AND SE MOST NT1 WTRS. THEREFORE FOR THIS GRADIENT PLAN ON CONTG TO POPULATE OUR LONG RANGE WIND GRIDS THRU FRI NITE WITH THE 12Z ECMWF BL WINDS. .SEAS...THE DIFFERENCES BTWN THE 12Z WAVEWATCH III AND 12Z ECMWF WAM MDLS ARE MINIMAL THRU MON NITE SO AS WAS DONE PREVLY WL USE A 50/50 BLEND OF THE TWO MDLS THRU THEN. THEN ON TUE THRU FRI NITE WL TRANSITION TO A 75/25 BLEND OF THE 12Z ECMWF WAM VS THE 12Z WAVEWATCH III SINCE THE 12Z ECMWF SOLUTION WL BE FAVORED (BUT ALSO WANT SOME WAVEWATCH III IN THE MIX DUE ITS LONG PERIOD ESE SWELL FM HURCN EDUARDO THAT IT BRINGS INTO THE OFSHR WTRS MON NITE INTO TUE). .EXTRATROPICAL STORM SURGE GUIDANCE...BY LATE THU INTO FRI THE 12Z ESTOFS CONTS TO FCST A SLIGHTLY MR SIG POSITIVE SURGE TO DVLP ALG THE SE COAST THAN THE 12Z ETSS WHICH LOOKS RSNBL. .WARNINGS...PRELIMINARY. .NT1 NEW ENGLAND WATERS... NONE. .NT2 MID ATLC WATERS... NONE. $$ .FORECASTER CLARK/VUKITS. OCEAN PREDICTION CENTER.

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