000 AGXX40 KNHC 121918 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 230 PM EST TUE JAN 12 2010 MARINE WEATHER DISCUSSION FOR GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W GULF OF MEXICO... THE PROBLEM OF THE DAY LIES WITH THE STRENGTH AND TRACK OF THE SURFACE LOW DEVELOPING IN THE GULF OF MEXICO ON FRI AND MOVING NE SAT. THE GFS CONTINUES TO BE A FAST OUTLIER. THERE APPEARS TO BE CONVECTIVE FEEDBACK WITH THE SHORTWAVE ENERGY EJECTED FROM THE DEEP LAYER LOW INTO THE RIDGE TO ITS E. THE GFS STAMPS OUT OVER 7 INCHES OF PRECIPITATION IN A 6 HR PERIOD FRI NIGHT BECAUSE OF THIS FEEDBACK AND CARRIES A MORE ZONALLY ELONGATED LOW PRES SYSTEM. THIS SOLUTION IS NOT SUPPORTED BY THE OTHER MODELS. PMDHMD PREFERS THE SLOWER ECMWF AND UKMET SOLUTIONS HERE. PAST PERFORMANCE WITH SOUTHERN STREAM CUT OFF LOWS MOVING THROUGH MEXICO AND THE SW U.S. INTO THE GULF FAVORS A SLOW SOLUTION AND THE ECMWF/UKMET FITS THE BILL. BELIEVE THE GFS WIND FIELD IS TOO STRONG DUE TO THE FEEDBACK WHICH HAS ALSO CAUSED THE WW3 TO BE OVERDONE WITH WAVE HEIGHTS. ADJUSTMENTS WERE MADE TO THE WW3 BASED ON THE DIFFERENCES BETWEEN THE GFS AND ECMWF/UKMET WIND FIELDS. GALE CONDITIONS ARE EXPECTED IN THE NW GULF AND THE MIDDLE GULF N OF 24N FRI AND SAT. CARIBBEAN AND TROPICAL N ATLC W OF 55W... A STRONG PRES GRADIENT AND UNUSUALLY STRONG COLD AIR ADVECTION CONTINUE TO AFFECT THE WESTERN CARIBBEAN BEHIND A DISSIPATING FRONTAL ZONE THAT CURRENTLY EXTENDS FROM THE MONA PASSAGE TO PANAMA. THE 1450 UTC ASCAT PASS SHOWS WINDS IN THE 20 TO 30 KT RANGE WITHIN 240 NM N AND 120 NM S OF THE FRONTAL TROUGH OVER THE WESTERN AND CENTRAL CARIBBEAN. THIS BOUNDARY WILL DISSIPATE WED...BUT HIGH PRES BUILDING IN OVER THE CENTRAL ATLC BEHIND THE COLD FRONT CURRENTLY MOVING INTO NW WATERS OF THE SW N ATLC ZONE WILL KEEP FRESH TO STRONG TRADE WINDS ACROSS GULF WATERS THU AND FRI. OVER THE WEEKEND...EXPECT THIS HIGH PRES TO BE FORCED SOUTHWARD BY A COLD FRONT OVER THE CENTRAL ATLC N OF THE HIGH SEAS FORECAST AREA. THE GRADIENT BETWEEN THIS HIGH AND THE LOW PRES SYSTEM OVER THE GULF OF MEXICO WILL CAUSE WINDS TO TURN MORE SOUTHEASTERLY AND STRENGTHEN SAT. THE PREFERRED TIMING OF THE COLD FRONT...SLOWER LIKE THE ECMWF/UKMET...TAKES THE WEAKENED FRONT THROUGH THE YUCATAN CHANNEL BY SUN MORNING AS THE MAIN SURFACE LOW ASSOCIATED WITH THE SYSTEM RACES NORTHEASTWARD. SEE THE SECTION ABOVE FOR FORECAST REASONING ON THE GULF OF MEXICO LOW. SW N ATLC S OF 31N W OF 55W... THE COLD FRONT CURRENTLY OVER EXTREME NW WATERS WILL SHIFT EASTWARD OVER FORECAST WATERS N OF 27N...INCREASING WINDS TO THE 20 TO 30 KT RANGE ON EITHER SIDE OF THE FRONT AND BRINGING A NEW SURGE OF NW SWELL TO THE REGION. THE FRONT WILL MOVE E OF THE AREA WED NIGHT AND THE SWELL WILL SUBSIDE BELOW 8 FT OVER EASTERN FORECAST WATERS DURING THE DAY FRI AS HIGH PRES MOVES OFFSHORE. LARGE DIFFERENCES IN THE FORECAST MODELS ARISE BY THE WEEKEND WITH THE TIMING OF THE INCREASE IN SE FLOW AHEAD OF THE SYSTEM DEEPENING OVER THE GULF OF MEXICO. AS MENTIONED IN THE GULF OF MEXICO SECTION...THE GFS APPEARS TOO STRONG WITH ITS WIND FIELD DUE TO CONVECTIVE FEEDBACK E OF THE MAIN LOW PRES SYSTEM. A SLOWER SOLUTION LIKE THE UKMET/ECMWF IS PREFERRED. THE ECMWF BRINGS WINDS TO 30 KT IN THE SW N ATLC NEAR THE FRONT SUN...BUT DOES NOT SUGGEST GALES AT THIS TIME. WARNINGS... ATLC... .NONE. CARIBBEAN... .NONE. GULF OF MEXICO... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER SCHAUER