000 AGXX40 KNHC 081823 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 230 PM EDT MON JUN 08 2009 MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. A DEEP LAYERED TROUGH CONTINUES TO DOMINATE THE WESTERN CARIBBEAN AND SW N ATLC. THE NORTHERN EDGE OF THE UPPER TROUGH IS EXPECTED TO BE NUDGED EASTWARD BY A WEAK TROUGH CURRENTLY MOVING OFF THE CANADIAN MARITIME/NEW ENGLAND COAST...WITH A MORE AMPLIFIED MID LATITUDE TROUGH EXPECTED TO MOVE OFF THE EASTERN U.S. COAST BY WED MORNING...INCORPORATING MUCH OF THE MID LEVEL ENERGY LINGERING OVER N WATERS OFF THE NE FL COAST. AS A RESULT...THE UPPER TROUGH WILL FILL SOMEWHAT AND BECOME MORE POSITIVE TILT...ROUGHLY ORIENTATED NE TO SW FROM BERMUDA TO CENTRAL AMERICA THROUGH THE MIDDLE OF THE WEEK...THEN WEAKEN FURTHER LATE THU INTO FRI. THE ATLC RIDGE CURRENTLY EXTENDS E TO W ALONG 28N TO THE W OF 55W AND WILL SHIFT SLIGHTLY NORTHWARD BY THU AS THE MID TO UPPER LEVEL TROUGH WEAKENS. THE PROBLEM OF THE DAY LIES ON THE SOUTHERN EDGE OF THIS TROUGH WITH THE BROAD LOW PRES CURRENTLY OVER THE SW CARIBBEAN. SOME MODEL GUIDANCE SUGGESTS SURFACE LOW DEVELOPMENT HERE...BUT THERE IS LITTLE AGREEMENT ON THE STRENGTH AND TIMING. TO COMPLICATE MATTERS...A TROPICAL WAVE CURRENTLY ALONG 68W WILL MOVE INTO THE W CARIBBEAN OVERNIGHT WED NIGHT. THERE IS AGREEMENT AMONGST THE GLOBAL GUIDANCE TO ALLOW THE NORTHERN VORTICITY MAXIMUM ASSOCIATED WITH THE TROPICAL WAVE TO WRAP INTO THE NORTHERN EDGE OF THIS TROUGH AXIS OVER THE WESTERN CARIBBEAN...BUT THERE IS A CONSIDERABLE AMOUNT OF UNCERTAINTY IN THE DETAILS. THE GFS BEGINS TO DEVELOP A WELL-DEFINED SURFACE LOW WITH THIS SYSTEM EARLIER THAN THE OTHER MODELS...EVEN BEFORE THE WAVE REACHES THE TROUGH AXIS. THIS SEEMS FAST COMPARED TO THE CONSENSUS. THE 00Z ECMWF IS SLOWER TO DEVELOP THE SURFACE LOW...BUT BECOMES THE STRONGEST SOLUTION WITH THE H85 LOW BY FRI NIGHT. THERE IS BETTER AGREEMENT AMONG THE REMAINING GUIDANCE TO ALLOW THE SW FLOW ON THE EASTERN SIDE OF THE DEEP LAYER TROUGH TO TRANSPORT THE VORTICITY PIECEMEAL NORTH-NORTHEASTWARD THROUGH CUBA AND THE BAHAMAS INTO THE SW N ATLC. GIVEN THE UNCERTAINTY IN THE FORECAST AND THE CURRENTLY AMPLITUDE OF THE TROUGH AND THE ASSOCIATED SW FLOW ON ITS EASTERN EDGE...FAVORED THE WEAKER SOLUTIONS. SUBSIDENCE ON THE W SIDE OF THE DEEP LAYER TROUGH AXIS SHOULD KEEP CONVECTION IN THE GULF OF MEXICO RELATIVELY QUIET. WINDS SHOULD REMAIN LIGHT AS HIGH PRES MEANDERS OVER N CENTRAL WATERS THROUGH THE PERIOD. FRESH TO STRONG ELY TRADES CAN CURRENTLY BE FOUND OVER THE CENTRAL AND EASTERN CARIBBEAN WITH A TROPICAL WAVE ALONG 68W. EXPECT WINDS TO 30 KT TO CONTINUE NEAR THE COAST OF COLOMBIA THROUGH TUE AS THE WAVE MOVES THROUGH. THESE ELY TRADES COULD BREAK UP AND BECOME CYCLONIC OVER THE W AND CENTRAL CARIBBEAN IF THE AFOREMENTIONED SURFACE LOW DEVELOPS. AN UPPER CYCLONE NEAR 22N55W HAS A LOW LEVEL REFLECTION AT THE SURFACE ANALYZED AS A TROUGH FROM 21N63W TO 26N57W. THE UPPER CYCLONE AND THE ASSOCIATED CONVECTION HAS WEAKENED OVER THE LAST 24 HOURS. HOWEVER...THE UPPER LOW IS EXPECTED TO HANG ON AS IT TRAVELS EASTWARD...EVENTUALLY GETTING PICKED UP BY WEAK TROUGHING IN THE CENTRAL ATLC NEAR 35W ON TUE/WED. THIS SCENARIO IN TANDEM WITH THE TROUGH MOVING OFF THE MID ATLC U.S. COAST WED WILL WEAKEN THE SUBTROPICAL RIDGE...SHIFTING THE HIGH PRES CENTER INTO THE EASTERN ATLC...AND WEAKEN THE EASTERLY TRADES OVER THE TROPICAL N ATLC. MEANWHILE...THE TROPICAL WAVE ALONG 27W IS EXPECTED TO APPROACH THE LESSER ANTILLES FRI...LIKELY BRINGING AN INCREASE IN EASTERLY FLOW BEHIND IT AS THE SUBTROPICAL HIGH BEGINS TO SHIFT WESTWARD...INCREASING THE PRES GRADIENT ON THE NORTHERN EDGE OF THE WAVE. WARNINGS ATLC... .NONE. CARIBBEAN... .NONE. GULF OF MEXICO... .NONE. FORECASTER SCHAUER CLARK. TROPICAL PREDICTION CENTER.