000 AGXX40 KNHC 080610 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 215 AM 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 ENTIRE DISCUSSION AREA TO THE W OF 78W. AN ASSOCIATED SURFACE LOW IS OVER SE GA TRAILING A VERY WEAK LOW LEVEL TROUGH S ACROSS FL. THIS WEAK TROUGH EFFECTIVELY SEPARATES SURFACE HIGH PRES OVER THE N CENTRAL GULF OF MEXICO FROM AN ATLC RIDGE THAT EXTENDS E TO W ALONG 27N TO THE W OF 55W. 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. BROAD LOW PRES OVER THE SW CARIBBEAN...AND MOST OF CENTRAL AMERICA IS EXPECTED TO PERSIST THROUGH THE MIDDLE OF THE WEEK WITH MODEL GUIDANCE SUGGESTING SURFACE LOW DEVELOPMENT ALTHOUGH NOT NECESSARILY IN AGREEMENT. TO FURTHER COMPLICATE THE FORECAST A TROPICAL WAVE CURRENTLY ALONG 67W WILL MOVE THROUGH THE W CARIBBEAN WED NIGHT THROUGH FRI. THUS THERE IS STILL PLENTY OF UNCERTAINTY IN THIS SURFACE LOW DEVELOPMENT...STRENGTH...PSN AND EVENTUAL TRACK IF ANY. IN FACT ITS POSSIBLE THAT A BROAD SURFACE TROUGH MEANDERS NEAR THE NICARAGUAN AND HONDURAN BORDER THROUGH NEXT WEEKEND. LATEST MODEL RUNS SUGGEST THAT THE LOW LEVEL TROUGH OVER FL SEPARATING RIDGES TO THE E AND W WILL PERSIST THROUGH AT LEAST THU IN THE FORM OF A TROUGH OVER THE BAHAMA CHANNEL...WITH A 10 TO 15 KT WIND SHIFT ALONG THE TROUGH AXIS. THIS FORECAST GRADIENT IS PROBABLY OVERDONE...BUT THIS PRES WEAKNESS ALONG FL SHOULD THE RESTRICT THE SLY RETURN FLOW N OF THE ATLC RIDGE TO MAX AT 15 KT ALONG 29N THROUGH THE WEEK. STILL EXPECTING SLY RETURN FLOW TO PULSE AT 15 TO 20 KT OVER THE NW GULF THROUGH FRI. FRESH ELY TRADES CURRENTLY CONTINUE OVER THE TROPICS S OF 17N WITH THE TROPICAL WAVE HAVING LITTLE EFFECT. LITTLE CHANGE EXPECTED E OF 75W THROUGH THE PERIOD...BUT THESE ELY TRADES COULD BREAK UP AND BECOME CYCLONIC OVER THE W CARIBBEAN IF THE SURFACE LOW DEVELOPS. AN UPPER CYCLONE NEAR 23N56W HAS A LOW LEVEL REFLECTION AT THE SURFACE ANALYZED AS A TROUGH FROM 22N60W TO 27N55W. THE NORTHERN EXTENSION OF A TROPICAL WAVE ALSO MADE SOME CONTRIBUTION TO THE ASSOCIATED CONVECTION THE PAST FEW DAYS...BUT THE UPPER CYCLONE AND THE ASSOCIATED CONVECTION SEEMS TO BE WEAKENING ATTM. HOWEVER MODELS SEEM TO HANG ONTO THE LOW LEVEL FEATURE AND MOVE IT W UNDER THE SURFACE RIDGE TO THE N...SO I HAVE REINTRODUCED A TROUGH INTO MARINE GRAPHICS...BUT EXPECT THE ASSOCIATED NE TO SE SURFACE WIND SHIFT ALONG THE TROUGH AXIS TO MAX AT 15 KT...SO LIKELY WILL NOT MENTION A TROUGH IN ALPHANUMERICAL PRODUCTS. WARNINGS ATLC... .NONE. CARIBBEAN... .NONE. GULF OF MEXICO... .NONE. FORECASTER NELSON. TROPICAL PREDICTION CENTER.