000
AGXX40 KNHC 170728
MIMATS

MARINE WEATHER DISCUSSION         
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
330 AM EDT FRI APR 17 2009

MARINE WEATHER DISCUSSION FOR GULF OF MEXICO...CARIBBEAN SEA AND 
SOUTHWEST NORTH ATLC S OF 31N W OF 55W.

GULF OF MEXICO...
NUMEROUS SHOWERS AND TSTMS CONTINUE OVER THE N CENTRAL GULF 
FUELED BY AN UPPER JET AND OVERALL DIFFLUENT UPPER PATTERN E OF 
A SHORTWAVE TROUGH OVER E TEXAS. ANOTHER TRIGGER FOR THE 
ACTIVITY IS A LOW-LEVEL STALLED BOUNDARY...TAIL END OF THE W 
ATLC FRONT...EXTENDING FROM W CUBA TO THE CENTRAL GULF. ELY 
20-25 KT WINDS ARE OCCURRING N OF THIS BOUNDARY OVER THE N 
CENTRAL AND W GULF...WITH HIGHER GUSTS IN TSTMS. THE 20-25 KT 
ELY FLOW IS FORECAST TO SPREAD E ACROSS THE N HALF THROUGH SAT 
AS HIGH PRES CURRENTLY OVER THE GREAT LAKES SHIFTS SE TO THE 
SC/GA AREA. SEAS ARE FORECAST TO BUILD TO 9 FT OVER THE NW 
WATERS WHERE THE FETCH IS GREATEST. BY SAT NIGHT AND SUN...THE 
HIGH IS EXPECTED TO MOVE INTO THE W ATLC WHILE LOW PRES TAKES 
SHAPE OVER THE S CENTRAL PLAINS. THERE IS NO LONGER A 
SIGNIFICANT SPREAD IN THE MODEL GUIDANCE WHICH GENERALLY SHOWS A 
FRONT MOVING INTO THE FAR NW GULF SAT NIGHT OR SUN MORNING. THE 
FRONT IS FORECAST TO STRENGTHEN...AS THE ASSOCIATED UPPER TROUGH 
DEEPENS...SUN NIGHT AND MON THEN WEAKEN AS IT CLEARS MOST OF THE 
GULF BY TUE. STRONGEST FLOW BEHIND THE FRONT (N 20-25 KT) IS 
EXPECTED IN THE TOPOGRAPHICALLY ENHANCED ZONE NEAR THE COAST OF 
MEXICO ON MON.  

CARIBBEAN AND TROPICAL N ATLC...
TRADE WINDS ARE NEAR OR SLIGHTLY BELOW CLIMATOLOGICAL NORMS DUE 
TO THE INTERRUPTION OF SUBTROPICAL RIDGING OVER THE W ATLC WHERE 
BROAD TROUGHING HOLDS. LATEST SCATTEROMETER AND SFC DATA SHOW 
20-25 KT ELY FLOW IN THE USUAL TOPOGRAPHICALLY ENHANCED 
ZONES...COAST OF COLOMBIA AND THE GULF OF HONDURAS. HIGH PRES 
OVER THE EASTERN CONUS IS FORECAST TO BUILD SE INTO THE W ATLC 
BY SAT NIGHT AND SUN WHILE LOW PRES SHIFTS E INTO THE CENTRAL 
ATLC. THIS WILL SET UP AN INCREASE OF N WINDS THROUGH THE 
WINDWARD PASSAGE THIS WEEKEND. IN ADDITION...NLY SWELL IS 
EXPECTED TO SPREAD THROUGH THE E CARIBBEAN PASSAGES THIS 
WEEKEND. BY EARLY NEXT WEEK...THE HIGH WILL BUILD OVER THE 
CENTRAL ATLC INCREASING TRADES SLIGHTLY OVER THE E CARIBBEAN AND 
TROP N ATLC BUT WILL DIMINISH OVER THE W CARIBBEAN DUE TO AN 
APPROACHING DISSIPATING FRONT.

SW N ATLANTIC...
THE PRESSURE GRADIENT BETWEEN LOW PRES ABOUT 200 NM N OF BERMUDA 
AND HIGH PRES OVER THE ERN CONUS IS PRODUCING NLY 20-25 KT N OF 
27N W OF THE COLD FRONT EXTENDING FROM 29N65W TO THE CENTRAL 
BAHAMAS. THE FRONT IS FORECAST TO SHIFT SLOWLY E EXITING MUCH OF 
THE AREA BY TONIGHT. MAIN MARINE ISSUE THROUGH SAT WILL BE THE 
INCREASING SEAS UP TO 15 FT OVER THE N WATERS IN PART DUE TO 
LONG PERIOD NLY SWELL. WINDS AND SEAS STEADILY DIMINISH SAT 
NIGHT AND SUN AS HIGH PRES BUILDS ACROSS THE AREA. THE HIGH 
BUILDS E OF THE AREA BY MON AS A COLD FRONT MOVES ACROSS THE 
GULF OF MEXICO. THIS PATTERN WILL INCREASE SLY WINDS OVER THE NW 
PORTION MON WITH THE FRONT ENTERING THE ZONE TUE.  

ATLC...
.NONE.. 

CARIBBEAN...
.NONE.

GULF OF MEXICO...
.NONE.

FORECASTER CANGIALOSI. TROPICAL PREDICTION CENTER.