000 AGXX40 KNHC 110556 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 130 AM EST MON DEC 11 2006 MARINE WEATHER DISCUSSION FOR GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. SRN BRANCH OF WESTERLIES AGAIN PROMINENT TONIGHT WITH SHORTWAVE TROUGHS MOVINNG ENE. ONE ALONG 60W AND ANOTHER ALONG 85W WITH A NEW ONE MOVING INTO THE SRN PLAINS. BROAD MID LEVEL RIDGE OVER BAHAMAS AND NRN CARIB TONIGHT WITH REX BLOCK E OF 50W. ON THE SURFACE TONIGHT A FRONTAL BOUNDARY CONTINUES OVER THE MID ATLC SW TO NEAR THE WINDWARD PASSAGE. THE BOUNDARY SEPARATES AN OLD ARCTIC AIRMASS THAT IS CENTERED ON THE CAR COAST AND THE ATLC RIDGE E OF 50W. BOTH REMAIN FAIRLY STRONG AND ARE AT A STALEMATE AS TO WHICH ONE WILL WIN OUT. THUS WINDS REMAIN ABOVE NORMAL OVER MOST SECTIONS TONIGHT. LATER DAY 1 PROGRESSIVE PATTERN AT MID LEVELS CONTINUES AS SHORTWAVES MOVE ABOUT 5 DEGREES E..OTHERWISE NO CHANGE TO PATTERN. ON THE SURFACE SOME SLIGHT WEAKENING OF THE HIGH PRESSURE SYSTEMS OTHERWISE WINDS OF 20 TO 25 KT CONTINUE OVER MOST SECTIONS. FOR DAY 2 LARGE POOL OF COLD AIR SPILLING S ALOFT OVER MID ATLC WILL BREAK REX BLOCK PATTERN OVER ERN ATLC. SHORTWAVE TROUGH OVER PLAINS GAINS AMPLITUDE AS IT MOVES INTO MS VALLEY. MID LEVEL RIDGING BUILDS ALONG 75W AHEAD OF THIS SYSTEM. ON THE SURFACE DAY 2 SLOW MOVEMENT OF OLD FRONT OVER MID ATLC AS DENSER AIR W OF FRONT PUSHES E. WEAK COLD FRONT MOVES INTO NW GULF DAY 2 BUT NO COLD AIR BEHIND IT THUS WINDS MOSTLY LIGHT. ELY TRADES OVER ATLC S OF 20N WEAKEN AS PRESSURE GRADIENT RELAXES. OUTLOOK PERIOD... LARGE UPPER TROUGH DIGS SE ALONG 40W DISLODGING BLOCKING PATTERN. MID LEVEL FLOW BECOMES MORE WLY WITH TROUGH OVER MS VALLEY MOVING E AND WEAKENING. ANOTHER SHORTWAVE TROUGH MOVING SE INTO NRN PLAINS DAY 3. FRONT OVER MID ATLC CONTINUES SLOW MOVEMENT EWD TO NEAR 31N38W TO 20N50W. WEAK COLD FRONT WASHING OUT AS IT MOVES TO NE GULF. 1024 MB HIGH FOLLOWING FRONT WITH SOME INCREASE IN NE WINDS OVER SRN GULF DAY 3. CARIB WINDS REMAIN MODERATE AND ATLC TRADES S OF 20N MOSTLY LIGHT TO MODERATE. FOR DAY 4 STRONG WLY FLOW SETS UP IN MID LEVELS BUT NOT MUCH IN THE WAY OF COLD AIR AVAILABLE..THUS SHORTWAVES LOOSE AMPLITUDE QUICKLY AS THEY MOVE EWD. ON THE SURFACE DAY 4 OLD ARCTIC AIRMASS OF PAST WEEK CONTINUES MOVING EWD TO MID ATLC AND STILL PRODUCING GUSTY WINDS TO 25 KT E OF 60W N OF 20N. S OF 20N TRADES REMAIN WEAK. CARIB WINDS LIGHT TO MODERATE AS IT GULF WINDS. FOR DAY 5 LARGE UPPER TROUGH OVER ERN ATLC CLOSES OFF NEAR 32N30W WITH MID LEVEL RIDGING BUILDING ALONG 50W. NEXT SHORTWAVE TROUGH TAPS SOME COLD AIR AS IT MOVES OVER NE US BUT WILL HAVE LITTLE AFFECT ON OUR REGION. NEW SHORTWAVE IN SRN BRANCH MOVES TO NW GULF. ON THE SURFACE DAY 5 GFS MODEL DEVELOPS WEAK LOW CENTER ON OLD FRONT OVER SE GULF WHICH COULD INCREASE WINDS TO 20 KT OVER NE GULF. COULD BE IN RESPONSE TO SHORTWAVE OVER NW GULF. OLD ARCTIC AIRMASS OVER MID ATLC STILL PRODUCING GUSTY WINDS E OF 55W N OF 18N. AIRMASS GETTING NEW SUPPORT FROM RIDGE ALOFT ALONG 50W. CARIB WINDS MOSTLY LIGHT TO MODERATE. WARNINGS... ATLANTIC... NONE. CARIBBEAN... NONE. GULF OF MEXICO... NONE. FORECASTER RRG