000 AXPZ20 KNHC 311600 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC FRI DEC 31 2010 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1500 UTC. ...ITCZ... THE INTERTROPICAL CONVERGENCE ZONE IS ANALYZED FROM A 1008 MB LOW PRES NEAR 07N79W TO 06N94W TO 09N118W TO 08140W. SCATTERED MODERATE CONVECTION IS WITHIN 90 NM S OF THE ITCZ AXIS BETWEEN 98W AND 105W AND WITHIN 180 NM N OF THE ITCZ AXIS BETWEEN 100W AND 106W. ...DISCUSSION... AN UPPER TROUGH CURRENTLY CENTERED OVER THE U.S. GREAT BASIN THROUGH NW MEXICO INTO THE NE WATERS WILL BE REINFORCED BY A SYSTEM WELL N OF THE AREA THAT IS EXPECTED TO DROP INTO THE BACKSIDE OF THE TROUGH OFF THE CALIFORNIA COAST BY SATURDAY... BROADENING THE TROUGHING OVER N WATERS. THE REINFORCING SYSTEM IS REFLECTED AS A 984 MB SURFACE LOW NEAR 50N142W ON THE 1200 UTC SURFACE ANALYSIS AND IS FORECAST TO DRAG A COLD FRONT EASTWARD THROUGH N WATERS OVER THE WEEKEND. WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW ADVISORY CRITERIA THROUGH THE NEXT 48 HOURS NEAR THE FRONT WITH THE 13-15 SECOND LONG PERIOD SWELL ASSOCIATED WITH THE SYSTEM NOT FORECAST TO REACH N WATERS UNTIL EARLY SUNDAY. 1022 MB HIGH PRES CURRENTLY RESIDES NEAR 31N132W. THE PRES GRADIENT BETWEEN THIS HIGH AND LOWER PRES ALONG THE ITCZ IS RESPONSIBLE FOR AN AREA OF FRESH TRADE WINDS W OF 130W PRIMARILY BETWEEN 08N AND 18N. THESE TRADES ARE EXPECTED TO RETREAT W OF 136W THROUGH SAT MORNING AS THIS HIGH PRES TO THE N IS WEAKENED BY THE AFOREMENTIONED APPROACHING COLD FRONT. BY SAT NIGHT... HIGH PRES WILL REBUILD W OF THE FRONT AND FRESH TRADES WILL EXPAND E TO 115W. MEANWHILE...THE PRES GRADIENT BETWEEN THE 1022 MB HIGH AND LOWER PRES OVER THE U.S. GREAT BASIN AND N CENTRAL MEXICO IS GENERATING FRESH TO STRONG NW TO N WINDS OFF THE COAST OF BAJA CALIFORNIA OUT TO 124W OVER N WATERS. AN EARLIER ASCAT PASS SHOWED AN AREA OF NW WINDS TO 25 KT PRIMARILY N OF 27N WITHIN 240 NM W OF BAJA CALIFORNIA. WINDS HERE ARE EXPECTED TO DIMINISH BELOW 20 KT DURING THE AFTERNOON HOURS FRIDAY AS THE HIGH PRES OVER THE PACIFIC WEAKENS AND THE TROUGHING OVER THE U.S. AND MEXICO PUSHES NORTHEASTWARD. FRESH NW TO N WINDS ARE EXPECTED IN THE GULF OF CALIFORNIA BY LATE SATURDAY AS HIGH PRES BUILDS OVER THE U.S. GREAT BASIN BEHIND THE NORTHEASTWARD MOVING SURFACE SYSTEM AND INCREASES THE PRES GRADIENT OVER THE GULF OF CALIFORNIA BETWEEN THIS HIGH AND TROUGHING OVER THE EASTERN SHORE OF THE GULF ON THE LEE SIDE OF THE SIERRA MADRE OCCIDENTAL. GAP WINDS... N TO NE WINDS THROUGH THE GULF OF PAPAGAYO ARE EXPECTED TO CONTINUE PULSING TO 20 KT IN THE EARLY MORNING HOURS THROUGH THE FORECAST PERIOD AS TRADE WINDS FROM THE WESTERN CARIBBEAN SEEP THROUGH THE CENTRAL AMERICA HIGH TERRAIN AND ARE ENHANCED BY MORNING MOUNTAIN DRAINAGE FLOW. TOWARD THE END OF THE PERIOD BY EARLY SUNDAY...NORTHERLY WINDS ARE EXPECTED TO BEGIN FILTERING THROUGH THE CHIVELA PASS ACROSS THE ISTHMUS OF TEHUANTEPEC INTO THE GULF OF TEHUANTEPEC AS A COLD FRONT SWEEPS ACROSS THE WESTERN GULF OF MEXICO. THIS EVENT WILL INTRODUCE N WINDS INITIALLY TO 20 KT...INCREASING THEREAFTER TO POTENTIALLY NEAR GALE FORCE BY LATE SUNDAY. $$ HUFFMAN