000 AXPZ20 KNHC 281006 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC FRI DEC 28 2012 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0945 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE COAST OF COSTA RICA AT 09N85W TO 07N91W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ WHICH CONTINUES W-SW TO 06N109W...THEN TURNS NW TO 09N120W...THEN TURNS W TO BEYOND 08N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION...WITH OCCASIONAL LIGHTNING STRIKES...IS OBSERVED WITHIN 30 NM N OF 06N80W AND 15 NM OF 07N83W. ISOLATED MODERATE CONVECTION IS NOTED ELSEWHERE ALONG THE MONSOON TROUGH. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 90 NM EITHER SIDE OF A LINE FROM 115N115W TO 10N122W TO 09126W AND WITHIN 30 NM EITHER SIDE OF A LINE FROM 08.5N132W TO 07N140W. ...DISCUSSION... ALOFT...A POSITIVE TILT LONGWAVE UPPER TROUGH OVER CENTRAL N AMERICA EXTENDS INTO THE DISCUSSION AREA FROM 32N108W TO 27N125W TO 14N135W ACCOMPANIED BY DRY UPPER AIR NOTED WITHIN 180 NM OF THE TROUGH AXIS. A REINFORCING SHORTWAVE TROUGH IS MOVING INTO THE AREA FROM 33N130W TO 30N133W. IMMEDIATELY TO THE W OF THE SHORTWAVE IS AN UPPER RIDGE WHICH IS SHIFTING E OVER THE FAR NW PORTION FROM 28N140W TO 32N135W. UPPER MOISTURE IS INDICATED TO THE W OF A LINE FROM CALIFORNIA AT 35N TO 24N140W. AN UPPER ANTICYCLONE IS CENTERED NEAR 11N100W WITH A RIDGE AXIS EXTENDING NW TO A CREST AT 26N126W. UPPER DIFFLUENCE SW OF THIS RIDGE AND SE OF THE LONG WAVE UPPER TROUGH IS ENHANCING THE CONVECTION BETWEEN 111-140W AS PREVIOUSLY DESCRIBED. UPPER DEBRIS MOISTURE IS OBSERVED ACROSS THE AREA FROM 09-26N BETWEEN 128-102W. THE MOISTURE THEN CONCENTRATES INTO A 660 NM WIDE PLUME FROM OVER OLD MEXICO AT 24N102W TO OVER THE NE GULF OF MEXICO AT 29N85W. AN UPPER CYCLONE NOTED OVER THE DEEP TROPICS AT 06N97W SEEMS TO BE ENHANCING A FEW CONVECTIVE CELLS WITHIN 120 NM OF 06N94W. AN UPPER RIDGE EXTENDS NW ACROSS CENTRAL AMERICA FROM 07N77W TO 13N86W AND IS PROVIDING THE UPPER SUPPORT FOR THE CONVECTION MENTIONED ALONG THE MONSOON TROUGH. THE RESULTANT DEBRIS MOISTURE IS ADVECTED NE ACROSS COSTA RICA AND PANAMA TO OVER THE SW CARIBBEAN. LOW LEVELS...A 1027 MB SURFACE HIGH IS CENTERED AT 31N129W WITH A RIDGE EXTENDING SE TO 21N106W. NW WINDS ARE AT 20-25 KT N OF 27N E OF THE RIDGE WITH SEAS AT 8-12 FT. ANTICYCLONIC WINDS ARE 10-20 KT ELSEWHERE N OF 23N BETWEEN 115W AND 137W...BUT SEAS ARE 8-11 FT PRIMARILY DUE TO MIXING N SWELL. A WEAK COLD FRONT IS APPROACHING AND IS EXPECTED TO MOVE INTO THE N CENTRAL WATERS MIDDAY SAT...REACH THE NORTHERN BAJA PENINSULA ON SUN...AND PASS THROUGH THE GULF OF CALIFORNIA SUN NIGHT. THE FRONT WILL ONLY BE ACCOMPANIED BY A 10-15 KT SW-W-NW WIND SHIFT ALONG ITS BOUNDARY. THE SURFACE HIGH WILL SHIFT A LITTLE S AND WEAKEN AS THE FRONT PASSES TO ITS N. POST FRONTAL HIGH PRESSURE WILL INCREASE THE NORTHERLY FLOW TO 15-20 KT WELL W OF THE FRONT WITH ANOTHER ROUND OF NW SWELL DRIVING THE COMBINED SEAS UP TO 10-13 FT ACROSS THE N-CENTRAL WATERS ON SUN...WITH 7-10 FT SEAS REACHING THE NORTHERN BAJA PENINSULA ON SUN EVENING...THEN SUBSIDING TO 6-8 FT ON MON. THE TRADES SW OF THE SURFACE RIDGE...FROM 10-20N BETWEEN 118-140W...ARE AT 15-20 KT WITH SEAS 8-10 FT IN MIXING NE AND NW SWELL. AS THE SURFACE HIGH SHIFTS S TODAY THE TRADES WILL INCREASE TO 20-25 KT W OF LINE FROM 20N112W TO 10N120W TO 08N140W WITH COMBINED SEAS OF 8-11 FT IN THE NE SWELL. EXPECT THESE TRADES TO CONTINUE THROUGH THE WEEKEND. ON MON...LARGE LONG PERIOD NW SWELL WILL PROPAGATE INTO THE NW WATERS DRIVING SEAS UP TO 14 FT. THESE SWELLS WILL CONTINUE EASTWARD GRADUALLY SUBSIDING WITH SEAS OF 7-10 FT REACHING THE NORTHERN BAJA PENINSULA ON TUE NIGHT...AND REACHING THE SOUTHERN BAJA PENINSULA BY EARLY WED NIGHT. GULF OF PAPAGAYO...NE-E 15-25 KT SURGES ARE EXPECTED TO DIMINISH BRIEFLY THIS EVENING...THEN RETURN LATE TONIGHT AND CONTINUE THROUGH EARLY MON. GULF OF TEHUANTEPEC...CURRENTLY LIGHT AND VARIABLE...MOSTLY SOUTHERLY...WINDS ARE OBSERVED. A COLD FRONT ALONG THE TEXAS COAST WILL REACH THE NW BAY OF CAMPECHE SAT MORNING WITH THE NORTHERLY WINDS SURGING THROUGH THE CHIVELA PASS INTO THE GULF OF TEHUANTEPEC BY NOON ON SAT. THESE N WINDS WILL RAPIDLY BUILD TO GALE FORCE SAT EVENING...WITH NEAR STORM CONDITIONS EXPECTED AROUND LATE SAT NIGHT TILL JUST AFTER SUNRISE ON SUN. GUIDANCE SUGGESTS GALE CONDITIONS WILL END BRIEFLY ON SUN...BUT MAY DEVELOP BRIEFLY LATE SUN NIGHT THROUGH JUST AFTER SUNRISE MON...WITH THE NORTHERLY WINDS DIMINISHING BELOW 20 KT LATE MON. $$ NELSON