000 AXPZ20 KNHC 310949 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC MON DEC 31 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 NW FROM THE COLOMBIAN COAST AT 07N77W TO ALONG THE PACIFIC COAST OF COSTA RICA TO 09N83W...THEN TURNS SW INTO AN EMBEDDED 1010 MB SURFACE LOW AT 04N90W...THEN THE TROUGH TURNS NW TO 05N97W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ. THE ITCZ THEN CONTINUES NW TO 10N107W THEN SW THROUGH 06N134W TO BEYOND 05N140W. SMALL ISOLATED CLUSTERS OF CONVECTION IS NOTED ALONG THE COAST OF COSTA RICA NEAR THE MONSOON TROUGH AND ALONG 06N BETWEEN COLOMBIA AND 93W. SCATTERED MODERATE ISOLATED STRONG CONVECTION ACCOMPANIED BY FREQUENT LIGHTNING IS OBSERVED FROM 11-19N BETWEEN 104-115W. ISOLATED MODERATE CONVECTION IS NOTED ELSEWHERE FROM 08-20N BETWEEN 102-120W. A SURFACE TROUGH EXTENDS NE FROM THE ITCZ AT 10N120W TO 15N115W. MODEL GUIDANCE SHIFTS THE TROUGH E TO A POSITION FROM 10N112W TO 20N106W ON TUE-WED ACCOMPANIED BY A NE-E-SE 10-15 KT WIND SHIFT ALONG THE TROUGH AXIS. MODEL GUIDANCE MAY BE ERRONEOUSLY MOVING THIS TROUGH EASTWARD WHEN IN FACT A SECOND TROUGH MAY DEVELOP UNDER THE LARGE AREA OF CONVECTION CURRENTLY CENTERED ON 15N107W. ...DISCUSSION... ALOFT...AN UPPER TROUGH EXTENDS ACROSS THE DISCUSSION AREA FROM 32N112W TO A BASE OVER THE DEEP TROPICS AT 09N134W. AN UPPER RIDGE AXIS HAS SHIFTED OVER THE NW PORTION FROM 26N140W TO 35N130W AND IS BECOMING SLIGHTLY UNSTABLE AND MAY BEGIN TO COLLAPSE SE IN A DAY OR SO. UPPER MOISTURE IS SPILLING ACROSS THE RIDGE AXIS OVER THE AREA N OF 26N W OF 124W. OTHERWISE VERY DRY UPPER AIR IS INDICATED W OF THE TROUGH AXIS. UPPER LEVEL ANTICYCLONES ARE CENTERED OVER COLOMBIA AT 05N70W AND OVER THE NW CARIBBEAN AT 16N82W WITH A LARGE UPPER RIDGE DOMINATING MOST OF THE E PORTION OF THE AREA...WITH THE RIDGE CRESTING FROM 23N112W TO WELL BEYOND 35N104W WITH SW 50-70 KT WINDS INDICATED BY CLOUD MOTION VECTORS. WEAK UPPER FLOW IS OBSERVED OVER THE DEEP TROPICS S OF 04N BETWEEN 108-140W AND COMBINES WITH THE LARGE UPPER TROUGH AND RIDGE PATTERN PREVIOUSLY DESCRIBED TO SET UP AN AREA OF UPPER DIFFLUENCE SUPPORTING THE INTENSE CONVECTION CENTERED AT 15N107W. THE RESULTANT UPPER DEBRIS MOISTURE IS ADVECTED NE ALONG THE PERIPHERY OF THE RIDGE...WITHIN 480 NM EITHER SIDE OF A LINE FROM 10N113W TO BEYOND 32N98W WHERE THE MOISTURE FANS OUT ACROSS THE CENTRAL CONUS AS WELL AS CONTRIBUTES TO A LARGE PLUME MOVING ACROSS THE NORTHERN GULF OF MEXICO AND THE SE CONUS. AN UPPER CYCLONE CONTINUES OVER THE DEEP TROPICAL PACIFIC NEAR 04N93W. WEAK UPPER DIFFLUENCE IS INDUCED BETWEEN CYCLONE AND THE UPPER RIDGE TO THE N OVER CENTRAL AMERICA...AND IS ENHANCING THE ISOLATED CLUSTERS OF CONVECTION ALONG THE MONSOON TROUGH AS PREVIOUSLY DESCRIBED. THE SURROUNDING UPPER LEVELS REMAIN DRY..AND THE DEBRIS MOISTURE SEEMS TO QUICKLY EVAPORATE NEAR THE DECAYING CELLS. LOW LEVELS...A 1029 MB SURFACE HIGH IS CENTERED AT 30N134W WITH A RIDGE EXTENDING SE TO 19N106W. ANTICYCLONIC NE-E-SE 10-15 KT WINDS ARE OBSERVED ACROSS THE SUB-TROPICS W OF 125W WHILE NW-N 15-20 KT WINDS ARE OBSERVED E OF 125W TO THE BAJA PENINSULA. NE TRADES ACROSS THE TROPICS S OF THE SURFACE RIDGE...FROM 10-20N W OF 115W...CONTINUE AT 20-25 KT WITH SEAS 8-12 FT IN MIXED NE AND NW SWELL. ELSEWHERE W OF LINE FROM 23N112W TO 12N112W TO 04N140W SURFACE WINDS ARE N-NE AT 10-20 KT WITH SEAS 7-10 FT PRIMARILY DUE TO MIXING LONG PERIOD NE AND NW SWELL. A SURFACE HIGH WILL DRIFT E TODAY AND TUE THEN SHIFT SLIGHTLY SE TO 28N128W ON WED. THIS WILL MAINTAIN THE FRESH-STRONG TRADES IN THE AREA FROM 07-17N W OF 130W WITH SEAS 9-12 FT IN A BROAD MIX OF SWELL. LARGE LONG PERIOD NW SWELL HAS ALREADY PROPAGATED INTO THE NW WATERS N OF 123N W OF 136W AND EXPECTED TO DRIVE SEAS UP TO 13 FT LATER TODAY. THESE NW SWELLS WILL CONTINUE EASTWARD... BUT GRADUALLY SUBSIDE WITH SEAS OF 6-9 FT REACHING THE NORTHERN BAJA PENINSULA LATE TUE NIGHT...AND REACHING THE SOUTHERN BAJA PENINSULA WED NIGHT. A COLD FRONT WILL ENTER THE WATERS NEAR 30N140W TUE NIGHT ACCOMPANIED BY A 20-25 KT SW-NW WIND SHIFT WITH SOUTHERLY GALE WINDS PRECEDING THE FRONT OVER THE WATERS N OF 31N. THE HIGH WILL BLOCK THE FRONT AND IT WILL DISSIPATE OVER THE NW WATERS WED-FRI. GULF OF TEHUANTEPEC...NORTHERLY WINDS HAVE DECREASED TO MINIMAL GALE AND SHOULD DIMINISH JUST AFTER THIS MORNINGS DIURNAL MAXIMUM DRAINAGE...BY 15 UTC...AND CONTINUE TO DIMINISH TO LESS THAN 20 KT BY THIS EVENING. THE NEXT EVENT STARTS WED NIGHT. GULF OF PAPAGAYO...NE-E 15-25 KT SURGES ARE EXPECTED TO CONTINUE AS FAR W AS 94W WHERE THE ASSOCIATED NE SWELLS ARE MIXING WITH SW CROSS EQUATORIAL SWELL...AS WELL AS N-NW SWELL PROPAGATING S FROM THE TEHUANTEPEC EVENT. THE GRADIENT WILL RELAX LATE TUE. GULF OF CALIFORNIA...NW WINDS AT 10-15 KT WILL INCREASE TO 15-20 KT TONIGHT AND 20-25 KT LATE TUE THROUGH EARLY THU. $$ NELSON