000 AXPZ20 KNHC 130339 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC THU DEC 13 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0330 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS W FROM THE NW COLOMBIAN COAST AT 09N75W ACROSS THE PANAMA AND COSTA RICA BORDER TO 07N98W... THEN TURNS NW TERMINATING AT AN EMBEDDED 1011 MB LOW PRESSURE CENTER AT 10.5N106W. LOW LEVEL WINDS INDICATE THAT THE ITCZ FORMS W OF THE LOW PRESSURE CENTER NEAR 09N108W AND CONTINUES WESTWARD THROUGH 11N133W TO BEYOND 09N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 45 NM EITHER SIDE OF A LINE FROM 07N81W TO 05N91W AND WITHIN 15 NM OF 08N139W. ISOLATED SHOWERS ARE NOTED ELSEWHERE WITHIN 150 NM OF 08N98W AND WITHIN 120 NM OF THE ITCZ W OF 125W. THE EMBEDDED SURFACE LOW AT 10.5N106W HAS LOST ALL SIGNIFICANT CONVECTION AND SHOULD SOON WEAKEN TO AN OPEN TROUGH AS IT CONTINUES WESTWARD. ...DISCUSSION... ALOFT...A BROAD UPPER LEVEL TROUGH DOMINATES THE DISCUSSION AREA N OF 22N BETWEEN 113-140W AND IS BEING REINFORCED BY A SECONDARY TROUGH CURRENTLY ALONG 32N122W TO 25N140W. UPPER MOISTURE IS NOTED TO THE N OF 29N E OF THIS SECONDARY TROUGH...AND IS ADVECTED NE ACROSS SOUTHERN CALIFORNIA AND NORTHERN ARIZONA. OTHERWISE STRONG UPPER LEVEL WESTERLIES ACCOMPANIED BY DRY UPPER AIR IS OBSERVED N OF 22N FROM ACROSS MEXICO TO BEYOND 140W. AN UPPER CYCLONE IS NOTED OVER THE DEEP TROPICS AT 03N115W. AN UPPER ANTICYCLONE IS CENTERED NEAR 01S138W WITH ANTICYCLONIC FLOW OBSERVED N OF EQUATOR TO THE S OF 13N BETWEEN 126-140W... WITH DRY UPPER AIR TRAPPED UNDER THE RIDGE TO THE S OF 10N W OF 124W AND SUPPRESSING CONVECTION TO ONLY A FEW TOWERING CUMULUS ALONG THE ITCZ. AN SMALL UPPER ANTICYCLONE IS CENTERED NEAR 09N108W. REMNANTS OF ANOTHER UPPER TROUGH STRETCH NE-SW FROM BELIZE INTO A SMALL UPPER CYCLONE AT 01N98W. A FEW CONVECTIVE CELLS ARE ENHANCED NEAR THE TROUGH AT 08N98W. AN UPPER ANTICYCLONE IS QUASI-STATIONARY OVER S AMERICA AT 07N72W WITH A RIDGE EXTENDING W CRESTING ALONG 05N91W TO 10N90W TO 14N87W. THE ASSOCIATED UPPER DIFFLUENCE IS ENHANCING CONVECTION ALONG THE MONSOON TROUGH AS PREVIOUSLY DESCRIBED...WITH THE RESULTANT DEBRIS MOISTURE NOW ADVECTED NE UNDER THE RIDGE ACROSS CENTRAL AMERICA TO THE E OF 90W. THE UPPER FLOW IS ZONAL ACROSS THE TROPICS FROM 10-22N TO THE W OF 105W. THESE STRONG WESTERLIES CONTINUE TO ADVECT DENSE UPPER MOISTURE...MOSTLY ORIGINATING IN THE CENTRAL PACIFIC...EASTWARD TO ALONG 105W. THE DEBRIS MOISTURE IS REINFORCED BY ISOLATED MODERATE AND STRONG CONVECTION THAT FLARED IN THE AREA BOUNDED BY 13-17N BETWEEN 107-118W. LIGHTNING DATA SUGGESTS THAT THIS CONVECTION PEAKED A COUPLE OF HOURS AGO AND IS RAPIDLY DISSIPATING. THIS 600 NM WIDE MOISTURE PLUME THEN TURNS NE IN RESPONSE TO A LONGWAVE TROUGH OVER THE CENTRAL CONUS...WITH THE MOISTURE FEEDING INTO THE CONVECTION ALONG A STATIONARY FRONT EXTENDING SW FROM N FLORIDA TO THE BAY OF CAMPECHE IN THE SOUTHERN GULF OF MEXICO. ELSEWHERE AT THE LOW LEVELS...A COLD FRONT EXTENDS FROM 32N126W TO 27N140W WITH A RIDGE WEAKENING JUST TO THE S OF THE FRONT. NE WINDS AT 20-25 KT...SEAS 8-11 FT...ARE OBSERVED W OF A LINE FROM 32N124W TO 22N140W. NE 15-20 KT TRADES ARE ALSO ENHANCED SW OF THE RIDGE FROM 09-16N W OF 137W WITH SEAS OF 6-8 FT. THE COLD FRONT IS EXPECTED TO CONTINUE E REACHING FROM 32N114W TO 24N119W ON THU AND THEN BEGIN TO WEAKEN AS IT PASSES ACROSS THE BAJA PENINSULA AND THE GULF OF CALIFORNIA ON FRI. POST FRONTAL NE WINDS AT 20-25 KT...SEAS 7-11 FT...WILL SPREAD EASTWARD ACROSS THE WATERS W OF A LINE FROM 32N118W TO 20N134W ON THU. THE GRADIENT WILL WEAKEN ON FRI WITH NW-N WINDS AT 10-15 KT ACROSS THE PACIFIC WATERS N OF 22N W OF 115W WITH SEAS 7-9 FT IN NW SWELL. THE TRADES WILL ALSO DIMINISH TO 15-20 KT ACROSS THE WATERS FROM 11-20N W OF 134W WITH SEAS 7-9 FT IN MIXED N SWELL. GENERALLY EXPECT SEAS OF 3-5 FT ALONG THE WESTERN BAJA PENINSULA THROUGH LATE THU...THEN SEAS WILL BUILD TO 5-8 FT IN THE NW SWELL FROM THU NIGHT INTO EARLY FRI ACROSS THE BAJA COASTAL WATERS TO THE N OF 27N. SURFACE WINDS ARE BECOMING SOUTHERLY ACROSS THE GULF OF CALIFORNIA AND EXPECTED TO INCREASE TO 20-25 KT OVER THE NORTHERN WATERS LATE TONIGHT AHEAD OF THE COLD FRONT ON FRI. THE POST FRONTAL NORTHERLY FLOW IS NOT EXPECTED TO BE VERY STRONG ACROSS THE GULF OF CALIFORNIA...GENERALLY IN THE 10-15 KT RANGE...FRI NIGHT AND SAT THEN INCREASING TO 15-20 KT ACROSS THE GULF WATERS S OF 26N ON SUN. GAP WINDS... GULF OF TEHUANTEPEC...NORTHERLY MINIMUM GALE WINDS WILL INCREASE SLIGHTLY LATER TONIGHT TO 35-40 KT...WITH THE FINAL GALE SURGE EXPECTED JUST AFTER SUNRISE ON THU. N WINDS EXPECTED AT 20-30 KT EXPECTED FROM THU NIGHT THROUGH SUNRISE FRI...THEN WINDS WILL QUICKLY DIMINISH. BEST GUESS IS THE NEXT NEAR GALE NORTHERLY EVENT WILL BEGIN LATE MON NIGHT AND CONTINUE THROUGH WED MORNING. GULF OF PAPAGAYO...NE WINDS WILL CONTINUE TO PULSE AT 15-20 KT WITH AN OCCASIONAL SURGES TO 20-25 KT THROUGH THU AFTERNOON AND REACH AS FAR SW OF THE GULF OF PAPAGAYO AS 09.5N91W. GUIDANCE SUGGESTS WINDS WILL REMAIN IN THE 10-15 KT RANGE WITH PULSES TO 15-20 KT FROM THU NIGHT THROUGH THE MIDDLE OF NEXT WEEK. $$ NELSON