000 AXPZ20 KNHC 132340 AAA TWDEP TROPICAL WEATHER DISCUSSION...UPDATED NWS NATIONAL HURRICANE CENTER MIAMI FL 2340 UTC SAT APR 13 2013 UPDATED CONVECTION UNDER ITCZ/MONSOON TROUGH 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH AXIS WAS ANALYZED FROM 07N77W TO 07N86W TO 06N100W TO 05N110W...WHERE SCATTEROMETER DATA AND MODEL SUGGEST THE ITCZ AXIS BEGINS AND CONTINUES TO 06N120W TO 04N129W TO 03N140W. SCATTERED STRONG CONVECTION IS WITHIN 120 NM S OF THE AXIS BETWEEN 80W AND 84W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 60 NM OF THE AXIS BETWEEN 93W AND 96W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM S OF THE AXIS BETWEEN 105W AND 110W. ...DISCUSSION... E OF 110W... A SHORTWAVE TROUGH SHIFTING EWD EXTENDS FROM 13N108W SE TO NEAR 06N102W. TO ITS E...A MID/UPPER RIDGE EXTENDS E TO W ALONG 10N...AND AS FAR E AS NRN COLOMBIA. AN UPPER LEVEL ANTICYCLONE IS JUST S OF THE EQUATOR AT 01S90W. DEEP ATMOSPHERIC MOISTURE AND INSTABILITY ASSOCIATED WITH THE TROUGH HAS INCREASED SOME SINCE 18-24 HRS AGO...ENHANCED BY UPPER DIFFLUENCE PRESENT E OF THE TROUGH TO 104W AND FROM 05N TO 11N. RELATED ONGOING CONVECTION ALONG AND NEAR THE MONSOON TROUGH IS DESCRIBED ABOVE UNDER ITCZ/MONSOON TROUGH. MODERATE SUBSIDENCE ALOFT IS ELSEWHERE ALONG AND NEAR THE RIDGE MAINTAINING MOSTLY CLEAR SKIES THERE...WITH THE EXCEPTION OF CUMULUS CLOUDS WITH POSSIBLE ISOLATED SHOWERS ALIGNED IN NE TO SW LINES N OF THE MONSOON TROUGH AXIS TO THE SW OF THE GULF OF TEHUANTEPEC. A JET STREAM BRANCH EXTENDS FROM 16N110W NEWD TO ACROSS CENTRAL MEXICO AT MANZANILLO. MODERATE SW TO W WINDS ALONG AND WITHIN 450 NM S OF THE JET STREAM BRANCH ARE ADVECTING BROKEN CIRRUS CLOUDS NEWD ACROSS CENTRAL MEXICO FROM ABOUT 15N TO 21N...AND E TO ACROSS THE WRN BAY OF CAMPECHE. THE SHORTWAVE TROUGH WILL SHIFT E OF THE DISCUSSION AREA SUN...AND WILL BE FOLLOWED BY A MOSTLY ZONAL UPPER FLOW ACROSS THIS PORTION OF THE AREA. CONVECTION ALONG AND NEAR THE MONSOON TROUGH IS EXPECTED TO DIMINISH SLIGHTLY THROUGH LATE SUN...THEN INCREASE AGAIN MON AS ANOTHER SHORTWAVE TROUGH SWINGS EWD ACROSS OVER THIS PORTION OF THE AREA. W OF 110W... A RIDGE ALOFT EXTENDS FROM AN ANTICYCLONE N OF THE AREA NEAR 34N136W SEWD TO 20N125W TO 18N122W. BROAD MID/UPPER LEVEL ANTICYCLONE ASSOCIATED WITH THE RIDGE COVERS THE AREA S OF 25N AND E OF ABOUT 130W. AN UPPER TROUGH STRETCHES FROM NERN NEW MEXICO SW THROUGH SONAR AND THE CENTRAL BAJA CALIFORNIA PENINSULA TO 24N116W. WATER VAPOR IMAGERY SHOWS DRY AIR ALOFT IN THE VICINITY OF THE TROUGH. THIS TROUGH IS FORECAST TO SHIFT EWD SUN...HOWEVER A MEAN TROUGH WILL LINGER OVER THE SW U.S. AND NW MEXICO AS A NEW TROUGH AXIS MOVES IN TO REPLACE IT. A RATHER WEAK/MID UPPER TROUGH EXTENDS FROM NEAR 23N132W SE TO NEAR 13N128W. THE TROUGH IS EMBEDDED IN A VERY DRY ENVIRONMENT NOT ALLOWING FOR ANY DEVELOPMENT OF ANY DEEP CONVECTIVE ACTIVITY UNDER OR IN ITS IMMEDIATE VICINITY. PATCHES OF LOW CLOUDS WITH ISOLATED SHOWERS MOVING WWD ARE NOTED FROM 10N TO 22N W OF 128W. AT THE SURFACE...A STATIONARY 1030 MB HIGH CENTER IS NW OF THE AREA AT 36.5NN141.5W WITH A RIDGE EXTENDING FROM IT SEWD TO 21N121W. HIGH PRES COVERS THE AREA N OF 17N AND W OF 121W. THE ASCAT PASS FROM 1854 UTC THIS AFTERNOON SUGGESTED THAT NE TRADES OVER MUCH OF THE WRN AND CENTRAL PORTION HAVE DIMINISHED TO 10- 20 KT. THE HIGH WILL REMAIN STATIONARY THROUGH SUN NIGHT...THEN BE REPLACED BY A PRETTY WELL PRONOUNCED RIDGE THAT WILL BUILD SE THROUGH 32N138W TO NEAR 22N127W. THE PRES DIFFERENCE BETWEEN THIS NEW RIDGE AND BROAD LOWER PRES OVER THE INTER-MOUNTAIN W REGION OF THE U.S. WILL KEEP GALE FORCE WINDS NE OF THE AREA...BUT TO THE W OF THE CALIFORNIA COAST. RESULTANT LARGE NW TO N SWELLS WILL MOVE INTO THE NE PORTION OF THE AREA BY SUN EVENING BRINGING SEAS OF UP TO 11 FT OR 12 FT N OF ABOUT 28N BETWEEN 119W AND 127W. A WEAK SURFACE TROUGH IS ANALYZED FROM 10N118W TO 04N122W. ONLY ISOLATED SHOWERS ARE WITHIN 60-90 NM OF THE TROUGH. CROSS-EQUATORIAL SWELLS WITH PERIODS IN EXCESS OF 20 SECONDS ON ITS LEADING EDGE IS MAKING ITS WAY NORTHWARD OVER THE OFFSHORE PACIFIC WATERS S OF 16N. AS A RESULT...SEAS TO 9 FT ARE PRESENT S OF 06N BETWEEN 93W AND 112W...AND ALSO S OF 04N BETWEEN 82W AND 87W. WAVEWATCH AND WAVE PERIOD MODEL GUIDANCE SUGGEST THAT THE LEADING EDGE OF THE SWELL TRAIN WILL PROPAGATE FAR ENOUGH N TO REACH THE COASTAL AREAS OF CENTRAL AMERICAN AND MAINLAND MEXICAN COAST OVERNIGHT TONIGHT...AND FARTHER NWD TO BORDER THE BAJA CALIFORNIA PENINSULA ON SUN. HEAVY COASTAL BEACH EROSION AND HAZARDOUS MARINE CONDITIONS MAY OCCUR ALONG THE AFOREMENTIONED COASTS. $$ AGUIRRE