000 AXPZ20 KNHC 130304 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI 0405 UTC FRI SEP 13 2013 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0215 UTC. ...TROPICAL LOW... SATELLITE IMAGERY THIS EVENING AND RECENT SHIP REPORTS SUGGEST THAT A SMALL LOW PRES CENTER IS ALONG THE MONSOON TROUGH NEAR 15N100W. SURFACE PRESSURES ACROSS THE REGION ARE VERY LOW... AND THE ESTIMATED CENTRAL PRES OF THIS LOW CENTER IS 1000 MB. SCATTERED MODERATE TO STRONG CONVECTION WAS OCCURRING WITHIN 150 NM ACROSS NW SEMICIRCLE OF LOW. SCATTERED STRONG CONVECTION WAS ELSEWHERE FROM 12.5N TO 15.5N BETWEEN 94.5W TO 98.5W. A BROAD ZONE OF FRESH SW WINDS 20 TO 25 KT EXTENDS WELL TO THE S AND SE OF THIS LOW TO 08.5N97W....WHERE A MID DAY ALTIMETER PASS THROUGH THIS AREA CONFIRMED SEAS OF 8 TO 12 FT. THIS BROAD AREA OF FRESH TO STRONG SW MONSOONAL FLOW IS EXPECTED TO CONTINUE FOR THE NEXT FEW DAYS AND WILL MAINTAIN AN ENVIRONMENT FAVORABLE FOR SMALL LOW CENTERS TO FORM IN THIS GENERAL AREA. ABUNDANT TROPICAL MOISTURE PERSISTS ACROSS THE REGION...AND WITH SURFACE PRESSURES BELOW NORMAL...IMPROVED ORGANIZATION OF THIS LOW CENTER COULD OCCUR DURING THE NEXT FEW DAYS AS THE LOW DRIFTS OFF TOWARDS THE NW. THIS SYSTEM HAS A MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE IN THE NEXT 48 HOURS. REGARDLESS OF TROPICAL CYCLONE DEVELOPMENT...CLUSTERS OF MODERATE TO STRONG CONVECTION WILL CONTINUE INTERMITTENTLY ACROSS THE PACIFIC COASTAL ZONES OF SOUTHERN MEXICO DURING THE NEXT 48 HOURS...AND WILL LEAD TO PERIODS OF HEAVY RAIN...WHICH COULD CAUSE LIFE-THREATENING FLASH FLOODING AND MUDSLIDES. A VERY LONG FETCH OF STRONG ONSHORE SW WINDS WILL ALSO PRODUCE VERY ROUGH SEAS AND STRONG CONFUSED SURF ALONG THE MEXICAN COASTLINE...LEADING TO DANGEROUS SURF CONDITIONS AND WIDESPREAD RIP CURRENTS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH IS RATHER ILL DEFINED ACROSS E PORTIONS OF THE AREA...AND EXTENDS FROM THE EXTREME SW CARIB NEAR 11N80W AND MEANDERS NW ACROSS CENTRAL AMERICA TO LOW PRES ACROSS THE BAY OF CAMPECHE...WHERE IT HAS BEGUN TO FRACTURE. THE TROUGH THEN RESUMES THROUGH THE CHIVELA PASS AND THE GULF OF TEHUANTEPEC TO LOW PRES NEAR 15N100W TO 17N108W TO LOW PRES 11.5N122W TO 08N128W TO 10N133W TO 09N137W...WHERE IT TRANSITIONS TO ITCZ...CONTINUING ON TO BEYOND 09N140W. SCATTERED MODERATE TO STRONG CONVECTION NOTED WITHIN 180 NM S OF TROUGH BETWEEN 105W AND 110W. SCATTERED STRONG CONVECTION NOTED WITHIN 60 NM OF MEXICAN COAST FROM MANZANILLO AREA TO E COAST OF GULF OF CALIFORNIA NEAR 25N108.5W. SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED FROM 09N TO 13N BETWEEN 99W AND 110W. ...DISCUSSION... AN UPPER LEVEL BLOCKING PATTERN PERSISTS ACROSS THE NE PACIFIC THIS EVENING...WITH LITTLE OVERALL MOVEMENT OF THE MAIN SYNOPTIC FEATURES. A DEEP LAYERED UPPER CYCLONE REMAINS TO THE NW OF THE AREA WITH TROUGH EXTENDING S TO NEAR 30N142W THEN SW...WHICH HAS PUSHED A WEAK FRONTAL TROUGH EXTENDING NE TO SW ACROSS THE EXTREME NW CORNER OF THE AREA HAS STALLED NEAR 30N140W. THE FRONT IS EXPECTED TO DRIFT SE THEN STALL DURING THE NEXT FEW DAYS AND GRADUALLY DISSIPATE FROM 32N133W TO 26140W ON SAT. EXPECT ONLY A 10-15 KT N TO NE WIND SHIFT ALONG THE FRONTAL BOUNDARY WITH SEAS 6-7 FT IN NW SWELL. AN UPPER RIDGE REMAINS TO THE E OF THIS ALONG 125W AND N OF 28N...WHILE A DEEP LAYERED UPPER CYCLONE REMAINS ACROSS THE SW U.S. BUT HAS SHIFTED SLIGHTLY NW DURING THE PAST 24 HOURS TO N NEVADA. UPPER RIDGING ALSO PREVAILS S OF THESE FEATURES... EXTENDING FROM AN UPPER ANTICYCLONE OVER N MEXICO NEAR 27N105W...EXTENDING SW TO THE S TIP OF BAJA CALIFORNIA THEN WWD ALONG 22N TO 133W THEN SW INTO THE DEEP TROPICS. THIS UPPER RIDGE CONTINUES TO PRODUCE MODEST NE TO E WINDS AT UPPER LEVELS ACROSS THE AREA S OF 20N AND E OF 110W...WHICH IS LIGHT VERTICAL SHEAR AND FAVORABLE FOR SUSTAINED CONVECTION ACROSS THE AREA. THESE FAVORABLE CONDITIONS ARE EXPECTED TO PERSIST THROUGH FRIDAY BEFORE STABILIZING SOMEWHAT THROUGH THE WEEKEND. AT LOWER LEVELS...A WEAK 1017 MB HIGH WAS CENTERED SE OF THE WEAK FRONT NEAR 28N130W...A MODEST PRES GRADIENT BETWEEN THIS HIGH AND BROAD LOW PRES ACROSS MEXICO WAS YIELDING A BROAD ZONE OF NLY WINDS 15-20 KT FROM WELL OFFSHORE TO THE COAST OF CENTRAL BAJA CALIFORNIA...WHERE SEAS WERE RUNNING 6 TO 7 FT. ELSEWHERE...THE MONSOON CIRCULATION ACROSS THE REGION E OF 120W REMAINS WELL ESTABLISHED...WITH FRESH TO STRONG W TO SW FLOW DRAWING ABUNDANT MOISTURE INTO E PORTIONS AND ACROSS CENTRAL AMERICA...THE SOUTH HALF OF MEXICO...AND THE BAY OF CAMPECHE. A ZONE OF STRONG S TO SW WINDS OF 20 TO 25 KT WITH ISOLATED AREAS TO 30 KT IS EXPECTED TO PREVAIL THROUGH SATURDAY...GENERALLY FROM 08N TO 15N BETWEEN 96W AND 104W THEN CONTINUING BETWEEN 08N AND 12N TO 110W. SEAS ACROSS THE REGION ARE EXPECTED TO REMAIN 8- 10 FT WITH AREAS TO 11 AND 12 FT...AND HIGHER...AS A VERY LONG FETCH DEVELOPS. THIS LOW LEVEL WIND AND WAVE PATTERN WILL SHIFT SLIGHTLY WWD ON SUN AND CONTINUE TO GENERATE HIGH SEAS OFFSHORE OF SOUTHERN MEXICO. $$ STRIPLING