000 AXPZ20 KNHC 120324 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC THU SEP 12 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 0200 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH AXIS CONTINUES ACROSS PORTIONS OF CENTRAL AMERICA FROM NEAR 16N90W MEANDERING W-SW THROUGH THE GULF OF TEHUANTEPEC TO 14N98W TO LOW PRES NEAR 12N112.5W 1009 MB TO LOW PRES NEAR 11.5N123W 1009 MB TO 10N131W...WHERE IT TRANSITIONS TO ITCZ...CONTINUING ON BEYOND 09N140W. SCATTERED MODERATE CONVECTION NOTED N OF 06N E OF 88W. SCATTERED STRONG CONVECTION NOTED N OF 12N BETWEEN 88W AND 102W. SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED ELSEWHERE FROM 08N TO 13N BETWEEN 93W AND 110W. SCATTERED STRONG CONVECTION WITHIN 90 NM OF COAST NEAR MANZANILLO MEXICO E OF 105.5W. ...DISCUSSION... AN ELONGATED UPPER TROUGH IS SLOWLY NUDGING TOWARDS THE FAR NW PORTION OF THE DISCUSSION AREA FROM 34N142W TO 25N147W...WITH EMBEDDED SHORT WAVE ENERGY LIFTING NE WITH TIME...AND HAS PUSHED AN OLD FRONTAL BOUNDARY TO NEAR THE NW CORNER OF THE AREA...AND EXPECTED TO PUSH SOUTHEAST AND REACH FROM 30N137W TO 28.5N140W BY 1800 UTC THU. THE FRONT WILL CONTINUE TO MOVE SLOWLY SE ON FRI...STALLING AND WASHING OUT FROM 32N133W TO 27N140W ON SAT. EXPECTING ONLY A 10-15 KT NE WIND SHIFT ALONG THE FRONTAL BOUNDARY WITH SEAS 6-8 FT PRIMARILY DUE TO NW SWELL. AN UPPER CYCLONE IS QUASI-STATIONARY OVER THE BORDER OF CALIFORNIA AND ARIZONA AT 37N114W...TRAILING AN UPPER TROUGH S ACROSS THE BAJA CALIFORNIA PENINSULA TO 27N114W. SUBSIDENCE PREVAILS W AND SW OF TROUGH TO 133W. UPPER LEVEL RIDGING GENERALLY PREVAILS S AND SE OF THESE TWO FEATURES...CENTERED ON AN UPPER ANTICYCLONE OVER MEXICO NEAR 26N106W EXTENDING SW TO 18N122W THEN W-SW TO 17N137W AND THEN SW TO S OF HAWAIIAN ISLANDS. A WEAK RIDGE EXTENDS SE FROM THE PARENT HIGH ACROSS SE MEXICO...WHILE A N TO S ALIGNED DEEP LAYERED TROUGH IS ACROSS THE W GULF OF MEXICO AND INTO THE BAY OF CAMPECHE...AND SEPARATES A SECOND DEVELOPING UPPER ANTICYCLONE ACROSS THE NW CARIBBEAN. ABUNDANT TROPICAL MOISTURE CONTINUES TO CONVERGE ACROSS CENTRAL AMERICA AND SE MEXICO FROM 04N TO 20N E OF 100W...AND IS MAINTAINING A VERY UNSTABLE LOWER ATMOSPHERE. WIDESPREAD CLUSTERS OF CONVECTION ARE DESCRIBED ABOVE AND ALSO OCCURRING OVER LAND ACROSS CENTRAL AMERICA...AND ARE AIDING IN MAINTAINING UPPER DIVERGENCE AND ANTICYCLONIC OUTFLOW ACROSS THIS REGION. GLOBAL MODELS SUGGEST THESE FAVORABLE UPPER LEVEL CONDITIONS WILL GRADUALLY BECOME LESS FAVORABLE ON FRIDAY. AT THE LOW LEVELS A 1017 MB SURFACE HIGH IS CENTERED NEAR 26N127W WITH ITS ANTICYCLONIC ENVELOPE DOMINATING THE AREA N OF 18N W OF 115W. A LOW LEVEL TROUGH ORIENTED FROM NNW TO SSE CONTINUES FROM THE SOUTHERN GULF OF CALIFORNIA TO A BASE NEAR 16N103W. CONVECTION OCCURRING TO THE W OF THIS TROUGH HAS DIMINISHED THIS EVENING. THIS TROUGH IS EXPECTED TO PERSIST FOR SEVERAL DAYS AND MAY GRADUALLY MERGE WITH MONSOON TROUGH PRESENTLY OFFSHORE OF MEXICO...WITH WEAK SURFACE LOWS FORECAST BY GLOBAL MODELS TO FORM INTERMITTENTLY ALONG THE EASTERN EXTENT OF THE TROUGH. SOUTHWESTERLY MONSOONAL FLOW AT 15-20 KT IS OBSERVED MOSTLY BY SCATTEROMETER DATA ACROSS THE TROPICS ROUGHLY FROM 05N TO 11N E OF 116W...WITH A FEW REGIONS OF 20-25 KT WINDS...AND SEAS TO 9 AND 10 FT. ONE SUCH AREA WAS FROM 07N TO 11N BETWEEN 97W AND 106W...WHILE A SECOND WAS FROM 10N TO 14N BETWEEN 88W AND 91W. A DISORGANIZED WEATHER SYSTEM SHIFTING W ACROSS THE YUCATAN PENINSULA DURING THE NEXT 24 HOURS WILL BEGIN TO FEED MOISTURE FROM THE ENHANCED SW MONSOON FLOW ACROSS A BROADENING AREA...AND THROUGH THE GULF OF TEHUANTEPEC...CONTINUING INTO FRI. SEAS ACROSS THIS AREA ARE EXPECTED TO BUILD TO 8-12 FT INTO SAT. $$ STRIPLING