000 AXPZ20 KNHC 111548 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC WED SEP 11 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1545 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS NW FROM COSTA RICA AT 10N85W TO 13N94W...THEN TURNS SW TO 12N104W....THEN NW AGAIN TO 15N114W...THEN SW THROUGH AN EMBEDDED 1011 MB LOW PRES AT 12N124W. THE MONSOON TROUGH THEN WIGGLES SW TO 09N138W WHERE SCATTEROMETER WINDS INDICATE A TRANSITION TO AN ITCZ WHICH CONTINUES W TO BEYOND 09N140W. SCATTERED MODERATE TO STRONG CONVECTION IS OBSERVED WITHIN 90 NM EITHER SIDE OF A LINE FROM 12N87W TO 12N94W TO 11N98W TO 15N102W. ISOLATED MODERATE TO STRONG CONVECTION IS OBSERVED ELSEWHERE N OF A LINE FROM 03N78W TO 09N104W...AND ALSO WITHIN 150 NM OF 09N107W. ...DISCUSSION... A NEGATIVE TILT UPPER TROUGH IS OVER THE FAR NW PORTION OF THE DISCUSSION AREA FROM 32N141W TO 29N139W...AND IS SWINGING NE WITH TIME...AND IS EXPECTED TO PUSH A WEAK SURFACE COLD FRONT INTO THE NW CORNER AT MIDDAY THU. THE FRONT WILL MOVE SLOWLY SE ON FRI...STALLING AND WASHING OUT FROM 32N133W TO 27N140W ON SAT. EXPECTING ONLY A 10 KT WIND SHIFT ALONG THE FRONTAL BOUNDARY WITH SEAS 4-6 FT PRIMARILY DUE TO NW SWELL. AN UPPER CYCLONE IS QUASI-STATIONARY OVER THE BORDER OF CALIFORNIA AND ARIZONA AT 35N115W...TRAILING AN UPPER TROUGH S ACROSS THE BAJA CALIFORNIA PENINSULA TO 28N113W. UPPER MOISTURE IS NOTED ONLY OVER THE NORTHERN SEMICIRCLE OF THIS CYCLONE TODAY. AN UPPER CYCLONE FURTHER TO THE SW HAS CUTOFF NEAR 20N133W WITH ITS ENVELOPE OF CYCLONIC WINDS OBSERVED ONLY WITHIN 150 NM OF CENTER...BUT LARGE ENOUGH TO SEPARATE THE UPPER FLOW ASSOCIATED WITH AN ANTICYCLONE TO THE N AND AN UPPER RIDGE TO SE OF THIS CYCLONE. THE UPPER ANTICYCLONE IS CENTERED AT 26N131W WITH A RIDGE AMPLIFYING N TO A CREST CURRENTLY AT 35N130W. AN UPPER ANTICYCLONE IS OBSERVED OVER CENTRAL OLD MEXICO AT 26N104W WITH AN UPPER RIDGE EXTENDING SW THROUGH 18N124W TO BEYOND 13N140W. A RIDGE ALSO EXTENDS SE FROM THIS ANTICYCLONE ACROSS CENTRAL AMERICA TO A CREST OVER PANAMA...BUT IS BEGINNING TO BE ERODED BY A DEEPENING UPPER CYCLONE OVER THE SW GULF OF MEXICO. THESE UPPER FEATURES COMBINE TO DRY OUT THE UPPER LEVELS AND STABILIZE THE LOWER LEVELS TO THE W OF 112W. UPPER DIFFLUENCE S OF THE CENTRAL AMERICAN RIDGE IS SUPPORTING THE CONVECTION PREVIOUSLY DESCRIBED...WITH THE DENSE DEBRIS MOISTURE ADVECTED SW ACROSS THE TROPICS E OF 112W. ELSEWHERE AT THE LOW LEVELS A 1017 MB SURFACE HIGH IS CENTERED NEAR 26N127W WITH ITS ANTICYCLONIC ENVELOPE DOMINATING THE AREA N OF 15N W OF 115W. A LOW LEVEL TROUGH ORIENTATED FROM NNW TO SSE CONTINUES FROM THE NORTHERN GULF OF CALIFORNIA TO ALONG THE COAST OF CENTRAL AMERICA TO A BASE NEAR 16N102W. ISOLATED MODERATE TO OCCASIONALLY STRONG CONVECTION IS OBSERVED FROM 15- 23N E OF 109W TO ABOUT 90 NM INLAND MEXICO. THIS TROUGH IS EXPECTED TO PERSIST FOR SEVERAL DAYS WITH WEAK SURFACE LOWS FORMING INTERMITTENTLY ALONG THE SOUTHERN EXTENT OF THE TROUGH. SOUTHWESTERLY MONSOONAL FLOW AT 15-20 KT IS OBSERVED MOSTLY BY SCATTEROMETER DATA ACROSS THE TROPICS ROUGHLY S OF 12N BETWEEN 90-122W WITH SEAS 7-10 FT PRIMARILY DUE TO SOUTHWESTERLY CROSS- EQUATORIAL SWELL. THIS SW FLOW IS EXPECTED TO INCREASE TO 20-25 KT WITHIN 210 NM S OF LINE FROM 14N96W TO 11N100W TONIGHT WITH COMBINED SEAS BUILDING TO 9-11 FT. THIS STRONG SW FLOW WILL PERSIST THROUGH THE WEEKEND...BUT THE STRENGTH OF THE SW FLOW WILL LIKELY BE AFFECTED BY LOW PRESSURE EXPECTED TO INCREASE OVER THE BAY OF CAMPECHE. $$ NELSON