000 AXPZ20 KNHC 121601 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1545 UTC. ...TROPICAL LOWS... LOW PRESSURE ESTIMATED AT 1004 MB HAS FORMED ALONG THE MONSOON TROUGH NEAR 14N97W...AND IS MOVING NW AT ABOUT 06 KT. ITS CLOSE PROXIMITY TO LAND AND STRONG UPPER LEVEL NORTHEASTERLY WINDS ARE EXPECTED TO INHIBIT SIGNIFICANT DEVELOPMENT DURING THE NEXT FEW DAYS. CURRENTLY SCATTERED MODERATE TO STRONG...BUT VERY DISORGANIZED...CONVECTION IS OBSERVED WITHIN 240 NM OVER THE W OF QUADRANT OF LOW...WITH SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED ELSEWHERE WITHIN 90 OF THE CENTER. ALTHOUGH THE HEAVIEST CONVECTION IS CURRENTLY OVER WATER...THERE IS THE POTENTIAL FOR CONVECTION TO DEVELOP OVER LAND BRINGING HEAVY RAINS TO PORTIONS OF EASTERN MEXICO FOR THE NEXT SEVERAL DAYS. THESE HEAVY RAINS COULD CAUSE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES. LOW PRESSURE IS EMBEDDED WITHIN THE MONSOON TROUGH NEAR 12N123W AND IS ESTIMATED AT 1010 MB. ONLY ISOLATED MODERATE CONVECTION IS NOTED WITHIN 60 NM OF CENTER. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS NW ACROSS SOUTHERN NICARAGUA TO THE PACIFIC COAST AT 13N87W...THEN CONTINUES WNW TO THE EMBEDDED 1004 MB SURFACE LOW PRESSURE AT 14N97W...THEN WSW TO A 1010 MB SURFACE LOW PRESSURE AT 12N123W...THEN WIGGLES SW TO 08N140W. NUMEROUS STRONG CONVECTION IS OBSERVED WITHIN 150 NM OF 14.5N104W ASSOCIATED WITH A MID LEVEL CYCLONE THAT IS MOVING WESTWARD UNDER STRONG UPPER NE FLOW. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED ALONG THE PACIFIC COAST OF COLOMBIA TO THE N OF 03N AND E OF 79W. SIMILAR CONVECTION IS OBSERVED WITHIN 120 NM EITHER SIDE OF A LINE FROM 11N87W TO 15N96W...AND ELSEWHERE FROM 08-17N BETWEEN 100-111W. ...DISCUSSION... AN UPPER TROUGH EXTENDS FROM 32N135W TO 26N140W. THE ASSOCIATED SURFACE WEAK COLD FRONT WILL MOVE INTO THE FAR NW CORNER OF THE DISCUSSION AREA WITHIN A FEW HOURS. A SURFACE HIGH WILL MEANDER NEAR 27N130W SLOWING THE EASTWARD ADVANCE OF THE FRONT TONIGHT...THEN WEAKEN ALLOWING THE FRONT TO STALL AND GRADUALLY DISSIPATE FROM 32N133W TO 26140W ON SAT. EXPECTING ONLY A 10 KT WIND SHIFT ALONG THE FRONTAL BOUNDARY WITH SEAS 4-6 FT PRIMARILY DUE TO NW SWELL. ANTICYCLONIC WINDS AT 10-15 KT ARE NOTED ALONG THE PERIPHERY OF THE SURFACE HIGH ACCOMPANIED BY SEAS OF 3-6 FT IN NE WIND WAVE/SWELL MIXING WITH CROSS EQUATORIAL S SWELL. AN UPPER TROUGH EXTENDS S ACROSS THE BAJA CALIFORNIA AREA FROM 33N115W TO 25N112W WITH UPPER MOISTURE ROTATING CYCLONICALLY THROUGH THE TROUGH TO THE N OF 32N. AN UPPER CYCLONE IS CUTOFF NEAR 20N132W WITH ITS ENVELOPE OF CYCLONIC WINDS OBSERVED ONLY WITHIN 90 NM OF ITS CENTER AND SEPARATING THE UPPER FLOW ASSOCIATED WITH ANTICYCLONES TO THE N AND TO THE WSW OF THIS CYCLONE. AN UPPER ANTICYCLONE IS CENTERED AT 23N129W WITH A RIDGE EXTENDING N TO A SHARP CREST AT 36N128W. A VERY SMALL UPPER ANTICYCLONE HAS FORMED NEAR 19N139W. AN UPPER ANTICYCLONE IS OBSERVED OVER N-CENTRAL OLD MEXICO AT 28N106W WITH AN UPPER RIDGE EXTENDING SW TO 21N126W. THESE UPPER FEATURES COMBINE TO DRY OUT THE UPPER LEVELS...AND STABILIZE THE LOWER LEVELS...OF THE DISCUSSION AREA TO THE W OF A LINE FROM 30N107W TO 18N115W TO 00N120W. AN UPPER CYCLONE IS OVER THE W-CENTRAL GULF OF MEXICO AT 29N96W TRAILING AN UPPER TROUGH S TO BASE OVER THE BAY OF CAMPECHE AT 19N95W. AN UPPER ANTICYCLONE HAS FORMED OVER GUATEMALA WITH AN UPPER RIDGE EXTENDING SE TO NW COLOMBIA. THE ASSOCIATED UPPER DIFFLUENCE IS ENHANCING THE CONVECTION PREVIOUSLY DESCRIBED... WITH THE DENSE DEBRIS MOISTURE ADVECTED SW ACROSS THE TROPICS TO THE E OF 112W. SOUTHWESTERLY MONSOONAL FLOW AT 20-25 KT...WITH SEAS 9-12 FT...IS OBSERVED ON SCATTEROMETER DATA WITHIN 150 NM SE OF A LINE EXTENDING FROM 14N96W TO 11N102W. SW WINDS AT 10-15 KT...WITH SEAS 7-10 FT IS NOTED ELSEWHERE WITHIN ACROSS THE PACIFIC WATERS FROM 06-15N BETWEEN 88-112W. THE SOUTHWESTERLY FLOW IS EXPECTED TO INCREASE ACROSS THE WATERS FROM 09-14N BETWEEN 96W-14W ON FRI...AND FROM 09-15N BETWEEN 95W-108W ON SAT....WITH LITTLE CHANGE THEN EXPECTED THROUGH THE REMAINDER OF THE WEEKEND. $$ NELSON