000 AXPZ20 KNHC 131603 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC TUE AUG 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 ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1545 UTC. ...SPECIAL FEATURE... SATELLITE IMAGERY FROM DURING THIS MORNING SHOWS A 1008 MB LOW PRES SYSTEM NEAR 15N131W MOVING W AT ABOUT 15 KT. THIS SYSTEM REMAINS DISORGANIZED AS SEVERAL LOW LEVEL CYCLONIC SWIRLS CONTINUE TO ROTATE AROUND THE AREA OF DEEP CONVECTION...WHICH CONSISTS OF THE SCATTERED STRONG TYPE WITHIN 150 NM OF THE CENTER IN THE SW QUADRANT WHERE THE BEST MOISTURE AND LOW-LEVEL CONVERGENCE AREA OCCURRING. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS SEEN WITHIN 30 NM OF 15N131W. THE LOW HAS A MEDIUM CHANCE OF INTENSIFYING INTO A TROPICAL CYCLONE OVER THE NEXT 48 HOURS AS IT TRACKS IN A GENERALLY WESTWARD MOTION. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH AXIS EXTENDS FROM CARIBBEAN LOW PRES NEAR 12N81W 1009 MB TO 10N85W TO 11N92W TO 1008 MB LOW PRES NEAR 09N114W TO 07N123W WHERE IT REMAINS FRACTURED. IT RESUMES FROM THE 1008 MB LOW AT 13N131W TO 11N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM S OF THE TROUGH BETWEEN 95W- 106W...AND ALSO WITHIN 60 NM S OF THE TROUGH BETWEEN 111W-115W. ...DISCUSSION... AN UPPER LEVEL ANTICYCLONE HAS SHIFTED ENE TO OVER FAR N CENTRAL MEXICO AT 31N106W WITH A RIDGE STRETCHING SW TO 26N124W TO A COLD REGION AT 21N136W...AND THEN CONTINUES SW TO W OF THE AREA AT 19N140W. BROAD UPPER LEVEL SW TO W FLOW PREVAILS TO THE N AND NW OF THE RIDGE...WITH WATER VAPOR IMAGERY SHOWING MODERATE TO STRONG SUBSIDENCE ALLOWING FOR DRY AND STABLE ATMOSPHERIC CONDITIONS WITHIN AND NW OF THE RIDGE. E TO NE WINDS ALOFT GENERALLY PREVAIL ACROSS THE REMAINDER OF THE AREA S AND SE OF THE RIDGE...CONTINUING TO PRODUCE A GENERALLY LIGHTLY SHEARED ENVIRONMENT. THE TROPICAL LOW DESCRIBED ABOVE IN SPECIAL FEATURES IS OBSERVED TO THE S OF THE AFOREMENTIONED RIDGE. AN INVERTED MID TO UPPER TROUGH TO THE E OF THIS TROPICAL LOW HAS BEEN MOVING WWD THE PAST SEVERAL DAYS...GRADUALLY GETTING CLOSER TO THE LOW...AND APPEARS TO HAVE MERGED WITH THE BROAD CIRCULATION OF THIS LOW. UPPER CONVERGENCE BEHIND THIS FEATURE CONTINUES TO ALLOW FOR STABLE CONDITIONS BETWEEN 124W AND 128W. THE UPPER ANTICYCLONE OVER N MEXICO IS AIDING IN PRODUCING A GENERAL NE TO E UPPER FLOW ACROSS PORTIONS OF THE AREA SE OF THE RIDGE AND E OF 120W. SATELLITE DERIVED WINDS INDICATED AN INVERTED MAINLY MID-LEVEL TROUGH OVER THE FAR EASTERN PART OF THE AREA TO THE S OF THE UPPER ANTICYCLONE...ROUGHLY FROM 25N115W TO 16N111W...DRIFTING WWD. INSTABILITY CREATED BY THIS FEATURE RESIDES OVER AN ABUNDANT POOL OF TROPICAL MOISTURE AND VERY WARM SEA SURFACE TEMPERATURES THERE...AND ALONG WITH A SURFACE TROUGH OFF THE SOUTHERN TIP OF BAJA CALIFORNIA THAT EXTENDS FROM NEAR 19N112W TO THE 1008 MB LOW EMBEDDED IN THE MONSOON TROUGH AT 09N114W. THE COMBINATION OF ALL THESE FEATURES CONTINUES TO RESULT IN PERIODS OF SCATTERED SHOWERS AND ISOLATE TSTMS FROM 15N TO 22N BETWEEN 111W AND 116W. THIS ACTIVITY HAS DIMINISHED DURING THE MORNING HOURS...BUT IS EXPECTED POSSIBLY REDEVELOP THIS AFTERNOON AND EVENING AS THE SURFACE TROUGH DRIFTS VERY SLOWLY W. ELSEWHERE AT THE SURFACE...A 1022 MB HIGH IS ANALYZED NEAR 30N136W WITH A RIDGE EXTENDING SE TO NEAR 25N117W. THE WEAK PRES GRADIENT BETWEEN THE HIGH AND PERSISTENT LOW PRES ALONG THE SIERRA MADRES OCCIDENTALES HAS BEEN PRODUCING NNW WINDS 15-20 KT ALONG AND OFFSHORE OF THE W COAST OF BAJA CALIFORNIA TO ABOUT 120W...WHERE WAVE MODEL GUIDANCE AND A FEW SHIP OBSERVATIONS FROM THE PAST 24 HOURS INDICATED PEAK SEAS ARE 5-6 FT. THESE CONDITIONS ARE FORECAST TO CHANGE LITTLE OVER THE NEXT 48 HOURS. THE HIGH IS FORECAST TO WEAKEN SLIGHTLY AS IT SHIFTS SW TO NEAR 29N139W BY EARLY WED. THE PRES GRADIENT BETWEEN THE HIGH AND THE MONSOON TROUGH CONTINUES TO SUPPORT NE WINDS OF 20-25 KT WITH SEAS PRESENTLY TO 9 FT WITHIN ABOUT 300 NM TO THE NW AND N OF THE SPECIAL FEATURE LOW 15N131W. THE LOW IS FORECAST TO CONTINUE ON A WESTWARD TRACK TO NEAR 15N138W BY EARLY WED...AND TO W OF THE DISCUSSION BY EARLY THU. A WEAKER PRES GRADIENT LEFT OVER THE FAR WESTERN PART OF THE AREA IN 48 HOURS FROM 15N TO 20N W OF 137W WILL REDUCE WINDS THERE TO 20 KT OR LESS WITH SEAS 8 FT IN NE SWELLS. $$ AGUIRRE