000 AXPZ20 KNHC 281522 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC SUN JUL 28 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 1500 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM 09N85W TO LOW PRES NEAR 09N92W 1010 MB TO 10N125W. THE ITCZ EXTENDS FROM 10N125W TO 10N135W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS NOTED FROM 05N TO 07N BETWEEN 80W AND 90W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 90 NM OF MONSOON TROUGH AXIS BETWEEN 110W AND 120W. ...DISCUSSION... A MID/UPPER SHORT WAVE TROUGH EXTENDING FROM THE NORTHERN CALIFORNIA COAST TO 28N127W IS SLOWLY DRIFTING SE...COMING IN PHASE WITH AN UPPER LOW NEAR 18N123W. A RELATED SURFACE TROUGH IS WELL DEFINED IN SCATTEROMETER IMAGERY FROM SOUTHERN CALIFORNIA NEAR 34N120W TO 31N125W. THE SURFACE TROUGH WILL PIVOT SE OFF THE SOUTHERN CALIFORNIA COAST AND CROSSING S OF 31N INTO THE DISCUSSION AREA THROUGH 48 HOURS. STRONG TO NEAR GALE FORCE CURRENTLY NOTED BEHIND THE TROUGH OFF CENTRAL AND NORTHERN CALIFORNIA WILL NOT FOLLOW THE TROUGH S OF 31N. GLOBAL WAVE MODELS INDICATE SEAS TO 7 FT IN N SWELL FOLLOW THE TROUGH INTO THE WATERS N OF 25N E OF 125W. THE UPPER LOW NEAR 18N123W IS INTERACTING WITH LOW LEVEL CONVERGENCE TO SUPPORT AREAS OF SCATTERED TO MODERATE CONVECTION ALONG THE MONSOON TROUGH BETWEEN 110W AND 120W. THE SUBTROPICAL RIDGE IS RE-ESTABLISHING ITSELF ACROSS THE WATERS N OF 15N W OF 110W...IN THE WAKE OF TROPICAL STORM FLOSSIE...NOW WELL W OF THE AREA. FOR MORE INFORMATION ON FLOSSIE PLEASE SEE BULLETINS UNDER AWIPS/WMO HEADERS HFOTCMCP1/WTPA21 PHFO WHICH CAN BE ACCESSED ONLINE AT WWW.PRH.NOAA.GOV. LATEST SCATTEROMETER DATA FROM 09 UTC SHOWS THE MAIN AREA OF WINDS ASSOCIATED WITH FLOSSIE ARE W OF 140W...BUT AN ALTIMETER PASS FROM NEAR 08 UTC SUPPORTED THE MWW3 INITIALIZATION SHOWING SEAS TO 8 FT LINGERING FROM 17N TO 25N W OF 135W. THESE SEAS WILL SHIFT W OF THE AREA THROUGH TODAY AS FLOSSIE CONTINUES W. THE MAIN FORECAST ISSUE ACROSS THE EASTERN PACIFIC CONCERNS THE DEVELOPMENT AND MOVEMENT OF AN AREA OF LOW PRES CURRENTLY NOTED NEAR 09N93W ALONG THE MONSOON TROUGH...WITH AN ESTIMATED MSLP OF 1010 MB. MODERATE TO STRONG CONVECTION WAS NOTED WITHIN 60 NM OF THE CENTER OF THE LOW DURING THE DIURNAL CONVECTIVE MAXIMUM THIS MORNING...BUT THIS HAS SINCE DIMINISHED. THE MAIN UPPER SUPPORT FOR THE LOW APPEARS TO BE THE DIVERGENCE BETWEEN AN UPPER LOW CENTERED OVER SOUTHERN MEXICO NEAR 17.5N96.5W AND A RIDGE CENTERED OVER NICARAGUA. DATA FROM A 0542 UTC OSCAT PASS AND OBSERVATIONS FROM SHIP ZDNC5 INDICATED 20 TO 25 KT SW WINDS ARE ALSO CONVERGING INTO THE MONSOON TROUGH S OF THE LOW PRES. LOWER LEVEL SUPPORT COULD BE DUE TO THE REMNANTS OF A WEAK TROPICAL WAVE THAT MIGRATED INTO THE EASTERN PACIFIC A COUPLE OF DAYS AGO. WHILE THIS WAVE BECAME DIFFUSE...CONDITIONS ARE FAVORABLE FOR WAVE GROWTH IN THE VICINITY OF THE LOW PRES. THE GFS REMAINS THE MOST AGGRESSIVE AND CONSISTENT GLOBAL MODEL WITH THE DEVELOPMENT OF THIS LOW PRES AREA FOLLOWED BY THE CMC. THE LATEST ECMWF AND NAVGEM JOIN THE GFS IN SHOWING A LOW DEVELOPING OVER THE NEXT COUPLE OF DAYS ALONG THE MONSOON TROUGH. WHILE ALL MODELS SEEM TO CONCUR THAT THE UPPER SUPPORT WILL DIMINISH THROUGH MID WEEK AS THE UPPER LOW WEAKENS AND SHIFTS FARTHER WEST...THE GFS SHOWS CONVECTIVE PROCESSES HELPING TO SUSTAIN THE LOW PRES...EVENTUALLY SHOWING WINDS TO GALE/TROPICAL STORM FORCE NEAR 13N110W BY EARLY WED. THE GFS HAS CONTINUED TO INITIALIZE BETTER WITH THIS LOW...AND THE OFFICIAL FORECAST REFLECTS THIS BY SHOWING A MORE MODERATED OUTLOOK FOR THE LOW. DEVELOPMENT WILL DEPEND IN PART ON HOW MUCH CONVECTION IS SUSTAINED OVER THE 24 TO 48 HOURS. CROSS EQUATORIAL SE AND SW SWELL RESULTING IN COMBINED SEAS OF OF 8 FT CONTINUE ACROSS THE DEEP TROPICS TO THE S OF 07N BETWEEN 95 TO 130W. THE AFFECTED AREA IS FORECAST TO SHIFT N COVERING THE WATERS S OF 12N E OF 115W TONIGHT...THEN SUBSIDE BELOW 8 FT BY TUE. $$ CHRISTENSEN