000 AXPZ20 KNHC 120957 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC TUE AUG 12 2008 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0945 UTC. ...SPECIAL FEATURE... TROPICAL STORM HERNAN IS CENTERED NEAR 18.5N 132.7W AT 0900 UTC MOVING W OR 265 DEG AT 08 KT. MAXIMUM SUSTAINED WINDS ARE 45 KT WITH GUSTS TO 55 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB. SCATTERED MODERATE CONVECTION IS NOTED WITHIN 90 NM NE AND WITHIN 30 NM SW SEMICIRCLES OF CENTER. HERNAN IS FORECAST TO GRADUALLY WEAKEN TO A TROPICAL DEPRESSION BY 36 HOURS. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS. ...TROPICAL LOWS... .LOW PRES IS ANALYZED NEAR 14.5N115W AND ESTIMATED AT 1008 MB. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED WITHIN 45 NM OF 15N116W. THE LOW IS FORECAST TO MOVE W THROUGH 48 HOURS. .BROAD LOW PRES OVER THE PACIFIC WATERS IS ANALYZED AS A SURFACE TROUGH FROM 11N102W TO 16N98W. EXPECT WEAK TO LOW PRES TO REDEVELOP ALONG THE TROUGH NEAR 16N107W 1009 MB IN ABOUT 24 HOURS...THEN DISSIPATE AGAIN. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 84W AT THE MOMENT AND HAS BEEN MOVING W AT ABOUT 18 KT THE PAST 24 HOURS. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED TO THE N OF 04N BETWEEN 84W AND 89W. ...ITCZ... THE ITCZ AXIS IS ALONG 10N85W TO 12N101W TO 09N114W TO 13N126W TO 11N140W. AS MENTIONED ABOVE ASSOCIATED WITH A TROPICAL WAVE...SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED N OF 04N BETWEEN 84W AND 89W. SIMILAR CONVECTION IS NOTED FROM 06N TO 10N BETWEEN 99W AND 105W AND ALSO WITHIN 15 NM EITHER SIDE OF LINE FROM 09N110W TO 09N118W. ...DISCUSSION... A POSITIVE TILT UPPER LEVEL TROUGH LIES OVER THE SUBTROPICAL PACIFIC ALONG 33N136W TO 27N142W. AN UPPER LEVEL ANTICYCLONE IS CENTERED NEAR 31N102W WITH A RIDGE EXTENDING SW ALONG 24N130W TO A SHARP CREST NEAR 17N145W. DIFFLUENCE UNDER THE RIDGE ENHANCED AFTERNOON CONVECTION AGAIN OVER NORTHERN OLD MEXICO ON MON WITH SOME OF THE DEBRIS MOISTURE SPREADING W OVER THE DISCUSSION AREA N OF 26N TO NEAR 120W. AN ATLC UPPER TROUGH EXTENDS W ACROSS THE CARIBBEAN AND OLD MEXICO ALONG 18N INTO THE E PACIFIC THROUGH AN UPPER CYCLONE AT 17N99W TO A WEAK UPPER CYCLONE AT 08N104W. THE UPPER LEVELS APPEAR MOIST FROM 14N TO 20N BETWEEN 100W AND 125W. THE UPPER LEVELS APPEAR VERY DRY W OF A LINE FROM 32N114W TO 20N136W WITH SOME OF THIS DRY AIR STILL ENTRAINING INTO THE NW QUADRANT OF TROPICAL STORM HERNAN. AT THE LOW LEVELS A RIDGE EXTENDS FROM 32N137W TO 20N112W. LOCALLY OVERCAST STRATOCUMULUS IS NOTED N OF 20N W OF 115W. AN E TO W UPPER RIDGE DOMINATES THE TROPICAL PACIFIC E OF 110W WITH THE ASSOCIATED UPPER DIFFLUENCE ENHANCING THE CONVECTION DESCRIBED ABOVE. THE DEBRIS MOISTURE REMAINS S OF 18N E OF 98W WITH SOME OF THE MOISTURE SPREADING S OF THE EQUATOR BETWEEN 78W AND 100W. $$ NELSON