000 AXPZ20 KNHC 081531 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC SUN AUG 08 2010 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1530 UTC. ...SPECIAL FEATURE... AT 08/1500 UTC...THE CENTER OF TROPICAL STORM ESTELLE WAS LOCATED NEAR 18.0N 111.0W MOVING TOWARD THE WEST OR 280 DEGREES AT 7 KT...AND THIS GENERAL MOTION...WITH A CONTINUED GRADUAL DECREASE IN FORWARD SPEED...IS EXPECTED DURING THE NEXT 48 HOURS. ESTIMATED MINIMUM CENTRAL PRESSURE IS 996 MB. MAXIMUM SUSTAINED WINDS HAVE DECREASED TO 50 KT WITH GUSTS TO 60 KT. DESPITE A RECENT FLARE UP OF COLD TOP CONVECTION OVER THE LOW LEVEL CENTER THE OVERALL ORGANIZATION OF ESTELLE HAS DECREASED SOMEWHAT. THIS WEAKENING TREND IS EXPECTED TO CONTINUE OVER THE NEXT FEW DAYS DUE TO A COMBINATION OF INCREASED VERTICAL WIND SHEAR AND COOLER SEA SURFACE TEMPERATURES. THE OFFICIAL FORECAST KEEPS ESTELLE AS A TROPICAL STORM THROUGH 36 HOURS. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP2/ WTPZ22 KNHC FOR MORE DETAILS. ...ITCZ... THE ITCZ AXIS IS ALONG 11N73W TO 12N90W TO 15N105W TO 11N122W TO 11N137W TO 10N140W. SCATTERED MODERATE TO STRONG CONVECTION WAS NOTED WITHIN 150 NM N AND 240 NM S OF AXIS E OF 102W. SCATTERED MODERATE TO STRONG CONVECTION WAS NOTED WITHIN 90 NM N AND 180 NM S OF AXIS BETWEEN 106W AND 123W. ...DISCUSSION... AN UPPER LEVEL ANTICYCLONE LOCATED NEAR 23N131W WITH AN UPPER RIDGE EXTENDING NW BEYOND 32N136W. THIS ANTICYCLONE APPEARS TO BE MERGING WITH ANOTHER ANTICYCLONE CENTERED IN THE DEEP TROPICS NEAR 17N130W. TOGETHER THESE FEATURES GOVERN THE FLOW OVER THE AREA N OF THE ITCZ AND W OF 125W. VERY DRY AIR ALOFT WITH MODERATE TO STRONG SUBSIDENCE IS PRESENT ACROSS THE SAME GENERAL AREA. A DIGGING UPPER LEVEL TROUGH ENTERS THE FORECAST AREA NEAR 32N120W AND CONTINUES SSW THROUGH 20N125W. THIS TROUGH WAS BECOMING IN PHASE WITH A CYCLONIC CIRCULATION NEAR 20N121W. THIS AREA OF TROUGHINESS SEPARATES THE ANTICYCLONES NOTED ABOVE FROM ANOTHER UPPER LEVEL ANTICYCLONE LOCATED OVER E-CENTRAL MEXICO NEAR 20N98W WITH A RIDGE AXIS EXTENDING WNW INTO THE E PACIFIC NEAR 23N117W. TROPICAL STORM ESTELLE IS EMBEDDED IN THE UPPER LEVEL SOUTHEASTERLY FLOW TO THE SW OF THIS ANTICYCLONE. A WEAK UPPER LEVEL TROUGH AXIS EXTENDS FROM A CYCLONIC CIRCULATION ALONG THE TEXAS GULF COAST WWD ACROSS NRN MEXICO ALONG 29N. ZONAL/EASTERLY FLOW PREVAILS ACROSS THE REMAINDER OF THE DISCUSSION AREA IN THE DEEP TROPICS S OF 12N. UPPER LEVEL MOISTURE RESULTING FROM ITCZ CONVECTION IS BEING ADVECTED TO THE WEST AS A RESULT OF THE PERSISTENT EASTERLY WINDS. UPPER LEVEL DIFFLUENCE IS HELPING TO INDUCE CONVECTION ALONG THE ITCZ PARTICULARLY IN THE AREA BETWEEN 115W AND 123W. AT THE SURFACE...A RIDGE DOMINATES THE NORTHERN WATERS ORIGINATING FROM 1027 MB HIGH PRES CENTERED NW OF THE AREA NEAR 36N145W ENTERING THE DISCUSSION AREA AT 32N137W AND CONTINUING THROUGH 22N112. NOAA CORPS SHIP 'MCARTHUR II' NOW LOCATED NEAR 28N133W HAS BEEN REPORTING NE WINDS OF ABOUT 15 KT DURING THE PAST FEW HOURS. THE FORECAST KEEPS AN AREA OF 15-20 KT WINDS N OF 28N BETWEEN 124W AND 132W DUE TO A RATHER TIGHT PRESSURE GRADIENT BETWEEN THE RIDGE AND LOWER PRESSURE OVER SOUTHERN CALIFORNIA. GLOBAL MODELS TRANSLATE THIS AREA TO THE SW OVER THE NEXT 24-36 HOURS AND GRADUALLY DIMINISHES THE WIND FIELD BELOW 20 KT AS A BROAD AREA OF MODERATE TRADES DEVELOPS W OF 133W. ELSEWHERE FARTHER WEST...A WEAK SURFACE TROUGH EMBEDDED WITHIN THE ITCZ EXTENDS FROM 13N135W TO 09N139W. THE TROUGH IS FORECAST TO DRIFT WESTWARD AT AROUND 5-10 KT OVER THE NEXT FEW DAYS. DISTURBANCES ALONG THE ITCZ CONTINUE TO PRODUCE AN AREA OF S TO SW WINDS OF 20-25 KT S OF THE ITCZ TO 08N BETWEEN 98W AND 120W AS CAPTURED BY EARLIER ASCENDING ASCAT PASSES AT 08/0352 UTC AND 08/0536 UTC RESPECTIVELY. COMBINED SEAS ARE 8 TO 12 FT FROM LONG PERIOD SW SWELL AND FRESHLY GENERATED WIND SEAS. THIS OVERALL WEATHER PATTERN WILL PERSIST DURING THE NEXT FEW DAYS. CROSS EQUATORIAL SW SWELLS DOMINATING THE MAJORITY OF THE FORECAST WATERS WILL GRADUALLY DECAY THROUGH MON. A NEW SWELL TRAIN WITH PERIODS OF 15-16 SECONDS IS EXPECTED TO CROSS THE EQUATOR BETWEEN 105W AND 125W MON...AND SPREAD OVER MOST OF THE BASIN S OF 13N-15N BY LATE TUE. $$ COBB