000 AXPZ20 KNHC 211004 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC TUE SEP 21 2010 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 0900 UTC. ...ITCZ... MONSOONAL S TO SW WINDS DOMINATE THE DEEP TROPICS. THE ASSOCIATED MONSOON TROUGH WAS ANALYZED FROM 19N107W TO 14N113W TO LOW PRES 13N123.5W 1009 MB TO 11N140W. SCATTERED TO LOCALLY NUMEROUS MODERATE ISOLATED STRONG CONVECTION WAS NOTED WITHIN 45 NM N AND 210 NM S OF AXIS W OF 117W. ...DISCUSSION... ALOFT... AN ANTICYCLONIC CIRCULATION CENTERED NEAR 27N117W EXTENDS A RIDGE W-SW ACROSS THE N WATERS TO BEYOND 20N140W. THE RIDGE WILL REMAIN NEARLY STATIONARY THE NEXT 12-24 HOURS THEN SHIFT ESE TUE THROUGH WED AS A SHORT WAVE TROUGH APPROACHES THE W COAST OF THE U.S. ANOTHER ANTICYCLONE LOCATED OVER N CENTRAL MEXICO DOMINATES THE GULF OF MEXICO AND MOST OF MEXICO. THIS BROAD UPPER RIDGE AXIS CONTINUES TO PRODUCE A NE TO E WINDS ALOFT ACROSS THE AREA S OF 20N...AND A SHEARED UPPER ENVIRONMENT ACROSS THE MONSOON FLOW CONDUCIVE FOR ACTIVE CONVECTION. STRONG CONVECTION MENTIONED ABOVE WAS OCCURRING IN THE CONFLUENT SWLY FLOW ON THE S SIDE OF THE MONSOON TROUGH...WHICH WAS ACTING TO INDUCE DIVERGENT FLOW ALOFT ACROSS SEVERAL ZONES S OF 16N SURFACE... THE LARGE CYCLONIC GYRE ON THE E END OF THE MONSOON TROUGH...AND LOCATED OFFSHORE OF MEXICO HAS EVOLVED INTO A WELL DEFINED LOW...THAT HAS SHOWN INTERMITTENT BURSTS OF CONVECTION DURING THE PAST 12 HOURS. AS AFTERNOON ASCAT PASS YESTERDAY REVEALED GALE FORCE WINDS...WHICH PROMPTED THE ISSUANCE OF A GALE WARNING. UPPER-LEVEL WINDS ARE INDUCING NE SHEAR ACROSS TSTM ACTIVITY ATTEMPTING TO DEVELOP NEAR THIS LOW...AND SIGNIFICANT DEVELOPMENT OF THIS SYSTEM IS NOT ANTICIPATED. HOWEVER...AN INCREASE IN THUNDERSTORMS WOULD LIKELY RESULT IN THE FORMATION OF A TROPICAL STORM. INTERESTS IN SOUTHERN BAJA CALIFORNIA AND THE ADJACENT WATERS SHOULD MONITOR THE PROGRESS OF THIS SYSTEM. THERE IS A HIGH CHANCE OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. PRES GRADIENT BETWEEN A SURFACE RIDGE EXTENDING FROM 30N140W TO 20N118W AND LOWER PRES OVER NW MEXICO IS PRODUCING NW WINDS AROUND 20 KT RANGE AND SEAS OF UP TO 9 FT N OF 23N BETWEEN 114W AND 122W. THESE MARINE CONDITIONS WILL PERSIST DURING THE NEXT 12-24 HOURS. MARINE... FRESH TO STRONG SW WINDS PERSIST UP TO 300 NM S OF THE MONSOON TROUGH AXIS...AND ARE PRODUCING SEAS 8 TO 10 FT IN A BROAD AREA PARTICULARLY FROM 09N TO 13N BETWEEN 105W AND 130W. WINDS ON THE S SIDE OF THE TROUGH ARE EXPECTED TO WEAKEN SOME OVER THE NEXT FEW DAYS AS THE TROUGH REALIGNS E OF 120W...AND A NEW SURFACE LOW DEVELOPS WITHIN THE TROUGH NEAR 12N129W AND SHIFT E. FRESHENING SW TO W FLOW S OF THIS LOW BETWEEN 120W AND 130W IS TO BE EXPECTED. $$ STRIPLING