000 AXPZ20 KNHC 170923 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC TUE NOV 17 2009 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... THE INTERTROPICAL CONVERGENCE ZONE IS CENTERED ALONG A LINE FROM 08N78W TO 06N92W TO 06N102W TO 05N110W TO 09N125W TO 07N138W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION CAN BE FOUND WITHIN 150 NM S OF THE ITCZ AXIS BETWEEN 79W AND 84W AND WITHIN 180 NM N OF THE ITCZ AXIS BETWEEN 92W AND 103W. SCATTERED MODERATE CONVECTION CAN BE FOUND WITHIN 210 NM N OF THE ITCZ AXIS BETWEEN 118W AND 125W AND BETWEEN 128W AND 138W. ...DISCUSSION... AN UPPER LEVEL TROUGH EXTENDS FROM THE U.S. LOWER MISSISSIPPI VALLEY TO 23N106W TO 24N118W TO 22N134W. A JET CORE OF 90 TO 95 KNOTS ALONG THE AXIS OF THE TROUGH CONTINUES TO INHIBIT CONVECTION OVER THE AREA N OF 22N. MEANWHILE UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THE RIGHT REAR QUADRANT OF THIS JET IS ENHANCING CONVECTION OVER THE W WATERS NEAR TWO SURFACE TROUGHS EMBEDDED IN THE ITCZ FROM 13N124W TO 08N126W AND FROM 12N137W TO 06N139W RESPECTIVELY. SATELLITE PRECIPITABLE WATER IMAGERY SHOWS A POOL OF MOISTURE IN THIS REGION...WITH PRECIPITABLE WATER VALUES IN EXCESS OF 2.25 INCHES. THE LEADING EDGE OF THE UPPER TROUGH WILL SHIFT E ACROSS MEXICO OVER THE NEXT FEW DAYS...WITH THE RIGHT REAR QUADRANT OF THE UPPER JET REMAINING OVER THE W WATERS WHICH WILL CONTINUE TO ALLOW FOR AN ELEVATED CHANCE OF SHOWERS AND THUNDERSTORMS OVER THAT AREA. OVER THE NW WATERS...A DEEP LAYER RIDGE IS IN PLACE WITH THE SURFACE RIDGE AXIS EXTENDING FROM HIGH PRES CENTERED NEAR 29N131W TO 22N121W TO 15N110W. THE PRES GRADIENT BETWEEN THIS RIDGE AND THE AFOREMENTIONED SURFACE TROUGHS OVER W WATERS AND ALONG THE ITCZ CONTINUES TO SUPPORT A LARGE AREA OF 20 TO 25 KT NE TO E TRADE WINDS S OF THE RIDGE AXIS. THE SURFACE HIGH WILL WEAKEN LATER TODAY BUT THE PRES GRADIENT WILL REMAIN TIGHT AS A STRONG COLD FRONT APPROACHES THE NW CORNER OF THE WATERS. BEHIND THE FRONT...WINDS WILL SHIFT TO THE NW AND EVENTUALLY NE BY TONIGHT INTO WED WITH THE FRONT EVENTUALLY DISSIPATING WED NIGHT. NW SWELL WILL ALSO PROPAGATE INTO THE N WATERS BEHIND THIS FRONT WITH SEAS BUILDING TO NEAR 15 FT BEGINNING LATE TONIGHT. AN AREA OF LOW PRES EMBEDDED IN THE ITCZ NEAR 06N102W IS BECOMING LESS DEFINED...NOW HAVING MORE OF THE APPEARANCE OF AN OPEN TROUGH. DIURNALLY DRIVEN CONVECTION ASSOCIATED WITH THIS FEATURE CONTINUES ITS CYCLE OF INCREASING AT NIGHT AND DISSIPATING DURING THE DAY. THIS TROUGH WILL TRACK W ALONG THE ITCZ OVER THE NEXT FEW DAYS AND WILL CONTINUE TO BE A FOCUS FOR CONVECTION. GAP WINDS... A TIGHT PRES GRADIENT REMAINS OVER THE GULF OF CALIFORNIA DUE TO THE COMBINATION OF THE HIGH PRES RIDGE TO THE W AND SW OF THE BAJA PENINSULA...A TROUGH OF LOW PRES ALONG THE E GULF OF CALIFORNIA COAST...AND HIGH PRESSURE OVER THE U.S. GREAT BASIN. AS A RESULT NW TO N WINDS OF 20 TO 25 KT CONTINUE OVER THE GULF OF CALIFORNIA AS CAPTURED BY A 0502 UTC ASCAT PASS. THE WINDS WILL GRADUALLY DIMINISH OVER THE NEXT SEVERAL HOURS AS THE PRES GRADIENT WEAKENS DUE TO STRONG COLD FRONT THAT WILL APPROACH THE W COAST OF THE U.S. AND LOW PRES MOVING INTO THE U.S. GREAT BASIN. A STRONG COLD FRONT IS CURRENTLY MOVING THROUGH THE S GULF OF MEXICO AND BAY OF CAMPECHE. N TO NE WINDS ARE BEGINNING TO FUNNEL THROUGH THE ISTHMUS OF TEHUANTEPEC AND AN 0318 UTC ASCAT PASS ALREADY SHOWED 20 TO 25 KT N TO NE WINDS IN THE GULF OF TEHUANTEPEC. THESE WINDS WILL CONTINUE TO INCREASE REACHING GALE FORCE AROUND 12 UTC THIS MORNING. MODEL GUIDANCE THEN DIMINISHES THE WINDS TO BELOW GALE FORCE IN 36 HOURS AS THE FLOW IN THE S GULF OF MEXICO JUST N OF THE ISTHMUS OF TEHUANTEPEC TURN MORE TO THE E AND EVENTUALLY SE. IN ADDITION...NE TO E WINDS IN THE 20 TO 25 KT RANGE ARE EXPECTED IN THE GULF OF PAPAGAYO AND ADJACENT AREA LATER THIS MORNING...CONTINUING THROUGH THE REMAINDER OF THE WEEK WITH A PERSISTENT N TO NE FLOW FROM THE SW CARIBBEAN TO OFF THE W COASTS OF NICARAGUA AND COSTA RICA. $$ LEWITSKY