000 AXPZ20 KNHC 202147 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC TUE OCT 20 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2130 UTC. ...SPECIAL FEATURE... TROPICAL STORM RICK AT 20.4W 110.1W AT 2100 UTC OCT OR 175 NM S OF CABO SAN LUCAS MEXICO AND ABOUT 305 NM SW OF MAZATLAN MEXICO. RICK IS MOVING NE OR 045 DEG AT 8 KT. ESTIMATED MINIMUM CENTRAL PRES 990 MB. MAXIMUM SUSTAINED WINDS ARE 55 KT WITH GUSTS TO 65 KT. NUMEROUS STRONG THUNDERSTORMS ARE NOTED WITHIN 90 NM DIRECTLY S OF CENTER WHILE SCATTERED MODERATE AND ISOLATED STRONG THUNDERSTORMS ARE NOTED ELSEWHERE WITHIN 210 NM OF CENTER. THE POTENTIAL FOR HEAVY RAINFALL TO PRODUCE LIFE THREATENING FLASH FOLDS AND MUD SLIDES. RICK IS UNDERGOING SW WIND SHEAR AND IS EXPECTED TO WEAKEN SLIGHTLY BEFORE MOVING INLAND ON WED NIGHT. SEE LATEST NHC FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP5/WTPZ25 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... NONE. ...ITCZ... INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 09N78W TO 08N99W TO 13N110W TO 08N130W TO 08N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED FROM 06N TO 11N BETWEEN 78W AND 106W AND ALSO WITHIN 30 NM EITHER SIDE OF LINE FROM 17N108W TO 10N115W TO 08N123W TO 11N127W. ...DISCUSSION... AN UPPER LEVEL RIDGE IS COLLAPSING SE OVER THE NW PORTION OF THE DISCUSSION AREA...GENERALLY TO THE N OF 25N W OF 130W. AN UPPER LEVEL ANTICYCLONE IS CENTERED OVER THE DEEP TROPICS NEAR 11N125W WITH A RIDGE EXTENDING NW TO A CREST AT 19N135W. ITCZ CONVECTION WAS ENHANCED ALONG 11N BETWEEN 125W AND 129W...BUT THE DEBRIS MOISTURE REMAINS UNDER THE RIDGE. A THIRD ANTICYCLONE IS OVER TROPICAL CYCLONE RICK WITH A RIDGE EXTENDING NE AND AMPLIFYING NE OVER CENTRAL TEXAS ATTM. DEBRIS MOISTURE FROM RICK IS ADVECTED NE ACROSS ALL OF OLD MEXICO N OF 20N...AND IS NOW SPREADING NE ACROSS SW TEXAS UNDER THE RIDGE. BETWEEN THESE ANTICYCLONES IS THE SOUTHERN EXTENSION OF A LONG WAVE TROUGH THAT EXTENDS N TO S ACROSS N AMERICA ALONG ROUGHLY 105W THEN TURNS SW INTO THE DISCUSSION AREA ALONG 32N113W TO A BASE NEAR 16N115W. SOUTHWEST WINDS AHEAD OF THIS TROUGH IS AFFECTING TROPICAL STORM RICK. DRY UPPER AIR IS NOTED N OF 14N W OF 112W AND OVER THE DEEP TROPICAL PACIFIC S OF THE ITCZ W OF 120W. BROAD UPPER RIDGING DOMINATES THE TROPICS S OF 15N E OF 105W ENHANCING ITCZ CONVECTION WITH THE RESULTANT DEBRIS MOISTURE REMAINING OVER THE THE ITCZ ATTM. AT THE LOW LEVELS HIGH PRES IS CENTERED AT 32N140W WITH A RIDGE EXTENDING ESE TO NEAR 25N117W. THE GRADIENT E OF THE RIDGE HAS INCREASED THE NORTHERLY FLOW TO 20 KT OVER THE WATERS N OF 28N ALONG THE BAJA COAST. THE GRADIENT SW OF THE RIDGE IS SUPPORTING NE WINDS TO 20 KT FROM 14N TO 24N W OF 127W. N AND NW SWELLS ARE MIXING OVER THE SUBTROPICAL WATERS. SOUTHERLY SWELLS ARE CROSSING THE EQUATOR AND MIXING WITH THE NORTHERLY SWELLS BETWEEN 10N AND 20N. GAP WINDS... WINDS HAVE DECREASED BELOW GALE STRENGTH IN THE GULF OF TEHUANTEPEC WITH THE NORTHERLY FLOW EXPECTED TO FURTHER DIMINISH BELOW 20 KT WED AFTERNOON. $$ NELSON