000 AXPZ20 KNHC 191539 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC SAT SEP 19 2009 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 1515 UTC. ...SPECIAL FEATURES... AT 19/1500 UTC...TROPICAL DEPRESSION MARTY IS LOCATED NEAR 22.5N 118.0W MOVING W-NW OR 285 DEG AT 9 KT. MAXIMUM SUSTAINED WIND SPEED HAS DECREASED TO 25 KT WITH GUSTS TO 35 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. INFRARED IMAGES SHOW ONLY SMALL PATCHES OF SHALLOW CONVECTION WITHIN 120 NM OF THE EXPOSED CENTER. THE DEPRESSION IS FORECAST TO DEGENERATE INTO A REMNANT LOW LATER TODAY AS IT ENCOUNTERS STRONGER VERTICAL WIND SHEAR...DRIER AIR...AND COOLER WATERS. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP1/WTPZ21KNHC FOR MORE DETAILS. A RATHER SMALL 1006 MB LOW PRESSURE SYSTEM IS CENTERED NEAR 20N108W...ABOUT 220 NM WEST OF MANZANILLO AND ABOUT 150 NM SSE OF THE SOUTHERN TIP OF BAJA CALIFORNIA...MOVING NW NEAR 10 KT. CONVECTION CONTINUES TO INCREASE IN INTENSITY NEAR THE LOW...WITH NUMEROUS MODERATE TO STRONG CONVECTION FROM 18N-20N BETWEEN 108W-110W. THIS SYSTEM COULD BECOME A TROPICAL DEPRESSION DURING THE NEXT DAY OR SO BEFORE IT ENCOUNTERS STRONG SOUTHWESTERLY UPPER LEVEL WINDS. THERE IS A HIGH CHANCE ...GREATER THAN 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. ...TROPICAL WAVE... A TROPICAL WAVE EXTENDS THROUGH THE GULF OF TEHUANTEPEC ALONG 94W N OF 10N MOVING W 15 KT. THE WAVE IS POOLING MOSITURE IN AN UPPER DIFFLUENT ZONE BETWEEN A LOW OVER THE SOUTHWESTERN CARIBBEAN AND AN ANTICYCLONE OVER SOUTHERN MEXICO. AS A RESULT...SCATTERED MODERATE AND EMBEDDED ISOLATED STRONG CONVECTION EXISTS FROM 9N-16N BETWEEN 95W-102W. ...THE ITCZ... THE INTERTROPICAL CONVERGENCE ZONE LIES ALONG A LINE FROM 06N77W TO 14N93W TO 09N110W TO 12N120W TO 10N140W. SCATTERED MODERATE CONVECTION IS FROM 03N TO 07N E OF 80W. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 08N TO 16N BETWEEN 96W AND 103W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS FROM 07N TO 10N BETWEEN 108W AND 112W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS WITHIN 180 NM S OF THE AXIS BETWEEN 125W-137W. ...DISCUSSION... W OF 120W...DEEP LAYER RIDGING DOMINATES THE PATTERN ACROSS THE SUBTROPICS CENTERED NEAR 34N134W. THE PRESSURE GRADIENT BETWEEN THE ASSOCIATED SURFACE HIGH AND THE ITCZ IS PRODUCING AN AREA OF 20 KT NE TRADES BETWEEN THE ITCZ AND 20N W OF 135W. SIMILAR MAGNITUDE OR SLIGHTLY WEAKER NLY WINDS ARE EVIDENT IN SCATTEROMETER DATA N OF 28N BETWEEN 127W AND 135W...SUPPORTED BY THE PRESSURE GRADIENT BETWEEN THE HIGH AND BROAD TROUGHING ASSOCIATED WITH MARTY AND LOW PRESSURE OVER THE SOUTHWESTERN UNITED STATES. THESE AREAS OF WIND ARE FORECAST TO WEAKEN OVER THE NEXT DAY OR TWO AS THE SURFACE HIGH TRACKS NORTHEASTWARD ...WEAKENING THE RIDGE ACROSS THE AREA. NW SWELL IS SUBSIDING OVER THE N CENTRAL WATERS BUT A NEW BATCH OF NW SWELL... ORIGINATING FROM THE SYSTEM CURRENTLY N OF HAWAII...SHOULD MOVE INTO NW WATERS TOMORROW. E OF 120W...THE MAIN SYNOPTIC SCALE FEATURES CONSIST OF A MID TO UPPER-LEVEL ANTICYCLONE CENTERED OVER SOUTHERN MEXICO AND AN ELONGATED UPPER-LEVEL TROUGH EXTENDING FROM THE NORTHERN BAJA PENINSULA SOUTHWESTWARD. DEEP LAYER SLY FLOW N OF 15N BETWEEN 105W AND 115W IS TRANSPORTING TROPICAL MOISTURE NORTHWARD. TOTAL PRECIPITABLE WATER IMAGERY SHOWS DEPICTS THIS MOIST SURGE WELL...SHOWING IT PROPAGATE NORTHWARD OVER THE GULF OF CALIFORNIA. ALTHOUGH THE ATMOSPHERE IS MOIST...DEEP CONVECTION IS CONFINED TO THE LOW NEAR 20N108W...TROPICAL WAVE...AND ITCZ. MEANWHILE...THE SW SWELL EVENT WITH PERIODS IN THE 14-16 SECOND RANGE CONTINUE TO AFFECT THE PACIFIC COASTS OF MEXICO AND CENTRAL AMERICA. WAVE WATCH GUIDANCE SHOWS A NEW SLY SWELL TRAIN WITH LEADING PERIODS OF 17-19 SECONDS REACHING THE COASTLINE TONIGHT AND SUN. $$ CANGIALOSI