000 AXPZ20 KNHC 170951 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC THU MAY 17 2012 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0845 UTC. ...SPECIAL FEATURES... ALETTA WAS DOWNGRADED TO A TROPICAL DEPRESSION AT 17/0900 UTC. AT THIS TIME...IT IS CENTERED NEAR 11.7N 114.6W MOVING W-NW OR 295 DEG AT 3 KT. ESTIMATED MINIMUM CENTRAL PRES 1005 MB. MAXIMUM SUSTAINED WINDS 30 KT GUSTS TO 40 KT. PLEASE REFER TO THE LATEST PUBLIC ADVISORY TCPEP1/WTPZ31 KNHC FOR MORE DETAILS. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS WITHIN 75 NM OF THE CENTER. ALETTA WILL CONTINUE TO WEAKEN DURING THE NEXT 48 HOURS AS VERTICAL SHEAR INCREASES AND DRY AIR APPROACHES. IN FACT... THE 0528 UTC HIGH RESOLUTION ASCAT PASS PROVIDED OBSERVATIONS OF 20 TO 25 KT WINDS IN ASSOCIATION WITH ALETTA. THE STRONGEST WINDS ARE IN THE NE QUADRANT. SHOWER ACTIVITY ASSOCIATED WITH A BROAD LOW PRESSURE AREA... ANALYZED NEAR 12N101W 1008 MB ON THE 0600 UTC SURFACE MAP REMAINS POORLY ORGANIZED. SATELLITE IMAGERY SHOWS SCATTERED MODERATE TO ISOLATED STRONG CONVECTION JUST N OF THE LOW CENTER TO THE COAST OF MEXICO NEAR ACAPULCO BETWEEN 98W AND 101W. ENVIRONMENTAL CONDITIONS ARE FORECAST TO BECOME MORE CONDUCIVE FOR SLOW DEVELOPMENT DURING THE NEXT FEW DAYS. GLOBAL MODELS SHOW A DEEPENING LOW PRES SYSTEM DURING THE UPCOMING WEEKEND. A SURGE OF NLY WINDS FROM THE GULF OF TEHUANTEPEC COULD ADD VORTICITY TO THE PRE-EXISTING CIRCULATION. THIS SYSTEM HAS A MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES SLOWLY TO THE NORTHWEST. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH FROM 07N78W TO LOW PRES NEAR 12N101W 1008 MB THEN RESUMES FROM 08N115W TO 05N123W. ITCZ FROM 05N123W TO 06N131W TO 03N140W. SCATTERED MODERATE ISOLATED STRONG WITHIN 60 NM EITHER SIDE OF TROUGH E OF 83W TO THE COAST OF COLOMBIA. SIMILAR CONVECTION IS NOTED N OF 10N BETWEEN 85W AND 88W. ...DISCUSSION... ALOFT...A TROUGH/RIDGE/TROUGH PATTERN DOMINATES THE N WATERS. A DEEP LAYER TROUGH CROSSES 30N140W AND EXTENDS SW TO A CUT-OFF LOW NEAR 21N146W. THE RIDGE WITH AXIS ROUGHLY ALONG 124W CONTINUES TO DOMINATE THE N PORTION OF THE DISCUSSION AREA. S AND SW WINDS BETWEEN THE TROUGH AND THE RIDGE ARE TRANSPORTING ABUNDANT MID/UPPER LEVEL MOISTURE ACROSS THE NW CORNER OF THE AREA. STRONG MID/UPPER LEVEL SUBSIDENCE AND IMPLIED DRY AIR MASS COVERS THE AREA N OF 20N E OF 120W INCLUDING THE BAJA CALIFORNIA PENINSULA AND NW MEXICO. A TROUGH IS NOTED IS THIS AREA EXTENDING FROM NW MEXICO TO NEAR 18N120W. AN ANTICYCLONIC CIRCULATION REMAINS CENTERED OVER CENTRAL AMERICA WITH A RIDGE DOMINATING THE WATERS E OF 110W. THIS FEATURE IS HELPING TO SUPPORT THE CONVECTIVE ACTIVITY NEAR THE MONSOON TROUGH AND THE LOW PRES AT 12N101W. A WEAK HIGH PRES RIDGE EXTENDING FROM 32N133W TO AROUND 20N120W IS SUPPORTING MODERATE NW WINDS N OF 28N W OF THE BAJA CALIFORNIA PENINSULA...WITH NLY SWELL MAINTAINING SEAS OF 6-7 FT IN NE PORTION OF THE DISCUSSION AREA. NE TRADE WINDS W OF 115W ARE RELATIVELY WEAK AND ARE EXPECTED TO REMAIN GENTLE TO MODERATE THROUGH THE WEEKEND DUE TO A WEAK SUBTROPICAL RIDGE N OF 30N AND NEAR-NORMAL PRESSURES WITHIN THE NEAR-EQUATORIAL TROUGH. HIGH PRES BUILDING SOUTHWARD ALONG THE GULF COAST OF MEXICO WILL INDUCE 20-25 KT N-NE WINDS INTO THE GULF OF TEHUANTEPEC THROUGH EARLY FRI. $$ GR