000 AXPZ20 KNHC 170311 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC FRI MAY 17 2013 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0300 UTC. ...SPECIAL FEATURES... TROPICAL STORM ALVIN CENTERED NEAR 9.8N 110.8W AT 17/0300 UTC OR ABOUT 770 MI SSW OF MANZANILLO MEXICO MOVING WNW AT 12 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP1/WTPZ21. SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 240 NM IN THE E QUADRANT AND SW SEMICIRCLE OF ALVIN...WITH VERY LITTLE CONVECTION ON THE N SIDE OF THE STORM. ALVIN REMAINS IN A HOSTILE ENVIRONMENT AND IT IS FORECAST TO GRADUALLY WEAKEN TO A TROPICAL DEPRESSION BY SAT MORNING...THEN TO A REMNANT LOW BY SUN EVENING. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS FROM 06N77W TO 1009 MB LOW PRES NEAR 06N81W TO 09N87W TO 07N96W TO 09N106W...THEN RESUMES FROM 09N113W TO 06N132W. THE ITCZ AXIS EXTENDS FROM 06N132W TO 04N140W. SCATTERED MODERATE CONVECTION IS WITHIN 180 NM EITHER SIDE OF THE MONSOON TROUGH BETWEEN 113W AND 117W...FROM 09N TO 12N BETWEEN 116W AND 122W...AND ALSO WITHIN 180 NM N OF A LINE FROM 05N127W TO 08N135W. SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 120 NM N OF THE MONSOON TROUGH BETWEEN 118W AND 125W. ...DISCUSSION... ALOFT...WATER VAPOR IMAGERY SHOWS A SWATH OF MODERATE TO STRONG SUBSIDENCE AND DRY AIR WITHIN 270 NM EITHER SIDE OF AN UPPER TROUGH EXTENDING FROM JUST W OF THE CALIFORNIA/MEXICO BORDER NEAR 32N118W THROUGH 25N122W TO 21N140W. AN ASSOCIATED JET STREAM BRANCH IS NOTED ALONG 15N W OF 120W...STRETCHING NE FROM 120W TO ACROSS SRN BAJA CALIFORNIA AND WELL INLAND OVER CENTRAL MEXICO. S OF THIS JET STREAM...ABUNDANT UPPER LEVEL MOISTURE IS SEEN STREAMING ENE FROM THE DEEP TROPICAL CENTRAL PACIFIC REGION. THIS MOISTURE IS FURTHER ENHANCED FROM UPPER LEVEL DEEP CLOUDINESS DUE TO THE VERY COLD CLOUD TO CONVECTION ASSOCIATED WITH THE MONSOON AND ITCZ FEATURES AS WELL...RELATING TO TROPICAL STORM ALVIN. AT THE SURFACE...1028 MB HIGH PRES IS LOCATED JUST W OF THE DISCUSSION WATERS NEAR 32N147W...WITH A RIDGE EXTENDING TO THE E- SE THROUGH 29N130W TO NEAR 19N111W. MAINLY MODERATE ANTICYCLONIC WINDS AND 5-7 FT SEAS COVER THE WATERS N OF 12N W OF 114W UNDER THIS RIDGING. MODEL GUIDANCE INDICATES THAT THE RIDGE WILL STRENGTHEN OVER THE NEXT 48 HRS INDUCING A SLIGHTLY TIGHTER PRES GRADIENT OVER THE FAR W CENTRAL WATERS OF THE AREA...ALLOWING FOR NE-E TRADE WINDS OF 15-20 KT FROM 16N TO 19N W OF 136W BY LATE TONIGHT...THEN SHIFTING TO COVER THE WATERS FROM 12N TO 19N W OF 136W BY FRI EVENING. SEAS OF 8-9 FT WILL ACCOMPANY THESE WINDS...IN FRESH NE WIND WAVES COMBINED WITH LONG PERIOD CROSS- EQUATORIAL SW SWELL. THE WINDS WILL THEN DIMINISH WITH SEAS SUBSIDING TO LESS THAN 8 FT BY SAT AFTERNOON AS THE PRES GRADIENT THEN SLACKENS. WEAK 1009 MB LOW PRES IS ANALYZED ALONG THE MONSOON TROUGH NEAR 06N81W...WITH ASSOCIATED SCATTERED MODERATE CONVECTION WITHIN 150 NM IN THE SW QUADRANT OF THE LOW. THE LOW IS FORECAST TO GRADUALLY DISSIPATE DURING THE NEXT 24 HOURS. EARLIER SCATTEROMETER AND ALTIMETER DATA INDICATED THAT WINDS ARE 20 KT OR LESS AND SEAS LESS THAN 8 FT. LONG PERIOD SW SWELLS MOVING UP FROM THE SRN HEMISPHERE WILL MIX WITH SWELLS GENERATED BY ALVIN...PRODUCING SEAS OF 8 FT OR GREATER IN THE EQUATORIAL WATERS BETWEEN 108W AND 120W S OF 18N DURING THE NEXT 48 HRS. $$ LEWITSKY