000 AXPZ20 KNHC 171556 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1545 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS FROM ALONG THE NW PORTION OF THE COAST OF COLOMBIA AT 10N76W TO 07N83W TO 08N91W TO 09N107W. IT IT RESUMES FROM REMNANT LOW PRES OF ALVIN NEAR 11N113W 1008 MB TO LOW PRES NEAR 08N125W 1009 MB TO 06N132W. SCATTEROMETER WINDS SUGGEST A TRANSITION TO AN ITCZ TO 06N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM S OF THE AXIS BETWEEN 121W-126W...AND ALSO WITHIN 60 NM S OF THE AXIS BETWEEN 116W-118W. ...DISCUSSION... ALOFT...WATER VAPOR IMAGERY SHOWS A SWATH OF MODERATE TO STRONG SUBSIDENCE AND DRY AIR WITHIN 275 NM EITHER SIDE OF AN UPPER TROUGH THAT EXTENDS FROM JUST W OF THE CALIFORNIA/MEXICO BORDER NEAR 32N118W SW THROUGH 25N121W TO 19N130W WHERE IT BECOMES A SHEAR AXIS TO A COL REGION AT 21N140W. TO THE NW OF THE SHEAR AXIS...BROAD ANTICYCLONIC FLOW COVERS THE AREA WITH THE ASSOCIATED ANTICYCLONE CENTERED NEAR 27N138W. A JET STREAM BRANCH ENTERS THE DISCUSSION AREA THROUGH 16N140W...AND STRETCHES ENE ROUNDING OUT THE BASE OF THE AFOREMENTIONED TROUGH NEWD TO WELL INLAND FAR NW AND NRN 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 CLOUDINESS DERIVED FROM THE VERY COLD CLOUD TOP CONVECTION ASSOCIATED WITH THE MONSOON TROUGH AND ITCZ AXIS AS WELL AS WITH THE EMBEDDED LOWS WITHIN THEM...ONE OF WHICH IS THE REMNANT LOW OF TROPICAL DEPRESSION ALVIN DESCRIBED BELOW. A SHORTWAVE TROUGH EMBEDDED IN THE SW FLOW S OF THE JET STREAM LIES ALONG 14N117W 10N117W. THE UPPER TROUGH WILL SHIFT E OF THE AREA SAT ALLOWING FOR THE LARGE ANTICYCLONE NEAR 27N138W TO TRANSLATE EWD TO OVER THE N CENTRAL PORTION OF THE AREA AS DEEP LAYER TROUGH TO THE NW OF THE AREA INTENSIFIES. AT THE SURFACE...THE 12 UTC SURFACE ANALYSIS HAS A 1025 MB HIGH CENTER NW OF THE AREA AT 31N146W WITH A RIDGE EXTENDING ESE THROUGH 30N140W 28N128W AND TO NEAR 22N114W. HIGH PRES COVERS THE AREA N OF 17N W OF 117W. THE RIDGE IS FORECAST TO REMAIN ABOUT STATIONARY THROUGH TONIGHT...THEN BEGIN TO INTENSIFY SOME ON SAT AS THE 1025 MB HIGH SHIFTS NE AND BECOMES REPLACED BY MUCH STRONGER HIGH PRES WELL TO THE N OF THE DISCUSSION AREA. THE TIGHTENING OF THE PRES GRADIENT WILL INDUCE AND OF STRONG TO NEAR GALE FORCE FORCE WINDS NE OF THE AREA NEAR THE COAST OF CALIFORNIA BY SUN. THE SRN TIER PORTION OF THIS AREA OF WINDS SHOULD BEGIN TO SEEP SEWD INTO THE FAR NE CORNER OF THE AREA LATE SUN AS NW 20 KT WINDS. SEAS THERE ARE EXPECTED TO BUILDS TO AROUND 8 FT BAY LATE SUN NIGHT. FORMER TROPICAL DEPRESSION ALVIN HAS DEGENERATED INTO A REMNANT LOW OF 1008 MB AT 11N113W DUE TO IT ENCOUNTERING SW UPPER LEVEL WINDS OF 60-90 KT TIED TO THE ABOVE MENTIONED JET STREAM BRANCH. LATEST SATELLITE IMAGERY DEPICTS NUMEROUS MODERATE TO STRONG CONVECTION WITHIN 150 NM OF THE CENTER IN THE E SEMICIRCLE...AND WITHIN 120 NM OF THE CENTER IN THE SW QUADRANT. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS ELSEWHERE FROM 08N TO 14N BETWEEN 108W AND 112W. THE REMNANT LOW IS FORECAST TO MOVE IN A GENERAL WNW DIRECTION OVER THE NEXT 48 HRS WITH RELATED DEEP CONVECTION EXPECTED TO REMAIN WITH IT. LONG PERIOD CROSS-EQUATORIAL MAINLY SW SWELLS WILL CONTINUE TO PROPAGATE WELL INTO THE CENTRAL PORTION OF THE AREA THROUGH SUN...AND REACH N TO THE VICINITY OF THE REMNANT LOW OF ALVIN. THESE SWELLS WILL MIX WITH SWELLS GENERATED BY ALVIN...AND BRING SEAS OF 8-11 FT OVER THE PORTION OF THE AREA FROM 08N-11N AND BETWEEN 108W-114W TODAY...THEN WITHIN 150 NM OF THE LOW IN THE N SEMICIRCLE AND SE QUADRANT BY EARLY SAT...AND WITHIN ABOUT 180 NM OF THE LOW IN THE NW SEMICIRCLE BY SUN. ELSEWHERE S OF 15N BETWEEN 105W-120W WINDS WILL BE ABOUT 15-20 KT WITH SEAS TO 9 FT PRIMARILY IN SW SWELLS. THIS AREA EXPANDS N TO 19N...AND W TO 125W BY SUN WITH SEAS UP TO 10 FT PRIMARILY IN SW SWELLS S OF 05N. $$ AGUIRRE