Tropical Storm MAYSAK Advisory Sat Apr 04

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 04W (MAYSAK) WARNING NR 30//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 04W (MAYSAK), LOCATED APPROXIMATELY 524 NM EAST OF
MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 10 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
INDICATES ERODING DEEP CONVECTION AND EXPOSED LOW-LEVEL CLOUD LINES,
HOWEVER, CORE CONVECTION HAS PERSISTED BUT REMAINED ASYMMETRIC. THIS
STRUCTURE IS CLEARLY EVIDENT IN A 030356Z TRMM IMAGE, WHICH SHOWS A
WEAK MICROWAVE EYE FEATURE ON THE WESTERN EDGE OF THE DEEP
CONVECTION. THE BULK OF THE DEEP CONVECTION REMAINS DISPLACED OVER
THE EASTERN SEMI-CIRCLE DUE TO MODERATE WESTERLY VERTICAL WIND SHEAR
(VWS) ASSOCIATED WITH A DEEP UPPER-LEVEL TROUGH. ADDITIONALLY, UPPER-
LEVEL ANALYSIS INDICATES SIGNIFICANT DRY AIR ADVECTION INTO THE
PHILIPPINE SEA BY THE AFOREMENTIONED TROUGH. THESE FACTORS ARE
OFFSETTING THE VIGOROUS POLEWARD OUTFLOW THAT IS EVIDENT ON THE
WATER VAPOR LOOP. THE INITIAL POSITION IS BASED ON MSI AND THE TRMM
IMAGE WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS HEDGED SLIGHTLY
LOWER THAN DVORAK CURRENT INTENSITY ESTIMATES OF T5.0 (90 KNOTS) TO
REFLECT THE SYSTEM'S ASYMMETRIC, WEAKENED STRUCTURE. TY MAYSAK IS
TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF THE DEEP LAYERED
SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 04W WILL CONTINUE TRACKING WEST-NORTHWESTWARD THROUGH TAU
72 UNDER THE STEERING INFLUENCE OF THE STR. UPPER-LEVEL
ENVIRONMENTAL CONDITIONS WILL REMAIN MARGINAL, WHICH WILL LEAD TO
SIGNIFICANT WEAKENING PRIOR TO LANDFALL. THEREAFTER, THE SYSTEM WILL
WEAKEN FURTHER AS IT TRACKS OVER LUZON. BEYOND TAU 48, TY 04W WILL
ENCOUNTER WESTERLY VWS AND WILL CONTINUE TO WEAKEN.
   C. IN THE EXTENDED TAUS, TY MAYSAK WILL DISSIPATE DUE TO HIGH VWS
AND POOR OUTFLOW ALOFT. NEAR TAU 96, A STRONG NORTHEASTERLY SURGE
THROUGH THE TAIWAN STRAIT WILL FORCE THE WEAKENED SYSTEM TO BEND
WESTWARD. IN ADDITION TO A POOR UPPER-LEVEL ENVIRONMENT, TY 04W WILL
ALSO ENCOUNTER SST BELOW 26 CELSIUS. DYNAMIC GUIDANCE REMAINS IN
GOOD AGREEMENT, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK.//
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