Tropical Storm SURIGAE Advisory 4月18日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 02W (SURIGAE) WARNING
NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
      SUPER TYPHOON 02W (SURIGAE), LOCATED APPROXIMATELY 448NM EAST-
SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 10
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY SHOWS AN INVARIABLY SYMMETRICAL SYSTEM WITH A
CENTRAL DENSE OVERCAST (CDO) MAINTAINING A SHARPLY OUTLINED 12-NM
EYE. THE VERY ROBUST AND TIGHTLY COMPACT SYSTEM HAS SPIRALED TIGHTER
INTO THE CDO, INDICATING IT HAS POTENTIALLY REACHED ITS PEAK
INTENSITY. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE OVER
THE WELL-DEFINED EYE. THE INITIAL INTENSITY OF 165KTS IS BASED ON A
CONSENSUS OF MULTIPLE AGENCY DVORAK FINAL-T ESTIMATES RANGING FROM
T7.5 TO T8.0 (155-170KTS) PGTW, KNES, RJTD, RCTP; AND THE OBJECTIVE
ESTIMATES OF T8.0/170KTS (ADT) AND 164KTS (SATCON), ALL REFLECTING
THE EXTREMELY INTENSE SYSTEM. ENVIRONMENTAL ANALYSIS INDICATES A
FAVORABLE ENVIRONMENT WITH ROBUST RADIAL OUTFLOW, LOW TO MODERATE
(10-15 KTS) VERTICAL WIND SHEAR, AND WARM (29-30C) SEA SURFACE
TEMPERATURES IN THE PHILIPPINE SEA. STY 02W IS TRACKING TOWARD A
BREAK IN THE RIDGE TO THE NORTH-NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. STY 02W WILL TRACK TO THE NORTHWEST AS THE AFOREMENTIONED
SPLIT IN THE SUBTROPICAL RIDGE (STR) TO THE NORTH-NORTHEAST BUILDS
AND TAKES OVER AS THE MAIN STEERING RIDGE DURING THE NEXT 12 HOURS.
AT THIS SAME TIME, THE SYSTEM WILL BEGIN DECREASING IN INTENSITY AS
IT ENCOUNTERS A REGION OF HIGHER SHEAR (20-25KTS) TO THE NORTH. AS
STY SURIGAE APPROACHES THE RIDGE AXIS, THE NORTHWARD TRAJECTORY WILL
SLOW AS IT ENTERS A SLIGHTLY WEAKER STEERING ENVIRONMENT. AS THE
SYSTEM GAINS LATITUDE, DIVERGENCE ALOFT WILL DECREASE, SHEAR WILL
INCREASE, AND CAUSE THE SYSTEM TO WEAKEN DOWN TO 110KTS BY TAU 48.
NUMERICAL MODELS ARE IN FAIR AGREEMENT DURING THIS PORTION OF THE
FORECAST WITH A GRADUAL AND EVEN CROSS-TRACK SPREAD TO 148NM AT TAU
48. THEREFORE, THERE IS FAIR CONFIDENCE IN THIS PORTION OF THE JTWC
FORECAST TRACK, WHICH IS LAID OVER BUT SLIGHTLY SLOWER THAN THE
MULTI-MODEL CONSENSUS DURING THE SLOW PROGRESSION DURING THE WEAK
STEERING SEGMENT. THE CROSS TRACK ERROR DIVERGES SLIGHTLY GREATER TO
180NM BY TAU 72 AS INDICATED BY THE FAR LEFT OUTLIER OF NVGM AND THE
FAR RIGHT OUTLIER OF JGSM.
   C. AFTER TAU 72, STY SURIGAE WILL BEGIN TO RECURVE TO THE
NORTHEAST ALONG THE WESTERN PERIPHERY OF THE STR, CREST THE AXIS,
THEN ACCELERATE NORTHEASTWARD ON THE POLEWARD SIDE. AS IT MOVES
FURTHER NORTH, THE ENVIRONMENT WILL CONTINUE TO BE LESS FAVORABLE AS
UPPER LEVEL DIVERGENCE DECREASES LEADING TO A NATURAL WEAKENING OF
THE SYSTEM TO 75KTS BY TAU 120. NUMERICAL MODELS HAVE CLUSTERED
CLOSER, WITH NVGM AS THE ONLY TRACK MEMBER AIMING TOWARDS LUZON AT
TAU 96. ALL OTHER MODELS REMAIN WELL TO THE EAST OF THE ISLAND AND
CONTINUE THE TRACK TO THE NORTHEAST. THE CROSS TRACK SPREAD IS NOW
DOWN TO 425NM AT TAU 120, LENDING FAIR CONFIDENCE IN THE EXTENDED
PORTION OF THE JTWC TRACK FORECAST.//
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