Tropical Storm SURIGAE Advisory dom, 18-04

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 02W (SURIGAE) WARNING
NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON 02W (SURIGAE), LOCATED APPROXIMATELY 399
NM EAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 09
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) SHOWS A DIMINISHING EYE MEASURING APPROXIMATELY 10NM,
LENDING TO HIGH CONFIDENCE ON THE INITIAL POSITION. A MOAT BEGAN TO
FORM ON THE EASTERN PORTION OF THE EYEWALL INDICATED ON THE 172211Z
SSMIS 91GHZ MICROWAVE IMAGE, FURTHER EVIDENCED BY AN EYEWALL
REPLACEMENT CYCLE(ERC) ON THE CIMSS M-PERC MODEL. THE INITIAL
INTENSITY OF 150KTS IS BASED ON A CONSENSUS OF MULTIPLE AGENCY
DVORAK FINAL-T ESTIMATES AT T7.0 (140KTS) PGTW, KNES, RJTD, AND
RCTP; AND THE OBJECTIVE ESTIMATES OF T7.6/158KTS (ADT), INDICATING
THE DECREASE IN INTENSITY DURING THE ERC. ANALYSIS INDICATES A
FAVORABLE ENVIRONMENT WITH CONTINUED ROBUST RADIAL OUTFLOW, LOW (5-
10KTS) VERTICAL WIND SHEAR, AND WARM (29-30C) SEA SURFACE
TEMPERATURES IN THE PHILIPPINE SEA. STY 02W CONTINUES 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 IS SLOWLY TRACKING TO THE NORTH-NORTHWEST AS THE
SUBTROPICAL RIDGE (STR) TO THE EAST-NORTHEAST BUILDS. THIS STR WILL
REMAIN THE MAIN STEERING RIDGE AS THE SYSTEM TRACKS TO THE NORTH-
NORTHEAST. STY SURIGAE WILL CONTINUE TO SLOWLY DECREASE IN INTENSITY
AS IT PROGRESSES THROUGH THE ERC AND DECREASES SSTS DUE TO GREATER
UPWELLING. AS STY 02W APPROACHES THE RIDGE AXIS WITHIN THE NEXT 12
TO 24 HOURS, THE NORTHWARD TRAJECTORY WILL SLOW AS IT ENTERS A
SLIGHTLY WEAKER STEERING ENVIRONMENT. OVER THE NEXT 36 TO 48 HOURS
THE ENVIRONMENT WILL BECOME LESS FAVORABLE AS THE POLEWARD OUTFLOW
DECREASES SLIGHTLY AND SHEAR INCREASES TO THE NORTH DECREASING THE
SYSTEM INTENSITY TO 85KTS BY TAU 72. NUMERICAL MODELS ARE IN FAIR
AGREEMENT DURING THIS PORTION OF THE FORECAST WITH A GRADUAL AND
EVEN CROSS-TRACK SPREAD TO 105NM AT TAU 48, WITH TRACK SPREAD
INCREASING TO 175NM BY TAU 72. 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.
   C. AFTER TAU 72, STY SURIGAE WILL BEGIN ITS RECURVE TO THE
NORTHEAST ALONG THE WESTERN PERIPHERY OF THE STR, CREST THE AXIS,
THEN ACCELERATE NORTHEASTWARD ON THE POLEWARD SIDE. HOWEVER, THE
CROSS-TRACK ERROR DIVERGES MORE AT THE APEX OF THE AXIS TO 245NM.
THE ENVIRONMENT BECOMES SLIGHTLY LESS FAVORABLE AS UPPER LEVEL
DIVERGENCE DECREASES AND VWS CONTINUES TO INCREASE, LEADING TO A
NATURAL WEAKENING OF THE SYSTEM TO 65KTS BY TAU 120. NUMERICAL
MODELS HAVE CLUSTERED CLOSER AND REMAIN IN THE PHILIPPINE SEA WITH
NO MODEL MEMBER TRACKING TOWARD LUZON. THE CROSS TRACK SPREAD NOW
DECREASES TO 329NM BY TAU 120, LENDING FAIR CONFIDENCE IN THE
EXTENDED PORTION OF THE JTWC TRACK FORECAST.//
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