Tropical Storm SURIGAE Advisory Mon Apr 19

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 02W (SURIGAE) WARNING NR 025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 02W (SURIGAE), LOCATED APPROXIMATELY 302 NM EAST OF
MANILA, PHILIPPINES, HAS TRACKED NORTH-NORTHWESTWARD AT 02 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY SHOWS A VERY INTENSE AND HIGHLY SYMMETRICAL SYSTEM THAT HAS
MAINTAINED A DEEP, ALBEIT SLIGHTLY WARMING, CENTRAL DENSE OVERCAST
WITH A LARGE AND WELL-DEFINED 34NM EYE. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE EYE IN THE EIR LOOP,
ADJUSTED FOR SLIGHT TILT AND LINED UP WITH A SEMI-CIRCULATION
FEATURE IN THE 191126Z ASCAT PASS. THE INITIAL INTENSITY OF 120KTS
IS BASED ON A CONSENSUS OF WEAKENING AGENCY DVORAK FINAL-T ESTIMATES
OF T6.0/115KTS (PGTW, RJTD, AND KNES) AND THE OBJECTIVE FINAL-T
ESTIMATES OF T5.7/110KTS (ADT) AND 121KTS (SATCON) AND REFLECTS THE
SUSTAINED INTENSE EIR SIGNATURE OF AND THE SLIGHT CONVECTIVE
WARMING. ANALYSIS INDICATES THE ENVIRONMENT REMAINS FAVORABLE WITH
GOOD RADIAL OUTFLOW, LOW (5-10KT) VERTICAL WIND SHEAR (VWS) AND WARM
(29C) SEA SURFACE TEMPERATURES (SSTS) IN THE PHILIPPINE SEA. THE
CYCLONE IS IN A COL BETWEEN THE SUBTROPICAL RIDGE (STR) TO THE WEST
AND STR TO THE EAST THAT IS SLOWLY DRIVING IT ALONG ITS WESTERN
PERIPHERY.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 02W WILL SLOWLY SPEED UP OUT OF THE COL AND CONTINUE ON ITS
NORTH-NORTHWESTWARD TRACK AS THE STR TO THE WEST QUICKLY DEFLATES
AND THE STR TO THE EAST BUILDS, ELONGATES MERIDIONALLY, AND BECOME
THE PRIMARY STEERING MECHANISM. AFTER TAU 48, IT WILL TURN MORE
NORTH-NORTHEASTWARD AND CREST THE STR AXIS. INCREASING VWS AND
DIMINISHING OUTFLOW ALOFT WILL GRADUALLY WEAKEN THE SYSTEM DOWN TO
85KTS BY TAU 72. NUMERICAL MODELS ARE IN GOOD AGREEMENT WITH NVGM
THE EXTREME LEFT OUTLIER BRINGING THE VORTEX TOWARD NORTHEASTERN
LUZON THEN ERRATICALLY CROSSING THE MODEL ENVELOPE DUE EASTWARD INTO
THE PHILIPPINE SEA AND EXPANDING THE CROSS-TRACK SPREAD TO 173NM BY
TAU 48. THE MAIN STRAND OF NUMERICAL MODELS, DISCOUNTING NVGM, HAS A
SPAN OF A MERE 52NM AT TAU 72. THERE IS OVERALL FAIR CONFIDENCE IN
THIS PORTION OF THE JTWC FORECAST TRACK WHICH IS LAID SLOWER THAN
THE MULTI-MODEL CONSENSUS (CONW) IN THE NEAR TERM AND TO THE RIGHT
OF CONW AFTER TAU 24 TO OFFSET THE UNLIKELY NVGM TRACK.
   C. AFTER TAU 72, TY SURIGAE WILL ACCELERATE EAST-NORTHEASTWARD ON
THE POLEWARD SIDE OF THE STR. THE ADDITION OF COOLING SSTS WILL
WEAKEN THE SYSTEM FASTER AND BY TAU 120, WILL BE REDUCED TO 50KTS.
ALSO BY TAU 96, IT WILL BEGIN EXTRATROPICAL TRANSITION AS IT ENTERS
THE COLD BAROCLINIC ZONE. DISCOUNTING NVGM, THE NUMERICAL MODELS ARE
IN TIGHT IN AGREEMENT AND SPREAD OUT TO JUST 116NM BY TAU 120,
LENDING ALSO FAIR CONFIDENCE IN THE EXTENDED PORTION OF THE JTWC
TRACK FORECAST THAT IS LAID TO THE LEFT OF AND SLIGHTLY FASTER THAN
CONW TO OFFSET THE ERRATIC TRACK OF NVGM.//
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