Tropical Storm SAUDEL Advisory Fri Oct 23

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 19W (SAUDEL) WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 19W (SAUDEL), LOCATED APPROXIMATELY 336 NM SOUTH-
SOUTHEAST OF HONG KONG, HAS TRACKED NORTH-NORTHWESTWARD AT 04 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) AND ENHANCED INFRARED SATELLITE IMAGERY INDICATES A GENERAL
WEAKENING OF THE CONVECTIVE CORD, WITH THE AREA OF DEEP CONVECTION
BECOMING MORE LIMITED IN AREAL EXTENT AND CONFINED TO THE EASTERN
SEMICIRCLE. A CIMSS SIX HOUR TEMPERATURE TREND ANALYSIS CONFIRMS THAT
CLOUD TOP TEMPERATURES NEAR THE CORE HAVE WARMED MORE THAN FIVE
DEGREES CELSIUS NEAR THE CORE. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON THE WELL DEFINED MICROWAVE EYE FEATURE IN A
220528Z AMSR2 36 GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY IS HELD
STEADY AT 65 KNOTS WITH HIGH CONFIDENCE BASED ON MULTI-AGENCY DVORAK
CURRENT INTENSITY ESTIMATES OF T4.0 (65 KNOTS) FROM PGTW AND RJTD, AN
ADVANCED DVORAK TECHNIQUE (ADT) ESTIMATE OF T3.9 (63 KNOTS) AND A
SATELLITE CONSENSUS ESTIMATE OF 58 KNOTS. ENVIRONMENTAL ANALYSIS
REVEALS THE SYSTEM LIES IN A FAVORABLE ENVIRONMENT WITH LOW (15-20
KNOTS) VWS, WARM (28-29 DEG C) SSTS AND GOOD DUAL CHANNEL OUTFLOW. TY
19W IS MOVING SLOWLY NORTHWARD IN IN A WEAK STEERING ENVIRONMENT IN
THE COL REGION BETWEEN SUBTROPICAL RIDGES LOCATED BOTH EAST AND WEST
OF THE SYSTEM AND THE PASSAGE OF A MID-LATITUDE MAJOR SHORTWAVE TROUGH
PASSING TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. IN THE NEAR-TERM, THROUGH TAU 12, TY 19W IS FORECAST TO CONTINUE
TO DRIFT SLOWLY NORTHWARD OR MEANDER SLIGHTLY UNDER A WEAK STEERING
REGIME AS IT REMAINS TRAPPED IN THE AFOREMENTIONED COL REGION. BY TAU
24, THE MAJOR SHORTWAVE TROUGH WILL MOVE EAST AND LIFT NORTHWARD,
ALLOWING FOR THE STR TO THE EAST TO BUILD AND EXTEND TO THE WEST AND
DRIVE TY 19W ONTO A WESTWARD TRACK THROUGH TAU 72. INTENSITY IS
FORECAST TO REMAIN STEADY THROUGH TAU 12 AS THE SYSTEM REMAINS QUASI-
STATIONARY, DUE TO UPWELLING OF COOLER WATERS BELOW 27 DEG CELSIUS,
LIMITING THE AVAILABLE ENERGY FOR INTENSIFICATION. HOWEVER, AFTER THE
SYSTEM STARTS MOVING WEST, IT WILL MOVE OVER WARMER WATERS ONCE AGAIN,
AND COMBINE WITH A FAVORABLE SHEAR ENVIRONMENT WILL INTENSIFY
SLIGHTLY, PEAKING AT 70 KNOTS BY TAU 36. AFTER TAU 48, INCREASING VWS
AND COOLING SSTS WILL COMBINE TO SLOWLY WEAKEN THE SYSTEM AS IT PASSES
SOUTH OF HAINAN. NUMERICAL MODELS ARE IN GENERAL AGREEMENT ON THE
OVERALL TRACK SCENARIO, THOUGH WITH THE EXCEPTION OF AFUM AND THE
UKMET ENSEMBLE, THE MAJORITY DO NOT CAPTURE THE NEAR-TERM NORTHWARD
TRACK MOTION. BUT WITH THE EXCEPTION OF THE TWO AFOREMENTIONED MODELS,
ALL OTHER MEMBERS OF THE CONSENSUS ARE TIGHTLY PACKED ON THE WESTWARD
TRACK AFTER TAU 24. DUE TO THE NEAR-TERM NORTHWARD TRACK, THE JTWC
OFFICIAL FORECAST LIES ON THE NORTHERN EDGE OF THE GUIDANCE ENVELOPE
THROUGH TAU 72 WITH FAIR CONFIDENCE.
   C. BEYOND TAU 72, TY SAUDEL WILL TRACK MORE WEST-SOUTHWESTWARD AS
THE STR TO THE WEST ASSUMES THE DOMINATE STEERING ROLE. THE SYSTEM IS
FORECAST TO MAKE LANDFALL NORTH OF HUE, VIETNAM BETWEEN TAUS 72 AND 96
BEFORE CONTINUING SOUTHWESTWARD ACROSS LAOS BEFORE DISSIPATING OVER
EASTERN THAILAND BY TAU 120. MODEL GUIDANCE SHOWS SIGNIFICANTLY MORE
UNCERTAINTY AFTER TAU 72, WITH THE ECMWF AND THE ENSEMBLE INDICATING A
WEST-NORTHWEST TRACK AFTER TAU 72, AND THE GFS SOLUTION INDICATING A
LOOP BACK TO THE EAST BY TAU 120. THE REMAINDER OF THE CONSENSUS
MEMBERS AGREE ON THE GENERAL WEST-SOUTHWEST TRACK AFTER TAU 72 THOUGH
LANDFALL, WITH SIGNIFICANT (UP TO 410 NM) ALONG AND CROSS-TRACK SPREAD
BY TAU 120. DUE TO THE WIDELY DIVERGENT SOLUTIONS IN THE EXTENDED
FORECAST TRACK GUIDANCE, THERE IS LOW CONFIDENCE IN THIS PORTION OF
THE JTWC FORECAST TRACK.//
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