Advisories

WDPN31 PGTW 031500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (KROVANH) WARNING NR 
010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.0N 128.9E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 107 NM NORTH-NORTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AFTER JOGGING WEST-NORTHWESTWARD FROM 0000Z TO 0600Z, TROPICAL
STORM (TS) 22W TURNED SHARPLY NORTHWARD DURING THE PAST SIX HOURS,
RESULTING IN AN AVERAGE NORTH-NORTHWESTWARD MOTION OF 10-12 KTS
OVER THE PAST 12 HOURS. THE 10-MINUTE WIND OBSERVATIONS FROM
TOKUNOSHIMA ISLAND AND RADAR IMAGERY WERE CRITICAL IN ASSESSING THE
INITIAL POSITION WITH HIGH CONFIDENCE. ANIMATED ENHANCED INFRARED
(EIR) SATELLITE IMAGERY DEPICTS PERSISTENT CONVECTION ALONG THE
SOUTHEASTERN PERIPHERY OF THE CIRCULATION, WITH IMPROVING
EQUATORWARD OUTFLOW ALOFT AS AN UPPER-LEVEL RIDGE AMPLIFIES
IMMEDIATELY EAST OF THE VORTEX. A 030934Z WSF-M MWI 37 GHZ IMAGE
REVEALED A PARTIALLY INTACT INNER CORE WITH AN OPENING ALONG THE
WESTERN SIDE. PARTIAL RCM-3 SAR AND ASCAT-B PASSES AT 030931Z AND
031117Z, RESPECTIVELY, CONFIRMED GALE-FORCE WINDS ALONG THE EASTERN
PERIPHERY. ALTHOUGH THE CIRCULATION IS TRAVERSING WATERS WITH SEA
SURFACE TEMPERATURES (SST) OF 27-29 DEGREES CELSIUS, THE MODERATE
NORTHWESTERLY VERTICAL WIND SHEAR (VWS) REMAINS UNRELENTING, WHILE
DRY AIR PERSISTS OVER THE NORTHERN SEMICIRCLE, RESULTING IN
MARGINAL ENVIRONMENTAL CONDITIONS. GIVEN THE UNCHANGED CONVECTIVE
SIGNATURE, THE INITIAL INTENSITY HAS BEEN HELD AT 40 KTS WITH
MEDIUM CONFIDENCE. THIS ASSESSMENT IS AT THE HIGHER END OF THE
OBJECTIVE INTENSITY ESTIMATES FROM CIMSS.

INITIAL WIND RADII BASIS: PARTIAL SCATTEROMETER AND SAR DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE SOUTHEAST OF JAPAN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 42 KTS AT 030710Z
   CIMSS ADT: 35 KTS AT 031140Z
   CIMSS AIDT: 37 KTS AT 031140Z
   CIMSS D-MINT: 35 KTS AT 030618Z
   CIMSS D-PRINT: 32 KTS AT 031210Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 27-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: DRY AIR MASS ON THE NORTH SIDE

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: THE SYSTEM WILL TRACK NORTH-NORTHWESTWARD
THROUGH TAU 12 UNDER THE STEERING INFLUENCE OF THE STR TO THE EAST.
MEANWHILE, AN EXTENSIVE RIDGE IS BUILDING SOUTHEASTWARD IN THE WAKE
OF A FAST-MOVING TROUGH CROSSING THE SEA OF JAPAN. THIS DEVELOPMENT
WILL CAUSE TS 22W TO STALL BETWEEN TAU 12 AND TAU 24 BEFORE
REVERSING COURSE AND TRACKING EQUATORWARD. BY TAU 60, THE
CIRCULATION WILL GRADUALLY COME UNDER THE INFLUENCE OF DEEP-LAYER
WESTERLY TO SOUTHWESTERLY FLOW, WHICH WILL DRIVE THE SYSTEM
EASTWARD. TOWARD THE END OF THE FORECAST PERIOD, THE STR POSITIONED
EAST OF HONSHU WILL EXTEND WESTWARD, INDUCING A POLEWARD TURN
TOWARD MAINLAND JAPAN. AS THE SYSTEM APPROACHES THE STALL POINT,
THE BUILDING RIDGE WILL INCREASE VWS AND BRING A NORTHEASTERLY
SURGE OF COOL, DRY AIR INTO THE CIRCULATION. THEREFORE, THE
FORECAST CALLS FOR SLIGHT WEAKENING BY TAU 24, THOUGH THE SYSTEM
COULD WEAKEN MORE THAN CURRENTLY FORECAST. THE EQUATORWARD AND
SUBSEQUENT EASTWARD TRAJECTORY AFTER TAU 36 WILL BRING TS 22W INTO
A MORE FAVORABLE ENVIRONMENT OF LOWER SHEAR AND HIGHER MOISTURE
CONTENT. HOWEVER, THE BROAD, WEAKENED CIRCULATION WILL REQUIRE
SUBSTANTIAL TIME TO CONSOLIDATE BEFORE REINTENSIFICATION CAN
COMMENCE. ACCORDINGLY, THE WIND FIELD WILL LIKELY BECOME
INCREASINGLY SYMMETRIC AFTER TAU 72, WITH GRADUAL STRENGTHENING TO
40 KTS BY TAU 120. THE BROAD WIND FIELD CONSISTS OF A LARGE CORE OF
LIGHT WINDS NEAR THE CENTER. THE GALE-FORCE WINDS ARE LOCATED 30-60
NM FROM THE CENTER. THEREFORE, THE WINDS NEAR THE CENTER WILL
REMAIN LIGHT, WITH THE STRONGEST WINDS DISPLACED WELL AWAY FROM THE
CENTER.

MODEL DISCUSSION: THE MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT
THROUGH TAU 120, BUT SIGNIFICANT SPREAD REMAINS, PARTICULARLY AFTER
TAU 60, WITH CROSS-TRACK SPREAD INCREASING FROM 150 NM AT TAU 60 TO
240 NM BY TAU 120. THE AI-BASED MODELS GENERALLY DEPICT A TIGHTER
TURN, WHILE THE DYNAMICAL MODELS SHOW A WIDER TURN. THE JTWC TRACK
FORECAST IS POSITIONED NEAR THE MULTI-MODEL CONSENSUS (CONW)
THROUGH TAU 60 AND THEN FOLLOWS THE AI CONSENSUS AND THE
EXPERIMENTAL GOOGLE DEEPMIND SOLUTION. INTENSITY GUIDANCE IS MIXED,
WITH MOST MODELS DEPICTING WEAKENING DURING THE FIRST 24 HOURS.
DEEPMIND IS THE SOLE GUIDANCE MEMBER TO DEPICT A NEAR-STEADY
INTENSITY TREND THROUGH TAU 36. THE JTWC INTENSITY FORECAST IS
CLOSEST TO THE CONSENSUS, WHICH INDICATES AN OVERALL WEAKER SYSTEM
AFTER TAU 24, FOLLOWED BY A LATE-PERIOD INTENSIFICATION TREND. THE
CONFIDENCE IN THE TRACK AND INTENSITY FORECAST BEYOND 72 HOURS IS
LOW, OWING TO UNCERTAINTIES IN THE EVOLUTION AND STRENGTH OF THE
RIDGES TO THE EAST AND WEST, AS WELL AS THE POTENTIAL FOR
INTERACTION WITH TROPICAL DISTURBANCE 97W.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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