WDPN31 PGTW 021500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (FOUR) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.2N 146.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 226 NM EAST-SOUTHEAST OF CHICHI JIMA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY REVEALS A
WELL-DEFINED AND FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC)
ASSOCIATED WITH TROPICAL STORM (TS) 04W. THE UNAMBIGUOUS
PRESENTATION OF THE LLCC ALLOWS FOR A HIGH-CONFIDENCE POSITION
ASSESSMENT. ENVIRONMENTAL ANALYSIS INDICATES MARGINALLY CONDUCIVE
ENVIRONMENT, AS WITNESSED BY A 15-20 KTS SOUTHERLY VERTICAL WIND
SHEAR (VWS), WARM (27-28 C) SEA SURFACE TEMPERATURES (SST), ROBUST
POLEWARD OUTFLOW, PARTIALLY NEGATED BY THE PROXIMITY OF A TUTT CELL
SITUATED TO THE SOUTHWEST OF THE LLCC, AS WELL AS DRY AIR
ENTRAINMENT AFFECTING THE CONVECTIVE STRUCTURE OF THE TS. BASED ON
A SYNTHESIS OF SCATTEROMETRY, DVORAK ESTIMATES AND OBJECTIVE
INTENSITY ESTIMATES LISTED BELOW, THE INITIAL INTENSITY IS ASSESSED
AT 35 KTS WITH HIGH CONFIDENCE.

INITIAL WIND RADII BASIS: 021057Z METOP-C ASCAT DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 34 KTS AT 021130Z
   CIMSS AIDT: 36 KTS AT 021130Z
   CIMSS D-MINT: 32 KTS AT 020823Z
   CIMSS D-PRINT: 31 KTS AT 021130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT, AS WELL AS TUTT CELL
ASSOCIATED SHEAR

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 04W IS PROJECTED TO TRACK NORTHWESTWARD
INITIALLY UNDER THE STEERING INFLUENCE OF A SUBTROPICAL RIDGE (STR)
POSITIONED TO THE NORTHEAST. BY TAU 24, THIS RIDGE WILL REORIENT
AND EXTEND ALONG A SOUTHWEST-NORTHEAST AXIS. THIS EVOLVING
SYNOPTIC PATTERN WILL RESULT IN A POLEWARD ACCELERATION, WITH THE
SYSTEM TRACKING NORTH TO NORTHEAST THROUGH TAU 96. BEYOND THIS,
FURTHER RIDGE AMPLIFICATION EAST OF THE SYSTEM WILL INITIATE A
SECONDARY POLEWARD TURN. THE INTENSITY FORECAST CALLS FOR STEADY
INTENSIFICATION THROUGH TAU 72 AS VWS BECOMES MORE FAVORABLE AND THE 
SYSTEM CONTINUES TO DISTANCE ITSELF FROM THE SUPPRESSIVE INFLUENCE OF 
THE TUTT CELL. PEAK INTENSITY IS FORECAST TO REACH 65 KTS DURING THIS 
PERIOD. THEREAFTER, INCREASED DRY AIR ENTRAINMENT, IN CONJUNCTION WITH 
PROGRESSIVELY DECREASING SST ALONG THE POLEWARD TRACK, ARE EXPECTED TO 
INDUCE WEAKENING. INTERACTION WITH AN APPROACHING UPPER-LEVEL TROUGH 
IS ANTICIPATED LATE IN THE FORECAST PERIOD, LIKELY RESULTING IN A 
SHARP INCREASE IN VWS.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE EXHIBITS MODERATE 
CONSENSUS THROUGH TAU 96, WITH ALL MEMBERS SUGGESTING AN
S-SHAPED TRAJECTORY. CROSS-TRACK SPREAD IS APPROXIMATELY 120 NM AT
TAU 72. BEYOND THAT, MODEL DIVERGENCE INCREASES SIGNIFICANTLY DUE
TO UNCERTAINTY REGARDING THE EVOLUTION AND ORIENTATION OF THE
UPPER-LEVEL TROUGH ADVANCING FROM THE WEST AND ITS TIMING RELATIVE
TO THE MOTION OF TS 04W. GALWEM AND DETERMINISTIC GFS FAVOR A
NORTHWESTWARD DEFLECTION JUST PRIOR TO TAU 120, WHILE NAVGEM AND JGSM
SUGGEST CONTINUED NORTHEASTWARD MOTION. THE REMAINDER OF GLOBAL
MODELS TREND TOWARD A POLEWARD TRACK, AND THE JTWC OFFICIAL
FORECAST REMAINS CLOSELY ALIGNED WITH THE MULTI-MODEL CONSENSUS
ENVELOPE. INTENSITY GUIDANCE SHOWS FAIR AGREEMENT ON THE 
INTENSIFICATION PHASE, PEAKING AROUND TAU 72, FOLLOWED BY WEAKENING. 
PEAK WIND SPEED PROJECTIONS SPAN A RANGE OF 50 KTS, WITH COAMPS-TC AT 
THE HIGH END (95 KTS) AND STATISTICAL-DYNAMICAL MODELS OSCILLATING 
NEAR 45-50 KTS. THE JTWC INTENSITY FORECAST IS ANCHORED NEAR THE 
CONSENSUS MEAN AND IS PREDICTING PEAK OF 65 KTS REACHED AROUND TAU 72. 
ADDITIONALLY, RAPID INTENSIFICATION (RI) CONSENSUS MODEL (RICN), AS 
WELL AS THE COAMPS-TC ENSEMBLE RI AID (CTR1) INDICATE POTENTIAL FOR 30 
KTS INTENSITY INCREASE WITHIN THE NEXT 24 HOURS.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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