WDPN32 PGTW 122100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (SON-TINH) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 34.1N 149.5E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 489 NM EAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FULLY
EXPOSED LLCC WITH NO DEEP CONVECTION. THERE IS 25-30 KTS OF
NORTHEASTERLY SHEAR DUE TO AN UPPER-LEVEL LOW SOUTH OF THE LLCC,
AND THE CIRCULATION IS NOW EMBEDDED IN A DEEPLY DRY AIR MASS. THE
INITIAL INTENSITY IS HELD AT 40 KTS BASED ON A SHIP OBSERVATION
CONTINUING TO OBSERVE 31 KT WINDS 105 NM NORTH-NORTHEAST OF THE
LLCC, INDICATING THAT THE MAX WIND BAND LIKELY RETAINS AT LEAST
GALE-FORCE WINDS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.0 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: DEEP-LAYER DRY AIR MASS NEAR AND NORTH OF THE
CIRCULATION

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: TROPICAL STORM 07W (SON-TINH) WILL CONTINUE TO
TRACK NORTHWESTWARD AROUND THE WESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE TO THE EAST, EVENTUALLY TURNING NORTHWARD BY 24-36 HOURS.
WHILE SEA SURFACE TEMPERATURES REMAIN ABOVE 26 DEGREES CELSIUS FOR
THE FIRST 24 HOURS, THE DEEP-LAYER DRY AIR MASS AND CONTINUING
MODERATE TO STRONG SHEAR IS EXPECTED TO PREVENT REGENERATION OF ANY
DEEP CONVECTIVE STRUCTURE, RESULTING IN GRADUAL DECAY OF THE MOSTLY
BARREN CIRCULATION, CULMINATING IN DISSIPATION AROUND 36 HOURS
SOUTHEAST OF HOKKAIDO OVER PROHIBITIVELY COOL WATERS.

MODEL DISCUSSION: MODELS ARE IN GOOD AGREEMENT ON THE TRACK
FORECAST THROUGH 36 HOURS, AND THE JTWC FORECAST IS CLOSE TO THE
MULTI-MODEL CONSENSUS. THE INTENSITY FORECAST IS CLOSER TO THE
DYNAMICAL GUIDANCE, WHICH SHOWS FASTER WEAKENING THAN THE
STATISTICAL GUIDANCE THROUGH 36 HOURS.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: HIGH//
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