WDPN31 PGTW 121500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (BEBINCA) WARNING NR 
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.2N 138.9E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 253 NM SOUTH-SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 20 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS WARMING
CLOUD TOPS AND A DISORGANIZED UPPER-LEVEL STRUCTURE THAT OBSCURES
THE LOW-LEVEL ENVIRONMENT AS TROPICAL STORM (TS) 14W HAS BEEN
PUMMELED BY UNFAVORABLE SHEAR AND DRY AIR. THE TROPICAL UPPER
TROPOSPHERIC TROUGH (TUTT) CELL TO THE NORTHWEST DIRECTLY
INTRODUCES 15-20KTS OF DRY VERTICAL WIND SHEAR INTO THE CENTER OF
CIRCULATION AS TS 14W APPROACHES THE CELL FROM THE SOUTHEAST,
RESULTING IN WEAKENING TO 50KTS. HOWEVER, THE DEGRADATION OF THE
SYSTEM IS COUNTERACTED SLIGHTLY BY WARM SEA SURFACE TEMPERATURES OF
29-30C AND STRONG POLEWARD AND EQUATORWARD OUTFLOW THAT IS ENHANCED
POLEWARD BY THE TUTT CELL. THE INITIAL POSITION IS PLACED WITH LOW
CONFIDENCE BASED ON THE AFOREMENTIONED OBSCURED LOW-LEVEL TURNING
DEPICTED IN EIR. THE INITIAL INTENSITY OF 50 KTS IS ASSESSED WITH
LOW CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE FIXES LISTED
BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: ON THE SOUTHEASTERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR) TO THE NORTHWEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T4.0 - 65 KTS
   CIMSS ADT: 49 KTS AT 122330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 14W WILL BE STEERED NORTHWESTWARD THROUGH
TAU 48 WHILE UNDER THE STEERING INFLUENCE OF A STR THAT EXTENDS
FROM THE KOREAN PENINSULA TO THE EAST OF JAPAN. FROM TAU 72-120,
THE SYSTEM WILL TAKE A WEST-NORTHWESTWARD TURN WHILE DRIVEN BY AN
EXTENSION OF THE STR, MAKING LANDFALL BETWEEN TAU 72-96. WHILE
TRACKING NORTHWESTWARD FOR THE FIRST 12 HOURS, THE SYSTEM WILL
WEAKEN SLIGHTLY WHILE THE NEARBY TUTT CELL CONTINUES TO INTRODUCE
HIGH VERTICAL WIND SHEAR OF 15-20KTS AND DRY AIR TO THE CIRCULATION
CENTER, CAUSING THE VERTICAL EXTENT OF THE STORM TO SHALLOW AND
INTENSITY TO WEAKEN TO 45KTS. AFTER THE TUTT MOVES
WEST-SOUTHWESTWARD AWAY FROM THE STORM BETWEEN TAU 24-72, THE
ENVIRONMENT WILL BECOME HIGHLY FAVORABLE FOR INTENSIFICATION AS
MOIST AIR IS RE-INTRODUCED TO THE SYSTEM AND VERTICAL WIND SHEAR
DECREASES (5-10KTS). OTHER ENVIRONMENTAL FACTORS SUCH AS WARM SEA
SURFACE TEMPERATURES (29-30C) AND FAVORABLE UPPER-LEVEL DIVERGENCE
WILL CONTINUE. THE SYSTEM WILL CONTINUE TO INTENSIFY TO A PEAK OF
95KTS AT TAU 72 JUST PRIOR TO MAKING LANDFALL, AT WHICH TIME TS 14W
WILL DISSIPATE RAPIDLY OVER LAND. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN TIGHT
AGREEMENT IN THE NEAR-TERM BUT OPENS GREATLY AFTER TAU 48 AS SOME
MODEL SOLUTIONS IN THE JTWC MULTI-MODEL CONSENSUS TRACK THE SYSTEM
AROUND THE RIDGE TO THE NORTH (UKMET, BRACKNELL) WHILE OTHERS TRACK
THE SYSTEM DIRECTLY WEST-NORTHWESTWARD. THE CROSS-TRACK SPREAD BY
THE END OF THE FORECAST OPENS TO 680NM, DECREASING THE LATE-TERM
FORECAST TO MEDIUM. ENSEMBLE GUIDANCE, GEFS AND ECENS, SHOW A HIGH
CONFIDENCE AS WELL IN THE NEAR-TERM FORECAST WITH A SPREAD OCCURRING
BETWEEN TAU 48-72. THE JTWC INTENSITY GUIDANCE IS IN GOOD AGREEMENT
THAT THE SYSTEM WILL EITHER STAGNATE OR WEAKEN SLIGHTLY WITHIN THE
FIRST 24 HOURS AND VARIES REGARDING HOW THE STAGNATION WILL
INFLUENCE THE PEAK INTENSITY WITH A SPREAD OF 55KTS AT TAU 72. THE
HIGHEST MODEL SOLUTION, THE GFS-BASED COAMPS-TC, CONVEYS THAT THE
STRONGEST RAPID INTENSIFICATION WILL OCCUR AFTER THE TUTT MOVES
AWAY BETWEEN TAU 48-72 CAUSING INTENSIFY AN EXTREME 55KTS TO A PEAK
OF 125KTS. GFS IS ON THE LOWER END REPRESENTING A MORE GRADUAL
INTENSIFICATION POSSIBLY DUE TO A LONGER PERIOD OF INFLUENCE WITH
THE TUTT CELL. AS A RESULT, THE JTWC INTENSITY GUIDANCE IS MADE
WITH MEDIUM CONFIDENCE IN THE NEAR-TERM AND LOW CONFIDENCE IN THE
LONG-TERM.

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