WDPN31 PGTW 131500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (BEBINCA) WARNING NR 
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.6N 134.0E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 354 NM EAST-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 21 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP
CONVECTION THAT PERSISTS OVER AN OBSCURED LOW-LEVEL CIRCULATION
CENTER (LLCC). MODERATE UPPER-LEVEL OUTFLOW IS DRAWN WESTWARD BY A 
TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL THAT HAS DRIFTED WEST-
SOUTHWESTWARD OVER THE LAST SIX HOURS. THE TUTT ALSO HAS IMPOSED 
SUBSIDENT DRY AIR TO 14W SURROUNDING THE SOUTHERN SEMICIRCLE, 
CREATING A MARGINALLY UNFAVORABLE ENVIRONMENT FOR THE SYSTEM TO 
INTENSIFY. OTHER FAVORABLE FACTORS, SUCH AS WARM SEA SURFACE 
TEMPERATURES (29-20KTS), MODERATE WESTWARD OUTFLOW, AND MODERATE 
SHEAR HAS ALLOWED TROPICAL STORM (TS) 14W TO INTENSIFY TO 45KTS 
GRADUALLY OVER THE LAST SIX HOURS. THE INITIAL POSITION IS PLACED 
WITH MEDIUM CONFIDENCE BASED ON THE OBSCURED LLCC ASSESSED TO BE 
UNDER DEEP CONVECTION. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED 
WITH HIGH CONFIDENCE BASED ON INTENSITIES OF 35-40KTS DEPICTED IN A 
131221Z METOP-B ASCAT WIND SPEED PRODUCT, WHICH IS KNOWN TO HAVE A 
SLIGHTLY LOW BIAS, ACCOMPANIED BY THE AGENCY AND OBJECTIVE FIXES 
LISTED BELOW.

INITIAL WIND RADII BASIS: SMAP DATA 

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE (STR) TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 48 KTS AT 131230Z
   CIMSS ADT: 37 KTS AT 131230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE WESTWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 14W WILL TRACK NORTHWESTWARD UNDER THE
STEERING INFLUENCE OF THE STR TO THE NORTH. CONSTRUCTIVE INTERACTION 
AS THE TS PASSES BETWEEN THE COMBINED FLOW OF THE NORTHERN STR AND 
THE WEST-SOUTHWESTERN TUTT CELL WILL ENHANCE THE TRACK SPEED IN THE 
NEAR-TERM FORECAST. AS THE TUTT CELL DRIFTS AWAY TO THE SOUTHWEST, 
THE TRACK IS EXPECTED TO GRADUALLY SLOW OVER THE OPEN OCEAN FROM 
22KTS AT TAU 0 TO 13KTS AT TAU 48. LAND FALL IS EXPECTED FOLLOWING 
TAU 48. THE CURRENT FORECAST REFLECTS A PEAK OF 70KTS BY TAU 36 AS 
THE ENVIRONMENT IS EXPECTED TO MOISTEN AND VERTICAL WIND SHEAR WILL 
CONTINUE TO DECREASE TO FAVORABLE LEVELS. HOWEVER, THE INTENSITY 
FORECAST IS CONTINGENT ON THE POSITION OF THE SYSTEM RELATIVE TO THE 
TUTT CELL, WHICH IF CLOSE BY MAY CONTINUE TO FEED DRY AIR AND 
MODERATE SHEAR TO THE CIRCULATION, INHIBITING RE-INTENSIFICATION. 
AFTER TAU 48, THE UPPER-LEVEL ENVIRONMENT IS EXPECTED TO BECOME LESS 
FAVORABLE AS TS 14W APPROACHES THE COAST, INITIATING A SLIGHT 
WEAKENING TREND JUST PRIOR TO LANDFALL BETWEEN TAU 48-72.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN STRONG
AGREEMENT THAT TS 14W WILL TRACK NORTHWESTWARD THROUGH THE END OF
THE FORECAST PERIOD WITH THE EXCEPTION OF UKMET AND THE UKMET
ENSEMBLE WHOSE SOLUTIONS LIE SIGNIFICANTLY NORTH OF THE MAJORITY OF 
THE JTWC MULTI-MODEL CONSENUS MEMBERS. GEFS AND ECENS ENSEMBLE TRACK
SOLUTIONS LIE NORTH OF OKINAWA, PASSING MUCH CLOSER TO AMAMI OSHIMA.
HOWEVER, THE SOUTHERNMOST FEW SOLUTIONS OF GEFS LEAVE SLIGHT
POTENTIAL FOR NORTHERN OKINAWA TO FALL WITHIN THE 35KT WIND RADII.
THE JTWC INTENSITY GUIDANCE HAS A SIGNIFICANT SPREAD WITH HAFS-A
PREDICTING A SLIGHT PEAK TO 50KTS OVER THE NEXT 12 HOURS AND A
GRADUAL DECLINE WHILE GFS ALTERNATIVELY FORECASTS A PEAK OF 70KTS
BT TAU 48. THE JTWC FORECAST LEANS CLOSELY TO THE GFS INTENSITY 
SOLUTION.

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