WDPN31 PGTW 122100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM TS (BEBINCA) WARNING NR 
012A RELOCATED//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.0N 137.5E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 310 NM SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 17 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED CIRA PROXY-VISIBLE IMAGERY (PVI) OVER THE PAST SIX HOURS
CONTINUES TO DEPICT A SIGNIFICANT DECLINE IN THE SATELLITE
PRESENTATION, WITH RAGGED DEEP CONVECTION DISPLACED TO THE NORTH OF
A FULLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC), DUE TO THE
PROXIMITY OF A TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL TO
THE WEST. THE TUTT IS INJECTING SUBSIDENT DRY AIR INTO THE
MID-LEVEL CORE OF TS BEBINCA, WHILE ALSO INDUCING AN ESTIMATED 25
KNOT DEEP LAYER SOUTHERLY VERTICAL WIND SHEAR (VWS) ACROSS THE LLCC,
ACCORDING TO THE CIMSS SHEAR ANALYSIS. PRIOR TO THE EMERGENCE OF
THE EXPOSED LLCC, POSITIONING AND STRUCTURAL ANALYSIS OVERNIGHT WAS
CHALLENGING DUE TO SPORADIC AVAILABILITY OF POLAR ORBITING
MICROWAVE DATA. ADDITIONALLY, THE 121156Z ASCAT FOOTPRINT COVERAGE
MISSED 14W COMPLETELY. A 121510Z OSCAT PARTIAL PASS CAPTURED THE
CENTER, HOWEVER, THE POSITION FIX IS SUSPECT OWING TO BEING 50NM
WEST OF THE ANALYZED LLCC IN PVI. THE INITIAL POSITION WAS BASED
WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC, AND REPRESENTS A
RELOCATION OF ABOUT 75 NM TO THE SOUTHWEST FROM THE PRIOR 12Z BEST
TRACK POSITION. THE DVORAK INTENSITY ANALYSIS IS ALSO CHALLENGING
DUE TO THE RAPID DECAY OF CONVECTION. IN THE ABSENCE OF AERIAL
RECONNAISSANCE OR RELIABLE SCATTEROMETER DATA TO AID THE ANALYSIS,
THE INTENSITY IS ASSESSED WITH LOW CONFIDENCE AT 45 KNOTS, WHICH
AGREES WITH AVAILABLE OBJECTIVE INTENSITY AIDS. VIGOROUS POLEWARD
OUTFLOW IS ENHANCED BY THE TUTT FLOW, WHILE THE EQUATORWARD FLOW IS
CONSTRAINED TO A WEAK CHANNEL ON THE EASTERN SIDE OF THE
CIRCULATION. WARM SEA SURFACE TEMPERATURES OF 29-30C REMAIN
FAVORABLE.

INITIAL WIND RADII BASIS: CIRA MULTIPLATFORM SATELLITE WIND ANALYSIS

CURRENT STEERING MECHANISM: TS BEBINCA IS TRACKING NORTHWESTWARD
ALONG THE ENHANCED GRADIENT BOUNDARY BETWEEN A SUBTROPICAL RIDGE TO
THE NORTHEAST AND THE BROAD UPPER LEVEL CYCLONIC TUTT FLOW.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 52 KTS AT 121400Z
   CIMSS ADT: 41 KTS AT 121930Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: UNFAVORABLE ENVIRONMENT DUE TO PROXIMITY TO TUTT
CELL TO THE WEST. 

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: INITIAL POSITION WAS RELOCATED 74NM
TO THE SW FROM PRIOR 12Z POSITION BASED ON CLEAR EVIDENCE OF AN
EXPOSED LLCC. THE RELOCATION RESULTED IN A PRIMARILY SOUTHWESTWARD
SHIFT OF THE FORECAST TRACK THROUGH TAU 48. PEAK INTENSITY
DECREASED DUE TO CONTINUED IMPACTS OF THE TUTT, WHICH WILL IMPROVE
AFTER TAU 36, BUT TOO LATE TO REACH PRIOR FORECAST PEAK. 

FORECAST DISCUSSION: ALTHOUGH SHIFTED DUE TO THE RELOCATION OF THE
INITIAL POSITION, THE OVERALL FORECAST TRACK PHILOSOPHY REMAINS THE
SAME. TS BEBINCA WILL CONTINUE TO TRACK ALONG THE STEERING RIDGE
AND IS EXPECTED TO MAKE LANDFALL SOUTH OF SHANGHAI, CHINA. THE
TRACK SHIFT RESULTS IN CPA MOVING BACK CLOSER TO OKINAWA, JAPAN.
THE GREATEST UNCERTAINTY IN TRACK AT THIS TIME IS THE POTENTIAL FOR
ALONG-TRACK DEVIATIONS. THE TUTT CELL FLOW IS HELPING TO ENHANCE
THE STEERING, RESULTING IN A FASTER THAN NORMAL MOTION. HOWEVER,
FORWARD SPEEDS SHOULD SLOW ONCE THE TUTT CELL MOVES FARTHER WEST
LATER IN THE FORECAST THE INTENSITY FORECAST REMAINS VERY
CHALLENGING DUE TO UNCERTAINTY IN THE EVOLUTION OF THE TUTT CELL,
AND ALSO DUE TO LIMITED GUIDANCE AVAILABLE AT THIS TIME. TS 14W IS
EXPECTED TO GRADUALLY RECOVER AS THE TUTT CELL MOVES WEST.
ADDITIONALLY WARMER WATERS NEAR THE RYUKUS WILL ALSO AID IN
RE-INTENSIFICATION AS THE SYSTEM MOVES THROUGH THE ISLAND CHAIN.  

MODEL DISCUSSION: MULTI-MODEL CONSENSUS IS IN GOOD AGREEMENT IN THE
CROSS-TRACK SPREAD, INDICATING PASSAGE NORTH OF OKINAWA. LIKEWISE,
THE GFS 30 MEMBER ENSEMBLE ALSO KEEPS TS BEBINCA TO THE NORTH OF
THE ISLAND. HOWEVER, THE 50 MEMBER ECENS ENSEMBLE CONTINUES TO SHOW A
NON-ZERO PROBABILITY THAT THE SYSTEM COULD MOVE OVER, OR EVEN SOUTH
OF THE ISLAND. REGARDLESS, OKINAWA REMAINS WITHIN THE SWATH OF
POTENTIAL 35 KNOT WINDS. WHILE MOST AVAILABLE GUIDANCE HAS
SIGNIFICANTLY BACKED OFF EARLIER AGGRESSIVE INTENSIFICATION AS THE
SYSTEM NEARS OKINAWA, THE COAMPS-TC MODEL STILL INDICATES A HIGH
PROBABILITY THAT BEBINCA WILL REACH TYPHOON INTENSITY AROUND OR
JUST AFTER THE TIME THE SYSTEM PASSES OKINAWA. THE FORECAST PEAK
WAS LOWERED BUT MAINTAINS A TYPHOON AT LANDFALL. DUE TO THE
NUMEROUS FACTORS DISCUSSED, OVERALL CONFIDENCE ESTIMATES ARE LOW. 

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