WDPN33 PGTW 122100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (TORAJI) WARNING NR 
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.0N 117.1E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 213 NM SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN
ERODED CENTRAL CONVECTION WITH SOME REMAINING SPIRAL BANDS OF DEEP
CONVECTION, AS THE SYSTEM IS TRANSITING THROUGH MARGINAL
ENVIRONMENT, WITH THE SEA SURFACE TEMPERATURES STILL RELATIVELY
WARM AND BELOW 15 KTS OF VERTICAL WIND SHEAR. THE SYSTEM IS HOWEVER
SURROUNDED BY DRY AIR FROM ALMOST ALL DIRECTIONS, EXCEPT THE
NORTHEASTERN QUADRANT. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON THE ANIMATED IR AND PROXYVIS LOOPS. THE INITIAL
INTENSITY OF 45 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
AGENCY AND OBJECTIVE ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 37 KTS AT 121730Z
   CIMSS AIDT: 38 KTS AT 121730Z
   CIMSS D-PRINT: 43 KTS AT 121800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 26W IS FORECAST TO CONTINUE
TRACKING NORTHWESTWARD UNDER THE INFLUENCE OF A STR TO THE
NORTHEAST, HOWEVER BETWEEN TAUS 12 AND 24 THE STEERING WILL WEAKEN,
AS THE SYSTEM MOVES AWAY FROM THE RIDGE. AT THAT STAGE THE DRY AIR
ENTRAINMENT WILL CAUSE FURTHER DETERIORATION OF THE CONVECTIVE
STRUCTURE, AMPLIFIED BY THE INCREASING SOUTHWESTERLY VERTICAL WIND
SHEAR AND COOLING SEA SURFACE TEMPERATURES. AS THE SYSTEM SHALLOWS
AND WEAKENS IT WILL BEGIN TURNING SOUTHWESTWARD AND EVENTUALLY
SOUTHWARD, WEAKENING TO WIND SPEEDS BELOW THE WARNING CRITERIA BY
TAU 72.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN FAIR
AGREEMENT WITH MAJORITY OF THE MODELS SUGGESTING A GRADUAL
WESTWARD, SOUTHWESTWARD AND EVENTUALLY SOUTHWARD TURN. ONLY JMA
AND UKMET DETERMINISTIC MODELS ARE STICKING TO A MORE
NORTHWESTWARD TRACK, HOWEVER JTWC FORECAST IS LAID CLOSE TO THE
MULTI-MODEL CONSENSUS. AS FAR AS INTENSITY GUIDANCE, JTWC FORECAST
IS HEDGED 5-10 KTS ABOVE THE CONSENSUS MEMBERS MEAN AND LEANING
CLOSER TO THE GFS AND HWRF DETERMINISTIC GUIDANCE, CONSISTENT WITH
THE ASSESSED AND FORECAST TRACK.

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