WDPN31 PGTW 272100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 01W (EWINIAR) WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.6N 124.4E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 566 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 34 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
LOW-LEVEL CIRCULATION CENTER (LLCC) COMPLETELY OBSCURED BY
INCREASING AND FLARING CONVECTIVE FEATURES, IDENTIFIED BY COOLING
AND EXPANDING TOPS. MODERATE VERTICAL WIND SHEAR (VWS) IS EVIDENT
ALONG THE NORTHWESTERN EDGE OF THE CONVECTION OVER THE LLCC,
DEFINED BY A SHARP THERMAL GRADIENT WITHIN THE NORTHWESTERN
QUADRANT OF THE UPPER-LEVEL CIRRUS SHIELD, BECOMING DIFFUSE TO THE
SOUTHEAST THROUGH VISIBLE STRIATIONS. DUAL-CHANNEL (POLEWARD AND
EQUATORWARD) UPPER-LEVEL OUTFLOW CAN ALSO BE OBSERVED IN SUPPORT OF
TYPHOON (TY) 01W, WITH INCREASED TRANSVERSE BANDING EXTENDING TO
THE NORTH AND A WELL-ESTABLISHED OUTFLOW CHANNEL TO THE SOUTH OVER
THE PHILIPPINES. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON A 271720Z ATMS MICROWAVE PASS, CONFIRMING THE
NORTHWESTERN CONVECTIVE STRUCTURE IS LOCATED IN CLOSE PROXIMITY TO
THE LLCC. THE INITIAL INTENSITY OF 80 KTS WAS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON SUBJECTIVE AGENCY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA AND SAR DATA

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 70 KTS AT 271435Z
   CIMSS ADT: 55 KTS AT 271730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 01W WILL CONTINUE TO TRACK NORTHEASTWARD
UNDER THE WELL-ESTABLISHED STEERING INFLUENCE OF THE STR POSITIONED
TO THE EAST THROUGHOUT THE REMAINDER OF THE 120 HOUR FORECAST
PERIOD. THE TYPHOON IS FORECAST TO REMAIN IN A CONDUCIVE
ENVIRONMENT FOR STEADY INTENSIFICATION THROUGHOUT THE NEXT 36 HOURS
AS DUAL-CHANNEL OUTFLOW, WARM SEA SURFACE TEMPERATURES (GREATER
THAN 26 C) AND LOW TO MODERATE VWS REMAINS PREVALENT IN THE WESTERN
PHILIPPINE SEA. NEAR TAU 36, AN EXTENSION OF AN UPPER-LEVEL
LONGWAVE TROUGH WILL TRACK EASTWARD, INTRODUCING STRONG VWS (20-30
KTS), BEGINNING THE INITIAL STAGES OF A STEADY WEAKENING TREND.
AFTER TAU 48 AND WHILE THE SYSTEM CONTINUES NORTHEASTWARD, COOLER
SEA SURFACE TEMPERATURES WILL WEAKEN THE SYSTEM JUST NORTH OF 26N. BY 
TAU 72, COOL AND DRY AIR WILL BEGIN TO WRAP CYCLONICALLY INTO THE 
SYSTEM FROM THE NORTHWEST, STARTING THE EXTRATROPICAL TRANSITION 
THROUGH TAU 120 AS VWS INCREASES ABOVE 30 KTS AND FURTHER SHEARS AWAY 
THE MID AND UPPER LEVELS, CAUSING THE VORTEX TO BECOME DECOUPLED. 

MODEL DISCUSSION: THE DETERMINISTIC AND ENSEMBLE MODELS ARE IN
STRONG AGREEMENT THAT TY 01W WILL CONTINUE TO TRACK NORTHEASTWARD
THROUGH TAU 120 AROUND THE WESTERN AND NORTHWESTERN PERIPHERY OF
THE STR. A FEW GEFS ENSEMBLE MEMBERS INTRODUCE A SLIGHT WESTWARD
TRACK, CLOSER TO MAINLAND JAPAN, HOWEVER, THE JTWC MULTI-MODEL
CONSENSUS REMAINS CLOSELY ALIGNED THAT TY 01W WILL REMAIN TO THE
EAST WHILE UNDERGOING THE EXPECTED EXTRATROPICAL TRANSITION BEGINNING
AT TAU 72. THE TAU 36 AND TAU 48 CROSS-TRACK SPREAD REMAIN IN TIGHT
AGREEMENT BETWEEN 80NM AND 100NM, RESPECTIVELY. INTENSITY GUIDANCE
IS IN FAIR AGREEMENT THAT AN INTENSIFICATION TREND WILL OCCUR OVER
THE NEXT 36 HOURS WHILE THE ENVIRONMENT REMAINS HIGHLY CONDUCIVE,
HOWEVER, JTWC SHIPS GUIDANCE, GFS, ECMWF, AND COAMPS-TC FORECASTS
WEAKENING FROM TAU 36 UNTIL THE END OF THE FORECAST PERIOD. THE 
COAMPS-TC INTENSITY PROBABILITY PRODUCT INDICATES A VERY LOW 
PROBABILITY OF RAPID INTENSIFICATION.

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