WDPN32 PGTW 012100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 04W (CHABA) WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.1N 112.1E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 177 NM SOUTHWEST OF HONG KONG
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP
CONVECTION PERSISTING AND WRAPPING AROUND A RELATIVELY BROAD
LOW-LEVEL CIRCULATION CENTER ALSO EVIDENT IN RECENT ANIMATED RADAR
DATA. ANIMATED WATER VAPOR IMAGERY AND UPPER-LEVEL ATMOSPHERIC
MOTION VECTORS INDICATE MODERATE POLEWARD AND EQUATORWARD OUTFLOW,
SUPPORTED BY RIDGING ALOFT. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE, GIVEN THE BROAD NATURE OF THE CENTER, BASED ON
RECENT SATELLLITE POSITION FIXES FROM PGTW AND RJTD AND THE
ANIMATED RADAR IMAGERY. THE INITIAL INTENSITY OF 65 KTS IS ASSESSED
WITH HIGH CONFIDENCE BASED ON AN AUTOMATED SATELLITE INTENSITY
CONSENSUS VALUE OF 67 KNOTS FROM 011834Z AND CONSISTENT SUBJECTIVE
DVORAK FIX VALUES FROM MULTIPLE REPORTING AGENCIES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF MID TO UPPER-LEVEL
SUBTROPICAL RIDGING TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 67 KTS AT 011834Z
   CIMSS ADT: 55 KTS AT 011740Z

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: 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: TY 04W WILL TRACK TOWARD AN ANTICIPATED
LANDFALL JUST TO THE EAST OF ZHANJIANG, CHINA JUST AFTER TAU 24
UNDER THE CONTINUED STEERING INFLUENCE OF THE MID TO UPPER-LEVEL
SUBTROPICAL RIDGING TO THE EAST. THE SYSTEM WILL CONTINUE INLAND
AND DISSIPATE RAPIDLY THEREAFTER, WITH FULL DISSPATION ANTICIPATED
BY TAU 48. ADDITIONAL NEAR-TERM INTENSIFICATION IS POSSIBLE AS THE
SYSTEM PASSES OVER VERY WARM WATER WITH FAVORABLY LOW VERTICAL WIND
SHEAR AND SUPPPORTIVE DIFFLUENCE ALOFT. HOWEVER, ANY INTENSIFICATION
PRIOR TO LANDFALL IS EXPECTED TO BE MINIMAL AS THE BROAD CONVECTIVE
RING AROUND THE CENTER OF THE CIRCULATION HAS LIMITED TIME TO
CONTRACT.

MODEL DISCUSSION: TRACK AND INTENSITY FORECAST ARE IN GOOD
AGREEMENT, LENDING HIGH CONFIDENCE TO THE CURRENT FORECAST. THE
TRACK FORECAST IS SITUATED NEAR THE MULTI-MODEL CONSENSUS AND LIES
SLIGHTLY TO THE WEST OF THE PREVIOUS FORECAST DUE TO A MORE
PRONOUNCED WESTWARD COMPONENT TO STORM MOTION OVER THE PAST SIX
HOURS THAN PREVIOUSLY ANTICIPATED. FURTHER SLIGHT ADJUSTMENTS TO
THE WEST ARE POSSIBLE, IN LINE WITH THE ECMWF DETERMINISTIC AND
ENSEMBLE MODEL FORECAST SOLUTIONS.

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