WDPN31 PGTW 211500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (DOKSURI) 
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.3N 131.6E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 863 NM SOUTHEAST OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
THE TROPICAL DISTURBANCE PREVIOUSLY KNOWN AS INVEST 98W HAS
INTENSIFIED TO TROPICAL DEPRESSION 05W (DOKSURI). ANIMATED ENHANCED
INFRARED IMAGERY DEPICTS IMPROVED FORMATIVE BANDING WRAPPING AROUND
A PARTIALLY OBSCURED LOW LEVEL CIRCULATION CENTER (LLCC) WITH
DEEPEST CONVECTION IN THE SOUTHERN AND EASTERN QUADRANTS. DEEP
CONVECTION WITH OVERSHOOTING TOPS IS PRESENT NEAR THE LLCC. A
210916Z SMOS WINDSPEED IMAGE DEPICTED A WELL-DEFINED WIND FIELD
AROUND THE LLCC, WITH MAX WINDS OF 25 TO 30 KNOTS IN THE NORTHEAST
QUADRANT AND 20 TO 25 KNOTS ELSEWHERE. THE INITIAL POSITION IS
PLACED WITH MEDIUM CONFIDENCE BASED ON THE AFOREMENTIONED SMOS
IMAGE. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE AFOREMENTIONED SMOS IMAGE AND EARLIER ASCAT
IMAGERY. MODERATE  OUTFLOW ALOFT IS ASSESSED BASED ON SUBSTANTIAL
FLOW INTO A TUTT CELL POSITIONED TO THE EAST-NORTHEAST OF THE
CYCLONE.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T1.5 - 25 KTS
   KNES: T1.5 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EASTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TD 05W IS EXPECTED TRACK WESTWARD OVER THE
NEXT 48 HOURS, STEERED PRIMARILY BY THE SUBTROPICAL RIDGE AXIS TO
THE NORTH. BEYOND THAT, A TURN TOWARD THE NORTHWEST IS EXPECTED AS
A MID-LATITUDE TROUGH PASSING THROUGH EAST ASIA CAUSES A WEAKENING
OF THE STEERING RIDGE TO THE NORTH, ALLOWING FOR TD 05W TO GAIN
LATITUDE. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE FAVORABLE FOR
INTENSIFICATION, WITH WARM SEA SURFACE TEMPERATURES (29 TO 30
CELSIUS) AND LOW VERTICAL WIND SHEAR (5 TO 10 KNOTS) AND IMPROVING
OUTFLOW, THE SYSTEM IS FORECAST TO STEADILY INTENSIFY AND MAY EVEN
EXPERIENCE A PERIOD OF RAPID INTENSIFICATION. THE OFFICIAL JTWC
FORECAST CALLS FOR TD 05W TO REACH TYPHOON INTENSITY BY TAU 36.

MODEL DISCUSSION: GLOBAL NUMERICAL MODELS AND ENSEMBLES ALL SUGGEST
A WESTWARD TRACK OF THROUGH TAU 48, WITH SIGNIFICANT ALONG-TRACK
ERRORS (170 NM SPREAD BY TAU 120). THE MODELS THEN TURN THE SYSTEM
TOWARD THE NORTHWEST BETWEEN TAU 48 AND 60, BUT THE TIMING AND
EXTENT OF THE TURN IS HIGHLY UNCERTAIN, WITH SIGNIFICANT
CROSS-TRACK ERRORS INCREASING TO OVER 400 NM. THE OVERALL TRACK AND
INTENSITY FORECAST CONFIDENCE IS MEDIUM THROUGH TAU 72 AND LOW
BEYOND.

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