WDPN32 PGTW 250900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 03W (THREE) WARNING 
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.5N 113.2E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 235 NM SOUTH-SOUTHWEST OF HONG KONG
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS EXPLOSIVE
DEEP CONVECTION BUILDING OVER THE LOW-LEVEL CIRCULATION CENTER WITH
CONVECTIVE BANDING FOLLOWING SUIT ON THE NORTHERN AND WESTERN
PERIPHERIES OF TROPICAL DEPRESSION (TD) 03W. WATER VAPOR IMAGERY
REVEALS A SLIGHTLY DIVERGENT UPPER-LEVEL ENVIRONMENT FEEDING INTO
AN APPROACHING UPPER-LEVEL TROUGH.THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON THE LOW-LEVEL CLOUD FEATURES
SURROUNDING THE CIRCULATION CENTER ON ANIMATED MSI, DESPITE THE
CENTER BEING OBSCURED BY DEEP CONVECTION. THE INITIAL INTENSITY OF
25 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON AN EARLIER 250121Z
METOP-B ASCAT IMAGE REVEALING 25KTS IN THE EASTERN PERIPHERY OF THE
CIRCULATION.

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

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE TO THE NORTH.

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

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK WESTWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: WHILE TD 03W IS CURRENTLY DRIVEN NORTHWESTWARD
ON THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE TO THE NORTH, A
DEEP-LAYER TROUGH WILL BREAK DOWN THE RIDGE BY TAU 24 AND ALLOW FOR
A MORE NORTH-NORTHWESTWARDLY TRACK FOR THE REMAINDER OF THE
FORECAST PERIOD. THE SYSTEM IS FORECAST TO SLIGHTLY INTENSIFY TO A
PEAK OF 35KTS OVER THE NEXT TWELVE HOURS IN A MODERATELY FAVORABLE
ENVIRONMENT OF WARM SEA SURFACE TEMPERATURES, MODERATELY FAVORABLE
OUTFLOW, AND LOW VERTICAL WIND SHEAR. HOWEVER, VERTICAL WIND SHEAR
WILL INCREASE AS THE SYSTEM APPROACHES LAND, RESULTING IN A
WEAKENING PERIOD AFTER TAU 12. THE SYSTEM IS FORECAST TO INITIALLY
MAKE LANDFALL IN THE VICINITY OF THE LEIZHOU PENINSULA AT TAU 24,
AND FINALLY DISSIPATE OVER LAND BY TAU 36.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS ALSO IN GOOD
AGREEMENT, WITH A CROSS-TRACK ERROR OF 75NM BY THE END OF THE
FORECAST. THE INTENSITY GUIDANCE IS IN GOOD AGREEMENT THAT THE
SYSTEM WILL POSSIBLY INTENSIFY OVER THE NEXT 12 HOURS TO A PEAK OF
30KTS BEFORE WEAKENING DUE TO TOPOGRAPHIC INTERACTION.

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