WDPN32 PGTW 021500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SAUDEL) WARNING 
NR 045//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.9N 117.9E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 208 NM EAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION 17W (SAUDEL) WITH A PARTIALLY EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC) WITH BUILDING DEEP CONVECTION OFFSET TO
THE NORTHWEST, ALONG THE COAST OF CHINA. THE SYSTEM HAS TRACKED
CLOSER TO THE COAST OVER THE PAST 6 HOURS, AND TERRAIN INTERACTION
APPEARS TO BE STARTING TO AFFECT THE STRUCTURE OF THE SURROUNDING
WIND FIELD. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE
BASED ON THE ANIMATED EIR. THE INITIAL INTENSITY OF 30 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE AND IS SET LOWER THAN THE AGENCY
DVORAK AND CIMSS INTENSITY ESTIMATES DUE TO THE RELATIVELY POOR
DEFINITION OF THE LLCC. ENVIRONMENTAL ANALYSIS INDICATES THAT 17W
REMAINS IN A MARGINAL ENVIRONMENT CHARACTERIZED BY WEAK OUTFLOW
ALOFT, LOW TO MODERATE (15-20 KTS) SOUTHEASTERLY VERTICAL WIND
SHEAR, PROXIMITY TO LAND, AND WARM (29-30 C) SEA SURFACE
TEMPERATURES.

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

CURRENT STEERING MECHANISM: THE NORTHERN PERIPHERY OF A NEAR
EQUATORIAL RIDGE (NER) POSITIONED TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 37 KTS AT 021210Z
   CIMSS ADT: 37 KTS AT 021140Z
   CIMSS AIDT: 38 KTS AT 021140Z
   CIMSS D-MINT: 29 KTS AT 020921Z
   CIMSS D-PRINT: 36 KTS AT 021140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK POLEWARD AND EQUATORWARD
   OTHER FACTORS: PROXIMITY TO THE COAST OF CHINA

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 17W (SAUDEL) IS FORECAST TO BEGIN SLOWING
DOWN OVER THE NEXT 12 HOURS AS THE STEERING PATTERN BECOMES MUCH
WEAKER DUE TO THE NER TO THE SOUTH MOVING OFF TO THE WEST. 17W IS
FORECAST TO DRIFT NORTHWARD THROUGH TAU 12 BEFORE TURNING WESTWARD
ONCE A SUBTROPICAL RIDGE (STR) BUILDS OVER EASTERN CHINA AND
ASSUMES STEERING OVER THE SYSTEM. LANDFALL ALONG THE COAST OF CHINA
IS FORECAST TO OCCUR SOON AFTER TAU 12. A WESTWARD TRACK ALONG THE
SOUTHERN PERIPHERY OF THE STR IS THEN EXPECTED TO PERSIST THROUGH
THE REMAINDER OF THE FORECAST PERIOD. REGARDING INTENSITY, 17W IS
FORECAST TO MAINTAIN ITS CURRENT INTENSITY THROUGH TAU 12 AS THE
VORTEX REMAINS OVER THE WARM WATERS. AFTER TAU 12, TERRAIN
INTERACTION AND SOUTHEASTERLY SHEAR WILL WEAKEN THE VORTEX.
DISSIPATION OVER LAND IS FORECAST TO OCCUR AROUND TAU 48, NORTH OF
HONG KONG. 

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT ON THE
WESTWARD TURN WITH THE EXCEPTION OF NAVGEM, WHICH DEPICTS A MUCH
SHARPER SOUTHWESTWARD TURN ALONG THE COAST AFTER TAU 12. THE JTWC
TRACK FORECAST IS PLACED NEAR THE MODIFIED CONSENSUS THROUGHOUT THE
FORECAST PERIOD WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE AGREES
ON QUICK WEAKENING AFTER THE SYSTEM MAKES LANDFALL, WITH NO NOTABLE
OUTLIERS. AS A RESULT, THE JTWC INTENSITY FORECAST IS PLACED NEAR
THE CONSENSUS WITH HIGH CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   INTENSITY 00-72 HR: HIGH//
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