Advisories

WDPN32 PGTW 020300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SAUDEL) 
WARNING NR 043//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.1N 116.7E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 139 NM EAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
DEPRESSION (TD) 17W WITH A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION

CENTER (LLCC) AND DEEP CONVECTION LIMITED TO THE WESTERN AND
NORTHERN SIDES. WEAK EQUATORWARD OUTFLOW IS STILL EVIDENT IN
ANIMATED WATER VAPOR IMAGERY. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC IN ANIMATED
MSI AS THE CENTER IS APPARENTLY ELONGATED ALONG THE COAST OF CHINA.
THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH HIGH CONFIDENCE
BASED ON THE AGENCY DVORAK FIXES AND CIMSS OBJECTIVE INTENSITY
ESTIMATES. THE ENVIRONMENT IS CHARACTERIZED AS MARGINALLY FAVORABLE
WITH WARM SEA SURFACE TEMPERATURES BEING OFFSET BY LOW TO MODERATE
VERTICAL WIND SHEAR (VWS), WEAK OUTFLOW ALOFT, AND THE PROXIMITY TO
THE COAST OF CHINA.

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

CURRENT STEERING MECHANISM: THE NORTHERN PERIPHERY OF A NEAR
EQUATORIAL RIDGE (NER) CENTERED OVER MINDANAO

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 32 KTS AT 012340Z
   CIMSS AIDT: 38 KTS AT 012340Z
   CIMSS D-MINT: 29 KTS AT 020001Z
   CIMSS D-PRINT: 30 KTS AT 020110Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: PROXIMITY TO THE COAST OF CHINA

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   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: TD 17W HAS CONTINUED TRACKING NORTHEASTWARD
UNDER THE STEERING INFLUENCE OF THE NER TO THE SOUTHEAST. THE
SYSTEM IS FORECAST TO CONTINUE ALONG A NORTHEASTWARD TRACK FOR THE
NEXT 12 HOURS BEFORE TURNING POLEWARD THEN WESTWARD BETWEEN TAU
24-36 AS IT ENTERS A WEAKER STEERING ENVIRONMENT. A RIDGE BUILDING
OVER EASTERN CHINA IS EXPECTED TO ASSERT SOME CONTROL AROUND TAU 36
AND STEER THE SYSTEM SOUTHWESTWARD ALONG THE COAST OF CHINA FOR THE
REMAINDER OF THE FORECAST PERIOD. THERE IS SOME UNCERTAINTY ABOUT
HOW SHARPLY THE TRACK WILL TURN SOUTHWESTWARD AND WHETHER THE
VORTEX WILL BE JUST ONSHORE OR JUST OFFSHORE OF SOUTHEASTERN CHINA.
THE FORECAST FAVORS THE FORMER SCENARIO WHICH IS EXPECTED TO RESULT
IN A STEADY INTENSITY THROUGH LANDFALL AROUND TAU 36, THEN
WEAKENING AND DISSIPATION OVER LAND BY TAU 72.

MODEL DISCUSSION: MODEL TRACK GUIDANCE HAS COME INTO BETTER
AGREEMENT ABOUT THE SHORT TERM NORTHEASTWARD TRACK FOLLOWED BY A
TURN SOUTHWESTWARD AFTER LANDFALL, AROUND TAU 36. THE JTWC TRACK IS
PLACED NEAR THE MULTI-MODEL CONSENSUS WITH MEDIUM CONFIDENCE GIVEN
THE IMPROVEMENT IN AGREEMENT. THE AVAILABLE INTENSITY GUIDANCE
REMAINS WITHIN A 10 KT ENVELOPE UP UNTIL LANDFALL AROUND TAU 36 AND
THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO THE MULTI-MODEL
CONSENSUS WITH MEDIUM CONFIDENCE. 

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