WDPN31 PGTW 120300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (WUTIP) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.0N 110.3E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 130 NM EAST-NORTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
RECENT MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A PARTIALLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) OF TROPICAL STORM (TS)
01W (WUTIP), WITH PERSISTENT, DEEP CONVECTION WITHIN THE WESTERN
SEMICIRCLE OF THE SYSTEM. INCREASING VERTICAL WIND SHEAR (20-25 KTS) 
IS RESTRICTING MOST OF THE CONVECTION TO THE SOUTHWESTERN PORTION OF 
THE STORM. RELATIVELY LARGE CONVECTIVE ENVELOPE IS WITNESSED BY AN 
ELONGATED DEEP-LAYER CONVECTIVE BANDING ALONG THE COAST OF NORTHERN 
VIETNAM AND SOUTHERN CHINA, WRAPPING INTO THE LLCC. THE INITIAL 
POSITION IS PLACED WITH MEDIUM CONFIDENCE, BASED ON THE ANIMATED 
VISIBLE IMAGERY LOOP. THE INITIAL ESTIMATED INTENSITY OF 40 KTS IS 
ALSO ASSESSED WITH MEDIUM CONFIDENCE, BASED ON AGENCY AND OBJECTIVE
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 37 KTS AT 112030Z
   CIMSS AIDT: 35 KTS AT 112030Z
   CIMSS D-MINT: 30 KTS AT 112050Z
   CIMSS D-PRINT: 35 KTS AT 120010Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD AND WESTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 01W IS EXPECTED TO CONTINUE MOVING
NORTHWESTWARD OVER THE NEXT 24 TO 36 HOURS UNDER THE INFLUENCE OF A
DEEP-LAYER SUBTROPICAL RIDGE POSITIONED TO ITS EAST. AS THE SYSTEM
TRAVELS OVER THE SHALLOW BUT VERY WARM WATERS (30-31 C) SOUTH OF
HAINAN ISLAND, IT IS FORECAST TO STRENGTHEN, REACHING AN ESTIMATED
PEAK OF 50-55 KTS BETWEEN TAUS 24 AND 36. AS THE SYSTEM MOVES AROUND 
THE RIDGE AXIS AND MAKES THE INITIAL LANDFALL OVER THE HAINAN ISLAND, 
INTERACTION WITH THE TERRAIN IS EXPECTED TO WEAKEN THE STORM. AFTER 
CROSSING THE ISLAND, THE SYSTEM WILL RE-ENTER WARM WATERS OF THE GULF 
OF TONKIN, POSSIBLY ALLOWING FOR SLIGHT RE-INTENSIFICATION. HOWEVER, 
SHORTLY THEREAFTER, TS 01W WILL BEGIN TO WEAKEN AGAIN DUE TO THE 
INTERACTION WITH TERRAIN OF MAINLAND CHINA AND IS FORECAST TO FULLY 
DISSIPATE BY TAU 96.

MODEL DISCUSSION: DETERMINISTIC TRACK MODEL GUIDANCE IS RELATIVELY
CONSISTENT THROUGHOUT THE FORECAST PERIOD, AS INDICATED BY A
CROSS-TRACK SPREAD OF 130 NM AT TAU 72, IMPROVING SLIGHTLY BEYOND
THAT POINT. THE ALONG-TRACK SPREAD HOWEVER, INCREASES UNCERTAINTY
OF THE FORECAST WITH SPREAD OF OVER 300 NM BETWEEN GFS AND OTHER
MODELS. BOTH DETERMINISTIC AND ENSEMBLE GFS GUIDANCE INDICATES A WIDER 
NORTHEASTWARD TURN, THEREFORE HAVING THE SYSTEM SPEND SLIGHTLY
MORE TIME OVER WATER, AND MAKING THE LANDFALL OCCUR FURTHER WEST - 
JUST NORTH OF THE WESTERN TIP OF HAINAN ISLAND. INTENSITY GUIDANCE
REMAINS IN FAIR AGREEMENT WITH ALL CONSENSUS MEMBERS INDICATING
STEADY INTENSIFICATION OVER THE NEXT 36 HOURS, FOLLOWED BY LANDFALL
AND LAND INTERACTION DRIVEN WEAKENING THROUGHOUT THE REMAINDER OF
THE FORECAST. 

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