WDPN31 PGTW 130300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (WUTIP) WARNING NR 
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.3N 108.5E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 219 NM SOUTHEAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS PERSISTENT
DEEP-LAYERED CONVECTION OVER THE LOW-LEVEL CIRCULATION CENTER (LLCC)
ASSOCIATED WITH TROPICAL STORM (TS) 01W (WUTIP). THE INITIAL POSITION 
IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE CENTER OF A CONVECTIVE 
WRAPPING PRESENT IN THE VISIBLE SATELLITE IMAGERY, CONSISTENT WITH THE 
RADAR DATA. THE SYSTEM HAS BENEFITED FROM PROLONGED TRANSIT OVER WARM 
WATERS AND INTENSIFIED OVER THE LAST 6 HOURS. ENVIRONMENTAL ANALYSIS 
REVEALS 15-20 KT NORTHEASTERLY VERTICAL WIND SHEAR, WARM (29-30 C) SEA 
SURFACE TEMPERATURES (SST), PLENTY OF ATMOSPHERIC MOISTURE THROUGHOUT 
THE VERTICAL COLUMN, AS WELL AS STRONG EQUATORWARD OUTFLOW, DRIVEN BY 
INTENSE UPPER-LEVEL DIVERGENCE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T4.0 - 65 KTS
   CIMSS ADT: 53 KTS AT 130000Z
   CIMSS AIDT: 44 KTS AT 130000Z
   CIMSS D-PRINT: 55 KTS AT 122300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

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 ROUNDING THE AXIS 
OF A STR TO THE NORTHEAST OVER THE NEXT 12 HOURS. DURING THIS TIME, 
THE LLCC IS FORECAST TO TRAVEL ALONG THE WESTERN EDGE OF HAINAN ISLAND 
BEFORE TURNING NORTHEASTWARD, EVENTUALLY MAKING LANDFALL SLIGHTLY TO 
THE WEST OF THE LEIZHOU PENINSULA. WHILE CROSSING THE WARM WATERS OF 
THE GULF OF TONKIN, THE STORM IS FORECAST TO MAINTAIN MAXIMUM WIND 
SPEED LEVELS, OR SLIGHTLY INCREASE, APPROACHING TYPHOON INTENSITY. 
HOWEVER, INTERACTION WITH THE TERRAIN WILL OFFSET THE OTHERWISE 
FAVORABLE IMPACTS OF THE ENVIRONMENT AND LIMIT THE INTENSIFICATION. 
ADDITIONALLY, TS 01W WILL LOSE THE UPPER LEVEL OUTFLOW SUPPORT OVER 
THE NEXT 12 HOURS. ONCE TS 01W MAKES LANDFALL OVER MAINLAND CHINA 
BETWEEN TAU 24 AND 36, THE SYSTEM IS FORECAST TO BEGIN DISSIPATION, 
WHICH IS EXPECTED TO OCCUR BEFORE THE END OF THE CURRENT FORECAST 
PERIOD.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE SHOWS GOOD 
CONSISTENCY THROUGHOUT THE FORECAST PERIOD, WITH A MAXIMUM CROSS-TRACK 
SPREAD OF 32 NM JUST PRIOR TO LANDFALL, INCREASING TO 96 NM BY TAU 72. 
DETERMINISTIC GFS REMAINS AN OUTLIER, FORECASTING A SLIGHTLY MORE 
WESTWARD PATH FOLLOWING THE LANDFALL. THIS DEVIATION IS ONLY 26 NM 
FROM THE CONSENSUS. INTENSITY GUIDANCE IS IN FAIR AGREEMENT, WITH ALL 
MODELS PREDICTING MAINTAINED LEVELS OVER THE INITIAL 12-24 HOURS, 
FOLLOWED BY GRADUAL WEAKENING. NOTABLE OUTLIER WITHIN THE CURRENT 
GUIDANCE IS STILL NAVGEM-DRIVEN COAMPS-TC, PROJECTING PEAK INTENSITY 
AROUND 75 KTS, OCCURRING AFTER LANDFALL, MAKING THIS GUIDANCE SCENARIO 
UNLIKELY. JTWC TRACK AND INTENSITY FORECASTS ALIGN CLOSELY WITH MULTI-
MODEL CONSENSUS GUIDANCE, WITH HIGH AND MEDIUM CONFIDENCE 
RESPECTIVELY.

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