WDPN31 PGTW 110900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W (WUTIP) WARNING 
NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.7N 112.4E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 240 NM EAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH BUILDING CENTRAL
CONVECTION SHEARED TO THE SOUTHWEST. LOW-LEVEL CLOUD BANDS ARE
VISIBLE SURROUNDING THE CIRCULATION. THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON THE CLEAR-CUT CIRCULATION CENTER
IDENTIFIABLE IN THE AFOREMENTIONED ANIMATED MSI. THE INITIAL
INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
PERSISTENCE FROM AN EARLIER 110202Z METOP-C PARTIAL ASCAT IMAGE
REVEALING 25-30KTS IN THE SOUTHWESTERN PERIPHERY OF THE CIRCULATION
COMPLEMENTED BY THE AGENCY AND OBJECTIVE FIXES LISTED BELOW.

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

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T1.5 - 25 KTS
   CIMSS ADT: 31 KTS AT 110530Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TROPICAL DEPRESSION 01W WILL CONTINUE TRACKING
WEST-NORTHWESTWARD FOR THE NEXT 48 HOURS ON THE SOUTHWESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE POSITIONED TO THE NORTHEAST.
BETWEEN TAU 48 AND 72, THE SYSTEM WILL CROSS THE RIDGE AXIS,
TRANSITIONING TO A NORTHEASTERN TRACK AFTER TAU 72. AS THE SYSTEM
WEAKENS AND BECOMES SHALLOW AFTER TAU 48, THE TRACK SPEED WILL
GRADUALLY INCREASE. TD 01W WILL SLOWLY INTENSIFY DESPITE 15-20KT
VERTICAL WIND SHEAR INDUCED BY A TROPICAL UPPER TROPOSPHERIC TROUGH
(TUTT) CELL TO THE NORTHEAST WHICH FILLS GRADUALLY THROUGHOUT THE
FORECAST. THE SYSTEM WILL REACH A PEAK OF 55KTS BY TAU 48, BUT
TOPOGRAPHIC INTERACTION WITH HAINAN ISLAND AND MAINLAND CHINA WILL
FORCE WEAKENING TO DISSIPATION BY THE END OF THE FORECAST PERIOD.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE HAS A WIDE SPREAD OF
MEMBERS IN THE ALONG TRACK FORECAST, WITH THE SLOWEST MEMBER BEING
GFS AND THE FASTEST BEING GALWEM. THE JTWC TRACK LIES SLIGHTLY WEST
OF CONSENSUS AND CLOSER TO ECMWF, HAFS-A, AND HWRF, WHICH ALL
REFLECT THE WEST-NORTHWESTWARD TRACK THAT THE SYSTEM IS CURRENTLY
ON. THE INTENSITY GUIDANCE INDICATES A PEAK INTENSITY BETWEEN TAU
36-48, AND A RANGE OF 40-65KTS.

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