WDPN31 PGTW 112100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (WUTIP) WARNING NR 
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.3N 110.9E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 151 NM EAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC) OF TROPICAL STORM (TS)
01W (WUTIP). DEEP CONVECTION HAS BEEN BUILDING NEAR THE LLCC OVER
THE LAST FEW HOURS, WITH THE CLOUD TOPS REACHING NEGATIVE 92
DEGREES CELSIUS. MODERATE (15-20 KTS) VERTICAL WIND SHEAR (VWS) IS
LIMITING THE CONVECTION TO THE SOUTHWESTERN QUADRANT OF THE SYSTEM. 
THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
EXTRAPOLATION OF A 111359Z METOP-B ASCAT PASS IN CONJUNCTION WITH
THE ANIMATED SHORTWAVE INFRARED IMAGERY LOOP, SHOWING NORTHERN AND
EASTERN QUADRANTS OF THE CIRCULATION. THE INITIAL INTENSITY OF 40
KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY FIXES
AND OBJECTIVE AIDS LISTED BELOW, AS WELL AS THE AFOREMENTIONED
ASCAT PASS SHOWING A BROAD BAND OF 35 KT WIND BARBS TO THE SOUTH,
WITH SOME RAIN-FLAGGED 40 KT WIND BARBS PRESENT AS WELL.

INITIAL WIND RADII BASIS: A 111359Z METOP-B ASCAT PASS

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 34 KTS AT 111730Z
   CIMSS AIDT: 33 KTS AT 111730Z
   CIMSS D-PRINT: 31 KTS AT 111800Z

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

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 01W IF FORECAST TO TRACK NORTHWESTWARD FOR
THE NEXT 36 HOURS, UNDER THE INFLUENCE OF A DEEP-LAYER SUBTROPICAL
RIDGE (STR) TO THE EAST. AS IT PROGRESSES OVER THE SHALLOW, BUT
VERY WARM (30-31 C) WATERS SOUTH OF HAINAN ISLAND, IT IS FORECAST
TO CONTINUE INTENSIFYING, REACHING 55 KTS AROUND TAU 24. AFTER THE
SYSTEM ROUNDS THE RIDGE AXIS, IT IS FORECAST TO TRANSIT OVER THE
HAINAN ISLAND, AND WHILE INTERACTING WITH THE TERRAIN, BEGIN
WEAKENING. AFTERWARDS, THE SYSTEM WILL YET AGAIN TAP INTO A SUPPLY
OF WARM WATER WHILE TRACKING NORTH-NORTHEASTWARD OVER THE GULF OF
TONKIN, ALLOWING FOR SOME POTENTIAL SLIGHT RE-INTENSIFICATION.
SHORTLY AFTER HOWEVER, THE TOPOGRAPHIC INTERACTION WITH MAINLAND
CHINA WILL RESULT IN WEAKENING, LEADING TO DISSIPATION BY, OR
BEFORE TAU 96.

MODEL DISCUSSION: DETERMINISTIC TRACK MODEL GUIDANCE IS IN FAIR
AGREEMENT FOR THE INITIAL 72 HOURS, AS INDICATED BY THE CROSS-TRACK
SPREAD OF 55 NM AT TAU 36, OPENING UP TO 110 NM AT TAU 72. SHORT
TERM ALONG-TRACK SPREAD REMAINS GOOD AT 30 NM, BUT IT INCREASES TO
160 NM BY TAU 72. FOR THE LONG TERM TRACK GUIDANCE, UNCERTAINTY
INCREASES SIGNIFICANTLY, DUE TO INCREASING ALONG-TRACK SPREAD
DRIVEN BY DIFFERENT MODEL INTERPRETATION OF POTENTIAL BAROCLINIC 
FORCING, WHILE THE SYSTEM TRANSITS OVER LAND. TOWARD THE END OF THE 
CURRENT FORECAST PERIOD, THE SYSTEM WILL LIKELY DISSIPATE AS A 
TROPICAL CYCLONE, HOWEVER SOME INTENSITY AIDS (GFS AND HAFS) INDICATE 
SLIGHT INTENSIFICATION, INDICATING A POTENTIAL FOR EXTRATROPICAL
TRANSITION BEYOND OR AROUND TAU 96, AS THE SYSTEM IS CUT OFF THE
WARM WATER SUPPLY AND SHALLOWS OUT.

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