WDPN31 PGTW 200300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (SANBA) WARNING NR 
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.3N 109.4E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 197 NM EAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED HIMAWARI-9 VISIBLE IMAGERY DEPICTS AN INCREASINGLY CHAOTIC
SCENE OVER THE PAST SIX HOURS AS TROPICAL STORM SANBA CAME ASHORE
AND STRETCHED OUT WITH THE UPPER LEVEL CIRCULATION MOVING
NORTHEASTWARD, WHILE THE LOW LEVEL CENTER (LLCC) STALLED UNDER THE
INCREASING INFLUENCE OF NORTHEASTERLY LOW LEVEL FLOW. VIGOROUS
THUNDERSTORMS ARE DROPPING COPIOUS AMOUNTS OF RAINFALL OVER THE
REGION. ANALYSIS OF THE INITIAL CONDITIONS IS HAMPERED BY LIMITED
OR AMBIGUOUS DATA. A FEW BREAKS IN THE MID TO UPPER LEVEL CLOUD
SOUP REVEAL SOME EXPOSED CLOUD LINES, SUGGESTING THE LLC IS JUST
OFF THE COAST. COASTAL RADAR DATA GENERALLY SUPPORTS THE POSITION.
THE INITIAL POSITION IS THEREFORE PLACED WITH LOW CONFIDENCE. THE
INITIAL INTENSITY WAS LOWERED TO 35 KNOTS BASED ON THE MID-POINT OF
AGENCY FINAL-T DVORAK ESTIMATES RANGING FROM T1.5 TO T3.0. THE
LATEST ROUND OF AUTOMATED OBJECTIVE INTENSITY ESTIMATES ARE
CURRENTLY ASSESSED TO BE TOO HIGH, ALTHOUGH IT IS POSSIBLE THE 
INTENSIFICATION PRIOR TO LANDFALL WAS STRONGER THAN ORIGINALLY 
ESTIMATED. THE POLAR OUTFLOW CHANNEL REMAINS STRONG AS THE SYSTEM IS 
NEARLY UNDER THE MID-LATITUDE WESTERLY FLOW. SEA SURFACE TEMPERATURES 
IN THE GULF OF TONKIN
REMAIN FAVORABLE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: QUASI STATIONARY UNDER THE INCREASING
INFLUENCE OF WEAK LOW LEVEL FLOW TRYING TO TURN THE LOW LEVEL
CIRCULATION CENTER BACK TOWARDS THE SOUTHWEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 49 KTS AT 2130Z
   CIMSS ADT: 51 KTS AT 192330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: AS THE VORTEX CONTINUES TO DECOUPLE, THE
FORECAST CONTINUES TO FOLLOW ALL DYNAMICAL GUIDANCE, WHICH CALLS
FOR A SOUTHERLY TO SOUTHWESTERLY TURN OF THE REMNANT LLC. THE
FORECAST IS HAMPERED BY THE POOR INITIAL ANALYSIS, LEADING TO LOW
CONFIDENCE. IF THE LLC IS OVER LAND, OR REMAINS OVER LAND, TS 16W
MAY DISSIPATE SOONER THAN EXPECTED GIVEN THE STRONG 25 TO 30 KNOT
VERTICAL WIND SHEAR AND FRICTIONAL EFFECTS. THE FORECAST CALLS FOR
CONTINUED WEAKENING OVER THE NEXT DAY AS THE DEEP CONVECTION
MOVES OFF TO THE NORTHEAST AND THE REMNANT CIRC DRIFTS SOUTH UNDER
PERSISTENTLY HIGH VERTICAL WIND SHEAR. DISSIPATION OVER WATER IS
EXPECTED WITHIN 24 HOURS. 

MODEL DISCUSSION: ALL AVAILABLE DYNAMICAL MODELS CONTINUE TO SHOW
A SLOW TRACK, WITH A TURN BACK TO THE SOUTHWEST. GUIDANCE SPREAD
CALLS FOR WEAKENING BELOW WARNING CRITERIA OVER THE NEXT 24 TO 36
HOURS.


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