WDPN31 PGTW 192100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (SANBA) WARNING NR 
010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.4N 109.3E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 192 NM EAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED HIMAWARI-9 INFRARED (EIR) SATELLITE IMAGERY AND
COASTAL RADAR INDICATES TROPICAL STORM 16W (SANBA) CONTINUED ITS
UNEXPECTED POLEWARD TRACK INTO THE SOUTHWESTERN COAST OF CHINA,
WITH A BRIEF BUT MARKED PERIOD OF INTENSIFICATION. AT THE ANALYSIS
TIME, THE INITIAL POSITION WAS PLACED WITH MEDIUM CONFIDENCE BASED
ON AFOREMENTIONED EIR AND RADAR DATA, IN ADDITION TO AN
EXTRAPOLATION OF 191431Z METOP-B ASCAT DATA, WHICH ALSO PROVIDED
JUSTIFICATION TO RAISE THE INITIAL INTENSITY TO 40 KNOTS. THIS
ASSESSMENT WAS SUPPORTED BY PGTW AND KNES DVORAK T3.0 DVORAK
ESTIMATES. AFTER THE ANALYSIS TIME, SANBA APPEARS TO HAVE MADE
LANDFALL. DEEP CONVECTION IS CONTINUING TO MOVE OFF TO THE
NORTHEAST UNDER THE MID-LEVEL SUB-TROPICAL RIDGE STEERING FLOW. THE 
LOWER
LEVEL FLOW REMAINS GENERALLY TO THE SOUTHWEST. THE DATA SUGGESTS
THE RESULTING HIGH VERTICAL SHEAR MAY BE DECOUPLING THE LOW LEVEL
CIRCULATION CENTER (LLCC), WHICH APPEARS TO BE REMAINING NEARLY 
STATIONARY
A BETTER ANALYSIS OF THE CURRENT SITUATION SHOULD BE POSSIBLE AFTER 
DAYLIGHT.

INITIAL WIND RADII BASIS: PARTIAL METOP-B SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: MID-LEVEL STEERING RIDGE TO THE SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   DEMS: T2.5 - 35 KTS
   CIMSS SATCON: 49 KTS AT 191900Z
   CIMSS ADT: 47 KTS AT 191730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
   OTHER FACTORS: VORTEX DECOUPLING SHOULD LEAD TO A WEAKENING OF
THE REMAINING LLCC, WHICH MAY MOVE BACK OUT OVER THE GULF OF
TONKIN.  

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   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 16W HAS CONTINUED TO DEFY MODEL AND
FORECASTER EXPECTATIONS. THE RAPID POLEWARD ACCELERATION OF TS
SANBA ALLOWED IT TO CROSS THE AXIS OF THE STEERING SUB-TROPICAL
RIDGE. RADAR DATA IS LIMITED AND INCONCLUSIVE TO ASSESS WHETHER OR
NOT THE LLCC IS DISSIPATING OVER LAND, OR TURNED BACK OVER WATER.
THE FORECAST STILL CALLS FOR A TURN BACK TO THE SOUTHWEST, HOWEVER,
THIS WOULD BE A RAPIDLY DISSIPATING REMNANT CIRCULATION. IT IS 
POSSIBLE THE LLCC MAY DISSIPATE OVER LAND DUE TO THE HIGH SHEAR. THE 
AVAILABILITY OF VISIBLE SATELLITE IMAGERY FOR THE NEXT WARNING CYCLE 
SHOULD PROVIDE BETTER EVIDENCE OF THE CURRENT ENVIRONMENT, AND CLARITY 
ON THE FATE OF THE LLCC. RATHER THAN INTRODUCING A NEW FORECAST 
PHILOSOPHY AT THIS TIME, THE FORECAST IS BEING KEPT CLOSE TO THE PRIOR 
FORECAST AND CONSENSUS GUIDANCE, UNTIL BETTER ANALYSIS DATA IS 
AVAILABLE TO CONFIRM WHETHER OR NOT A FINAL WARNING IS WARRANTED 
NEEDLESS TO SAY, THERE IS LOW CONFIDENCE IN THE FORECAST TRACK AND 
INTENSITY. 

MODEL DISCUSSION: ALL AVAILABLE DYNAMICAL MODELS CONTINUE TO SHOW A
SLOW TRACK, WITH A TURN BACK TO THE SOUTHWEST. AT THIS POINT TS
SANBA IS ALREADY BEING ABSORBED BY MID-LATITUDE FLOW, SO IF
GUIDANCE CAN SALVAGE ANY HOPE OF VERIFICATION, IT WILL BE THAT THE
LLCC DOES INDEED DECOUPLE AND TURN BACK. THE SIMPLE BETA AND ADVECTION
MODELS INDICATE TS SANBA WILL CONTINUE INLAND AND DISSIPATE. 

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