WDPN32 PGTW 032100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (MAYSAK) WARNING NR 
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.8N 108.7E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 173 NM EAST-SOUTHEAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) OF TROPICAL
STORM (TS) 10W (MAYSAK) AS IT REEMERGES OVER THE WARM WATERS OF THE
GULF OF TONKIN, JUST NORTHWEST OF HAINAN ISLAND. THE LOCAL
THERMODYNAMIC REGIME AND CYCLONE ENVIRONMENT ARE ASSESSED AS
MARGINALLY FAVORABLE FOR SOME SLIGHT INTENSIFICATION, DRIVEN BY LOW
TO MODERATE (15-20 KTS) DEEP-LAYER VERTICAL WIND SHEAR (VWS),
RESTRAINED LAND INTERACTION WHILE TRANSLATING OVER HAINAN ISLAND,
ALTHOUGH MITIGATED TO AN EXTENT BY SUSTAINED MODERATE EQUATORWARD
UPPER-LEVEL OUTFLOW VENTILATION AND VERY WARM (29-30 C) SEA SURFACE
TEMPERATURES. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE
BASED ON AN ANIMATED RADAR LOOP IN CONJUNCTION WITH LOCAL SURFACE
WIND DIRECTION OBSERVATIONS. THE INITIAL INTENSITY ANALYSIS OF 40
KTS IS ALSO ESTABLISHED WITH MEDIUM CONFIDENCE, AND IS DERIVED BY
INTERPOLATING RJTD AGENCY DVORAK ASSESSMENT AND CIMSS OBJECTIVE
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: A 031636Z OCEANSAT-3 OSCAT PASS

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR)
CENTERED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RJTD: T2.5 - 35 KTS
   CIMSS D-MINT: 38 KTS AT 031830Z
   CIMSS D-PRINT: 43 KTS AT 031900Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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 10W IS FORECAST TO CONTINUE TRACKING
NORTHWESTWARD OVER THE NEXT 12-24 HOURS UNTIL IT MAKES LANDFALL
NEAR THE CHINA-VIETNAM BORDER. DURING THIS SHORT TRANSIT, TS MAYSAK
IS EXPECTED TO REMAIN AT ITS WIND SPEED MAXIMUM, OR SLIGHTLY
INTENSIFY; HOWEVER, SHORTLY AFTER LANDFALL, TERMINAL WEAKENING WILL
COMMENCE. FRICTIONAL EFFECTS OF THE LAND INTERACTION WILL RESULT IN
FULL DISSIPATION BY OR BEFORE TAU 48.

MODEL DISCUSSION: DETERMINISTIC NUMERICAL MODEL TRACK PREDICTIONS
MAINTAIN HIGHLY COHERENT SPATIAL CONVERGENCE REGARDING THE CORE
TRAJECTORY OF TS 10W, DISPLAYING VERY TIGHT CROSS-TRACK AND
ALONG-TRACK ENVELOPE SPREADS. JTWC OFFICIAL TRACK FORECAST IS
THEREFORE PLACED WITH HIGH CONFIDENCE. MODEL INTENSITY GUIDANCE IS
LIKEWISE IN EXCELLENT AGREEMENT, WITH ENVELOPE SPREADS DEVIATING BY A
MAX OF ONLY 5 KTS CONCERNING THE INTENSIFICATION TRANSIT PHASE OVER
THE GULF OF TONKIN BEFORE POST-LANDFALL DECAY AND DISSIPATION TAKES
OVER. CONSEQUENTLY, THE JTWC OFFICIAL INTENSITY PREDICTION IS
LAID NEAR THE CONVERGENCE OF DYNAMICAL MODEL OUTPUTS WITH HIGH
CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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