WDPN33 PGTW 160300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (NESAT) 
WARNING NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.3N 121.2E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 282 NM NORTH OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 19 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SATELLITE
IMAGERY DEPICTS A MORE SYMMETRICAL AND CONSOLIDATED SYSTEM WITH
SPIRAL BANDS OF DEEP CONVECTION OVER THE NORTHERN AND EASTERN
SEMICIRCLES, WRAPPING INTO AND OBSCURING THE LOW LEVEL CIRCULATION
CENTER (LLCC). A 152258Z SSMIS 91 GHZ MICROWAVE IMAGE DEPICTS
FORMATIVE CONVECTIVE BANDING IN ALL QUADRANTS WRAPPING AROUND THE
LLCC. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED
ON AGENCY DVORAK POSITION FIXES, AND A 152258Z SSMIS 37 GHZ
MICROWAVE IMAGE THAT SHOWS A MICROWAVE EYE FEATURE. THE INITIAL
INTENSITY OF 50 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
PGTW, KNES, AND RJTD DVORAK CURRENT INTENSITY ESTIMATES OF T3.0,
ALSO SUPPORTED BY THE ADT AND AIDT AS WELL AS THE CIMSS DEEP
MICRONET (DMN) ESTIMATING AN INTENSITY OF 50 KNOTS AT 0000Z.
ENVIRONMENTAL CONDITIONS REMAIN OVERALL FAVORABLE WITH MODERATE
WESTWARD OUTFLOW, WARM (28-29C) SEA SURFACE TEMPERATURES (SSTS),
AND MODERATE (10-15KTS) VERTICAL WIND SHEAR (VWS).

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED SOUTHEAST OF KYUSHU


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 55 KTS AT 152040Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE WESTWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 23W (NESAT) WILL CONTINUE
TRACKING WEST-NORTHWESTWARD AWAY FROM THE NORTHERN COAST OF LUZON,
ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE
(STR) CENTERED SOUTHEAST OF KYUSHU. BY TAU 12, A MID-LATITUDE
TROUGH WILL MOVE IN FROM THE WEST WHICH WILL ERODE THE STR AND
INDUCE A WEAKNESS WHICH WILL PULL TS 23W SLIGHTLY MORE POLEWARD.
HOWEVER, AFTER TAU 24, AS THE TROUGH TRANSITS EASTWARD, THE SYSTEM
WILL THEN BEGIN TO SLOW AND MOVE SOUTHWESTWARD AS A STR CENTERED
OVER NORTHERN MYANMAR WILL BUILD TOWARDS THE EAST AND ASSUME THE
DOMINANT STEERING ROLE. AS THIS OCCURS, AN ASSOCIATED SURFACE HIGH
PRESSURE SYSTEM WILL INDUCE STRONG NORTHEASTERLY FLOW WHICH WILL
CONTINUE TO STEER THE SYSTEM SOUTHWESTWARD THROUGH TAU 72. BY TAU
96, THE STR SHIFTS EASTWARD AND BUILDS OVER THE TAIWAN STRAIT,
ALLOWING FOR TS 23W TO TURN NORTHWESTWARD AND TRACK JUST SOUTH OF
HAINAN BEFORE ULTIMATELY MOVING TOWARD THE COAST OF CENTRAL
VIETNAM. TS 23W WILL STEADILY INTENSIFY IN A FAVORABLE ENVIRONMENT
THROUGH TAU 48, AS POLEWARD OUTFLOW IMPROVES BY ENHANCED UPPER
LEVEL WESTERLIES WHILE THE SYSTEM TRACKS OVER WARM (28-29C) SSTS
AND HIGH OCEAN HEAT CONTENT. BETWEEN TAU 96 AND TAU 120, THE
NORTHEASTERLY SURGE EVENT WILL INCREASE VERTICAL WIND SHEAR (VWS)
WHILE INCREASING DRY AIR AROUND THE SYSTEM WHICH WILL RESULT IN
STEADY WEAKENING THROUGH THE END OF THE FORECAST.

MODEL DISCUSSION: TRACK GUIDANCE IS IN OVERALL GOOD AGREEMENT
THROUGH TAU 72, HOWEVER BETWEEN TAU 96 AND TAU 120 TRACK
UNCERTAINLY INCREASES, WITH CROSS-TRACK SPREAD INCREASING TO 200NM.
ADDITIONALLY, THE BULK OF THE ECMWF ENSEMBLE (EPS) AND GFS ENSEMBLE
(GEFS) SOLUTIONS SUPPORT THE JTWC FORECAST TRACK THROUGH TAU 72,
WITH INCREASING UNCERTAINLY BETWEEN TAU 96 AND TAU 120. THEREFORE,
THE JTWC FORECAST TRACK IS POSITIONED CLOSE TO THE MULTI-MODEL
CONSENSUS WITH HIGH CONFIDENCE THROUGH TAU 72 AND ASSESSED WITH
MEDIUM CONFIDENCE THROUGH THE END OF THE FORECAST. THE INTENSITY
GUIDANCE IS IN FAIR AGREEMENT, WITH  HWRF REPRESENTING THE HIGH END
OF INTENSITY GUIDANCE, WHILE CTCI, COTI AND DECAY SHIPS (NAVGEM AND
GFS) REPRESENTS THE LOW END OF INTENSITY GUIDANCE. ENSEMBLE
INTENSITY GUIDANCE CONTINUES TO SHOW VERY HIGH PROBABILITIES OF
MODERATE INTENSIFICATION, WITH A 10 PERCENT CHANCE OF RAPID
INTENSIFICATION BETWEEN TAU 24 AND TAU 48. THE JTWC INTENSITY
FORECAST IS PLACED WITH MEDIUM CONFIDENCE AND LIES CLOSE TO THE
HWRF SOLUTION AND ABOVE THE CONSENSUS MEAN. 

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