WDPN32 PGTW 071500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W (DANAS) WARNING NR 
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.1N 121.7E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 120 NM NORTH OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY INDICATES A
FRAGMENTED AND BROAD LOW-LEVEL CIRCULATION (LLCC) OF TROPICAL STORM
(TS) 05W (DANAS). THE INITIAL POSITION IS ASSIGNED WITH LOW
CONFIDENCE BASED ON LOW LEVEL FLOW PRESENT IN EIR, IN CONJUNCTION WITH 
VAGUELY INDICATED LLCC IN RADAR IMAGERY. ENVIRONMENTAL ANALYSIS 
REVEALS LOW (0-5 KTS) VERTICAL WIND SHEAR (VWS), WARM (28-29 C) SEA 
SURFACE TEMPERATURES (SST), DEEP-LAYER MOISTURE, AND MODERATE UPPER-
LEVEL OUTFLOW. WITH THE VORTEX CURRENTLY POSITIONED WITHIN A FAVORABLE 
ENVIRONMENT, DEEP CONVECTION IS SLOWLY CONSOLIDATING WITHIN SPIRAL 
BANDS WRAPPING INTO A BROAD LLCC. THE INITIAL INTENSITY OF 45 KTS IS 
ESTIMATED WITH MEDIUM CONFIDENCE, DERIVED FROM A BLEND OF AGENCY 
DVORAK AND OBJECTIVE FIXES DETAILED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT -
NEAR-EQUATORIAL RIDGE (NER) TO THE SOUTHEAST AND BUILDING SUBTROPICAL 
RIDGE (STR) TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   DEMS: T3.0 - 45 KTS
   CIMSS SATCON: 52 KTS AT 071036Z
   CIMSS ADT: 57 KTS AT 071130Z
   CIMSS AIDT: 53 KTS AT 071130Z
   CIMSS D-MINT: 33 KTS AT 071039Z
   CIMSS D-PRINT: 31 KTS AT 071230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 0-5 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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: TS 05W HAS SIGNIFICANTLY SLOWED DOWN SINCE
LAST FORECAST AS A RESULT OF A BUILDING STR TO THE NORTHEAST, AND
OCCURRING EARLIER THAN ANTICIPATED SHIFT IN THE STEERING ENVIRONMENT. 
TS DANAS IS HOWEVER STILL FORECAST TO CONTINUE ON A NORTHEASTWARD 
TRACK ALONG THE NORTHWESTERN PERIPHERY OF A NER TO THE SOUTHEAST, 
UNTIL THE RIDGE TO THE NORTH BUILDS ENOUGH TO STEER THE SYSTEM 
WESTWARD. AS A RESULT, THE SYSTEM IS EXPECTED TO MAKE LANDFALL OVER 
CHINA AROUND TAU 24. POST LANDFALL, THE SYSTEM IS FORECAST TO TRACK 
WEST-SOUTHWESTWARD OVER LAND AND DISSIPATE BY TAU 72. TS 05W IS 
FORECAST TO MAINTAIN INTENSITY AROUND 45 KTS UNTIL LANDFALL, AS A 
RESULT OF COMPETING IMPACT OF MARGINALLY FAVORABLE ENVIRONMENT AND 
LAND INTERACTION WITH THE EXTENDED PORTION OF THE VORTEX AND THE 
ASSOCIATED WIND FIELD. THEREAFTER, A GRADUAL WEAKENING PHASE AND 
EVENTUAL DISSIPATION BY TAU 72 ARE ANTICIPATED.

MODEL DISCUSSION: NUMERICAL TRACK MODEL GUIDANCE EXHIBITS FAIR
AGREEMENT THROUGHOUT THE FORECAST PERIOD, DEMONSTRATED BY A
CROSS-TRACK SPREAD OF APPROXIMATELY 30 NM AT LANDFALL, AMONG MAJORITY 
OF THE MULTI-MODEL CONSENSUS MEMBERS. MAJOR OUTLIERS TO THIS GUIDANCE 
ARE GFS AND GFS ENSEMBLE, WHICH PREDICT A NEARLY FULL U-TURN AROUND 
TAU 24, RESULTING IN A SOUTHWESTWARD TRACK ALONG THE COASTLINE OF 
CHINA. INTENSITY GUIDANCE HOWEVER IN CONSISTENT AMONG NEARLY ALL
CONSENSUS MEMBERS, INDICATING WEAKENING TREND BEGINNING BETWEEN
TAUS 24 AND 36, ALIGNING WITH THE LANDFALL TIMELINE. ONE OUTLIER
IN THIS INSTANCE IS THE GUIDANCE FROM COAMPS-TC, WHICH PREDICTS
SLIGHT INTENSIFICATION THROUGH TAU 36, WITH THE SYSTEM REACHING
50-55 KTS PRIOR TO LANDFALL. ADDITIONALLY, SOME MODELS, LIKE GFS,
INDICATE THAT THE SYSTEM WILL LINGER AROUND 30 KTS BEYOND TAU 72,
LIKELY DUE TO ITS CURRENT ASSOCIATED TRACK ASSESSMENT MUCH CLOSER
TO THE TAIWAN STRAIT, AS COMPARED TO OTHER AVAILABLE GUIDANCE. JTWC 
TRACK AND INTENSITY PREDICTIONS ARE THEREFORE ASSESSED WITH MEDIUM 
CONFIDENCE AND ARE LAID CLOSE TO THE MULTI-MODEL CONSENSUS.

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