WDPN32 PGTW 052100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 05W (DANAS) WARNING NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.1N 118.1E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 305 NM SOUTHWEST OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
05W (DANAS) WITH COMPACT CORE OF DEEP CONVECTION OBSCURING THE
LOW-LEVEL CIRCULATION CENTER (LLCC). BANDS OF DEEP CONVECTION CAN
BE SEEN SURROUNDING THE EASTERN PERIPHERY OF THE SYSTEM, EXTENDING
DOWN TO THE NORTHWESTERN CORNER OF LUZON. THERE IS SOME SLIGHT
VORTEX TILT, WITH THE CENTER ASSESSED TO BE WITHIN THE NORTHEASTERN
PORTION OF THE DEEP CONVECTION. ENVIRONMENTAL ANALYSIS INDICATES
THAT 05W IS IN A HIGHLY FAVORABLE ENVIRONMENT CHARACTERIZED BY
STRONG POLEWARD AND EASTWARD OUTFLOW, LOW (5-10 KTS) VERTICAL WIND
SHEAR, AND WARM (29-30 C) SEA SURFACE TEMPERATURES. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE TIGHT
CIRCULATION IN ANIMATED RADAR IMAGERY.  THE INITIAL INTENSITY OF 65
KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK
AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A DEEP LAYER
NEAR-EQUATORIAL RIDGE CENTERED TO THE SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T4.5 - 77 KTS
   DEMS: T3.5 - 55 KTS
   CIMSS SATCON: 58 KTS AT 051530Z
   CIMSS ADT: 55 KTS AT 051750Z
   CIMSS AIDT: 56 KTS AT 051750Z
   CIMSS DPRINT: 66 KTS AT 051750Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: TAUS 24-48 ARE FORECAST TO BE LOWER
INTENSITY THAN PREVIOUSLY FORECASTED.

FORECAST DISCUSSION: TY 05W IS FORECAST TO CONTINUE TRACKING
NORTH-NORTHEASTWARD, ALONG THE NORTHWESTERN PERIPHERY OF THE
NEAR-EQUATORIAL RIDGE TO THE SOUTHEAST THROUGH TAU 48. NEAR TAU 48,
RIDGING IS FORECAST TO BUILD IN TO THE NORTH OF THE SYSTEM, WHICH
WILL INITIATE A SHARP WESTWARD TURN INTO MAINLAND CHINA. 05W WILL
THEN CONTINUE ON A GENERALLY WESTWARD TRACK THROUGH THE REMAINDER
OF THE FORECAST PERIOD AS IT TRACKS FURTHER INLAND. OF NOTE, THE
PASSAGE THROUGH THE TAIWAN STRAIT HAS SHIFTED SLIGHTLY CLOSER TO
THE WESTERN COAST OF TAIWAN. REGARDING INTENSITY, 05W IS FORECAST
TO CONTINUE INTENSIFYING THROUGH TAU 12-18 AS THE ENVIRONMENT
REMAINS HIGHLY CONDUCIVE. HOWEVER, AFTER TAU 18, INTERACTION WITH
THE WESTERN COAST OF TAIWAN WILL HINDER DEVELOPMENT AND WEAKEN THE
VORTEX. THIS WEAKENING TREND IS FORECAST TO PERSIST THROUGH TAU 48
AS 05W ENTERS A POOL OF COOL WATER THAT EXTENDS SOUTHWARD, TO
AROUND 28N, AND EASTERLY SHEAR INCREASES. AFTER TAU 48, THE RUGGED
TERRAIN OF EASTERN CHINA WILL CAUSE 05W TO QUICKLY WEAKEN WITH
DISSIPATION FORECAST TO OCCUR NO LATER THAN TAU 96. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN VERY GOOD
AGREEMENT THROUGH TAU 48, WITH A MERE 55 NM CROSS-TRACK SPREAD AT
TAU 48. SPREAD THEN INCREASES TO 120 NM AT TAU 72, AS THE SYSTEM
TURNS WESTWARD. AFTER TAU 72, MODELS DIVERGE AS THE WEAKENED VORTEX
TRAVELS FURTHER INLAND. ONE OUTLIER IS THE GFS DETERMINISTIC, WHICH
HAS THE SYSTEM MAKE A SHARP SOUTH-SOUTHWESTWARD TURN AFTER TAU 72.
OVERALL, THE JTWC TRACK FORECAST IS PLACED WITH MEDIUM CONFIDENCE
THROUGH TAU 72 AND LOW CONFIDENCE THEREAFTER. INTENSITY GUIDANCE IS
IN RELATIVELY GOOD AGREEMENT ON INTENSIFICATION THROUGH TAU 12 AND
THEN WEAKENING THEREAFTER. THE STATISTICAL DYNAMICAL MODELS ARE THE
MAIN OUTLIERS, KEEPING THE SYSTEM TYPHOON STRENGTH THROUGH TAU 60.
THE JTWC INTENSITY FORECAST IS PLACED SLIGHTLY BELOW THE
MULTI-MODEL CONSENSUS TO OFFSET THE OUTLIERS AND BE MORE IN LINE
WITH THE MAIN GROUPING. CONFIDENCE IS LOW DUE TO THE POSSIBILITY
FOR MORE OR LESS LAND INTERACTION WITH WESTERN TAIWAN, WHICH COULD
HEAVILY AFFECT INTENSITIES.

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