WDPN32 PGTW 062100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 05W (DANAS) WARNING NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.8N 120.5E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 95 NM SOUTHWEST OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: OVER LAND

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
05W (DANAS) WITH A SIGNIFICANTLY WEAKENED APPEARANCE SINCE MAKING
LANDFALL WITHIN SOUTHWESTERN TAIWAN AT AROUND 1500Z. THE DEFINED
EYE HAS NOW FILLED AND THE MOUNTAINOUS TERRAIN OF CENTRAL TAIWAN
IS RAPIDLY WEAKENING THE VORTEX. ENVIRONMENTAL ANALYSIS INDICATES
THAT 05W IS IN AN UNFAVORABLE ENVIRONMENT DUE PRIMARILY TO THE
SYSTEM BEING OVER LAND. OTHER ENVIRONMENTAL FACTORS ARE RELATIVELY
FAVORABLE WITH MODERATE EQUATORWARD OUTFLOW ALOFT AND LOW (10-15
KTS) VERTICAL WIND SHEAR. THE INITIAL POSITION IS PLACED WITH LOW
CONFIDENCE BASED ON ANIMATED EIR AND RADAR IMAGERY. THE INITIAL
INTENSITY OF 70 KTS IS ASSESSED WITH LOW CONFIDENCE BASED ON A
WEAKENING TREND OVER LAND.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RJTD: T4.5 - 77 KTS
   CIMSS SATCON: 70 KTS AT 061600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 10-15 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: RUGGED TERRAIN INTERACTION

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: 05W IS FORECAST TO CONTINUE TRACKING
NORTHEASTWARD, ALONG THE NORTHWESTERN PERIPHERY OF THE
NEAR-EQUATORIAL RIDGE THROUGH TAU 24. A JUMP IN THE TRACK IS
POSSIBLE OVER THE NEXT 6 HOURS AS THE LOW-LEVEL CENTER QUICKLY
TRAVERSES ACROSS WESTERN AND NORTHERN TAIWAN. NEAR TAU 24, RIDGING
WILL EXTEND OVER TO THE NORTH OF THE VORTEX, WHICH WILL TURN THE
SYSTEM SHARPLY WESTWARD TOWARDS MAINLAND CHINA. A WESTWARD TO
SOUTHWESTWARD TRACK WILL THEN CONTINUE THROUGH THE REMAINDER OF THE
FORECAST PERIOD AS THE REMNANT VORTEX TRACKS FURTHER INLAND.
REGARDING INTENSITY, 05W IS FORECAST TO CONTINUE FEELING THE EFFECTS
OF TERRAIN INTERACTION THROUGH TAU 12, CAUSING FURTHER WEAKENING.
ONCE THE SYSTEM EMERGES TO THE NORTH OF TAIWAN, OUTFLOW WILL ALMOST
ENTIRELY CEASE AND NORTHEASTERLY SHEAR WILL BEGIN TO INCREASE. THIS
WILL CREATE A MARGINAL ENVIRONMENT, AND 05W IS EXPECTED TO CONTINUE
WEAKENING AS IT APPROACHES THE EASTERN COAST OF CHINA. A SECOND
LANDFALL IS CURRENTLY FORECAST TO OCCUR JUST AFTER TAU 36. AFTER
THE SECOND LANDFALL, 05W IS EXPECTED TO RAPIDLY DETERIORATE OVER
LAND WITH DISSIPATION NEAR TAU 72.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 36 WITH AN 80 NM CROSS-TRACK SPREAD AT TAU
36. AFTER TAU 36, BOTH CROSS-TRACK AND ALONG-TRACK SPREAD INCREASE
AS THE WEAKENED VORTEX TRACKS OVER LAND. THE MAIN OUTLIER IS GFS,
WHICH HAS THE SYSTEM TAKE A WIDER TURN AT TAU 24 AND THEN A MUCH
SHARPER SOUTH-SOUTHWESTWARD TURN, NEARLY BACK INTO THE TAIWAN
STRAIT, AFTER TAU 36. THE JTWC TRACK FORECAST FOLLOWS MORE CLOSELY
TO THE MAIN GROUPING OF GUIDANCE WITH MEDIUM CONFIDENCE. INTENSITY
GUIDANCE AGREES ON WEAKENING THROUGHOUT THE FORECAST PERIOD WITH
ALL MODELS (EXCEPT FOR GFS) SUGGESTING DISSIPATION BY TAU 72. AS A
RESULT, THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO THE
MULTI-MODEL CONSENSUS THROUGHOUT THE FORECAST PERIOD. THERE IS SOME
UNCERTAINTY REGARDING HOW WEAK THE SYSTEM WILL BE AFTER IT PASSES
OVER WATER, SO THE INTENSITY FORECAST IS PLACED WITH ONLY MEDIUM
CONFIDENCE.

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