WDPN31 PGTW 081500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 12W (YUN-YEUNG) 
WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.6N 138.0E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 132 NM SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED PROXY VISIBLE SATELLITE IMAGERY (PSI) SHOWS A WEAK,
SHALLOW CIRCULATION NOW MOVING RAPIDLY TOWARDS THE SOUTHERN COAST
OF HONSHU. AFTER MEANDERING IN ROUGHLY THE SAME POSITION FOR ABOUT
18 HOURS, TROPICAL DEPRESSION (TD) 12W HAS FINALLY DETERMINED TO
MAKE ITS VISIT TO JAPAN AFTER ALL AND EJECTED NORTHWARD AT AN
ACCELERATING PACE. TRACK SPEEDS ARE NOW UP TO 11 KNOTS AND BY ALL
APPEARANCES LOOK TO PICK UP ANOTHER KNOT OR TWO OVER THE NEXT
COUPLE OF HOURS. A 090911Z GPM 37GHZ MICROWAVE IMAGE SHOWED SHALLOW
BANDING FEATURES DRAPED ACROSS THE NORTHERN HEMISPHERE, WRAPPING
INTO THE WELL-DEFINED LOW LEVEL CIRCULATION CENTER (LLCC), WITH AN
ELONGATED BAND OF SHALLOW CONVECTION EXTENDING NORTHEASTWARD TO THE
SOUTHERN TIP OF THE BOSO PENINSULA. A PARTIAL 091112Z ASCAT-C PASS
SHOWED A SHARP BOUNDARY EXTENDING FROM THE LLCC TO THE SAME AREA
SUGGESTIVE OF A DEVELOPING WARM FRONT. THE INITIAL POSITION IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC AND
EXTRAPOLATION OF THE MICROWAVE CENTER NOTED ABOVE. THE INITIAL
INTENSITY OF 30 KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE, ON THE
HIGHER END OF THE AGENCY CURRENT INTENSITY ESTIMATES AND THE CIMSS
ADT ESTIMATE. THE ENVIRONMENT REMAINS HIGHLY UNFAVORABLE, WITH
EXTREMELY HIGH (35-40 KNOTS) SOUTHERLY SHEAR AND MID-LEVEL DRY AIR
SMOTHERING THE SYSTEM, OFFSETTING THE ROBUST POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A SHALLOW,
NORTH-SOUTH ORIENTED SUBTROPICAL (STR) RIDGE CENTERED TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   CIMSS ADT: 27 KTS AT 081130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 35-40 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: MID-LEVEL DRY AIR. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: WITH THE RIDGE TO THE NORTH HAVING MOVED OFF
TO THE EAST AND INTEGRATED INTO A MUCH LARGER, NORTH-SOUTH ORIENTED
STR SITUATED ALONG THE 15OE LONGITUDE, TD 12W HAS BEEN KICKED OUT
ONTO A NORTHWARD TRAJECTORY OVER THE PAST SIX HOURS. THIS GENERAL
MOTION IS EXPECTED TO CONTINUE THROUGH THE SHORT DURATION OF THE
FORECAST PERIOD. TRACK SPEEDS ARE LIKELY TO PICK UP ANOTHER KNOT OR
TWO BEFORE THE SYSTEM MAKES LANDFALL, ALONG THE WESTERN SIDE OF
SURUGA BAY WITHIN THE NEXT FEW HOURS. ONCE IT MAKES LANDFALL, THE
CENTER WILL TRACK VERY NEAR MT. FUJI AND THEN CONTINUE FURTHER
INLAND TO CENTRAL HONSHU. DUE TO THE SHALLOW NATURE OF THE
CIRCULATION, MT. FUJI WILL HAVE AN OUTSIZE EFFECT ON THE SYSTEM,
WHICH WILL SLOW DOWN AND MOVE AROUND THE MOUNTAIN, WHILE AT THE
SAME TIME RAPIDLY DISINTEGRATING AS A DISCRETE CIRCULATION CENTER.
THE SYSTEM WILL CONTINUE TO WEAKEN AS IT APPROACHES THE COASTLINE,
THEN FULLY DISSIPATE WITHIN THE NEXT 24 HOURS OVER CENTRAL HONSHU. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE CONTINUES TO
STRUGGLE TO ACCURATELY PORTRAY THE FUTURE TRACK OF TD 12W, WITH
SOME MODELS (NAVGEM) TURNING THE SYSTEM SLOWLY TOWARDS THE
NORTHWEST, WHILE OTHER (ECENS MEAN) RACING THE SYSTEM TO A POSITION
EAST OF MISAWA BY TAU 24. THE JTWC FORECAST IS BASED PRIMARILY ON
AN EXTRAPOLATION OF THE RECENT TRACK MOTION AND EXPECTATIONS OF THE
LOCALIZED TERRAIN INFLUENCES. THE TRACK FORECAST REMAINS CONSISTENT
WITH THE PREVIOUS FORECAST WITH LOW CONFIDENCE. INTENSITY GUIDANCE
IS IN GOOD AGREEMENT ON THE RAPID WEAKENING TREND AND DISSIPATION
BY TAU 24, LENDING HIGH CONFIDENCE TO THE JTWC INTENSITY FORECAST. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: LOW
   INTENSITY 0 - 72 HR: HIGH//
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