WDPN31 PGTW 110900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 15W (FIFTEEN) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.3N 159.8E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 401 NM WEST-NORTHWEST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 11 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE SYSTEM HAS
MAINTAINED A WEAK, RAGGED, BROAD AND PARTIALLY EXPOSED LOW-LEVEL
CIRCULATION (LLC). LOW-LEVEL CLOUD LINES AND FRAGMENTED FORMATIVE
BANDING ARE WRAPPING INTO THE LLC. THE INITIAL POSITION IS PLACED
WITH MEDIUM CONFIDENCE BASED ON THE LLC IN THE MSI LOOP AND LINED
UP WITH A WEAK LLC IN THE 110445Z SSMIS 91GHZ MICROWAVE IMAGE. THE
INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE AND
IS HELD HIGHER THAN THE PGTW DVORAK ESTIMATE TO REFLECT THE SUSTAINED
6-HR STRUCTURE. THE ENVIRONMENT IS MARGINALLY FAVORABLE WITH A TUTT 
CELL TO THE NORTH-NORTHEAST LIMITING POLEWARD OUTFLOW BUT PROVIDING AN 
EASTWARD CHANNEL. LOW VERTICAL WIND SHEAR AND WARM SST VALUES ARE
FAVORABLE FOR 
DEVELOPMENT.

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

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


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.0 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS ADT: 35 KTS AT 110510Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EASTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   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: TD 15W WILL CONTINUE ON ITS CURRENT TRACK
UNDER THE STEERING INFLUENCE OF THE NER. AFTER TAU 36, THE LOW- TO
MID-LAYER OF THE SUBTROPICAL RIDGE (STR) TO THE NORTHEAST WILL
ASSUME STEERING AND DRIVE THE CYCLONE MORE POLEWARD. AFTER TAU 72,
TD 15W WILL CREST THE STR AXIS AND ACCELERATE NORTHEASTWARD. THE
MARGINALLY FAVORABLE CONDITIONS WILL FUEL A STEADY INTENSIFICATION
TO 60KTS BY TAU 36. AFTERWARD, INCREASED POLEWARD OUTFLOW AS THE
TUTT CELL MOVES FURTHER NORTH WILL PROMOTE RAPID INTENSIFICATION TO
A PEAK OF 85KTS BY TAU 72. AFTER TAU 72, INCREASING VWS AND COOLING
SST WILL BEGIN TO ERODE THE SYSTEM. CONCURRENTLY BY TAU 72, IT WILL
BEGIN EXTRA-TROPICAL TRANSITION (ETT) AS IT APPROACHES THE
BAROCLINIC ZONE. BY TAU 120, 15W WILL COMPLETE ETT AND TRANSFORM
INTO A 45KT COLD-CORE LOW WITH AN EXPANDING WIND FIELD. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN VERY TIGHT AGREEMENT,
LENDING HIGH CONFIDENCE IN THE JTWC TRACK FORECAST. THERE IS MEDIUM
CONFIDENCE IN THE INTENSITY FORECAST. 

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