WDPN31 PGTW 300900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (ELEVEN) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.8N 154.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 311 NM NORTH OF OROLUK
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SPIRAL BANDS
OF PERSISTENT DEEP CONVECTION OBSCURING THE LOW-LEVEL CIRCULATION
CENTER (LLCC). A 300531Z SSMIS 91GHZ MICROWAVE IMAGE DEPICTS
CONVECTIVE BANDING WRAPPING INTO AN ELONGATED LOW-LEVEL CIRCULATION
(LLC). ANIMATED WATER VAPOR IMAGERY DEPICTS A MODERATE POLEWARD
OUTFLOW CHANNEL ENHANCED BY AN UPPER-LEVEL LOW TO THE NORTHEAST.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
SSMIS IMAGE IN COMBINATION WITH AGENCY DVORAK POSITION FIXES. A
300336Z AMSR2 WINDSPEED IMAGE SHOWS A 30-35 KNOTS SWATH ON THE
NORTHERN SEMICIRCLE. THE INITIAL INTENSITY OF 35 KNOTS IS ASSESSED
WITH HIGH CONFIDENCE BASED ON THE AMSR2 WINDSPEED IMAGE, RECENT
ASCAT IMAGERY AND AGENCY DVORAK INTENSITY ESTIMATES. ENVIRONMENTAL
CONDITIONS ARE FAVORABLE WITH MODERATE EQUATORWARD OUTFLOW,
IMPROVING POLEWARD OUTFLOW INTO A UPPER-LEVEL LOW POSITION TO THE
NORTHEAST, AND LOW VERTICAL WIND SHEAR.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) POSITIONED TO
THE NORTHEAST. 


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   CIMSS ADT: 25 KTS AT 300220Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 11W IS FORECAST TO TRACK NORTHWARD 
ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) POSITIONED 
TO THE NORTHEAST THROUGH TAU 12. THE STR IS EXPECTED TO STRENGTHEN TO
THE NORTHEAST AND EXTEND TO THE WEST, WHICH WILL TURN THE SYSTEM
NORTHWESTWARD, INITIALLY, THEN WEST-NORTHWESTWARD THROUGH TAU 120.
IN TERMS OF INTENSITY, 11W IS EXPECTED TO STEADLY INTENSIFY THROUGH
TAU 24, AS A UPPER-LEVEL LOW TO THE NORTH SHIFTS WESTWARD WHICH
WILL PROVIDE ENHANCED POLEWARD OUTFLOW. HOWEVER, AFTER TAU 36,
OUTFLOW BECOMES LESS FAVORABLE WHILE VERTICAL WIND SHEAR (VWS), AND
DRY AIR ENTRAINMENT INCREASE RESULTING IN A GRADUAL WEAKENING
TREND.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT
THROUGH TAU 72 WITH ONLY A 115NM SPREAD IN THE SOLUTIONS. AFTER TAU
72, THE CROSS-TRACK SPREAD INCREASES TO 347 NM BY TAU 120, SPANNING
FROM AMAMI OSHIMA TO KYOTO. OVERALL, THE JTWC FORECAST TRACK
FOLLOWS CLOSE TO THE MULTI-MODEL CONSENSUS AND IS PLACED WITH HIGH
CONFIDENCE THROUGH TAU 72, WITH MEDIUM CONFIDENCE THEREAFTER. THE
INTENSITY GUIDANCE IS IN GOOD AGREEMENT AND SUPPORTS A STEADY
INTENSIFICATION PHASE, WITH RAPID INTENSIFICATION (RI) GUIDANCE
TRIGGERED OVER THE NEXT 24-36 HOURS. AFTER TAU 36, ASIDE FROM
COAMPS-TC, WHICH SHOWS A GRADUAL DECREASE IN INTENSITY, THE BULK OF
THE INTENSITY GUIDANCE SHOWS A STEADY WEAKENING TREND THROUGHOUT
THE FORECAST PERIOD. OVERALL, THE JTWC INTENSITY FORECAST IS PLACED
WITH MEDIUM CONFIDENCE THROUGHOUT THE FORECAST PERIOD. 

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