WDPN31 PGTW 301500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (ELEVEN) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.3N 154.3E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 340 NM NORTH OF OROLUK
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM 11W CONTINUES TO CONSOLIDATE WITH IMPROVED SPIRAL
BANDS OF PERSISTENT DEEP CONVECTION OBSCURING THE LOW-LEVEL
CIRCULATION CENTER (LLCC), EVIDENT IN ANIMATED ENHANCED INFRARED
(EIR). ANIMATED WATER VAPOR IMAGERY ALSO INDICATES AN INCREASE IN
CENTRAL CONVECTION WITH AN INCREASE IN POLEWARD OUTFLOW AS THE
SYSTEM TAPS INTO AN UPPER-LEVEL TROUGH TO THE NORTHEAST; THUS
ENVIRONMENTAL CONDITIONS CONTINUE TO IMPROVE. THE INITIAL POSITION
IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE ANIMATED EIR IMAGERY
IN COMBINATION WITH AGENCY DVORAK POSITION FIXES. THE INITIAL
INTENSITY OF 40 KNOTS IS ASSESSED WITH MEDIUM  CONFIDENCE BASED ON
THE IMPROVING CONVECTIVE STRUCTURE AS WELL AS A COMBINATION OF
AGENCY DVORAK INTENSITY ESTIMATES, WHICH ARE SLIGHTLY LAGGED AT
T2.0 AND T2.5 AND D-PRINT SHOWING 45 KNOTS. 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
   RJTD: T2.0 - 30 KTS
   CIMSS ADT: 34 KTS AT 301140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

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
GENERALLY NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST THROUGH TAU 48.
ENVIRONMENTAL CONDITIONS ARE FORECAST TO REMAIN FAVORABLE THROUGH
TAU 72 WITH MODERATE EQUATORWARD OUTFLOW, IMPROVING POLEWARD
OUTFLOW INTO AN UPPER-LEVEL LOW WHICH IS EXPECTED TO SHIFT WESTWARD,
ALONG WITH LOW VERTICAL WIND SHEAR (VWS). AFTER TAU 72, THE STR IS
FORECAST TO STRENGTHEN TO THE NORTHEAST AND BECOME ORIENTED MORE
EAST-WEST, WHICH WILL ULTIMATELY TURN AND STEER THE SYSTEM
WEST-NORTHWESTWARD THROUGH THE END OF THE FORECAST PERIOD. HOWEVER,
TRACK UNCERTAINTY INCREASES IN THE LATER PART OF THE FORECAST AS
THE SYSTEM COULD INTERACT WITH ANOTHER DEVELOPING LOW-PRESSURE
SYSTEM IN THE VICINITY OF 11W. ADDITIONALLY, IN TERMS OF INTENSITY,
AFTER TAU 72, OUTFLOW BECOMES LESS FAVORABLE WHILE VERTICAL WIND
SHEAR (VWS) AND DRY AIR ENTRAINMENT INCREASE RESULTING IN A GRADUAL
WEAKENING TREND THROUGH TAU 120.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE CONTINUES TO BE IN
OVERALL GOOD AGREEMENT THROUGH TAU 72 WITH ONLY A 57NM SPREAD IN
THE SOLUTIONS. AFTER TAU 72, THE CROSS-TRACK SPREAD INCREASES TO 317 
NM BY TAU 120, SPANNING FROM AMAMI OSHIMA TO SOUTHERN KYUSHU. BETWEEN 
TAU 96 AND TAU 120, A STRAND OF MODELS, INCLUDING NVGM, ECMF, UEMN, 
DEVIATE FROM THE PACK AND REPRESENT THE NORTHERN EDGE OF THE GUIDANCE 
ENVELOPE, WHILE AVNO MAKES UP THE SOUTHERN EDGE. GIVEN THIS, THERE IS 
HIGH CONFIDENCE IN THE JTWC TRACK FORECAST UP TO TAU 72, THEN MEDIUM
CONFIDENCE AFTERWARD. 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, THE BULK OF THE INTENSITY GUIDANCE SHOWS A GRADUAL
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: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
NNNN