WDXS31 PGTW 010300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11S (ELEVEN) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.4S 107.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 695 NM NORTH-NORTHWEST OF LEARMONTH,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 11S WITH A HIGHLY COMPACT CORE OF DEEP CONVECTION AND SOME
EXPOSED LOW-LEVEL CLOUD LINES WITHIN THE NORTHERN PORTION OF THE
LLCC. A 312310Z F16 SSMIS 91 GHZ MICROWAVE IMAGE REVEALED THE
LOW-LEVEL CLOUDS TO THE NORTH TIGHTLY WRAPPING INTO THE ASSESSED
CENTER, LENDING HIGH CONFIDENCE TO THE INITIAL POSITION. THE
INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE PGTW FIX OF T2.0 AND CIMSS OBJECTIVE INTENSITY
ESTIMATES RANGING FROM 32-35 KTS. ENVIRONMENTAL ANALYSIS INDICATES
THAT 11S IS IN A FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE
RADIAL OUTFLOW ALOFT, LOW (5-10 KTS) VERTICAL WIND SHEAR, AND WARM
(28-29 C) SEA SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: EASTERN PERIPHERY OF A LOW TO MID-LEVEL
NEAR-EQUATORIAL RIDGE (NER) POSITIONED TO THE WEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 312300Z
   CIMSS AIDT: 32 KTS AT 312300Z
   CIMSS D-PRINT: 32 KTS AT 312300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL

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: TC 11S IS FORECAST TO TRACK SOUTHEASTWARD,
ALONG THE EASTERN PERIPHERY OF THE LOW TO MID-LEVEL NER TO THE WEST
THROUGH TAU 36. NEAR TAU 36, THE STEERING MECHANISM WILL SWITCH TO
A LARGE SUBTROPICAL RIDGE TO THE SOUTH OF THE SYSTEM, CAUSING 11S
TO TURN SHARPLY WESTWARD. A WESTWARD TRACK, ALONG THE NORTHERN
PERIPHERY OF THE STR IS THEN EXPECTED TO PERSIST THROUGH THE
REMAINDER OF THE FORECAST PERIOD. IN TERMS OF INTENSITY, 11S IS 
FORECAST TO INTENSIFY THROUGH TAU 36 AS SHEAR REMAINS LOW. NEAR TAU 
36, NORTHWESTERLY SHEAR IS EXPECTED TO INCREASE TO OVER 20 KTS, 
CAUSING 11S TO WEAKEN AS IT MAKES THE WESTWARD TURN. IN ADDITION TO 
THE INCREASING SHEAR, DRY AIR ENTRAINMENT FROM THE WEST IS EXPECTED TO 
BEGIN IMPACTING THE VORTEX, FURTHER AIDING IN THE WEAKENING TREND. 11S 
IS FORECAST TO WEAKEN BELOW 35 KTS AROUND TAU 72 AS IT TRAVELS FURTHER 
WESTWARD. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN MODERATE
AGREEMENT THROUGHOUT THE FORECAST PERIOD WITH NO SIGNIFICANT
OUTLIERS. GFS CONTINUES TO BE THE FASTEST MODEL AFTER MAKING THE
WESTWARD TURN AND NAVGEM IS THE SLOWEST. CROSS-TRACK SPREAD AT TAU
72 IS AROUND 95 NM WHILE ALONG TRACK SPREAD IS 190 NM. THE JTWC
TRACK FORECAST IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS THROUGH
TAU 48 AND THEN CLOSER TO THE GOOGLE DEEPMIND ENSEMBLE MEAN
THEREAFTER. INTENSITY GUIDANCE GENERALLY AGREES ON INTENSIFICATION
THROUGH TAU 24-36 BEFORE STEADY WEAKENING. THE JTWC INTENSITY
FORECAST IS PLACED CLOSE TO THE CONSENSUS THROUGHOUT THE FORECAST
PERIOD WITH MEDIUM CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM//
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