WDPS31 PGTW 221500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18P (EIGHTEEN) WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.8S 150.2E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 283 NM EAST-NORTHEAST OF CAIRNS, AUSTRALIA
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS
COLLAPSING CONVECTION OVER A PARTIALLY OBSCURED LOW-LEVEL
CIRCULATION CENTER (LLCC). WATER VAPOR IMAGERY REVEALS STRONG
POLEWARD AND EASTWARD OUTFLOW IN A DIVERGENT UPPER-LEVEL
ENVIRONMENT. THE INITIAL POSITION IS PLACED WITH LOW CONFIDENCE
BASED ON APPARENT CONFUSED MID- AND UPPER-LEVEL FLOW. THE INITIAL
INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
AGENCY AND OBJECTIVE FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: A COMPETING STEERING ENVIRONMENT
BETWEEN A RIDGE TO THE NORTHEAST AND A RIDGE TO THE SOUTHWEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 39 KTS AT 221130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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 CYCLONE (TC) 18P WILL REMAIN IN A
COMPETING STEERING ENVIRONMENT TRAPPED BETWEEN TWO RIDGES FOR THE
FIRST 48 HOURS OF THE FORECAST. AFTER TAU 48, THE NEAR EQUATORIAL
RIDGE TO THE NORTHEAST WILL DRIVE THE SYSTEM SOUTHEASTWARD, THEN
SOUTHWARD THROUGH THE END OF THE FORECAST PERIOD. THE SYSTEM WILL
INTENSIFY IN A FAVORABLE ENVIRONMENT OF LOW VERTICAL WIND SHEAR,
STRONG UPPER LEVEL DIVERGENCE, AND WARM SEA SURFACE TEMPERATURES
FOR THE FIRST 72 HOURS OF THE FORECAST. AFTERWARDS, VERTICAL WIND
SHEAR WILL BECOME UNFAVORABLY HIGH AND RESULT IN WEAKENING THROUGH
THE REMAINDER OF THE FORECAST PERIOD. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE HAS A SIGNIFICANT
TRACK SPREAD (EXCLUDING THE OUTLIER OF NAVGEM) OPENING TO 350NM BY
TAU 120. THE JTWC MULTI-MODEL CONSENSUS SOLUTIONS DEPICT DIFFERENT
ANGLES OF HOW SHARPLY THE SYSTEM MAY TRACK SOUTHWARD, AND AT
DIFFERING TRACK SPEEDS, LEADING TO INCREASED UNCERTAINTY IN THE
LATE-TERM FORECAST. THE INTENSITY GUIDANCE HAS A SPREAD OF PEAK
INTENSITIES BETWEEN 60-100KTS. THE BULK OF GUIDANCE INDICATES A
PEAK BETWEEN TAU 60-96 BEFORE VERTICAL WIND SHEAR OVERCOMES THE
SYSTEM. THE PRIMARY OUTLIER IS HWRF, WHICH CONTINUOUSLY INCREASES
TO 100KTS BY TAU 120.

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