WDXS31 PGTW 090900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18S (EIGHTEEN)       
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.3S 126.1E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 912 NM NORTHEAST OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
EASTERLY VERTICAL WIND SHEAR HAS DECREASED WITH UPPER-LEVEL WINDS
DIVERGING AROUND THE INTENSE CONVECTIVE MASS AS INDICATED IN THE
UW-CIMSS UPPER-LEVEL WINDS. ANIMATED PROXYVIS SATELLITE IMAGERY
INDICATES IMPROVED OUTFLOW OVER THE EASTERN SEMICIRCLE AS WELL AS
VIGOROUS EQUATORWARD AND POLEWARD OUTFLOW. CONSEQUENTLY, CORE
CONVECTION HAS CONSOLIDATED OVER THE OBSCURED LOW-LEVEL CIRCULATION
CENTER (LLCC) LEADING TO MEDIUM CONFIDENCE IN THE INITIAL POSITION.
A 090522Z ATMS 88.2GHZ MICROWAVE IMAGE REVEALS DEEP CONVECTIVE
BANDING OVER THE SOUTHERN SEMICIRCLE WRAPPING INTO THE SOUTHWEST
QUADRANT WITH THE INITIAL POSITION LOCATED TO THE NORTHEAST OF
THE CORE CONVECTION. BOTH THE PGTW AND KNES FIXES ARE POSITIONED
UNDER THE CORE CONVECTION, PERHAPS TOO FAR INTO THE CENTRAL
CONVECTION, LIKELY CONTRIBUTING TO THE KNES T3.5 (55 KNOTS)
ESTIMATE. HOWEVER, BASED ON THE IMPROVED ORGANIZATION, THE INITIAL
INTENSITY OF 45 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
PGTW AND APRF DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSIIONED TO THE SOUTH AND SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   APRF: T3.0 - 45 KTS
   CIMSS SATCON: 51 KTS AT 090054Z
   CIMSS ADT: 49 KTS AT 090220Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   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 18S IS EXPECTED TO TRACK WEST-SOUTHWESTWARD
TO SOUTHWESTWARD THROUGH TAU 48 ALONG THE NORTHWEST PERIPHERY OF
THE STR. AFTER TAU 48, THE SYSTEM WILL RECURVE SOUTHWARD AS A
MIDLATITUDE SHORTWAVE TROUGH DIGS INTO WESTERN AUSTRALIA WEAKENING
THE STR. THE SYSTEM WILL ACCELERATE SOUTHEASTWARD AFTER TAU 96 WHEN
ANOTHER SHORTWAVE TROUGH PROPAGATES OVER WESTERN AUSTRALIA.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
WITH A 190NM CROSS-TRACK SPREAD IN SOLUTIONS AT TAU 72 REFLECTING 
UNCERTAINTY IN THE RECURVE POINT. AFTER TAU 72, CROSS-TRACK SPREAD 
DECREASES, HOWEVER, ALONG TRACK UNCERTAINTY INCREASES AS THE SYSTEM 
INTERACTS WITH THE AFOREMENTIONED SHORTWAVE TROUGH AND ACCELERATES 
SOUTHEASTWARD. THE RAPID INTENSIFICATION CONSENSUS (RICN) GUIDANCE HAS 
TRIGGERED SUPPORTING RAPID INTENSIFICATION (RI) OVER THE NEXT TWO 
DAYS. ADDITIONALLY, THE 090000Z COAMPS TC ENSEMBLE (CTCXEPS) CONTINUES 
TO INDICATE A 100 PERCENT PROBABILITY OF RI FROM TAU 54 TO TAU 84 
SUPPORTING THE RI FORECAST IN THE DAY 2 TO DAY 3 PERIOD. ADDITIONAL 
INTENSIFICATION ABOVE 130 KNOTS IS POSSIBLE PRIOR TO LANDFALL NEAR TAU 
84.  

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