WDXS32 PGTW 142100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18S (EIGHTEEN) WARNING 
NR 015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.3S 115.4E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 309 NM NORTH-NORTHEAST OF LEARMONTH,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE
FLARING
DEEP CENTRAL CONVECTION SHEARED WESTWARD OF A PARTIALLY EXPOSED LOW
LEVEL CIRCULATION CENTER (LLCC). THERE IS MODERATE POLEWARD OUTFLOW
BUT NO ORGANIZED FEEDER BANDS. ANALYSIS INDICATES A MARGINAL
ENVIRONMENT
WITH VERY WARM SST AND MODERATE POLEWARD OUTFLOW ALOFT GREATLY
OFFSET
BY 20-25 KTS OF VERTICAL WIND SHEAR (VWS). THE INITIAL POSITION IS
PLACED WITH MEDIUM CONFIDENCE BASED ON THE PARTLY EXPOSED LLCC IN
THE EIR LOOP. THE INITIAL INTENSITY IS ALSO PLACED WITH MEDIUM
CONFIDENCE BASED ON OVERALL ASSESSMENT OF AGENCY AND OBJECTIVE
DVORAK INTENSITY ESTIMATES AND REFLECTS THE SUSTAINED 6-HR
CONVECTIVE SIGNATURE.

INITIAL WIND RADII BASIS: MOST RECENT STORM-CENTERED SCATTEROMETER
DATA. 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
SOUTHEAST ANCHORED OVER CENTRAL AUSTRALIA.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T1.5 - 25 KTS
   CIMSS ADT: 32 KTS AT 141730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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 WILL TRACK MORE SOUTHWESTWARD AS THE
STR BUILDS AND EXTENDS WESTWARD. AS THE STORM MOTION BECOMES MORE
IN-PHASE WITH THE UPPER-LEVEL WIND FLOW, VWS IS EXPECTED TO WEAKEN,
AND POLEWARD OUTFLOW TO IMPROVE, PROMOTING A STEADY INTENSIFICATION, 
REACHING 65KTS BY TAU 96.

MODEL DISCUSSION: NUMERICAL MODELS EVENLY SPREAD OUT TO 145NM BY
TAU 72, LENDING
MEDIUM CONFIDENCE TO THE NEAR- TO MID-PORTION OF THE JTWC TRACK
FORECAST. AFTERWARD, THE SPREAD BECOMES A LOT MORE UNEVEN AND WIDER
TO
440NM BY TAU 120 WITH GFS ON THE RIGHT AND NAVGEM ON THE LEFT
MARGIN OF THE MODEL ENVELOPE, LENDING LOW CONFIDENCE TO THE
EXTENDED PORTION OF THE JTWC TRACK FORECAST. 

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