WDXS32 PGTW 140300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18S (EIGHTEEN) WARNING 
NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.6S 113.9E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 402 NM NORTH OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: EASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE FLARING
CENTRAL CONVECTION SHEARED WESTWARD OF A FULLY EXPOSED LOW LEVEL
CIRCULATION CENTER (LLCC). THERE IS MINIMAL POLEWARD OUTFLOW AND NO
ORGANIZED FEEDER BANDS. ANALYSIS INDICATES A MARGINAL ENVIRONMENT
WITH VERY WARM SST AND WEAK POLEWARD OUTFLOW ALOFT GREATLY OFFSET
BY STRONG (30-40 KTS) VERTICAL WIND SHEAR (VWS). THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC
IN THE MSI LOOP. THE INITIAL INTENSITY IS PLACED WITH MEDIUM
CONFIDENCE BASED ON OVERALL ASSESSMENT OF AGENCY AND OBJECTIVE
DVORAK INTENSITY ESTIMATES.

INITIAL WIND RADII BASIS: MOST RECENT SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A NEAR EQUATORIAL
RIDGE (NER) TO THE NORTH.


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 34 KTS AT 132330Z
   CIMSS AIDT: 33 KTS AT 132330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 30-40 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: WEAK POLEWARD

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 18S WILL CONTINUE EAST-SOUTHEASTWARD UNDER
THE NER. AFTER TAU 24, A SUBTROPICAL RIDGE TO THE EAST, ANCHORED
OVER AUSTRALIA, WILL ASSUME STEERING AND DRIVE THE SYSTEM SOUTHWARD
THEN SOUTHWESTWARD. AS THE STORM MOTION BECOMES MORE IN-PHASE WITH
THE UPPER-LEVEL WIND FLOW, VWS IS EXPECTED TO WEAKEN, AND POLEWARD
OUTFLOW TO IMPROVE, A STEADY INTENSIFICATION IS EXPECTED, PEAKING
AT 70KTS BY TAU 96. AFTERWARD, COOLING SST AND INCREASING VWS WILL
BEGIN TO ERODE THE SYSTEM, AND BY TAU 120, WILL BE REDUCED TO 60
KTS AS IT COMES TO WITHIN 120NM TO THE NORTH OF LEARMONTH. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN BETTER AGREEMENT
SPREADING OUT TO 1103NM AT TAU 72 AND 287NM AT TAU 120, LENDING
MEDIUM CONFIDENCE TO THE NEAR- TO MID-PORTION OF THE JTWC TRACK
FORECAST. AFTERWARD, THE SPREAD BECOMES MORE UNEVEN AND WIDER TO
241NM BY TAU 120, 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: LOW//
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