WDXS31 PGTW 101500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18S (EIGHTEEN)   
WARNING NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.4S 122.5E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 717 NM NORTHEAST OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED PROXYVIS SATELLITE IMAGERY DEPICTS A PARTIALLY EXPOSED LOW-
LEVEL CIRCULATION CENTER (LLCC) POSITION ON THE NORTHEAST EDGE OF A 
DEVELOPING CENTRAL DENSE OVERCAST. VERTICAL WIND SHEAR (VWS) FINALLY 
APPEARS TO BE DECREASING WITH OUTFLOW CLEARLY EXPANDING NORTHEASTWARD 
OVER THE PAST FEW HOURS. THERE IS INCREASED CONFIDENCE IN THE INITIAL 
POSITION BASED ON THE PROXYVIS IMAGERY AS WELL AS A 101049Z 91GHZ 
COLOR COMPOSITE MICROWAVE IMAGE WHICH SHOWS SHALLOW BANDING WRAPPING 
INTO A DEFINED LLCC. CONFIDENCE IN THE INITIAL INTENSITY, HOWEVER, 
REMAINS LOW DUE TO A WIDE SPREAD OF DVORAK INTENSITY ESTIMATES. ADT 
ESTIMATES REMAIN UNREALISTICALLY HIGH BASED ON THE WEAK CONVECTIVE 
STRUTURE WHILE OPEN-AIIR ESTIMATES HAVE FLUCTUATED SIGNIFICANTLY OVER 
THE PAST SIX HOURS AND ARE NOW AT ABOUT 35 KNOTS. THE INITIAL 
INTENSITY REMAINS ASSESSED CONSERVATIVELY AT 45 KNOTS BASED ON THE 
APRF DVORAK ESTIMATE. ASCAT DATA (101309Z ASCAT-C IMAGE JUST RECEIVED) 
SUPPORTS THE INITIAL POSITION AND SHOWS AN ASYMMETRIC WIND FIELD WITH 
35-40 KNOT WINDS OVER THE SOUTHWEST QUADRANT, WHICH SUPPORTS THE 
INITIAL INTENSITY ESTIMATE AS WELL. 

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   KNES: T3.5 - 55 KTS
   APRF: T3.0 - 45 KTS
   CIMSS ADT: 53 KTS AT 101130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TC 18S IS EXPECTED TO TRACK SOUTHWESTWARD TO 
SOUTHWARD THROUGH TAU 60 AS IT ROUNDS THE STR. TC 18S HAS STRUGGLED
TO CONSOLIDATE DUE TO THE VWS, HOWEVER, VWS APPEARS TO BE ABATING 
WHICH WILL FINALLY ALLOW THE SYSTEM TO CONSOLIDATE. THEREFORE, THE 
SYSTEM IS EXPECTED TO RAPIDLY INTENSIFY AFTER TAU 12. A PEAK INTENSITY 
NEAR 130 KNOTS IS STILL EXPECTED BY TAU 60 JUST PRIOR TO LANDFALL 
AIDED BY HIGH OCEAN HEAT CONTENT NEAR THE AUSTRALIAN COAST AND 
ENHANCED POLEWARD OUTFLOW. AFTER TAU 60, TC 18S WILL ACCELERATE 
SOUTHEASTWARD AS IT INTERACTS WITH A MAJOR SHORTWAVE TROUGH AND WILL 
WEAKEN RAPIDLY OVER LAND.

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, NUMERICAL MODEL 
GUIDANCE IS IN GOOD AGREEMENT WITH A 107NM SPREAD IN SOLUTIONS AT TAU 
48. AFTER TAU 72, ALONG TRACK UNCERTAINTY INCREASES AS THE SYSTEM 
INTERACTS WITH THE AFOREMENTIONED SHORTWAVE TROUGH AND ACCELERATES 
SOUTHEASTWARD. THE RAPID INTENSIFICATION (RI) CONSENSUS (RICN) 
GUIDANCE HAS TRIGGERED SUPPORTING RAPID INTENSIFICATION (RI) OVER THE 
NEXT TWO DAYS. ADDITIONALLY, THE 100600Z COAMPS TC ENSEMBLE (CTCXEPS)
CONTINUES TO INDICATE A HIGH PROBABILITY (70-80 PERCENT) OF RI FROM 
TAU 24 TO TAU 60 SUPPORTING THE RI FORECAST IN THE DAY 1 TO DAY 3 
PERIOD. 

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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