WDPS31 PGTW 251500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18P (ALFRED) WARNING NR 
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.3S 155.1E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 807 NM NORTH OF BRISBANE, AUSTRALIA
   MOVEMENT PAST 6 HOURS: EASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE (TC) 18P (ALFRED) RECENTLY BECOMING QUASI-STATIONARY, WHILE
DEVELOPING A PERSISTENT, CENTRAL CONVECTION AND A STRONG POLEWARD
OUTFLOW. ENVIRONMENTAL CONDITIONS ARE FAVORABLE, WITH HIGH (29-30
C) SEA SURFACE TEMPERATURES (SST) AND MODERATE VERTICAL WIND SHEAR
(20-25 KTS). THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE
BASED ON THE EXTRAPOLATION OF A 250932Z GMI MICROWAVE PASS. THE
INITIAL INTENSITY OF 75 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON A COMBINATION OF AGENCY DVORAK FIXES AND OBJECTIVE
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NEAR EQUATORIAL RIDGE (NER) TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   ABRF: T4.0 - 65 KTS
   CIMSS ADT: 72 KTS AT 251130Z
   CIMSS AIDT: 74 KTS AT 251130Z
   CIMSS D-MINT: 58 KTS AT 250928Z
   CIMSS D-PRINT: 61 KTS AT 251240Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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 18P IS FORECAST TO BEGIN TRACKING
SOUTH-SOUTHEASTWARD UNDER THE INFLUENCE OF A WEAK, BUT BUILDING NER
TO THE NORTHEAST. WHILE THE SYSTEM SLOWED DOWN OVER THE LAST 12
HOURS, IT CONTINUES TO CONSOLIDATE AND INTENSIFY AND IS FORECAST TO
REACH PEAK INTENSITY OF 90 KTS WITHIN THE NEXT 24 HOURS. SOME SHORT-
TERM RAPID INTENSIFICATION (RI) GUIDANCE (RIPA, AI-RI) IS BEING 
TRIGGERED, BUT THE PROBABILITY REMAINS LOW TO MODERATE (20-40 
PERCENT). THE TRACK GUIDANCE TOWARDS THE END OF THE FORECAST PERIOD 
BECOMES ERRATIC ACROSS THE MODELS, BUT MAJORITY OF THE MODELS, AND THE 
JTWC FORECAST PREDICT A SOUTHWESTWARD TURN, TOWARDS AUSTRALIA.

MODEL DISCUSSION: JTWC INTENSITY FORECAST IS ASSESSED CLOSE TO THE
MULTI-MODEL CONSENSUS, BUT THE PEAK INTENSITY VARIES QUITE
SIGNIFICANTLY BETWEEN THE MODELS, WITH GFS DETERMINISTIC ESTIMATE
OF 75-80 KTS ON ONE END, AND RI GUIDANCE AS HIGH AS 115 KTS ON THE 
OTHER. PAST TAU 24, NEARLY ALL GUIDANCE PREDICTS A STEADY WEAKENING, 
WITH THE EXCEPTION OF HAFS, WHICH INDICATES INTENSIFICATION THROUGHOUT 
TAU 60, AS THE ONLY OUTLIER IN THIS TIMEFRAME. JTWC INTENSITY GUIDANCE 
IS LAID WITH MEDIUM CONFIDENCE THROUGH TAU 72 AND LOW CONFIDENCE 
BEYOND THAT, DUE TO A LARGE SPREAD BETWEEN THE CONSENSUS MEMBERS. AS 
FAR AS TRACK GUIDANCE, THE CROSS-TRACK SPREAD AT TAU 72 IS 145 NM,
INCREASING TO OVER 500 NM, LEADING TO A MEDIUM CONFIDENCE OF THE
SHORT TERM ASSESSMENT, FOLLOWED BY LOW CONFIDENCE FOR TAUS 72-120.

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