WDXS31 PGTW 242100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 27S (TWENTYSEVEN) 
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.6S 110.5E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 398 NM NORTH-NORTHWEST OF LEARMONTH,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A NEARLY
FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) OF TROPICAL
CYCLONE (TC) 27S. STRONG (20-25 KTS) NORTHEASTERLY VERTICAL WIND
SHEAR (VWS) IS CAUSING THE CONVECTION TO BE DISPLACED SOUTHWESTWARD, 
WHILE BEING ENHANCED BY STRONG POLEWARD OUTFLOW, IDENTIFIABLE THROUGH
PRONOUNCED TRANSVERSE BANDING. ADDITIONAL ENVIRONMENTAL ANALYSIS
REVEALS MARGINALLY FAVORABLE ENVIRONMENT, WITH WARM (29-30 C) SEA
SURFACE TEMPERATURES (SST), DEEP MOISTURE CONTENT, STEADILY IMPROVING
POLEWARD OUTFLOW, OFFSET BY PERSISTENT VWS. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE EXTRAPOLATION FROM A
241424Z METOP-B ASCAT PASS AND THE ANIMATED SHORTWAVE IR IMAGERY.
THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH HIGH CONFIDENCE
BASED ON AFOREMENTIONED ASCAT PASS, CONSISTENT WITH THE AGENCY
DVORAK FIXES OF T2.0-2.5 AND OBJECTIVE ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: 241424Z METOP-B ASCAT SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR) OVER
SOUTHWESTERN AUSTRALIA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   APRF: T2.0 - 30 KTS
   CIMSS SATCON: 41 KTS AT 241630Z
   CIMSS ADT: 35 KTS AT 241730Z
   CIMSS AIDT: 34 KTS AT 241730Z
   CIMSS D-PRINT: 34 KTS AT 241830Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TC 27S IS FORECAST TO CONTINUE TRACKING
WESTWARD, WITH SOME SLIGHT OSCILLATION, ASSOCIATED WITH
THE CHANGES IN THE STEERING ENVIRONMENT. OVER THE NEXT 36 HOURS,
THE SYSTEM WILL TRANSIT ALONG THE NORTHWESTERN PERIPHERY OF A STR
OVER SOUTHWESTERN AUSTRALIA. AFTER THAT, AN UPPER LEVEL TROUGH IS
EXPECTED TO PASS TO THE SOUTH OF THE SYSTEM, WEAKENING THE
STEERING. BY TAU 60, ANOTHER UPPER-LEVEL RIDGE LOCATED TO THE SOUTH 
OF THE SYSTEM WILL TRANSIT EASTWARD, KEEPING TC 27S TO THE NORTH
OF IT, AND EVENTUALLY OPENING A POLEWARD PATH BETWEEN TAUS 96 AND
120. IN TERMS OF INTENSITY, MOST MODELS ARE IN GENERALLY GOOD
AGREEMENT INDICATING SLOW INTENSIFICATION. PERSISTENT AND STRONG
VWS OVER THE NEXT 48 HOURS WILL HINDER THE INITIAL DEVELOPMENT,
ALLOWING TC 27S TO ONLY REACH 45-50 KT MAXIMUM WIND SPEEDS. AFTER
THAT, THE VWS IS EXPECTED TO SUBSIDE, WHILE THE AFOREMENTIONED
UPPER LEVEL TROUGH IS FORECAST TO PASS TO THE SOUTH OF TC 27S,
IMPROVING THE ENVIRONMENTAL CONDITIONS. COMPARED WITH THE PREVIOUS
FORECAST HOWEVER, THE MODEL CONSENSUS INDICATES A SLIGHTLY LOWER 
INTENSITY PEAK WITH 60-65 KTS TOWARDS THE END OF THE CURRENT FORECAST 
PERIOD.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GENERALLY
FAIR AGREEMENT, WITH NEARLY ALL MODELS PREDICTING SIMILAR PATH. THE
EXCEPTION REMAINS NAVGEM, WHICH INDICATES A SIGNIFICANT DECREASE IN
THE TRANSLATION SPEED OVER THE NEXT 48 HOURS, WHICH ALSO IMPACTS
THE PREDICTED TRACK AFTER TAU 96, AS A RESULT OF TIMELINE
DIFFERENCES ASSOCIATED WITH THE STEERING PATTERN SHIFT. ALL OTHER
MODELS ARE IN TIGHT AGREEMENT, AS WITNESSED BY A 75 NM CROSS-TRACK
SPREAD AT BOTH TAU 72 AND 120, ALLOWING THE JTWC TRACK TO BE
ASSESSED WITH MEDIUM CONFIDENCE. MOST RECENT INTENSITY GUIDANCE 
INDICATES A MORE CONSERVATIVE PEAK INTENSITY, CURRENTLY ASSESSED AT 
60-65 KTS BETWEEN TAUS 96 AND 120. THE INTENSITY SPREAD AT TAU 48 IS 
CURRENTLY 20 KTS, WITH HAFS AND COAMPS-TC ON THE LOWER END, AND 
STATISTICAL DYNAMICAL MODEL AS WELL AS HWRF ON THE HIGHER END. AFTER 
THE INITIAL TWO DAYS HOWEVER, INTENSITY GUIDANCE SPREAD INCREASES TO 
35 KTS, WITH COAMPS-TC REMAINING THE MOST CONSERVATIVE AT 45 KTS, AND 
HWRF REACHING AS HIGH AS 75 KTS. JTWC INTENSITY FORECAST IS ASSESSED 
CLOSE TO THE MULTI-MODEL CONSENSUS GUIDANCE WITH MEDIUM INITIAL
CONFIDENCE, FOLLOWED BY LOW CONFIDENCE OF THE LONG-TERM GUIDANCE.

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