WDXS31 PGTW 132100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 29S (TWENTYNINE) 
WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.3S 123.1E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 281 NM NORTH OF BROOME, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE (TC) 29S SHOWING SIGNS OF CONSOLIDATION AND DEVELOPING
PERSISTENT CENTRAL CONVECTION. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON THE AREA OF CALM WINDS VISIBLE IN A
131609Z OCEANSAT-3 IMAGE, CONSISTENT WITH THE LOW-LEVEL TURNING
PRESENT IN THE EIR LOOP. ENVIRONMENTAL CONDITIONS ARE FAVORABLE FOR
DEVELOPMENT, DRIVEN BY WARM (29-30 C) SEA SURFACE TEMPERATURES
(SST), DEEP MOISTURE, MODERATE POLEWARD AND EQUATORWARD OUTFLOW, AS
WELL AS LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS). THE INITIAL
INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
IMPROVING CONVECTIVE STRUCTURE, AS WELL AS AGENCY DVORAK AND
OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: 131610Z OCEANSAT-3 IMAGE

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED OVER
WESTERN AUSTRALIA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   APRF: T2.0 - 30 KTS
   CIMSS SATCON: 45 KTS AT 131800Z
   CIMSS ADT: 41 KTS AT 131800Z
   CIMSS AIDT: 33 KTS AT 131800Z
   CIMSS D-PRINT: 26 KTS AT 131800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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 29S IS FORECAST TO TRACK WEST-SOUTHWESTWARD
OVER THE NEXT 12-24 HOURS, BEFORE MAKING A WESTWARD TURN, UNDER THE
INFLUENCE OF THE STR TO THE SOUTH. AROUND TAU 72, A PASSING LONG
WAVE TROUGH WILL BREAK THE RIDGE, RESULTING IN A SUDDEN CHANGE IN
THE STEERING ENVIRONMENT FOR TC 29S. THE SYSTEM WILL SLOW DOWN AND
TURN TOWARDS THE COASTLINE OF AUSTRALIA BY TAU 96. ENVIRONMENTAL
CONDITIONS ARE FORECAST TO IMPROVE FURTHER, WITH SUBSIDING
MID-LEVEL SHEAR, LEADING TO STEADY INTENSIFICATION, WITH THE SYSTEM
REACHING PEAK INTENSITY OF 90-95 KTS AROUND TAU 72. AFTERWARDS, AND 
WHILE THE LONG WAVE TROUGH BEGINS TO INTERACT WITH TC 29S, FORECAST 
CALLS FOR QUICK WEAKENING, DUE TO RAPIDLY INCREASING WESTERLY SHEAR, 
AS WELL AS INCREASINGLY DRY ENVIRONMENT. DUE TO THE COMPACT SIZE OF 
THE SYSTEM, RAPID INTENSIFICATION (RI) IS POSSIBLE, AS INDICATED BY 
FRIA RI MODEL SUGGESTING JUMP TO 95 KTS WITHIN THE INITIAL 48 HOURS, 
AS WELL AS HAFS INDICATING PEAK INTENSITY OF OVER 145 KTS.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN FAIR AGREEMENT 
FOR THE INITIAL 72 HOURS FORECAST WITH CROSS-TRACK SPREAD OF 90 NM 
AND ALONG-TRACK SPREAD OF 120 NM. AFTER TAU 72 HOWEVER GUIDANCE 
BECOMES WAY LESS RELIABLE, WITH CROSS-TRACK SPREAD OF OVER 400 NM BY 
TAU 120. THE UNCERTAINTY AND THE SPREAD OF POSSIBLE SCENARIOS ARE 
HIGH, WITH SOME MODELS (UKMET AND GALWEM) KEEPING THE TRACK TO THE 
NORTH OF THE MULTI-MODEL CONSENSUS AND FORECASTING A SHARP U-TURN 
EASTWARD. THE REST OF THE CONSENSUS MEMBERS CONTINUE TO PREDICT A 
SOUTHWARD TURN BETWEEN TAUS 72 AND 96, FOLLOWED BY ANOTHER TURN 
TOWARDS THE COASTLINE OF AUSTRALIA. THE LONG TERM TRACK FORECAST IS 
ASSESSED WITH LOW CONFIDENCE GIVEN THE HIGH CROSS-TRACK AND ALONG-
TRACK SPREAD VALUES, AS WELL AS UNCERTAINTY ASSOCIATED WITH THE 
TIMELINE OF THE PASSING LONG WAVE TROUGH. JTWC TRACK IS LAID CLOSE TO 
THE MULTI-MODEL CONSENSUS, LEANING TOWARDS MAJORITY OF SOLUTIONS. IN 
TERMS OF INTENSITY, MOST OF THE GUIDANCE IS STARTING TO COME 
TOGETHER, WITH ALL MODELS PREDICTING INTENSIFICATION THROUGH TAU 72, 
FOLLOWED BY RAPID WEAKENING. AS PREVIOUSLY MENTIONED, FRIA IS 
PREDICTING RI OVER THE NEXT 48 HOURS, WHILE COAMPS-TC REMAINS THE 
MOST CONSERVATIVE. IN TERMS OF PEAK INTENSITY, THE SPREAD REMAINS 
HIGH ACROSS THE GUIDANCE, WITH STATISTICAL-DYNAMICAL MODELS, JOINED 
BY DETERMINISTIC GFS OFFERING PEAKS OF 75-80 KTS, WHILE HAFS IS STILL 
THE MOST AGGRESSIVE, REACHING MAXIMUM WIND SPEEDS OF 145-150 KTS BY 
TAU 60. THEREFORE THE JTWC INTENSITY FORECAST IS ASSESSED WITH MEDIUM 
CONFIDENCE FOR THE INITIAL 72 HOURS, FOLLOWED BY LOW CONFIDENCE 
THEREAFTER. 

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