WDXS31 PGTW 131500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 29S (TWENTYNINE) 
WARNING NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.2S 124.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 301 NM NORTH-NORTHEAST OF BROOME,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 29S WITH BUILDING CONVECTION OVER THE CENTER OF AN OBSCURED
LOW-LEVEL CIRCULATION CENTER (LLCC). A 131012Z SSMIS 91 GHZ
MICROWAVE IMAGE REVEALED THE LOW-LEVEL BANDING WITHIN THE SOUTHERN
SEMICIRCLE AND THE DEEP CONVECTIVE BURSTS BEGINNING TO FORM.
MID-LEVEL SHEAR APPEARS TO HAVE LESSENED, AT LEAST MOMENTARILY,
ALLOWING THE SYSTEM TO BECOME MORE VERTICALLY STACKED.
ENVIRONMENTAL ANALYSIS INDICATES THAT 29S IS IN A FAVORABLE
ENVIRONMENT CHARACTERIZED BY MODERATE POLEWARD AND EQUATORWARD
OUTFLOW ALOFT, LOW (5-10 KTS) VERTICAL WIND SHEAR, AND WARM (29-30
C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON THE ANIMATED EIR IMAGERY AND THE
MENTIONED SSMIS MICROWAVE IMAGE. THE INITIAL INTENSITY OF 35 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE HIGH END OF AGENCY DVORAK 
AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) CENTERED OVER WESTERN AUSTRALIA.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   APRF: T1.5 - 25 KTS
   CIMSS SATCON: 34 KTS AT 131049Z
   CIMSS ADT: 32 KTS AT 131200Z
   CIMSS AIDT: 31 KTS AT 131200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: SLIGHT DRY AIR ENTRAINMENT WITHIN THE NORTHERN
PERIPHERY.

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 29S IS FORECAST TO TRACK
WEST-SOUTHWESTWARD ALONG THE NORTHERN PERIPHERY OF THE STR TO THE 
SOUTH THROUGH TAU 12. NEAR TAU 12, THE STR OVER WESTERN AUSTRALIA IS 
EXPECTED TO PROPAGATE EASTWARD AND THEN AN EXTENSION OF RIDGING FROM 
THE WEST WILL JUT UNDERNEATH THE SYSTEM AND DRIVE IT MORE WESTWARD 
THROUGH TAU 72. NEAR TAU 72, AN INCOMING LONG WAVE TROUGH WILL BREAK 
DOWN THE RIDGE AND CAUSE 29S TO SLOW AND BEGIN A SHARP TURN TOWARD THE
SOUTH AND THEN EAST. REGARDING INTENSITY, 29S IS FORECAST TO
MARGINALLY INTENSIFY OVER THE NEXT 24 HOURS AS THE VORTEX BECOMES
MORE VERTICALLY ALIGNED. THE INITIAL INTENSIFICATION TREND COULD
OCCUR SOONER IF THE CURRENT CENTRAL CONVECTION IS ABLE TO HOLD
TOGETHER THOUGH. AFTER TAU 24, ENVIRONMENTAL PARAMETERS ARE EXPECTED 
TO BE HIGHLY FAVORABLE WITH LOW VWS AND GOOD OUTFLOW, ALLOWING 29S TO 
FURTHER INTENSIFY. A PEAK OF 90 KTS IS CURRENTLY FORECAST TO OCCUR AT 
TAU 72, THOUGH IF HAFS-A IS RIGHT, IT COULD BE HIGHER. AFTER TAU 72, 
WESTERLY SHEAR AND DRY AIR ENTRAINMENT WILL QUICKLY RISE DUE TO THE 
LONG WAVE TROUGH INTERACTING WITH THE SYSTEM. AS A RESULT, A RAPID 
WEAKENING TREND WILL ENSUE THROUGH THE REMAINDER OF THE FORECAST 
PERIOD AS THE SYSTEM IS DECAPITATED AND SHEARED APART.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 72 WITH A 150 NM CROSS-TRACK SPREAD AT TAU
72. AFTER TAU 72, MODELS BEGIN TO DIVERGE DUE TO VARYING RESPONSES
TO INTERACTION WITH THE LONG WAVE TROUGH. GFS CONTINUES TO BE THE
WESTERNMOST MEMBER WHILE ECMWF HAS THE VORTEX COME TO A HALT AND
BEGIN ITS EASTWARD TURN SOONER. THE JTWC TRACK FORECAST IS PLACED
SLIGHTLY CLOSER TO THE ECMWF SOLUTIONS WITH HIGH CONFIDENCE THROUGH
TAU 72 AND LOW CONFIDENCE THEREAFTER. INTENSITY GUIDANCE IS IN
BETTER AGREEMENT COMPARED TO PREVIOUS RUNS. COAMPS-TC, HWRF, AND
GFS ALL DEPICT A PEAK INTENSITY OF 85-100 KTS NEAR TAU 72. HAFS-A
CONTINUES TO BE AN OUTLIER AND HAS A PEAK INTENSITY OF 145 KTS. GFS
HAS A MUCH QUICKER INTENSIFICATION TREND IN THE SHORT-TERM THAN THE
REMAINDER OF GUIDANCE, DEPICTING 70 KTS AT TAU 24. ALL MODELS ARE
IN AGREEMENT ON A RAPID WEAKENING TREND AFTER TAU 72. THE JTWC
INTENSITY FORECAST IS PLACED SLIGHTLY LOWER THAN CONSENSUS THROUGH
TAU 24 TO OFFSET GFS AND THEN CLOSE TO THE CONSENSUS THEREAFTER
WITH LOW CONFIDENCE DUE TO THE RECENT HIGH VARIABILITY IN INTENSITY
GUIDANCE.

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