WDXS32 PGTW 150900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 06S (SIX)         
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.5S 93.7E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 251 NM NORTHWEST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A CONSOLIDATING 
LOW-LEVEL CIRCULATION WITH IMPROVED CONVECTIVE BANDING OVER THE WESTERN 
SEMICIRCLE AND FLARING CORE CONVECTION OBSCURING THE CENTER. A 150727Z 
AMSR2 89 GHZ MICROWAVE IMAGE REFLECTS THE IMPROVED ORGANIZATION AND 
REVEALS A COMPACT CORE WITH DEEP CONVECTIVE BANDING WRAPPING FROM THE 
WESTERN QUADRANT INTO THE NORTHEAST QUADRANT. THE AMSR2 37 GHZ 
MICROWAVE IMAGE SHOWS SHALLOW BANDING OVER THE SOUTHERN SEMICIRCLE, 
WHICH WRAPS INTO A DEFINED LOW-LEVEL CIRCULATION CENTER. THE INITIAL 
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE AMSR2 IMAGERY. 
DESPITE SOME WEAK PRESSURE OVER THE EASTERN PERIPHERY OF THE SYSTEM, 
UPPER-LEVEL OUTFLOW IS ROBUST WITH STRONG EQUATORWARD AND POLEWARD 
OUTFLOW. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM 
CONFIDENCE BASED ON THE KNES, PGTW AND DEMS DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT WITH A
WEAK NEAR-EQUATORIAL RIDGE (NER) TO THE NORTH AND A WEAK SUBTROPICAL 
RIDGE (STR) TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   DEMS: T2.5 - 35 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 06S IS TRACKING SLOWLY
AND ERRATICALLY WITHIN A WEAK STEERING ENVIRONMENT BUT IS EXPECTED
TO TURN EASTWARD TO SOUTHEASTWARD THROUGH TAU 36 ALONG THE SOUTHERN
PERIPHERY OF THE WEAK NER. AS TC 06S BECOMES BETTER ALIGNED OVER
THE NEXT DAY, IT IS EXPECTED TO INTENSIFY SLOWLY. AFTER TAU 24, THE
SYSTEM WILL INTENSIFY AT A FASTER RATE WITH IMPROVING POLEWARD
OUTFLOW INTO A SHARP UPPER-LEVEL TROUGH AND ASSOCIATED JET.
CONSEQUENTLY, THE SYSTEM WILL PEAK AT 65 KNOTS BY TAU 72. THROUGH
TAU 72, THE SYSTEM WILL TRACK SLOWLY SOUTHWARD ALONG AN EXTENSION
OF THE STEERING RIDGE POSITIONED TO THE EAST. AFTER TAU 72, THE
SYSTEM IS EXPECTED TO STALL AND BECOME QUASI-STATIONARY AS IT
WEAKENS RAPIDLY DUE TO INCREASING EASTERLY VERTICAL WIND SHEAR
(20-35 KNOTS) AND SIGNIFICANT DRY AIR ENTRAINMENT.       

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, NUMERICAL GUIDANCE
IS IN FAIR AGREEMENT THROUGH TAU 72 WITH A 180 NM SPREAD IN
SOLUTIONS AT TAU 72. IN GENERAL, THE GUIDANCE INDICATES A
SOUTH-SOUTHWESTWARD TO SOUTH-SOUTHEASTWARD TRACK THROUGH TAU 72
WITH TWO DISCRETE CLUSTERS. GFS AND THE GFS ENSEMBLE MEAN REMAIN ON
THE EASTERN SIDE OF THE ENVELOPE AND SHOW A SOUTHEASTWARD TO
EASTWARD TRACK AFTER TAU 72. THE REMAINING GUIDANCE (ECMWF, ECMWF
ENSEMBLE MEAN, GALWEM, UKMET AND THE UKMET ENSEMBLE MEAN) IS
SHOWING A MORE REALISTIC SOUTHWARD TO SOUTH-SOUTHWESTWARD TRACK.
NAVGEM IS A MAJOR OUTLIER INDICATING AN UNREALISTIC FAST TRACK INTO
THE STR SO IS DISCOUNTED. BOTH THE 150000Z ECMWF (EPS) AND GFS
(GEFS) ENSEMBLES INDICATE HIGH UNCERTAINTY IN THE EXTENDED FORECAST
PERIOD LENDING LOW CONFIDENCE TO THE JTWC FORECAST TRACK, WITH A
BIFURCATION IN THE GUIDANCE.  

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