WDXS32 PGTW 180900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 06S (ANGGREK)   
WARNING NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.5S 93.8E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 185 NM WEST-NORTHWEST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 19 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A BROAD, 
PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION (LLC) WITH DEEP CONVECTIVE 
BANDING OVER THE NORTHERN SEMICIRCLE. A PARTIAL 180637Z ATMS 183 GHZ 
MICROWAVE IMAGE SHOWS THE BULK OF THE DEEP CONVECTION CONFINED TO THE 
NORTHERN SEMICIRCLE WITH A WEAKLY-DEFINED CENTER ON THE SOUTHERN EDGE 
OF THE CONVECTIVE BAND, WHICH SUPPORTS THE INITIAL POSITION WITH 
MEDIUM CONFIDENCE. THE 180000Z HAFS-A 700-300 MB RELATIVE HUMIDITY 
PRODUCT INDICATES DRY AIR ENTRAINMENT IS CURRENTLY OCCURRING OVER THE 
SOUTHERN SEMICIRCLE. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH 
MEDIUM CONFIDENCE BASED ON THE CURRENT INTENSITY ESTIMATES FROM PGTW, 
KNES AND APRF. ADDITIONALLY, IT IS SUPPORTED BY THE CIMSS ADT 
ESTIMATE. 

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T2.5 - 35 KTS
   DEMS: T3.0 - 45 KTS
   APRF: T3.0 - 45 KTS
   CIMSS SATCON: 49 KTS AT 180530Z
   CIMSS ADT: 45 KTS AT 180530Z
   CIMSS DPRINT: 43 KTS AT 180800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD AND POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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: TROPICAL CYCLONE (TC) 06S IS DRIFTING SLOWLY 
SOUTHWARD WITHIN THE COMPETING STEERING ENVIRONMENT, ALONG AN 
EXTENSION OF THE STEERING RIDGE TO THE EAST. HOWEVER, THE SYSTEM IS 
EXPECTED TO TURN WESTWARD WITHIN THE NEXT 24 TO 36 HOURS AS IT 
TRANSITIONS TO THE STEERING INFLUENCE OF THE WEAK STR POSITIONED TO 
THE SOUTH. AFTER TAU 48, TC 06S WILL TRACK SLOWLY WEST-NORTHWESTWARD 
ALONG THE NORTHEASTERN PERIPHERY OF THE LOW- TO MID-LEVEL STR. TC 06S 
SHOULD INTENSIFY TO A PEAK INTENSITY OF 55 KNOTS WITHIN THE NEXT DAY 
DUE TO THE FAVORABLE OUTFLOW, HINDERED SLIGHTLY BY THE PRESENCE OF 
DRY AIR. THE SYSTEM WILL MAINTAIN INTENSITY NEAR 50 KNOTS FROM TAU 24 
TO TAU 72 THEN FINALLY SUCCUMB TO SIGNIFICANT DRY AIR ENTRAINMENT.           

MODEL DISCUSSION: IN GENERAL, NUMERICAL MODEL GUIDANCE REMAINS IN 
FAIR AGREEMENT SUPPORTING THE JTWC FORECAST TRACK THROUGH TAU 36. 
AFTER TAU 36, THE GUIDANCE DIVERGES WITH INCREASING UNCERTAINTY IN 
THE EXACT TRACK AND TRACK SPEEDS. THE LATEST ECMWF TRACKER INDICATES 
A SLOW LOOPING MOTION WHILE THE GFS TRACKER INDICATES A FASTER 
(UNREALISTIC) WESTWARD TRACK. THE 171800Z ECMWF ENSEMBLE RUN, 
HOWEVER, SHOWS THE BULK OF THE SOLUTIONS WITH A SLOW WESTWARD TRACK. 
BOTH THE GFS AND HAFS-A INDICATE SIGNIFICANT DRY AIR ENTRAINMENT IN 
THE EXTENDED PERIOD.     

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