WDXS32 PGTW 261500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 09S (GRANT) WARNING NR 
019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.9S 91.4E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 323 NM WEST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: WESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE (TC) 09S (GRANT) WITH A LOW-LEVEL CIRCULATION CENTER (LLCC)
AND DEEP CONVECTION THAT IS BEING SHEARED TO THE SOUTHWEST. CLOUD
TOP TEMPERATURES SURROUNDING THE CENTER HAVE CONTINUED TO COOL OVER
THE PAST TWELVE HOURS THOUGH THE STRUCTURE HAS BECOME MORE TILTED.
ADDITIONAL ENVIRONMENTAL ANALYSIS REVEALS WARM (27-28 C) SEA
SURFACE TEMPERATURES (SST), OFFSET BY HIGH (20-25 KTS) VERTICAL
WIND SHEAR (VWS). THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON AGENCY FIXES AND A 261139Z SSMIS IMAGE OF THE
LLCC. THE INITIAL INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON OBJECTIVE AND SUBJECTIVE ESTIMATES LISTED
BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE POSITIONED TO THE
SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   DEMS: T3.0 - 45 KTS
   APRF: T3.0 - 45 KTS
   CIMSS SATCON: 50 KTS AT 261300Z
   CIMSS ADT: 53 KTS AT 261300Z
   CIMSS AIDT: 42 KTS AT 261300Z
   CIMSS D-MINT: 49 KTS AT 261139Z
   CIMSS D-PRINT: 51 KTS AT 261300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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) 09S WILL CONTINUE TO
TRACK WESTWARD TO WEST-SOUTHWESTWARD UNDER THE INFLUENCE OF THE
SUBTROPICAL RIDGE TO THE SOUTH. IMPROVING ENVIRONMENTAL CONDITIONS,
INCLUDING REDUCED VWS AND WARM SSTS, WILL ALLOW THE SYSTEM TO
INTENSIFY AT A STEADY PACE WITH A PEAK INTENSITY OF 75 KTS
FORECASTED AT TAU 96, AS LONG AS THE SYSTEM MANAGES TO LIMIT THE
TILT OF THE VERTICAL STRUCTURE. THOUGH LOW TO MODERATE (15-20 KTS)
VWS AND IMPROVING OUTFLOW ARE EXPECTED, DRY AIR ENTRAINMENT IS
FORECAST TO KEEP THE SYSTEM FROM INTENSIFYING RAPIDLY. 

MODEL DISCUSSION: CROSS TRACK SPREAD AMONG MODEL GUIDANCE IS LESS
THAN 100 NM UNTIL TAU 72 AT WHICH POINT NAVGEM, GALWEM, AND THE UK
DETERMINISTIC PUSH THE SYSTEM MORE SOUTHWEST THAN THE REST OF THE
MODELS. THE JTWC FORECAST TRACK IS PLACED CLOSE TO THE MULTI MODEL
CONSENSUS WITH HIGH CONFIDENCE. SLIGHT CHANGE IN PREDICTED VERTICAL
WIND SHEAR AND OUTFLOW MECHANISMS HAVE CREATED A LARGER SPREAD IN
INTENSITY GUIDANCE AS WELL AS INCREASED CONSENSUS ON A
STRENGTHENING TREND FOLLOWING TAU 12. THE JTWC INTENSITY FORECAST
IS PLACED CLOSE TO THE MULTI MODEL CONSENSUS WITH MEDIUM CONFIDENCE
IN THE SHORT TERM BUT LOW CONFIDENCE PAST TAU 72 ACCOUNTING FOR
UNCERTAINTY IN THE MODELED ENVIRONMENTAL CONDITIONS AND THE CURRENT
TILTED STATE OF THE VORTEX.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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