WDXS32 PGTW 260300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 09S (GRANT) WARNING NR 
018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.4S 93.4E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 206 NM WEST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: WESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY-
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC), WITH A CENTRAL DENSE 
OVERCAST (CDO) FEATURE SHEARED SLIGHTLY TO THE SOUTHWEST DUE TO 
NORTHEASTERLY VWS. ENHANCED INFRARED SATELLITE IMAGERY CLEARLY REVEALS 
A TIGHT TEMPERATURE GRADIENT ALONG THE NORTHEASTERN EDGE OF THE CDO AND 
RAGGED APPEARANCE DUE TO THE VWS. A 260033Z SSMIS 91GHZ MICROWAVE IMAGE 
SHOWS ASYMMETRIC CORE CONVECTION WRAPPING INTO A WEAK UPPER-LEVEL 
CIRCULATION CENTER POSITIONED ALONG THE EASTERN EDGE OF THE CDO. 
ANIMATED MSI AND THE SSMIS 37GHZ IMAGERY INDICATES A SLIGHT TILT TO THE 
VORTEX, WITH THE LOW-LEVEL CIRCULATION CENTER DISPLACED A BIT FURTHER 
TO THE NORTH UNDER THE NORTHEASTERN EDGE OF THE CDO. CONSEQUENTLY, 
THERE IS MEDIUM CONFIDENCE IN THE INITIAL POSITION. DESPITE THE 
PERSISTENT VWS, THE SYSTEM HAS INTENSIFIED OVER THE PAST 12 HOURS TO 50 
KNOTS, WITH CIMSS OBJECTIVE INTENSITY ESTIMATES RANGING FROM 39 TO 62
KNOTS. IN TERMS OF THE CONVECTIVE ORGANIZATION, THE SYSTEM APPEARS
TO HAVE PEAKED AROUND 251800Z AS EVIDENCED IN THE  251914Z AMSR2
89GHZ COLOR COMPOSITE MICROWAVE IMAGE, WHICH SHOWED A SMALL, WELL-
DEFINED MICROWAVE EYE FEATURE TYPICALLY CORRESPONDING TO A 50-55 KNOT 
INTENSITY. HOWEVER, THE SYSTEM STRUCTURE DEGRADED SINCE THAT TIME.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR)
POSITIONED TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   APRF: T3.0 - 45 KTS
   CIMSS SATCON: 53 KTS AT 252100Z
   CIMSS ADT: 47 KTS AT 260000Z
   CIMSS AIDT: 39 KTS AT 260000Z
   CIMSS D-MINT: 62 KTS AT 252159Z
   CIMSS D-PRINT: 50 KTS AT 260000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE 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) 09S IS FORECAST TO TRACK
WESTWARD TO WEST-SOUTHWESTWARD ALONG THE NORTHERN PERIPHERY OF THE
STR THROUGH THE FORECAST PERIOD. TC 09S WILL CONTINUE TO INTENSIFY
SLIGHTLY OVER THE NEXT 24 HOURS TO ABOUT 55 KNOTS, LIMITED BY
PERSISTENT LOW TO MODERATE (15-20 KNOTS) VERTICAL WIND SHEAR (VWS)
AND DRY AIR ENTRAINMENT. FROM TAU 24 TO TAU 48, THE INTENSITY WILL 
REMAIN FLAT DUE TO MARGINALLY FAVORABLE CONDITIONS. AFTER TAU 72, 
ENVIRONMENTAL CONDITIONS ARE FORECAST TO IMPROVE, WITH MOISTENING OF 
THE CORE AND DECREASING VWS LEADING TO A SIGNIFICANT PERIOD OF 
INTENSIFICATION AND A PEAK INTENSITY OF 75 KNOTS BY TAU 120. 

MODEL DISCUSSION: DETERMINISTIC AND PROBABILISTIC TRACK GUIDANCE 
REMAINS IN TIGHT AGREEMENT THROUGH THE FORECAST PERIOD LENDING HIGH 
CONFIDENCE TO THE JTWC TRACK FORECAST. THE JTWC INTENSITY FORECAST,
HOWEVER, IS ASSESSED WITH MEDIUM CONFIDENCE THROUGH TAU 72 DUE TO
THE RAPIDLY EVOLVING ENVIRONMENT. IN THE LATER TAUS, RELIABLE INTENSITY
GUIDANCE IS IN POOR AGREEMENT, WITH HAFS-A INDICATING A PEAK OF 137
KNOTS AT TAU 120 AND COAMPS-TC (GFS BOUNDARY CONDITIONS) SHOWING A
MUCH LOWER PEAK OF 72 KNOTS AT TAU 120. 

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