WDXS31 PGTW 230900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 17S (SEVENTEEN) 
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.1S 120.3E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 253 NM NORTH-NORTHWEST OF BROOME,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 19 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 17S WITH A CONSOLIDATING STRUCTURE AS PERSISTENT
CONVECTION CONTINUES TO DEVELOP THROUGHOUT THE CIRCULATION,
OBSCURING THE LOW-LEVEL CIRCULATION CENTER. THE ENVIRONMENT REMAINS
SUPPORTIVE FOR FURTHER INTENSIFICATION, WITH MINIMAL VERTICAL WIND
SHEAR (VWS) OF LESS THAN 5 KTS, GOOD EQUATORWARD OUTFLOW ALOFT, AND
WARM SEA SURFACE TEMPERATURES BETWEEN 29-30 C. THE GENERAL
STRUCTURE OF TC 17S HAS IMPROVED OVER THE LAST FEW HOURS, WITH
FORMATIVE CONVECTIVE BANDING WRAPPING IN CLOSE PROXIMITY TO THE
LLCC. THE INITIAL POSITION HAS BEEN PLACED WITH LOW CONFIDENCE
BASED ON ANIMATED MSI IMAGERY. THE INITIAL INTENSITY HAS BEEN
ASSESSED WITH MEDIUM CONFIDENCE BASED ON SUBJECTIVE AGENCY DVORAK
ESTIMATES AND CIMSS OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NEAR-EQUATORIAL RIDGE (NER) CENTERED TO
THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   CIMSS ADT: 43 KTS AT 230540Z
   CIMSS AIDT: 34 KTS AT 230540Z
   CIMSS D-MINT: 26 KTS AT 230519Z
   CIMSS D-PRINT: 29 KTS AT 230610Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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 17S IS FORECASTED TO CONTINUE TRACKING TO
THE SOUTHEAST THROUGH THE NEXT 24 HOURS AND INTO LANDFALL ALONG THE
SOUTHERN PERIPHERY OF THE NER TO THE NORTH. FOLLOWING TAU 24, THE
TRACK FOR TC 17S IS EXPECTED TO BECOME SOUTHWARD UNTIL DISSIPATION
AS THE VORTEX WEAKENS DUE TO TOPOGRAPHICAL INTERACTION BY TAU 48.
REGARDING INTENSITY, THE CYCLONE IS FORECASTED TO CONTINUE
INTENSIFYING THROUGHOUT THE NEXT 24 HOURS, AS THE ENVIRONMENT
REMAINS FAVORABLE WITH WARM SEA SURFACE TEMPERATURES BETWEEN 29-30
C, MINIMAL VERTICAL WIND SHEAR OF LESS THAN 10 KTS, AND SUPPORTIVE
OUTFLOW ALOFT. THE RELATIVELY SHORT PERIOD BEFORE LANDFALL IS
FORECASTED TO LIMIT INTENSIFICATION, HOWEVER, HIGHER INTENSITIES
ABOVE 55 KTS ARE NOT OUT OF THE REALM OF POSSIBILITY. BETWEEN TAU
24 AND TAU 36, TC 17S IS EXPECTED TO MAKE LANDFALL AND QUICKLY
DISSIPATE OVER LAND TOWARD 30 KTS BY TAU 48.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE REMAINS IN GOOD
AGREEMENT DURING THE ENTIRETY OF THE TRACK FORECAST, WITH A
CROSS-TRACK SPREAD OF JUST 58 NM INTO LANDFALL. THE JTWC TRACK
FORECAST HAS BEEN PLACED WITH HIGH CONFIDENCE AND ALIGNED CLOSELY
WITH THE JTWC CONSENSUS. REGARDING INTENSITY, ALL JTWC CONSENSUS
SOLUTIONS ILLUSTRATE A PERIOD OF INTENSIFICATION THROUGHOUT THE
NEXT 24 HOURS, WITH RAPID INTENSIFICATION MEMBERS TRIGGERING OVER
THE NEXT 12 HOURS. FOLLOWING TAU 24, ALL JTWC CONSENSUS MODELS
CHARACTERIZE A RAPID WEAKENING PHASE INTO DISSIPATION BY TAU 48.
DUE TO THE UNCERTAINTY WITH THE RATE OF INTENSIFICATION DURING THE
POTENTIAL RAPID INTENSIFICATION PHASE OVER THE NEXT 12 HOURS, THE
JTWC INTENSITY FORECAST HAS BEEN ASSESSED WITH MEDIUM CONFIDENCE.

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