WDXS31 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 27P (NARELLE) WARNING 
NR 025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.8S 124.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 195 NM NORTHEAST OF BROOME, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 10 KTS

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 27P (NARELLE) CONTINUES TO TRACK
WEST-SOUTHWESTWARD AND IS APPROACHING THE WATERS EAST OF MANGROVE
POINT, AUSTRALIA AS DEPICTED BY ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI). DEEP CONVECTION PERSISTS, MAINLY WITHIN THE NORTHERN
HALF OF THE CIRCULATION, THOUGH CLOUD TOP TEMPERATURES HAVE WARMED
OVER THE PAST SIX HOURS. THE ENVIRONMENT IS ASSESSED AS MARGINAL.
CONTINUED DEVELOPMENT OF THE CYCLONE IS EXPECTED WITH THE CENTER 
TRACKING THROUGH AN AREA OF LOW VERTICAL WIND SHEAR (10-15 KTS), AND
APPROACHING WARM WATERS WITH SEA SURFACE TEMPERATURES BETWEEN 29 C
TO 30 C. THE INITIAL POSITION IS PLACED WITH LOW CONFIDENCE DUE THE
CENTER HAVING BECOME HEAVILY OBSCURED BY FRAGMENTED CONVECTIVE
BANDING AND BROAD TURNING IDENTIFIED THROUGHOUT THE NORTHERN
PORTION OF WESTERN AUSTRALIA. THE INITIAL INTENSITY OF 35 KTS IS
ASSESSED WITH LOW CONFIDENCE BASED ON WIND REPORTS FROM ADELE
ISLAND AND THE CIMSS OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: A DEEP LAYER SUBTROPICAL RIDGE (STR)
POSITIONED TO THE SOUTHEAST, OVER CENTRAL AUSTRALIA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   CIMSS D-MINT: 37 KTS AT 232250Z
   CIMSS D-PRINT: 38 KTS AT 240020Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: TERRAIN INTERACTION

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: LOW
   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 27P (NARELLE) WILL TRACK WEST-SOUTHWESTWARD
UNDER THE STEERING INFLUENCE OF THE STR CENTERED OVER AUSTRALIA
UNTIL TAU 48. AFTER TAU 48, NARELLE WILL BEGIN TO TRACK ALONG THE
WESTERN PERIPHERY OF THE STR AND ASSUME A SOUTHWARD TO
SOUTH-SOUTHEASTWARD TRACK THROUGH TAU 120 AS IT CONTINUES AROUND
THE RIDGE AXIS. NARELLE IS FORECAST TO STEADILY INTENSIFY AS IT 
REEMERGES OVER WATER OVER THE NEXT SIX HOURS, AND MOVES OVER KING 
SOUND. ONCE THE CENTER PASSES OVER THE DAMPIER PENINSULA, THE RATE 
OF INTENSIFICATION WILL INCREASE DRAMATICALLY WITHIN THE HIGHLY 
FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND SHEAR (10-15 KTS), WARM 
SEA SURFACE TEMPERATURES BETWEEN 29 C TO 30 C, AND RAPIDLY IMPROVING 
OUTFLOW ALOFT. RAPID INTENSIFICATION IS FORECAST TO OCCUR BETWEEN TAU 
24-48. 27P WILL CONTINUE TO INTENSIFY UNTIL LANDFALL NORTHWEST OF 
LEARMONTH, AUSTRALIA. THOUGH THE FORECAST GRAPHIC REFLECTS A MAXIMUM 
INTENSITY OF 95 KTS, HIGHER WIND SPEEDS ARE POSSIBLE BETWEEN THE TAU 
72-96 INTERVAL. AFTER 27P MAKES LANDFALL BETWEEN TAU 72-96, IT IS 
EXPECTED TO WEAKEN THROUGH THE REMAINDER OF THE FORECAST PERIOD DUE 
TO TOPOGRAPHIC INTERACTION, DRY AIR ENTRAINMENT, AND HIGH VERTICAL 
WIND SHEAR INDUCED BY THE UPPER-LEVEL JET. 27P IS FORECASTED TO 
BEGIN SUBTROPICAL TRANSITION AROUND TAU 96 WITH COMPLETION EXPECTED 
BY TAU 120.

MODEL DISCUSSION: CROSS TRACK SPREAD AMONGST MODEL GUIDANCE IS
UNDER 50 NM UNTIL TAU 72. A FEW OF THE MEMBERS STILL REFLECT A MORE
WESTWARD TURN AROUND THE STR AXIS, BUT THE MAJORITY OF THE GUIDANCE
STILL REFLECTS A TIGHTER TURN THAT BRINGS THE CENTER JUST NORTHWEST
OF LEARMONTH, AUSTRALIA BEFORE LANDFALL. THE JTWC FORECASTED TRACK
IS PLACED EVER SO SLIGHTLY EAST OF THE MULTI-MODEL CONSENSUS WITH
HIGH CONFIDENCE. AFTER TAU 72 TRACK SPREAD INCREASES, RESULTING IN LOW 
TRACK CONFIDENCE THEREAFTER. INTENSITY GUIDANCE IS SPREAD UP TO 45 
KTS, WITH THE CONSENSUS REFLECTING A PEAK INTENSITY OF 90 KTS. THE 
JTWC FORECASTED INTENSITY REFLECTS SLIGHTLY HIGHER VALUES WITH MEDIUM
CONFIDENCE, TAKING RAPID INTENSIFICATION GUIDANCE INTO ACCOUNT WITH
THE FORECASTED VERY FAVORABLE ENVIRONMENTAL CONDITIONS. 

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