WDPS31 PGTW 190900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 27P (NARELLE) WARNING 
NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.6S 146.5E
   INITIAL INTENSITY: 125 KTS
   GEOGRAPHIC REFERENCE: 202 NM NORTH-NORTHEAST OF CAIRNS,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 39 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 27P (NARELLE) WITH A WELL-DEFINED AND INCREASINGLY
CLEAR EYE-FEATURE (12 NM IN DIAMETER), SURROUNDED BY UNIFORM AND
TIGHTLY WRAPPED CONVECTION. SINCE THE PREVIOUS WARNING, TC 27P HAS
CONTINUED TO INTENSIFY TO 125 KTS, DESPITE MODERATE VERTICAL WIND
SHEAR (VWS) OF 15-20 KTS. ENVIRONMENTAL ANALYSIS REVEALS CONTINUED
FAVORABLE CONDITIONS, WITH WARM SEA SURFACE TEMPERATURES OF 28-29
C, STRONG RADIAL OUTFLOW ALOFT, AND MODERATE VWS. THE INITIAL
POSITION HAS BEEN PLACED WITH HIGH CONFIDENCE BASED ON THE
OBSERVABLE EYE-FEATURE ON ANIMATED MSI. THE INITIAL INTENSITY HAS
BEEN ASSESSED WITH MODERATE CONFIDENCE BASED ON A MIXTURE OF
SUBJECTIVE AGENCY DVORAK ESTIMATES AND CIMSS OBJECTIVE INTENSITY
ESTIMATES LISTED BELOW. ADDITIONALLY, THE CLOUD CANOPY TOPS
SURROUNDING THE EVIDENT EYE HAVE WARMED SLIGHTLY OVER THE LAST FEW
HOURS TO 84 C, WHILE THE EYE TEMPERATURE HAS INCREASED
CONSIDERABLY, TO 11 C AT 190730Z.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: NORTHEASTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) POSITIONED TO THE SOUTHWEST, OVER WESTERN
AUSTRALIA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   KNES: T7.0 - 140 KTS 
   ABRF: T6.5 - 127 KTS
   CIMSS SATCON: 128 KTS AT 190355Z
   CIMSS ADT: 137 KTS AT 190530Z
   CIMSS AIDT: 130 KTS AT 190530Z
   CIMSS D-MINT: 130 KTS AT 190607Z
   CIMSS D-PRINT: 131 KTS AT 190600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL

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: TC 27P IS FORECASTED TO TRACK GENERALLY
WESTWARD THROUGH THE FORECAST PERIOD, ALONG THE NORTHERN PERIPHERY
OF THE DEEP-LAYER STR CENTERED OVER WESTERN-CENTRAL AUSTRALIA.
BETWEEN TAU 96 AND TAU 120, THE WESTERN EXTENT OF THE STR
POSITIONED TO THE SOUTH IS FORECASTED TO WEAKEN SLIGHTLY AND
RETREAT SOUTHEASTWARD, ALLOWING TC 27P TO BEGIN TRACKING
WEST-SOUTHWESTWARD UNTIL THE END OF THE FORECAST PERIOD. REGARDING
INTENSITY, TC NARELLE IS EXPECTED TO SLOWLY WEAKEN TOWARD 115 KTS
BEFORE THE LOW-LEVEL CIRCULATION CENTER (LLCC) AND ASSOCIATED
EYEWALL APPROACHES EASTERN QUEENSLAND BETWEEN TAU 12 AND TAU 18 AS
MODERATE VWS BETWEEN 15-20 KTS PERSISTS DURING THE SHORT-TERM
FORECAST. FOLLOWING INITIAL LANDFALL, SURFACE INTENSITIES WILL
CONTINUE TO DECREASE TOWARD 80 KTS BY TAU 24 AS VWS NEARS 20 KTS AND 
LAND INTERACTION PERSISTS. BETWEEN TAU 24 AND TAU 36, TC 27P IS 
FORECASTED TO REEMERGE OVER THE EASTERN GULF OF CARPENTARIA WITH A 
RELATIVELY BROAD SURFACE CIRCULATION AND WEAKENED SURFACE INTENSITIES 
TOWARD 70 KTS. DURING THE SYSTEMS WESTWARD TRANSIT THROUGH THE 
CENTRAL GULF OF CARPENTARIA, GRADUAL INTENSIFICATION IS EXPECTED AS 
ENVIRONMENTAL CONDITIONS BECOME INCREASINGLY FAVORABLE WITH WARM SEA 
SURFACE TEMPERATURES AND DECREASED VWS TO LESS THAN 15 KTS. AS TC 27P
CONTINUES WESTWARD, A SECOND LANDFALL IS FORECASTED ALONG THE
EASTERN COASTLINE OF THE NORTHERN TERRITORY WITH INTENSITIES NEAR
80 KTS. TC 27P WILL CONTINUE WESTWARD THROUGH THE NORTHERN EXTENT
OF THE NORTHERN TERRITORY WHILE PERSISTENT LAND INTERACTION WILL
WEAKEN SURFACE INTENSITIES TO 60 KTS BY TAU 72. FOLLOWING TAU 72, A
BRIEF TREK ACROSS THE JOSEPH BONAPARTE GULF WILL NOT ALLOW FOR ANY
CONSIDERABLE OPPORTUNITY FOR INTENSIFICATION BEFORE A THIRD
LANDFALL IN THE EXTREME NORTHERN EXTENT OF WESTERN AUSTRALIA. NEAR
TAU 108, TC 27P WILL REEMERGE OVER OPEN WATER, OFF THE NORTHWEST
COAST OF WESTERN AUSTRALIA WITH SURFACE INTENSITIES NEAR 40 KTS. DUE
TO PROLONGED PERIODS OF LAND INTERACTION BETWEEN TAU 60 AND TAU
120, GRADUAL WEAKENING IS EXPECTED; HOWEVER, THE ENVIRONMENT IS
EXPECTED TO REMAIN FAVORABLE OFF THE NORTHWEST COAST OF WESTERN
AUSTRALIA, POTENTIALLY ALLOWING FOR A PERIOD OF INTENSIFICATION
AFTER TAU 120.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN VERY GOOD
AGREEMENT THROUGHOUT THE FORECAST PERIOD, WITH A CROSS-TRACK SPREAD
OF 42 NM AT TAU 72, INCREASING TO 84 NM BY TAU 120. THE JTWC TRACK
FORECAST HAS BEEN PLACED WITH HIGH CONFIDENCE THROUGHOUT THE
FORECAST PERIOD, ALIGNED CLOSELY TO THE JTWC MULTI-MODEL TRACK
CONSENSUS. REGARDING INTENSITY, THE GFS DETERMINISTIC SOLUTION
REMAINS AN OUTLIER THROUGH THE NEAR-TERM, ILLUSTRATING A SHARP
WEAKENING TREND THROUGHOUT THE ENTIRE FORECAST PERIOD. THE MAJORITY
OF OTHER SOLUTIONS CHARACTERIZE SIMILAR EXPECTED INTENSITIES, WITH
GRADUAL WEAKENING INTO TAU 12, AND A QUICKER WEAKENING TREND
THEREAFTER DUE TO THE EXPECTED LAND INTERACTION PHASE OVER
QUEENSLAND. LATER IN THE FORECAST, COAMPS-TC CHARACTERIZES A RAPID
INTENSIFICATION PHASE WHILE TC 27P TRACKS WESTWARD ACROSS THE GULF
OF CARPENTARIA. THEREFORE, THE JTWC INTENSITY FORECAST HAS BEEN
ASSESSED WITH MEDIUM CONFIDENCE, AND ALIGNED JUST ABOVE THE JTWC
MULTI-MODEL INTENSITY CONSENSUS.

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