WDPS31 PGTW 201500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 27P (NARELLE) WARNING 
NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.4S 140.8E
   INITIAL INTENSITY: 85 KTS
   GEOGRAPHIC REFERENCE: 358 NM NORTHWEST OF CAIRNS, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE (TC) 27P (NARELLE) HAVING REEMERGED OVER THE EASTERN GULF
OF CARPENTARIA OVER THE LAST FEW HOURS, WITH REDEVELOPING DEEP
CONVECTION THROUGHOUT THE WESTERN SEMICIRCLE WRAPPING INTO THE
NORTHERN QUADRANT. MUCH OF THE SOUTHWEST QUADRANT REMAINS
RELATIVELY CONVECTION FREE WITH A SMALL INJECTION OF DRY AIR INTO
THE SOUTHERN SEMICIRCLE WHILE PERSISTENT MODERATE VERTICAL WIND
SHEAR (VWS) OF 20-25 KTS REMAINS EVIDENT ALONG THE SYSTEMS EASTERN
PERIPHERY, ADDING PRESSURE TO THE CONVECTIVE STRUCTURES EASTERN
FACE. THE LOW-LEVEL CIRCULATION HAS REMAINED MOSTLY OBSCURED OVER
THE LAST FEW HOURS DUE TO WIDESPREAD AND BUILDING CONVECTION IN
CLOSE PROXIMITY TO THE LLCC. THE ENVIRONMENTAL ANALYSIS HAS
REVEALED A MARGINALLY FAVORABLE ENVIRONMENT, WITH WARM SEA SURFACE
TEMPERATURES (SSTS) OF 29-30 C AND SUPPORTIVE RADIAL OUTFLOW ALOFT,
OFFSET BY THE AFOREMENTIONED EASTERLY VWS OF 20-25 KTS. THE INITIAL
POSITION HAS BEEN PLACED WITH MEDIUM CONFIDENCE BASED ON THE
OBSCURED LLCC IDENTIFIED ON ANIMATED EIR SATELLITE IMAGERY. THE
INITIAL INTENSITY HAS BEEN ASSESSED WITH LOW CONFIDENCE BASED ON
UNCERTAINTIES FROM HAVING JUST REEMERGED BACK OVER OPEN WATER AFTER
A PERIOD OF RAPID WEAKENING WHILE CROSSING QUEENSLAND, AUSTRALIA.

INITIAL WIND RADII BASIS: NORTHWEST AND SOUTHWEST QUADRANTS FROM A
PARTIAL 200854Z RCM-1 SAR DATA COVERING THE WESTERN SEMICIRCLE

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   ABRF: T3.0 - 45 KTS
   CIMSS ADT: 84 KTS AT 201140Z
   CIMSS AIDT: 75 KTS AT 201140Z
   CIMSS D-MINT: 70 KTS AT 200814Z
   CIMSS D-PRINT: 59 KTS AT 201230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: LOW
   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 CONTINUE TRACKING
WESTWARD ALONG THE NORTHERN PERIPHERY OF THE STR CENTERED OVER
WESTERN AUSTRALIA INTO TAU 48. AFTER TAU 48, A WESTWARD EXTENSION
OF THE STR IS FORECASTED TO WEAKEN SLIGHTLY AND RETREAT EASTWARD,
CAUSING THE TRACK FOR TC 27P TO BECOME LARGELY WEST-SOUTHWARD UNTIL
THE END OF THE FORECAST PERIOD. REGARDING INTENSITY, TC NARELLE IS
EXPECTED TO GRADUALLY DECAY TO 80 KTS PRIOR TO LANDFALL ALONG THE
EASTERN COASTLINE OF THE NORTHERN TERRITORY, JUST WEST OF ISLE
WOODAH. ALTHOUGH WARM SSTS BETWEEN 29-30 C AND SUPPORTIVE OUTFLOW
ALOFT WILL PERSIST DURING THE SYSTEMS WESTWARD TREK ACROSS THE GULF
OF CARPENTARIA, ENHANCED EASTERLY VWS NEAR 25 KTS WILL LIMIT
OPPORTUNITIES FOR CONSIDERABLE INTENSIFICATION BEFORE A SECOND
LANDFALL. FOLLOWING TAU 24 AND AFTER LANDFALL IN THE NORTHERN
TERRITORY, SURFACE INTENSITIES WILL CONTINUE TO DECAY DUE TO
CONTINUOUS LAND INTERACTION AND MODERATE VWS BETWEEN 15-20 KTS. AS
TC 27P APPROACHES A SECOND REEMERGENCE OVER WATER IN THE JOSEPH
BONAPARTE GULF, INTENSITIES NEAR 45 KTS ARE FORECASTED. A BRIEF
WESTWARD TRACK OVER OPEN WATER IS EXPECTED UNTIL A THIRD LANDFALL
IN THE EXTREME NORTHERN PORTION OF WESTERN AUSTRALIA. DURING THIS
PERIOD, STEADY SURFACE INTENSITIES NEAR 50 KTS ARE EXPECTED UNTIL
THE SYSTEM REEMERGES BACK OVER OPEN OCEAN WATER IN THE TIMOR SEA.
FOLLOWING TAU 72 AND OVER OPEN WATER IN THE TIMOR SEA,
REINTENSIFICATION IS FORECASTED TOWARD 70 KTS BY TAU 120 AS THE
ENVIRONMENT BECOMES LARGELY CONDUCIVE FOR ONGOING TC SUPPORT. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE REMAINS IN GREAT
AGREEMENT THROUGHOUT THE MAJORITY OF THE FORECAST PERIOD,
ILLUSTRATING A CROSS-TRACK SPREAD OF 53 NM BY TAU 72, INCREASING TO
146 NM BY TAU 120. THE ALONG-TRACK SPREAD OF TC 27P CONTINUES TO
LENGTHEN BETWEEN TAU 72 AND TAU 120 DUE TO BRIEF PERIODS OF LAND
INTERACTION THROUGHOUT THE ENTIRE FORECAST PERIOD; HOWEVER, THE
MULTI-MODEL GUIDANCE ENVELOPE REMAINS UNDER 200 NM. THE JTWC TRACK
FORECAST HAS BEEN PLACED WITH HIGH CONFIDENCE THROUGH THE INITIAL
72 HOURS, AND MEDIUM CONFIDENCE THEREAFTER DUE TO VARYING DEGREES
IN THE SPEED OF APPROACH FOR ALL JTWC TRACK SOLUTIONS IN THE LATTER
PORTION OF THE FORECAST. REGARDING INTENSITY, MOST JTWC INTENSITY
CONSENSUS SOLUTIONS CONTINUE TO ALIGN CLOSELY THROUGH TAU 120. THE
ONLY OUTLIER THAT REMAINS IS THE GFS DETERMINISTIC SOLUTION,
WHICH CHARACTERIZES A SHARPER DROP-OFF IN SURFACE INTENSITIES INTO
TAU 36; HOWEVER, BECOMES ALIGNED TO THE CONSENSUS THEREAFTER.
THEREFORE, THE JTWC INTENSITY FORECAST HAS BEEN ASSESSED WITH
MEDIUM CONFIDENCE AND ALIGNED SLIGHTLY ABOVE THE MULTI-MODEL
CONSENSUS THROUGHOUT THE FORECAST PERIOD.

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