WDXS32 PGTW 281500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 28S (DIANNE) WARNING 
NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.6S 123.8E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 166 NM NORTHEAST OF BROOME, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS CYCLING
DEEP CONVECTION, LACKING ANY DISTINCT ORGANIZATION AROUND THE
ASSESSED CENTER. THE LOW LEVEL CIRCULATION CENTER (LLCC) IS FULLY
OBSCURED BY THE CONVECTION AND CIRRUS BLOWOFF AND THE SYSTEM LIES
ON THE EXTREME EDGE OF THE BROOME RADAR COVERAGE. HOWEVER, A
HIGH-RESOLUTION WSF-M 37GHZ MICROWAVE IMAGE CAME IN AND SAVED THE
DAY, SHOWING A RELATIVELY LARGE LLCC WITH CYCLONICALLY CURVED BANDS
OF STRONG CONVECTION WRAPPING INTO THE LOW EMISSIVITY REGION (LER).
COMBINED WITH AN ANALYSIS OF THE SURFACE WIND REPORTS FROM ADELE
ISLAND, SUGGESTING THAT THAT THE LLCC PASSED SOUTH OF A LINE
EXTENDING DUE EAST OF THE STATION AROUND 1100Z, PROVIDED ADDITIONAL
CONFIDENCE TO THE INITIAL POSITIONING. THE INITIAL INTENSITY IS
ASSESSED WITH MEDIUM CONFIDENCE, BASED ON A BLEND OF THE OBJECTIVE
AND SUBJECTIVE INTENSITY ESTIMATES NOTED ABOVE. THE ENVIRONMENT
REMAINS FAVORABLE WITH LOW WIND SHEAR, VERY WARM SSTS AND DECENT
OUTFLOW ALOFT, THOUGH THE SHORT TIME REMAINING OVER WATER WILL BE
THE PRIMARY FACTOR IN KEEPING A LID ON THE INTENSIFICATION OF TC
28S.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   APRF: T3.0 - 45 KTS
   CIMSS ADT: 47 KTS AT 281140Z
   CIMSS AIDT: 39 KTS AT 281140Z
   CIMSS D-MINT: 27 KTS AT 280956Z
   CIMSS D-PRINT: 40 KTS AT 281140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE WESTWARD
   OTHER FACTORS: PROXIMITY TO LAND. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TROPICAL CYCLONE (TC) 28S (DIANNE) WILL
CONTINUE TRACKING SOUTHWARD ALONG THE WESTERN SIDE OF THE STEERING
RIDGE THROUGH THE ENTIRETY OF THE FORECAST PERIOD. LANDFALL IS
EXPECTED IN THE VICINITY OF KOOLAN ISLAND WITHIN THE NEXT SIX HOURS
OR SO. CONTINUING ITS TREK SOUTHWARD, TC 28S MAY BRIEFLY PASS BACK
OVER THE FAR SOUTHEASTERN PORTION OF KING SOUND AROUND TAU 12
BEFORE MOVING FURTHER INLAND FOR THE REMAINDER OF THE FORECAST
PERIOD. THE SYSTEM COULD INTENSIFY A BIT MORE IN THE FEW HOURS LEFT
OVER WATER AS THE SSTS IN THIS AREA ARE ZESTY, AND SHEAR IS LOW.
HOWEVER, INGESTION OF DRY AIR FROM THE AUSTRALIAN LANDMASS AND
DISRUPTION OF THE INFLOW LAYER DUE TO TERRAIN INTERACTION MEAN THAT
FURTHER INTENSIFICATION WILL BE LIMITED TO JUST 5-10 KNOTS. ONCE
THE SYSTEM IS ASHORE IT WILL START TO WEAKEN BUT THE FURTHER WEST
THE TRACK IS, THE LONGER IT WILL MAINTAIN A RELATIVELY HIGH
INTENSITY. BUT ONCE IT IS FIRMLY ASHORE TO THE SOUTHEAST OF DERBY,
TC 28S WILL RAPIDLY WEAKEN AND DISSIPATE BETWEEN TAU 24 AND TAU 36.
 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD
AGREEMENT, THE CROSS-TRACK SPREAD IN THE GUIDANCE PACKAGE HAVING
LOWERED EVEN MORE FROM SIX HOURS AGO. THE UKMET ENSEMBLE AND EGRR
DETERMINISTIC TRACKER REMAIN ON THE WESTERN EDGE OF THE PACKAGE,
AND GFS REMAINS ON THE EASTERN EDGE BUT OVERALL THE GUIDANCE HAS
COME INTO BETTER AGREEMENT. THE JTWC FORECAST IS CONSISTENT WITH
BOTH THE PREVIOUS FORECAST AND THE MULTI-MODEL CONSENSUS. INTENSITY
GUIDANCE IS IN GOOD AGREEMENT SHOWING STEADY TO RAPID WEAKENING
FROM THE BEGINNING OF THE FORECAST. THE JTWC FORECAST DIVERGES FROM
THE GUIDANCE IN MAINTAINING A 40 KNOT INTENSITY THROUGH TAU 12 BUT
THEN REJOINS THE PACK THEREAFTER. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: HIGH//
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