WDXS32 PGTW 020900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 15S (ANIKA) WARNING 
NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.5S 120.7E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 128 NM EAST-NORTHEAST OF PORT HEDLAND,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A VERY SMALL
BUT WELL ORGANIZED MASS OF DEEP CONVECTION OBSCURING A SMALL LOW
LEVEL CIRCULATION CENTER (LLCC), JUST OFF THE COAST OF NORTHWEST
AUSTRALIA, NEAR THE TOWN OF MANDORA. ANIMATED RADAR FROM BROOME
INDICATES A VERY TIGHT CIRCULATION CENTER, WITH A BROAD ARC OF
CONVECTIVE ACTIVITY SPIRALING IN ON THE SOUTHERN SIDE, WITH WEAKER
SPIRAL BANDS TO THE NORTH AND EAST. THE INITIAL POSITION IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE RADAR DATA AS WELL AS
SURFACE OBSERVATIONS FROM MANDORA. THE INITIAL INTENSITY OF 40
KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE, ABOVE THE AVAILABLE
AGENCY FIXES, AND MORE IN LINE WITH THE ADT ESTIMATE, AS WELL AS AN
EARLIER 020041Z ASCAT-B PASS WHICH SHOWED 40 KNOT MAX WINDS IN THE
SOUTHWESTERN QUADRANT. THE SYSTEM HAS QUICKLY INTENSIFIED AFTER
MOVING OVER WATER EARLIER IN THE DAY IN RESPONSE TO VERY FAVORABLE
ENVIRONMENTAL CONDITIONS OF VERY WARM (30-31C) SSTS, LOW VERTICAL
WIND SHEAR AND ROBUST POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A LOW TO MID-LEVEL
SUBTROPICAL RIDGE (STR) OVER CENTRAL AUSTRALIA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   APRF: T2.5 - 35 KTS
   CIMSS ADT: 39 KTS AT 020540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: PROXIMITY TO LAND. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TC 15S IS EXPECTED TO TURN SHARPLY SOUTHWARD
AND MAKE LANDFALL WITHIN THE NEXT THREE HOURS, NEAR THE TOWN OF
MANDORA, AUSTRALIA. ONCE ASHORE IT IS FORECAST TO TURN STEADILY
MORE SOUTHEASTWARD IN RESPONSE TO THE APPROACH OF A MID-LEVEL
TROUGH APPROACHING FROM THE WEST. AS IT MOVES INLAND, FRICTIONAL
EFFECTS WILL STEADILY WEAKEN THE SYSTEM, AND TC 15S IS FORECAST TO
WEAKEN BELOW WARNING CRITERIA NO LATER THAN TAU 24. WHILE THE
SYSTEM IS EXPECTED TO FALL BELOW 35 KNOTS BY TAU 24, THE REMNANT
CIRCULATION CENTER WILL VERY LIKELY CONTINUE TRACKING WELL INTO
WEST CENTRAL AUSTRALIA WHILE CONTINUING TO WEAKEN STEADILY. 

MODEL DISCUSSION: TRACK GUIDANCE IS IN VERY GOOD AGREEMENT THROUGH
THE DURATION OF THE FORECAST PERIOD, THOUGH MODEL TRACKERS DIVERGE
SIGNIFICANTLY IN THE LATER TAUS ONCE THE SYSTEM WEAKENS. THE JTWC
FORECAST TRACK LIES CLOSE TO THE MEDIAN OF THE TRACKER ENVELOPE
WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT,
THOUGH THE HWRF PREDICTS INTENSIFICATION TO 50 KNOTS BY TAU 12.
THIS IS UNLIKELY AS THE SYSTEM WILL BE OVER LAND AGAIN WITHIN A
VERY SHORT TIME. THE JTWC FORECAST LIES NEAR THE CONSENSUS MEAN
WITH HIGH CONFIDENCE. 

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