Tropical Cyclone EWETSE (15S)

WTXS31 PGTW 091500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 20S (MITCHELL) WARNING NR 015//
RMKS/
1. TROPICAL CYCLONE 20S (MITCHELL) WARNING NR 015    
   02 ACTIVE TROPICAL CYCLONES IN SOUTHIO
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
   WIND RADII VALID OVER OPEN WATER ONLY
    ---
   WARNING POSITION:
   091200Z --- NEAR 25.3S 113.8E
     MOVEMENT PAST SIX HOURS - 155 DEGREES AT 09 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY A COMBINATION OF 
     SATELLITE, RADAR AND SYNOPTIC DATA
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   RADIUS OF 034 KT WINDS - 070 NM NORTHEAST QUADRANT
                            065 NM SOUTHEAST QUADRANT
                            060 NM SOUTHWEST QUADRANT
                            060 NM NORTHWEST QUADRANT
   REPEAT POSIT: 25.3S 113.8E
    ---
   FORECASTS:
   12 HRS, VALID AT:
   100000Z --- 27.2S 115.4E
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER LAND
    ---
REMARKS:
091500Z POSITION NEAR 25.8S 114.2E.
09FEB26. TROPICAL CYCLONE 20S (MITCHELL), LOCATED APPROXIMATELY
181 NM SOUTH OF LEARMONTH, AUSTRALIA, HAS TRACKED SOUTH-
SOUTHEASTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED 
INFRARED SATELLITE IMAGERY (EIR) DEPICTS A DECOUPLING VORTEX, WITH THE 
UPPER-LEVEL ROTATION ALREADY LOCATED OVER THE SOUTHERN PORTION OF 
SHARK BAY, WHILE THE LOW-LEVEL CIRCULATION CENTER (LLCC) IS LOCATED 
JUST SOUTH OF CARNARVON, AUSTRALIA BASED ON RADAR ANALYSIS. SURFACE 
WINDS AT CARNARVON SHIFTED FROM NORTHERLY TO WESTERLY BETWEEN 1100Z-
1200Z, ACCOMPANIED BY A MINIMUM IN SEA LEVEL PRESSURE OF 988.4MB AT 
THE SAME TIME, SUPPORTING THE PASSAGE OF THE LLCC OVER THE STATION IN 
THAT WINDOW OF TIME. ANIMATED RADAR DATA SUGGESTS A SMALL LLCC 
STRADDLING THE COASTLINE SOUTHWEST OF CALLAGIDDY AT 1200Z, MOVING 
SOUTHEASTWARD ALONG THE EASTERN COAST OF SHARK BAY. A 091106Z WSF-M 
37GHZ MICROWAVE IMAGE DEPICTED AN ELONGATED LLCC JUST WEST OF 
CARNARVON. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED 
ON THE RADAR ANALYSIS AND EXTRAPOLATION OF THE LLCC IN THE WSF-M 
IMAGE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, BASED 
ONA PGTW DVORAK ESTIMATE OF T3.0-T3.5, A RAW ADT OF T3.0, AIDT OF 
46KTS, CIMSS DPRINT ESTIMATE OF 41KTS AND A DMINT ESTIMATE OF 42KTS. 
TC 20S WILL CONTINUE TO TRACK SOUTHEASTWARD, STRADDLING THE COASTLINE 
FOR THE NEXT COUPLE OF HOURS BEFORE MOVING FURTHER INLAND TO A 
POSITION NORTHEAST OF GERALDTON BY TAU 12. ENVIRONMENTAL CONDITIONS 
ARE ALREADY UNFAVORABLE, AND THE SYSTEM WILL RAPIDLY WEAKEN OVER THE 
NEXT 12 HOURS AS INCREASING SHEAR LEADS TO RAPID VORTEX DECOUPLING AND 
FRICTIONAL EFFECTS REDUCE THE WIND SPEEDS SURROUNDING THE LOWER-LEVEL 
VORTEX. THE SYSTEM IS FORECAST TO DISSIPATE AS A TROPICAL CYCLONE WITH 
THE NEXT 12 HOURS. THIS IS THE FINAL WARNING ON THIS SYSTEM BY THE 
JOINT TYPHOON WRNCEN PEARL HARBOR HI. THE SYSTEM WILL BE CLOSELY 
MONITORED FOR SIGNS OF REGENERATION. MINIMUM CENTRAL PRESSURE AT 
091200Z IS 991 MB. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 091200Z IS 18 
FEET. REFER TO TROPICAL CYCLONE 21S (GEZANI) WARNINGS (WTXS32 PGTW)
FOR TWELVE-HOURLY UPDATES.//
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WDXS31 PGTW 090900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 20S (MITCHELL) WARNING 
NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.5S 113.4E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 138 NM SOUTH-SOUTHWEST OF LEARMONTH,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI), SURFACE OBSERVATIONS, 
AND METEOROLOGICAL RADAR IMAGERY INDICATE THAT TROPICAL CYCLONE (TC) 
20S IS TRANSITING ALONG THE LITTORAL REGION OF WESTERN AUSTRALIA, 
NORTH OF CARNARVON. RECENT RADAR DATA SUGGESTS THE SYSTEM HAS TURNED 
SOUTHEASTWARD AND THAT IT IS GENERALLY PARALLELING THE COAST TOWARDS 
SHARK BAY. SURFACE WINDS AT CARNARVON REMAIN EASTERLY, CONSTRAINING 
THE LOW-LEVEL CIRCULATION CENTER (LLCC) TO THE NORTH OF THE STATION. 
HOWEVER, A RAPID SHIFT SHOULD BEGIN SHORTLY AS THE LLCC PASSES VERY 
CLOSE TO THE STATION IN THE NEXT HOUR. THE INITIAL INTENSITY IS 
ASSESSED WITH MEDIUM CONFIDENCE, WEIGHTED TOWARDS THE UPPER QUARTILE 
OF OBJECTIVE INTENSITY ESTIMATES. ENVIRONMENTAL CONDITIONS ARE 
DEGRADED AS THE SYSTEM ACCELERATES SOUTHEASTWARD. SEA SURFACE 
TEMPERATURES (SSTS) ARE NOW SUB-26C, AND LAND MASS PROXIMITY IS 
INDUCING FRICTIONAL ATTENUATION AND ENTRAINMENT OF ADIABATICALLY DRY 
CONTINENTAL AIR FROM THE EAST, WHILE VERTICAL WIND SHEAR (VWS) IS 
RAPIDLY INCREASING.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: GRADIENT BETWEEN A MID-LEVEL
SUBTROPICAL RIDGE (STR) OVER CENTRAL AUSTRALIA AND A MID- TO
UPPER-LEVEL TROUGH TO THE SOUTHWEST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   DEMS: T3.0 - 45 KTS
   APRF: T3.0 - 45 KTS
   CIMSS SATCON: 54 KTS AT 090548Z
   CIMSS ADT: 51 KTS AT 090630Z
   CIMSS AIDT: 43 KTS AT 090630Z
   CIMSS D-MINT: 45 KTS AT 090548Z
   CIMSS D-PRINT: 52 KTS AT 090600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: TERRAIN INTERACTION, ENTRAINMENT OF DRY MID-LEVEL
CONTINENTAL AIR INTO THE CORE FROM THE EAST. 

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST IS TRUNCATED TO 24
HOURS. 

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 20S (MITCHELL) HAS 
RECURVED AROUND THE STR AXIS AND IS NOW ACCELERATING SOUTHEASTWARD 
ALONG THE STEEPENING PRESSURE GRADIENT BETWEEN THE STR OVER CENTRAL 
AUSTRALIA AND AN APPROACHING BAROCLINIC UPPER-LEVEL TROUGH TO THE 
SOUTHWEST. THE SYSTEM IS FORECAST TO TRACK ALONG THE EASTERN 
PERIPHERY OF SHARK BAY, WITH LANDFALL ANTICIPATED AT THE SOUTHERN 
TERMINUS OF THE BAY WITHIN THE NEXT 12 HOURS. THE SYSTEM WILL 
SUBSEQUENTLY TRAVERSE FURTHER INLAND THROUGH THE REMAINDER OF THE 
FORECAST PERIOD. REGARDING INTENSITY, THE SYSTEM WILL CONTINUE TO 
WEAKEN AS IT TRAVERSES SHARK BAY DUE TO ENHANCED SHEAR, DRY AIR 
ENTRAINMENT, AND TERRAIN INTERACTION. UPON LANDFALL, THE SYSTEM WILL 
UNDERGO RAPID CYCLOLYSIS DUE TO INCREASED FRICTIONAL DRAG AND 
THERMODYNAMIC DECOUPLING OF THE VORTEX.

MODEL DISCUSSION: NUMERICAL WEATHER PREDICTION (NWP) CONSENSUS 
EXHIBITS HIGH CORRELATION THROUGH THE SHORT FORECAST PERIOD, 
DEPICTING MINIMAL CROSS- OR ALONG-TRACK SPREAD. THE JTWC FORECAST IS 
ALIGNED WITH THE MULTI-MODEL MEAN WITH HIGH CONFIDENCE. INTENSITY 
GUIDANCE IS ALSO CONGRUENT, WITH ALL DYNAMICAL MEMBERS DEPICTING 
RAPID WEAKENING CONCLUDING IN DISSIPATION WITHIN 24 HOURS, LENDING 
HIGH CONFIDENCE TO THE JTWC FORECAST.

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