Tropical Cyclone 09S (Iggy) Northwest of Learmonth, Australia

270300Z POSITION NEAR 18.3S 110.2E.
TROPICAL CYCLONE (TC) 09S (IGGY), LOCATED APPROXIMATELY 340 NM 
NORTHWEST OF LEARMONTH, AUSTRALIA, HAS TRACKED SOUTHEASTWARD AT 07 
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE 
IMAGERY INDICATES IMPROVED CONSOLIDATION WITH CURVED DEEP CONVECTIVE 
BANDING WRAPPING INTO A MORE DEFINED LOW-LEVEL CIRCULATION CENTER. 
TC 09S HAS TRACKED SOUTHEASTWARD AND IS NOW CLOSER TO THE UPPER-
LEVEL SUBTROPICAL RIDGE AXIS WITH DECREASED EASTERLY VERTICAL WIND 
SHEAR (NOW 10-20 KNOTS). A 270024Z SSMIS 37GHZ IMAGE SUPPORTS THE 
CURRENT POSITION WITH GOOD CONFIDENCE AND DEPICTS TIGHTLY-CURVED 
BANDING WRAPPING INTO A WELL-DEFINED CENTER. ANIMATED WATER VAPOR 
IMAGERY DEPICTS GOOD EQUATORWARD OUTFLOW WITH WEAK POLEWARD OUTFLOW. 
THE CURRENT INTENSITY IS BASED ON AN AVERAGE OF DVORAK ESTIMATES 
RANGING FROM 45 TO 55 KNOTS. TC 09S IS TRACKING SLOWLY SOUTHEASTWARD 
ALONG THE SOUTHWEST PERIPHERY OF THE NEAR-EQUATORIAL RIDGE AND IS 
FORECAST TO CONTINUE TRACKING SOUTHEASTWARD THROUGH TAU 72. AFTER 
TAU 72, THE DYNAMIC MODELS DIVERGE WITH THE JGSM TRACKER INDICATING 
LANDFALL EAST OF LEARMONTH WHILE THE GFDN, ECMWF, GFS AND NOGAPS 
TRACKERS SHOW A TRACK WEST OF LEARMONTH. OVERALL THERE IS GENERAL 
AGREEMENT THAT THE SYSTEM WILL TURN SOUTHWESTWARD AND TRACK SLOWLY 
DUE TO A WEAKENING SUBTROPICAL RIDGE (STR) RESULTING FROM THE 
PASSAGE OF A DEEP MIDLATITUDE SHORTWAVE TROUGH OVER SOUTHWESTERN 
AUSTRALIA. THIS FORECAST FAVORS THE ECMWF, NOGAPS, GFDN AND GFS 
SOLUTIONS WITH A TRACK WEST OF LEARMONTH AND A SIGNIFICANT SLOW-DOWN 
IN TRACK SPEEDS OR PERHAPS A QUASI-STATIONARY MOTION IN THE EXTENDED 
TAUS. TC 09S IS EXPECTED TO SLOWLY INTENSIFY THROUGH TAU 24 DUE TO 
THE MODERATE VERTICAL WIND SHEAR BUT SHOULD STRENGTHEN SIGNIFICANTLY 
AFTER TAU 24 AS IT CONTINUES TO TRACK UNDER THE UPPER-LEVEL STR AND 
VWS RELAXES. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 270000Z IS 23 FEET. 

- Joint Typhoon Warning Center (JTWC)