Wednesday, 20 February 2013

Current Southern Hemisphere Tropical Systems: Tropical Cyclone 16S (Haruna)



 
 
200300Z POSITION NEAR 21.4S 40.7E.
TROPICAL CYCLONE (TC) 16S (HARUNA), LOCATED APPROXIMATELY 385 NM 
WEST-SOUTHWEST OF ANTANANARIVO, MADAGASCAR, HAS TRACKED WESTWARD AT 
04 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE 
IMAGERY INDICATES RAPID CONSOLIDATION OVER THE PAST TWELVE HOURS 
WITH TIGHTLY-CURVED DEEP CONVECTIVE BANDING WRAPPING INTO A WELL-
DEFINED CENTER. A 200023Z SSMI 37 GHZ IMAGE DEPICTS A MICROWAVE EYE 
FEATURE AND SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. 
BASED ON THE SSMI IMAGE AND PREVIOUS MICROWAVE IMAGERY, THE SYSTEM 
MOTION HAS BECOME QUASI-STATIONARY AND APPEARS TO BE LOOPING. UPPER-
LEVEL CONDITIONS REMAIN VERY FAVORABLE WITH WEAK VERTICAL WIND 
SHEAR, RADIAL OUTFLOW AND WARM SST. OVER THE PAST TWELVE HOURS, THE 
SUBTROPICAL STEERING RIDGE (STR) HAS WEAKENED DUE TO AN APPROACHING 
SHORTWAVE TROUGH AND TC 16S IS CURRENTLY TRACKING SLOWLY AND 
ERRATICALLY WITHIN A WEAK STEERING ENVIRONMENT. DYNAMIC MODEL 
GUIDANCE SUPPORTS SLOW TRACK MOTION THROUGH TAU 48 UNTIL A DEEP 
SHORTWAVE TROUGH DEEPENS SOUTH OF MADAGASCAR. THEREAFTER, THE SYSTEM 
WILL ACCELERATE SOUTHEASTWARD WHILE UNDERGOING EXTRA-TROPICAL 
TRANSITION (ETT). TC 16S IS FORECAST TO WEAKEN DUE TO LAND 
INTERACTION NEAR TAU 72, THEN MORE SIGNIFICANT WEAKENING AS IT 
TRACKS OVER COOLER SST AND ENCOUNTERS INCREASING VERTICAL WIND SHEAR 
SOUTH OF MADAGASCAR. THE SYSTEM IS FORECAST TO COMPLETE ETT BY TAU 
120. OVERALL, THE DYNAMIC MODEL GUIDANCE IS IN FAIR AGREEMENT AND 
SUPPORTS THE JTWC FORECAST TRACK; HOWEVER, THERE IS LOW CONFIDENCE 
IN THE JTWC FORECAST DUE TO THE WEAK STEERING ENVIROMENT AND 
UNCERTAINTIES IN TRACK SPEED AFTER TAU 72. THE SYSTEM IS NOW 
EXPECTED TO INTENSIFY TO A PEAK OF 75 KNOTS BY TAU 36 DUE TO 
FAVORABLE CONDITIONS. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 200000Z IS 
20 FEET.
 
- JTMC 

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