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Tuesday, 6 March 2012

Cyclone Season 2012: Tropical Cyclone Irina (Southern Indian Ocean) 6 March 2012 07h30 SAST


060300Z POSITION NEAR 30.2S 38.2E.
TROPICAL CYCLONE (TC) 14S (IRINA), LOCATED APPROXIMATELY 380 NM SOUTHEAST OF MAPUTO, MOZAMBIQUE, HAS TRACKED EAST-NORTHEASTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. RECENT 12-HOUR ENHANCED ANIMATED INFRARED SATELLITE IMAGERY SHOWS THE ASSOCIATED CONVECTION BECAME MORE FRAGMENTED AND WAS DISPLACED FURTHER AWAY FROM THE LOW LEVEL CIRCULATION CENTER. FURTHERMORE, CONVECTIVE TOPS HAS BECOME SHALLOWER. THE INITIAL POSITION WAS BASED ON THE ABOVE ANIMATION AND A 052306Z AMSR-E MICROWAVE IMAGE SHOWING A WELL-DEFINED, EXPOSED LOW LEVEL FEATURE DETACHED FROM THE HIGHER REFLECTIVITY CONVECTION. THE INITIAL INTENSITY WAS BASED ON CONGRUENT DVORAK ESTIMATES FROM PGTW, KNES, AND FMEE. UPPER LEVEL ANALYSIS INDICATES THE CYCLONE IS TO THE SOUTH OF THE RIDGE AXIS IN AN AREA OF MODERATE (15-20 KNOT) NORTH-WESTERLY VERTICAL WIND SHEAR (VWS). IT IS CURRENTLY TRACKING ALONG THE SOUTHERN PERIPHERY OF A BUILDING RIDGE TO THE EAST. AS TC IRINA'S VERTICAL STRUCTURE CONTINUES TO REDUCE, A LOW-LAYER RIDGE EXTENDING FROM THE CAPE OF GOOD HOPE WILL NUDGE THE CYCLONE EQUATORWARD AFTER TAU 12 AND CONTINUED EXPOSURE TO MODERATE VWS WILL DISSIPATE THE SYSTEM BY TAU 36. THE AVAILABLE NUMERICAL GUIDANCE IS IN OVERALL AGREEMENT WITH THIS TRACK FORECAST WITH WBAR AS THE SOLE OUTLIER PROJECTING A CONTINUED LINEAR EASTWARD MOTION. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 060000Z IS 16 FEET.

- JTWC + CIMSS

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