TROPICAL CYCLONE 12S (GIOVANNA), LOCATED APPROXIMATELY 490 NM SOUTHEAST OF ANTANANARIVO, MADAGASCAR, HAS TRACKED NORTH-NORTHWESTWARD AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) REVEALS THAT THE LOW LEVEL CIRCULATION CENTER (LLCC) BECAME COMPLETELY EXPOSED OVER THE PAST 12 HOURS AS THE DEEP CONVECTION WAS STRONGLY SHEARED DOWN STREAM. AS A RESULT OF THIS DE-COUPLING THE LLCC IS NOW BEING STEERED SLOWLY EQUATORWARD UNDER THE INFLUENCE OF A LOW- TO MID-LEVEL ANTICYCLONE LOCATED OVER EASTERN SOUTH AFRICA. THE CURRENT POSITION IS BASED ON THE EXPOSED LLCC IN MSI WITH EXCELLENT CONFIDENCE. THE CURRENT INTENSITY IS ASSESSED AT 45 KNOTS BASED ON THE DVORAK ESTIMATES FROM PGTW AND KNES. ANIMATED WATER VAPOR IMAGERY DEPICTS THE QUICK DEMISE OF TC 12S. UPPER LEVEL ANALYSIS INDICATES THE LLCC REMAINS SOUTH OF THE SUBTROPICAL RIDGE AXIS AND IS UNDER 30-40 KNOTS OF VERTICAL WIND SHEAR (VWS). DUE TO THE DE-COUPLING OF THE LLCC, THE FORECAST HAS NOW CHANGED TO A NORTH-NORTHWESTERLY TRACK, WITH CONTINUED WEAKENING OVER THE NEXT 24 HOURS DUE TO SUSTAINED HIGH VWS AND DRIER AIR. TC 12S IS FORECAST TO BE BELOW TROPICAL STORM STRENGTH BY TAU 24. THE MAJORITY OF THE NUMERICAL MODEL GUIDANCE TRACKS THE SYSTEM EASTWARD UNDER THE INFLUENCE OF AN ANTICYCLONE TO THE NORTH THAT IS BEING SPUN UP BY TC 13S. THE ECMWF AND UKMO MODELS CORRECTLY PICKED UP ON THE LLCC SEPARATION AND SUBSEQUENT NORTHWARD MOVEMENT. THEREFORE, THE FORECAST IS HEAVILY BIASED TOWARDS THESE MODELS VICE CONSENSUS. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 201200Z IS 18 FEET.
- CIMSS + JTWC
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