150300Z POSITION NEAR 25.9S 83.7E. TROPICAL CYCLONE (TC) 15S (GINO), LOCATED APPROXIMATELY 1275 NM SOUTH-SOUTHEAST OF DIEGO GARCIA, HAS TRACKED SOUTHEASTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY SHOWS THAT THE LOW-LEVEL CIRCULATION CENTER (LLCC) HAS STARTED TO ELONGATE AND DEEP CONVECTION IS NOW SHEARED 30NM FROM THE LLCC, INDICATIVE OF THE BEGINNING OF EXTRA-TROPICAL TRANSITION (ETT). A RECENT 150006Z SSMIS 91GHZ MICROWAVE IMAGE ALSO DEPICTS THE BEGINNING OF ETT, AS THE DEEP CONVECTION HAS BECOME CONFINED TO THE SOUTHEAST QUADRANT AND DRY AIR IS BEGINNING TO WRAP AROUND THE SYSTEM. THE INITIAL POSITION IS BASED UPON A BROAD LLCC IN THE MICROWAVE IMAGE WITH FAIR CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 50 KNOTS WHICH IS SLIGHTLY LOWER THAN CONGRUENT DVORAK CURRENT INTENSITY ESTIMATES OF 55 KNOTS FROM PGTW AND FMEE. TC 15S IS FORECAST TO TRACK SOUTHEASTWARD ALONG THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE AND CONTINUE TO ENCOUNTER STRONG (40 TO 60 KNOTS) VERTICAL WIND SHEAR (VWS) AND COOL SSTS (24 TO 25C), WHICH WILL FURTHER WEAKEN THE SYSTEM. TC 15S WILL CONTINUE ETT THROUGH TAU 12 AND COMPLETE ETT BY TAU 24. THE DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT WITH THIS SCENARIO, THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK. DUE TO THE STRONG VWS AND COOLER SST, THERE IS A POSSIBILITY THAT THE SYSTEM WILL WEAKEN BELOW 35 KNOTS PRIOR TO COMPLETING ETT. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 150000Z IS 18 FEET.
- JTWC + Eumetsat
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