Image: NOAA18 (00H39 SAST) (Nic Cronje, Nelspruit) Click on image for larger view.
170300Z POSITION NEAR 25.6S 42.7E.
TROPICAL CYCLONE 12S (GIOVANNA), LOCATED APPROXIMATELY 465 NM SOUTH-SOUTHWEST OF ANTANANARIVO, MADAGASCAR, HAD TRACKED EAST-SOUTHEASTWARD AT 05 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY INDICATES THAT THE SYSTEM HAS WEAKENED SLIGHTLY OVER THE PAST 12 HOURS WITH SIGNIFICANT WARMING OF CONVECTIVE CLOUD TOPS AND FRAGMENTED CONVECTIVE BANDING. A 162254Z AMSU IMAGE DEPICTS A WELL-DEFINED BUT BROAD LOW-LEVEL CIRCULATION CENTER (LLCC) WITH DEEP CONVECTION CONFINED TO THE SOUTH SEMI-CIRCLE. A 161832Z ASCAT IMAGE SHOWED 40-45 KNOT WINDS OVER THE SOUTH SEMI-CIRCLE. THERE IS FAIR CONFIDENCE IN THE CURRENT POSITION DUE TO THE BROAD BUT DEFINED NATURE OF THE LLCC. THE CURRENT INTENSITY IS HEDGED A LITTLE HIGHER THAN THE ASCAT HAD INDICATED BASED ON AN AVERAGE OF DVORAK CURRENT INTENSITY ESTIMATES RANGING FROM 45 TO 55 KNOTS. TC 12S IS TRACKING SLOWLY ALONG THE SOUTHWEST PERIPHERY OF A WEAK EXTENSION OF THE SUBTROPICAL RIDGE, BUILT OVER NORTHERN MADAGASCAR, AND IS EXPECTED TO CONTINUE TRACKING EASTWARD THROUGH THE FORECAST PERIOD. DYNAMIC MODEL GUIDANCE, WHICH HAD BEEN IN VERY POOR AGREEMENT, HAS NOW SHIFTED TO AN EASTWARD TRACK AND, WITH THE EXCEPTION OF GFDN, IS IN FAIR AGREEMENT. THE JTWC FORECAST FAVORS THE ECMWF TRACKER, WHICH HAS EXCELLED THUS FAR AND IS POSITIONED CLOSE TO THE MODEL CONSENSUS AS WELL. TC 12S IS FORECAST TO INTENSIFY SLIGHTLY BUT UPPER-LEVEL CONVERGENCE ASSOCIATED WITH A DEEP SHORT-WAVE TROUGH MAY HAMPER ANY DEVELOPMENT. ADDITIONALLY, LAND INTERACTION WILL SOON HINDER DEVELOPMENT AND EVENTUALLY LEAD TO DISSIPATION BY TAU 72. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 170000Z IS 15 FEET.
- JTWC
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