Sunday, 13 January 2013

Tropical Storm Activity: South Indian Ocean (13 January 2013)

Tropical Cyclone 09S (Nine)  - Issued at 12/2100Z




TROPICAL CYCLONE (TC) 09S LOCATED APPROXIMATELY 545 NM EAST-
SOUTHEAST OF DIEGO GARCIA HAS TRACKED WESTWARD AT 01 KNOT, 
EXHIBITING QUASISTATIONARY MOVEMENT.  ANIMATED INFRARED SATELLITE 
IMAGERY DEPICTS A CONSOLIDATING SYSTEM WITH IMPROVED DEEP CONVECTIVE 
BANDING WRAPPING INTO A WELL-DEFINED LOW-LEVEL CIRCULATION CENTER 
(LLCC). A 121427Z SSMIS MICROWAVE IMAGE WIND PRODUCT SHOWS 30 TO 35 
KNOT WINDS LOCATED IN THE FORMATIVE BANDING TO THE SOUTH. BASED ON 
THIS, AND OVERALL IMPROVED STORM STRUCTURE, THE INTENSITY IS 
ASSESSED AT 35 KNOTS. UPPER LEVEL ANALYSIS REVEALS TC 09S IS LOCATED 
SLIGHTLY EQUATORWARD OF THE SUBTROPICAL RIDGE AXIS AND VERTICAL WIND 
SHEAR HAS DECREASED TO MODERATE (10-20 KNOT) LEVELS ALLOWING FOR THE 
RECENT IMPROVEMENT. TC 09S IS CURRENTLY LOCATED IN A WEAK STEERING 
ENVIRONMENT BETWEEN THE STEERING INFLUENCES OF THE LOW TO MID-LEVEL 
NEAR EQUATORIAL RIDGE AND SUBTROPICAL RIDGE (STR). TC 09S IS 
FORECAST TO REMAIN NEARLY QUASISTATIONARY FOR THE NEXT 24 HOURS AS 
IT SLOWLY INTENSIFIES. AFTER TAU 24, TC 09S WILL SLOWLY TRACK MORE 
SOUTHWEST AS THE MID TO DEEP LEVEL SUBTROPICAL RIDGE TO THE 
SOUTHEAST BECOMES THE MORE DOMINANT STEERING INFLUENCE AND CAUSE A 
MORE WESTWARD TRACK THROUGH TAU 120. TC 09S WILL STRUGGLE TO 
INTENSIFY THROUGH THE FORECAST AS VWS WILL REMAIN AT MODERATE LEVELS 
AND INCREASE TO STRONG LEVELS IN THE LATER TAUS. DYNAMIC MODEL 
GUIDANCE IS WIDELY SPREAD BUT GENERALLY AGREES ON SLOW TRACK TO THE 
SOUTH TO SOUTHWEST AND SLOW INTENSIFICATION. DUE TO THIS POOR 
AGREEMENT AMONG THE MODELS, FORECAST CONFIDENCE IS LOW. MAXIMUM 
SIGNIFICANT WAVE HEIGHT AT 121800Z IS 12 FEET.
 
- JTWC + Eumetsat 

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