Direction Interrégionale de LA REUNION
B.P.4    97491 Ste Clotilde Cedex
Téléphone                02.62.92.11.00
Fax exploitation      02.62.92.11.48
Fax direction           02.62.92.11.47

RSMC / TROPICAL CYCLONE CENTRE / LA REUNION TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN) 0.A WARNING NUMBER : 8/4/20072008 1.A TROPICAL DEPRESSION 4 (0420072008) 2.A POSITION 2007/12/14 AT 0600 UTC : WITHIN 20 NM RADIUS OF POINT 14.0S / 69.6E (FOURTEEN DECIMAL ZERO DEGREES SOUTH AND SIXTY NINE DECIMAL SIX DEGREES EAST) 3.A DVORAK ANALYSIS : 2.5/2.5 /D 0.5/24 H 4.A CENTRAL PRESSURE : 999 HPA 5.A MAX AVERAGE WIND SPEED (10 MN) : 30 KT 6.A EXTENSION OF WINDS BY QUADRANTS (KM): 30 KT NE: 045 SE: 045 SO: 045 NO: 045 7.A FIRST CLOSED ISOBARE (PRESSURE / AVERAGE DIAM): 1004 HPA / 900 KM 8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: MEDIUM 1.B FORECASTS: 12H: 2007/12/14 18 UTC: 14.3S/69.4E, MAX WIND=030KT, TROP. DEPRESSION. 24H: 2007/12/15 06 UTC: 14.6S/68.9E, MAX WIND=030KT, TROP. DEPRESSION. 36H: 2007/12/15 18 UTC: 15.1S/67.8E, MAX WIND=030KT, TROP. DEPRESSION. 48H: 2007/12/16 06 UTC: 15.7S/66.5E, MAX WIND=040KT, MODERATE TROP. STORM. 60H: 2007/12/16 18 UTC: 16.5S/65.0E, MAX WIND=040KT, MODERATE TROP. STORM. 72H: 2007/12/17 06 UTC: 17.2S/63.4E, MAX WIND=040KT, MODERATE TROP. STORM. 2.B OTHER INFORMATIONS: T AND CI=2.5- THE LLCC IS EXPOSED AND THE LOCATION HAS A GOOD FIX. THE SYSTEM UNDERGOES A MODERATE NORTHESARLY VERTICAL WINDSHEAR WHICH EJECTS DEEP CONVECTION SOUTHWESTWARDS. NEVERTHELESS, THIS LLCC SHOWS A LIGHLY IMPROVED ORGANIZATION, WHAT EXPLAINS THE UPGRADED INTENSITY TO THE TROPICAL DEPRESSION STAGE WITH NEAR GALE FORCE WINDS NEAR THE CENTER. DUE TO THE VERTICAL WINDSHEAR AND THE STANDSTILL OF THE SYSTEM, CONDITIONS ARE NOT FAVORABLE FOR AN INTENSIFICATION. MOREOVER, THE LOW LEVEL CONVERGENCE REMAINS POOR DUE TO WAKE TRADEWIND INFLOW (TROUGH TO THE SOUTH), AND ONLY MODERATE UPPER LEVEL DIVERGENCE. THE SYSTEM REMAINS CAUGHT BETWEEN COMPETING STEERING INFLUENCES, SOUTH OF THE EQUATORIAL WESTERLIES NORTHWARD (WELL ESTABLISHED UP TO 400 HPA) AND A SUBTROPICAL MIDLEVEL RIDGE SOUTHEASTWARD. BEYOND THE NEXT 36 HOURS, THE SUBTROPICAL RIDGE IS EXPECTED TO PROGRESSIVELY "TAKE THE LEAD" ON THE CONTRIBUTION OF THE STEERING FLOW, WHAT SHOULD ALLOW A FASTER SOUTHWESTWARDS MOTION, AS A LIGHT INTENSIFICATION DUE TO A TEMPORARY WEAKENING OF THE VERTICAL WINDSHEAR.