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 : 19/4/20072008 1.A TROPICAL DEPRESSION 4 (0420072008) 2.A POSITION 2007/12/17 AT 0000 UTC : WITHIN 20 NM RADIUS OF POINT 18.5S / 63.2E (EIGHTEEN DECIMAL FIVE DEGREES SOUTH AND SIXTY THREE DECIMAL TWO DEGREES EAST) 3.A DVORAK ANALYSIS : 2.5/2.5 /S 0.0/18 H 4.A CENTRAL PRESSURE : 997 HPA 5.A MAX AVERAGE WIND SPEED (10 MN) : 30 KT 6.A EXTENSION OF WINDS BY QUADRANTS (KM): 30 KT NE: 050 SE: 200 SO: 300 NO: 050 7.A FIRST CLOSED ISOBARE (PRESSURE / AVERAGE DIAM): 1006 HPA / 1300 KM 8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: MEDIUM 1.B FORECASTS: 12H: 2007/12/17 12 UTC: 19.3S/61.7E, MAX WIND=035KT, MODERATE TROP. STORM. 24H: 2007/12/18 00 UTC: 19.9S/60.3E, MAX WIND=035KT, MODERATE TROP. STORM. 36H: 2007/12/18 12 UTC: 20.1S/59.1E, MAX WIND=030KT, TROP. DEPRESSION. 48H: 2007/12/19 00 UTC: 20.2S/57.8E, MAX WIND=030KT, TROP. DEPRESSION. 60H: 2007/12/19 12 UTC: 20.1S/56.5E, MAX WIND=025KT, TROP. DISTURBANCE. 72H: 2007/12/20 00 UTC: 19.8S/55.3E, MAX WIND=025KT, TROP. DISTURBANCE. 2.B OTHER INFORMATIONS: THE SYSTEM HAS ACCELERATED OVER THE LAST 6 HOURS, AS IT TRACKS ALONG THE NORTHWESTERN EDGE OF THE SUBTROPICAL RIDGE CENTRED IN THE SOUTHEAST. THE SYSTEM STILL SHOWS A SHEAR PATTERN. NORTHEASTERLY WINDSHEAR MAINTAINS THE LLCC PARTIALLY EXPOSED NORTH-EAST OF THE DEEP CONVECTION THAT HAS SOMEWHAT CONSOLIDATED OVER THE LAST 24 HOURS. THE SYSTEM TRACKS SOUTHWESTWARDS TOWARDS A MID-LATITUDE TROUGH SOUTHEAST OF MADAGASCAR. AVAILABLE NWP ARE IN GOOD AGREEMENT WITH A SOUTWESTWARDS TRACK FOR THE NEXT 24 HOURS BECOMING WESTWARDS AT A SLOWER SPEED AS THE TROUGH SHIFTS IN THE SOUTH, AND THEN WEST-NORTHWESTWARDS AS THE SUBTROPICAL RIDGE REBUILDS. PRESENT FORECAST CLOSELY FOLLOWS THE DYNAMICAL AIDS CONSENSUS. ENVIRONMENTAL CONDITIONS ARE RATHER UNFAVORABLE. IN ADDITION OF THE WINDSHEAR, ENVIRONMENT, ESPECIALLY AT THE LOWER LEVEL, IS DRY AS DEPICTED BY MICROWAVE IMAGERY. LOWER CONVERGENCE IS ONLY PRESENT ON THE TRADEWIND SIDE. NEVERTHELESS, AS THE SHEAR IS STILL FORECAST TO SLIGHTLY WEAKEN WITHIN THE NEXT 12 TO 24 HOURS, A SLIGHT INTENSIFICATION TO MINIMAL TROPICAL STORM STAGE IS STILL EXPECTED. THEN A WEAKENING IS EXPECTED WITH COOLER SST, A STILL DRY ENVIRONMENT AND WEAKER LOWER LEVEL CONVERGENCE (AS THE MID-LATITUDE TROUGH PASSES SOUTHWARD). WINDS EXTENSION IS ESTIMATED ACCORDING TO 1704 UTC ASCAT SWATH.