Direction Interrégionale de LA REUNION
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RSMC / TROPICAL CYCLONE CENTRE / LA REUNION TROPICAL CYCLONE FORECAST WARNING (SOUTH-WEST INDIAN OCEAN) 0.A WARNING NUMBER : 9/3/20072008 1.A SEVERE TROPICAL STORM 3 (BONGWE) 2.A POSITION 2007/11/20 AT 1200 UTC : WITHIN 30 NM RADIUS OF POINT 11.6S / 74.0E (ELEVEN DECIMAL SIX DEGREES SOUTH AND SEVENTY FOUR DECIMAL ZERO DEGREES EAST) 3.A DVORAK ANALYSIS : 3.0/3.5 /W 0.5/12 H 4.A CENTRAL PRESSURE : 985 HPA 5.A MAX AVERAGE WIND SPEED (10 MN) : 50 KT 6.A EXTENSION OF WINDS BY QUADRANTS (KM): 30 KT NE: 100 SE: 150 SO: 250 NO: 250 50 KT NE: 030 SE: 030 SO: 030 NO: 030 7.A FIRST CLOSED ISOBARE (PRESSURE / AVERAGE DIAM): 1010 HPA / 700 KM 8.A VERTICAL EXTENSION OF CYCLONE CIRCULATION: DEEP 1.B FORECASTS: 12H: 2007/11/21 00 UTC: 12.1S/72.7E, MAX WIND=040KT, MODERATE TROP. STORM. 24H: 2007/11/21 12 UTC: 12.5S/71.6E, MAX WIND=040KT, MODERATE TROP. STORM. 36H: 2007/11/22 00 UTC: 12.8S/70.8E, MAX WIND=050KT, SEVERE TROP. STORM. 48H: 2007/11/22 12 UTC: 13.0S/70.1E, MAX WIND=050KT, SEVERE TROP. STORM. 60H: 2007/11/23 00 UTC: 13.1S/69.7E, MAX WIND=050KT, SEVERE TROP. STORM. 72H: 2007/11/23 12 UTC: 13.1S/69.2E, MAX WIND=050KT, SEVERE TROP. STORM. 2.B OTHER INFORMATIONS: T=3.0 AND CI=3.5 "BONGWE" IS SUFFERRING TODAY IN ONE HAND WITH SOME SLIGHT EASTERLY WIND SHEAR BUT MORE PROBABLY WITH SOME INTRUSION OF DRY AIR FROM THE WEST AS IT CAN BE CLEARLY SEEN IN THE MIMIC-TPW PRODUCT FROM CIMSS ...CONSEQUENTLY, CURRENT INTENSITY HAS BEEN LOWERED TO 50 KT. THE BIG QUESTION FOR THE INTENSITY FORCAST IS TO KNOW IF THE DRY AIR INTRUSION IS JUST TEMPORARY OR NOT .... PRESENT FORECAST CALL NOW FOR A SLIGHT DECREASE IN STRENGH FOR THE NEXT 24 HOURS THAT SHOULD BRING BACK "BONGWE" TO MODERATE TROPICAL STORM STATUS THEN AN INCREASE TO SEVERE TROPICAL STORM STATUS AGAIN. TRACK HAS BEEN NEAR DUE WEST DURING THE LAST SIX HOURS, SO GUIDANCE HAS BEEN ADJUST TO THE RIGHT. AFTER DAY 1, SOME RELIABLE MODELS (AS GFDN, GFS) SLOW DOWN A LOT THE SYSTEM AND EVEN RECURVE THE TRACK SOUTH-EASTWARDS AS "BONGWE" COULD BE AGAIN ON THE INFLUENCE OF THE MID-LEVEL RIDGE THAT IS STILL NORTH-EAST OF THE SYSTEM. THE PRESENT GUIDANCE DOESN'T REFLECT THIS SCENARIO BUT STILL FOLLOWS THE ECMWF AND EPS TRACKS WITH A WESTWARDS TRACK, BUT SLOW DOWN "BONGWE" AT DAY 2 AND 3.