All Seasons not active in the southwest basin since 30 years

This first part of the 2016/2017 hurricane season in the southwestern Indian Ocean basin is particularly poor in activity. In these cyclonic outlook published in mid-November, Météo France forecast a season with cyclonic activity below the seasonal average. Nevertheless, a not very active season does not mean absence of danger.

8 seasons below average over the past 30 years

The southwest basin of the Indian Ocean ranges from 30 ° E to 90 ° E and from Ecuador to 40 ° S. This vast area is under the responsibility of the Cyclone Center of la Réunion, which has the task of ensuring cyclone monitoring. In the last 3 decades (from the cyclone season 1985/86 to 2015/16), we have recorded 8 seasons for the southwestern basin with a number of systems baptized below the seasonal normal. As a reminder, the average activity is about 9 cyclonic systems per season. During these 8 seasons, it is 2010/11 that holds the record of inactivity with only 3 disturbance baptized without counting an unbaptized Subtropical Depression which evolved during the month of April 2011.

Below are the cyclone seasons below the seasonal average since the 1985/86 season. * Note that the column "unbaptized systems" corresponds to disturbances that have reached at least Moderate Storm or Subtropical Depression stage and were not baptized at the time.

1986/1987 5 1 6
1990/1991 7 1 8
1997/1998 7 1 8
1998/1999 5 1 6
2000/2001 5 2 7
2005/2006 5 2 7
2010/2011 3 1 4
2015/2016 7 1 8

Cyclones which have marked during these less active seasons

After surveying the least active seasons in the last 30 years, we wanted to see if, during these seasons, the habited lands had been relatively spared. In order to do so, we have retained only systems that have passed within 100 km of an habited region and with a minimum intensity of Moderate Tropical Storm. It turns out that of these 8 less active seasons, only 1 (2000/01) was lenient for the populations. All others have seen at least 1 system affect populated areas. Some of them even marked impress. Among the most striking are Cyclone CLOTILDA (Fev 1987), which hit Reunion hard, cyclone BELLA (Jan 1991) which swept Rodrigues or cyclone BINGIZA (Fev 2011), which caused desolation in the north-east of Madagascar. One can also speak of the case of this unbaptized Storm of February 2006 which had passed 70 km to the north of Mauritius. For reasons unknown, the Meteorological Mauritius Services did not baptize at the time, whereas the RSMC of Reunion considered that this system had at the height of its intensity reached the stage of Strong Tropical Storm. And what about 2015/16 that saw the FANTALA monster plunge the Farquhar into chaos.

Cyclone CLOTILDA à la Réunion Fev. 1987

Maintain vigilance

All these examples remind us that despite a low cyclone season, there is always a risk for inhabited lands. If the first part of this 2016/17 cyclone season turns out to be low in activity, the populations of the southwest basin of the Indian Ocean must always be vigilant and carefully monitor the hurricane current situation in the basin. With the gradual entry into the heart of the season, the cyclone risk increases. It only takes a single cyclone to transform a season that was thought calm and harmless in a nightmare season.


Source : / Meteo France


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