Cyclone HEROLD: Reunion spared, Mauritius affected

Through Quentin PERCEROU, editor
Posted on 03/13/20, updated on 3/15/20 at 6:04 a.m.-
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A tropical depression has formed in the northeast of Madagascar. According to current forecasts, this depression, named HEROLD, has a strong potential for development in tropical cyclones. Reunion Island and especially Mauritius are threatened.

The cyclonic season in the southwest Indian Ocean has a jagged activity, with calm phases and violent jolts of activity. One thinks in particular of the month of November, virgin of any system, and in the month of December when two systems, Ambali and Belna, were born at the same time. The first of them, Ambali, even became a very intense tropical cyclone, with average winds of 220 km / h over 10 minutes.

Since the end of January, apart from the anecdotal tropical cyclone Gabekile, no system in sight. The cyclone truce ended on Friday with tropical storm Herold, which lies northeast of Madagascar.

Storm Herold: the future tropical cyclone

Currently, tropical storm Herold is located 750 km northwest of the Reunion coast. The estimated system pressure, one of the important indicators for estimating the power of a tropical system, is 985 hPa. The lower this value, the more powerful the system will be. The satellite images allow us to observe a significant convection and a low pressure winding characteristic of an ongoing cyclogenesis and intensification.

#Meeting : the moderate tropical storm #Herold is strengthening and should reach the stage of #cyclone Sunday. Reunion Island threatened by this phenomenon? Our article —> https://t.co/MONXRprY9y pic.twitter.com/xyLcFty3r2

– The Weather Channel (@lachainemeteo) March 14, 2020

During this weekend, this tropical storm is getting stronger and will turn into a cyclone Sunday.

Evolution and planned trajectory

This storm “Herold” Sunday reverses its trajectory in the east-southeast, towards Reunion and Mauritius. And as the tropical storm encounters conditions favorable to its intensification, with warm water of 29 ° C and a variation in altitude winds in direction as in low speed, this allows the future cyclone Herold to organize itself well.

Consequences for Reunion and Mauritius

Given the current trajectory, this tropical system passes as close to the islands Sunday and Monday. For the time being, the expected impacts are moderate because this tropical system remains far from the coastlines of Réunion. But just because the system will be remote doesn’t mean it won’t be without consequences.

Thus, the Reunion coastlines experience a significant cyclonic swell. On Monday, the waves could reach 3 to 4 meters on the north and east coasts. It is mainly Mauritius that is impacted, with waves that can reach 5 to 7 meters.

In connection with this system, thunderstorm showers occur on Reunion, especially in the southeast. These showers do not bring significant cumulative rain. On the other hand, Mauritius, located as close as possible to Herold’s trajectory, suffers from heavy rain until Monday, increasing the risk of floods for this island.

Reunion is therefore outside the zone of strong winds according to current forecasts. Mauritius, on the other hand, will experience gusts of 130 km / h when this future tropical cyclone passes near its coastlines on Monday. It will also be necessary to follow the evolution of the trajectory for Rodrigues which could encounter difficult conditions.

Finally, we draw attention to the fact that you should regularly follow the update of this article. The trajectory planned at this time seems globally reliable as well as the future intensification of the system. However, variations in the current scenario cannot be excluded.