Published on 30 Oct 2015

Cyclone Chapala could bring years of rain to Yemen and Oman in days

A powerful cyclone has formed in the Arabian Sea and is set to make landfall close to the border of Oman and Yemen early on Monday (local time), with a significant threat to life and property.

Cyclone Chapala is currently equivalent to a category four hurricane and if it reaches category five, which is possible, it would be one of the strongest cyclones on record in the Arabian Sea.

Cyclones are exactly the same as hurricanes and typhoons, it’s just that different parts of the world describe them differently.

chapala_sat_CIMSS_wp

Whilst the Arabian Sea commonly has a few cyclones each year, there are none on record that have made landfall at hurricane strength in Yemen, according to NOAA’s historical hurricane track database.

Cyclone Chapala – small but perfectly formed

At the moment, Cyclone Chapala is over the very warm waters of the Arabian Sea, with sustained winds of 155mph and gusts of around 190mph.

The reason for the storm developing so quickly is the warmer than average sea water in this part of the world at the moment – 2 to 3C warmer than normal in places.

sst_arabiansea_NOAA_wpWarm waters provide the fuel on which these tropical storms thrive, so when the waters are warmer than normal, the available energy increases.

In addition, the weather conditions high up in the atmosphere have been favourable for the storm to flourish, providing an outflow of air aloft, leading to the storm strengthening.

However, as the storm approaches the coast of Oman and Yemen, it will rapidly weaken, as drier air gets drawn into the storm.

Nevertheless, as a part of the world that sees these kinds of storms make landfall infrequently, the impacts could be devastating locally.

Years’ worth of rain possible in days

Although the storm will lead to damaging gusts of wind along the coastline, as well as a storm surge, the most dangerous element of Cyclone Chapala will be the amount of rainfall it will deliver.

A narrow zone in the far east of Yemen and just over the border into Oman could see around 500mm of rain fall in a few days.

chapala_track_JTWC_wp

Whilst weather records are extremely difficult to obtain for Yemen, in neighbouring Oman, Salalah typically sees 100mm of rain in a whole year.

So, 500mm – five years’ worth of rain – falling in the space of a few days will cause devastating flash floods – especially as it falls on dry, hard ground.

Parts of the landscape that are normally desert-like will quickly turn into raging torrents of water, threatening lives, property and infrastructure from significant damage.

It is worth adding that cyclones in this part of the world are notoriously difficult to forecast, as their relatively small size means they are highly susceptible to small changes in atmospheric conditions.

Even so, the threat is certainly there for some people to experience amounts of rainfall that they will probably never see again in their lifetime.

Images: CIMSS, NOAA, JTWC

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