Severe flooding in Sri Lanka

Severe flooding in Sri Lanka

15 May 2016 00:00–12:00 UTC

Severe flooding in Sri Lanka
Severe flooding in Sri Lanka

Pre-monsoon heavy downpours caused widespread, severe flooding in Sri Lanka in mid May 2016.

Last Updated

22 October 2020

Published on

15 May 2016

By Ian Mills and Jochen Kerkmann (EUMETSAT)

The heavy rains were caused by a large area of low pressure that formed in the southern Bay of Bengal on Thursday evening.

It was reported in 24 hours up 06:00 UTC on 15 May 144 mm of rainfall was recorded in Pottuvil, on the eastern coast of the island. Meanwhile Colombo, the capital city of Sri Lanka had 128mm — a third of the city's average May rainfall in just one day.

The Meteosat-7 infrared image from 15 May 03:00 UTC (Figure 1) shows a large storm cloud over the east of Sri Lanka.

 Meteosat-7 infrared 15 May 03:00 UTC
Figure 1: Meteosat-7 infrared 15 May 03:00 UTC

The Meteosat-7 infrared animation , 15 May 00:00–06:00 UTC shows the development of large severe storms over Sri Lanka associated with the developing tropical storm.

The bright white area expanding over Sri Lanka shows rapidly developing very cold cloud tops. Very cold clouds tops are associated with severe storms leading to heavy rainfall and consequent flooding.

The enhanced infrared animation , 15 May 00:00–12:00 UTC highlights the very cold cloud tops of the storm clouds (orange, yellow and blue). The blue colour indicates extremely cold cloud tops, signalling the likelihood of severe storms at the surface.

In the visible imagery animation , 15 May 01:30–11:30 UTC, at around 04:30-05:00 UTC small shadows can be seen cast on the cloud below from the overshooting tops These overshooting tops indicate very vigorous updrafts in the cloud. This too is a signal of severe storms at the surface.

The BBC reported on 18 May that at least 32 people had been killed in flooding on Sri Lanka, according to official figures, with nearly 350,000 people displaced.

More than 200 families were feared to have been buried in mudslides that hit three villages in central Kegalle district.

On the INSAT-3 Day Microphysics RGB images (Figure 2) the development of a cyclone in the days after it hit Sri Lanka can be seen.

The system, officially named Tropical Cyclone 01b (later Cyclone Roanu), moved northwards along the east coast of India bringing heavy rains to eastern India.

Image comparison

Image from 19 May compare1
compare2
 

Figure 2: Comparison of INSAT-3 Day Microphysics RGB images from 17 May and 19 May. Full resolution image, 17 May . Full resolution image, 19 May .

Addendum

Cyclone Roanu was the first tropical cyclone of the 2016 North Indian Ocean season. Between 18-21 May it followed a northeastward track just off the east coast of India, moving over very warm waters (30–31º C). It failed to rapidly intensify due to moderate amounts of deep-layer wind shear.

On the INSAT-3D Infrared Window (10.8 µm) imagery , 17–21 May you can see a number of convective bursts with a large areal coverage of cloud-top IR brightness temperatures colder than -90ºC (Source: CIMSS Blog).

 

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