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The tropical cyclone Roanu formed from a cyclonic vortex north of Sri Lanka and moved along the Indian coast and finally made landfall in Bangladesh. A huge landslide in Sri Lanka caused more than 90 deaths after three consecutive days of heavy rain (http://www.bbc.co.uk/news/world-asia-36355980). Mass The worst rainfall seems to have happened on 15 May. Later mass evacuations took place along Indian and Bangladeshi coasts. The vortex seems to have been associated with an MJO event. The cyclone took place a the same time as a heatwave in western India 201605 - Heatwave - India.
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In the early stages of the cyclone development in Sri Lanka we have noted a large region with wind increments in the lower troposphere covering most of the Bay of Bengal at the begin of the 4DVar window 17@21. The adjustment of the wind field affects not only the circulation near the tropical depression but also the large scale monsoon circulation to south and east of the Bay of Bengal. The inset box shows the analysis of winds at 850 hPa valid at 18@00.
3.2 HRES
The plots below shows the 24-hour accumulated precipitation for 15 May 00z to 16 May 00z from HRES forecasts from difference initial times.
3.3 ENS
The plots below show the forecast of tropical cyclone activity 20-22 May. In early forecast the highest probabilities were for the cyclone to be on the western side of India but changed on the 16 May to mainly be on the eastern side.
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The plots below show the EFI and SOT for rainfall valid 14-16 May; the period when flash floods took place in Sri Lanka.
The plots below shows the same as above but only for 15 May:
The plots below shows the probability of more than 150 mm precipitation on 15 May from different initial times:
The plot below shows the 24-hour precipitation from ENS and HRES valid 15 May for a point east of Colombo (7N, 80E):
3.4 Monthly forecasts
The plot below shows the verification of precipitation anomaly for 9 May to 15 May (left) and 16 May to 22 May (right).
The plots below show the MJO forecasts:
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- Shift from west-coast to east-coast around 16 May.
6. Additional
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