The Bangladesh Meteorological Department on Tuesday issued signal number three for all four maritime ports of the country after a low pressure was formed over the northwest Bay of Bengal in the morning.
The low pressure formed as a rather historic monsoon passed over Bangladesh, engulfing almost the entire country by Tuesday, four days after it first formed on the country鈥檚 southeastern coast.
Coincidence of the low pressure with the monsoon onset is an indication of an impending spell of heavy rainfall, forecasters at the BMD warned, raising alarm over potential landslides caused by very heavy rainfall for days.
鈥楢t least two days of continuous rainfall is very likely,鈥� said meteorologist Omar Faruque.
The low pressure is likely to move onto land over parts of West Bengal and Bangladesh between tomorrow night and the morning after, the BMD said, predicting a temperature drop of up to 3C during day on May 29.
The rain will occur across Bangladesh with scattered heavy to very heavy rain, the BMD said, with a heavy rainfall warning commencing this morning remaining in effect for 72 hours.
A very heavy rainfall event occurs when 88mm of more rainfall occurs in 24 hours.
The places under landslide warning are Chattoram, Rangamati, Bandarban, Khagrachari and Cox鈥檚 Bazar.
A monsoon usually occurs within the first week of June. Data released by the BMD revealed that this year the monsoon arrived earliest in 45 years, since when credible weather data is available.
The Flood Forecasting and Warning Centre in its daily weather bulletin said that there was very little chance of the forthcoming rain spell triggering flash floods.
In the past 24 hours until 9:00am on Tuesday, the FFWC said, Chapainawabganj recorded 77mm of rainfall, half of the month鈥檚 overall rainfall of 136mm.
Chapainawabganj is country鈥檚 one of the most extreme weather-hit regions, recording Bangladesh鈥檚 highest temperature often during summer and lowest temperature during winter. The border district grew rather dry.
Jaflong, a popular tourist destination in northeastern Sylhet, recorded more than three times of normal average rainfall for the month with 913mm rain recorded until Tuesday. The normal average monthly rainfall for May is 271.4mm. In over three decades Jaflong did not see so much rain in May. The historic highest May rainfall in the area was 892mm. Jaflong recorded 100mm of rain in the 24 hours until Tuesday morning.
Another northeastern area, Moheshkhola, recorded 712.6mm of rainfall until Tuesday this month, far higher than the month鈥檚 normal rainfall of 143.7mm. In the 24 hours until Tuesday morning, Moheshkhola recorded 58.3mm of rainfall.
The BMD, however, in long range forecast predicted normal rainfall in the ongoing monsoon.
In the 24 hours until 6:00pm on Tuesday, the BMD recorded Bangladesh鈥檚 highest rainfall of 98mm in Sylhet, where the country鈥檚 highest maximum temperature of 38.4C was also recorded.
The India Meteorological Department predicted below normal rainfall in Bangladesh鈥檚 adjacent region, mainly in northeast India, where monsoon days predicted to be hotter than usual.
The monsoon in India, however, started on almost equal note as it did in Bangladesh. The Times of India reported on Tuesday that Mumbai saw the wettest May in a century with 439mm rain recorded after monsoon made a historic arrival.
The IMD said that probabilistically the long-range monsoon forecast had a maximum of 58 per cent chance of materialising.