Dhaka: Bangladesh has been experiencing excessive rainfall since the pre-monsoon period this time due to westerly disturbance and persisting active monsoon over the country, demonstrating unusual behavior of climate, say meteorologists.

They said the higher amount of rainfall was recorded during the pre-monsoon time -- March, April and May -- this year compared to several years in the last decade due to westerly disturbance which they said a freaky behavior of the nature.

As the monsoon is active over the Bangladesh this year, the meteorologists said, the country has been receiving a high rainfall during the traditional monsoon period as well since June and the trend continues.

"Heavy rainfall may continue to occur at different parts of the country until August 17, aggravating the current flood situation here further," said Omar Farroque, a meteorologist at the Bangladesh Meteorological Department (BMD).

He said over 300 mm of average rain were recorded within 12 days of this August, which is very higher than the normal rainfall. "The country was supposed to receive 403 mm of average rain throughout the month. Around 371 mm average rain was recorded all through August in 2016."

Abul Kalam Mallik, another BMD meteorologist, said monsoon in Bangladesh spans over four months--June, July, August and September--while light rainfall usually starts occurring after the Bangla month of Baishakh.

"This year the rain started before the Baishakh. We experienced downpour even in March, an unusual pattern," he said.

BMD senior meteorologist Abdul Mannan said the country has been receiving an excessive precipitation this year due to 4-5 depressions formed over the Bay of Bengal during the pre-monsoon period and persisting active monsoon since June, a trend that has not been seen in the past decade.

He said Chittagong and Sylhet regions have been experiencing unusual amount of rainfall over the last few years as well as this year. "The unusual behaviour of the weather is a major reason behind it."

The meteorologists, however, are unwilling to call it a cause of climate change effect without an extensive research on climate variability or examining the 50 years' rainfall pattern of the country.

But, they fear that country's weather pattern is going to be more unpredictable in the future as the nature is showing its strange behaviour.

They also viewed that although the country is receiving excessive precipitation, it has less contributions to frequent floods this year as waters from the upstream are mainly responsible for flooding in the downstream.

According to Met office statistics, the country's average rainfall was recorded 622 mm in July which is 32.7 percent higher than the normal rainfall. The country experienced 557.8 mm average rainfall last year during the period.

In June this year, 457 mm average rain was recorded in the country, which is 3.7 percent higher than the normal rainfall and 144 mm higher than last year's.

The average precipitation was 16 percent lower than that of normal rain in the country in May this year while it was 106 percent higher in April and 152 percent higher in March.

Contacted, eminent climate expert Dr Atiq Rahman said the country is receiving higher rainfall this season than the previous years. "The 50 years' record-breaking rainfall was recorded in April this year. "This is surely an unusual behaviour of the climate."

He said the global temperature is rising gradually as the 2015 was the warmest year in the history of the earth while the 2016 was warmer than 2015. "So, there's no doubt that temperature has increased in Bangladesh as well, which is one of the reasons for the rise in rainfall here."

"We don't find equilibrium in temperature, humidity and rainfall. We call it erratic behaviour of climate, which is casting adverse impacts on agriculture, ecosystem and biodiversity," Atiq observed.

Another Climate expert Dr Ainun Nishat said the country's this year's rainfall is not very unusual. "The other countries in the region like India, China and Myanmar are receiving very excessive rain this year, which is a major reason for frequent flooding in the downstream Bangladesh."

He said Bangladesh may face a severe flood in the coming days as the monsoon is very active over the upstream countries of the region.