The wait for monsoon 2016 is almost over, weathermen have said. 

India Meteorological Department (IMD), in its bulletin on Thursday, said the southwest monsoon was most likely to hit the state in another two to three days. 

Patna meteorological centre director Ashish Sen told The Telegraph on Thursday that the monsoon was expected to foray into Bihar through the north-eastern part by the weekend — June 18 to be specific. 

The sky has been overcast from Wednesday evening and it has been raining intermittently in some places of the state for the past few days. 

In the run-up to monsoon 2016 in the city, The Telegraph tries to answer some of your queries about the rain-bearing winds: 

 

What exactly is the monsoon wind? 

Simply put, it is a wind pushed from the sea to the land. The phenomenon starts towards the end of summer. Being rich in moisture, this wind causes clouding and rain in most parts of the country between June and September.

 

Till where has the monsoon reached? 

The northern limit of monsoon — an imaginary line drawn on the map by meteorologists to mark till where they deem the wind has reached — has touched the Northeast and parts of Darjeeling in north Bengal by Tuesday. It further advanced till Gangtok by Wednesday but it did not 
show further progress on Thursday. The monsoon has been stuck over the northern Bay of Bengal for a few days before reaching the Northeast and north Bengal. 

 

When will it reach Bihar?

The IMD’s mid-day bulletin on Thursday stated that conditions were favourable for further advance of southwest monsoon into remaining parts of central Arabian Sea, Konkan and Goa, some parts of south Chhattisgarh, central Maharashtra, Marathawada, remaining parts of north interior Karnataka, Rayalaseema and coastal Andhra Pradesh, some parts of Telangana, remaining parts of Bay of Bengal and some parts of Odisha, Gangetic Bengal, Jharkhand and Bihar during next two to three days. The normal date of arrival in Bihar is June 10 and 12. However, it is making delayed onset in Bihar since 2010.

 

Many places in north Bihar and even Patna have been receiving intermittent rain and the sky has been mostly cloudy for a few days. Then, why is it not monsoon in Bihar? 

Rainfall is just one of the parameters the weather department takes into consideration before declaring the 
arrival of monsoon. Most other conditions have not yet been fulfilled. 

 

What are the conditions?

Patna Met chief Ashish Sen claimed that six aspects of the weather are factored in to confirm the onset of the monsoon.

The criteria are: 

Spatial distribution of rainfall: The rainfall has to be regular not just at a particular place but at most places, between it and the last point on the map till where the monsoon has progressed. “Though the eastern and north-eastern parts of the state are receiving light to moderate rainfall, it is not continuous. We observe the spatial distribution of rainfall for 3-4 days to determine whether this condition is being fulfilled,” said Sen.

Depth of the south-westerly wind: The north-westerly wind of summer has to give way to south-westerly wind and it has to blow at a height of at least 3.1km. Met chief Sen claimed though the south-westerly component is a criterion for majority of the country but easterly winds play a major role in bringing monsoon rains through the north- eastern parts of Bihar. 

Rainfall distribution: At least 65 per cent of a region has to get more than 2.5mm rain before the Met office declares that the monsoon has arrived there. 

Cloud movement: The monsoon wind comes from the southwest in most parts of the country but places like Bihar in eastern India arrives from the northeast. 

Temperature: The maximum temperature during monsoon has to remain around and below the normal mark. Patna and many other parts of the state, especially north Bihar, fulfil this criteria for the past couple of days. 

Incoming solar radiation: The solar radiation should comparatively reduce owing to obstruction from cloud cover and high level of moisture in the atmosphere. 

The Met office expects Bihar to meet all the parameters related to the onset of the monsoon by the weekend.