Yesterday saw weather over Tamil Nadu take a decisive step towards Summer with hottest day recorded in many places across the state. Salem became the first IMD Observatory in the state to touch 100°F for the year 2018. Many observatories of the state saw max temperatures climb couple of degrees in the last week.
Under the effect of the High Pressure Zone sitting over Bay of Bengal the day time wind pattern over large parts of Peninsular India is more Southerlies than Easterlies thereby making it a relatively drier wind pattern increasing the daytime temperatures across the region. When the Easterlies are strong there is a tinge of moisture in the air as it comes from Bay modulating the day time temperatures. Yesterday the IMD Automatic Weather Station at Nungambakkam recorded lowest humidity of 26% around mid afternoon indicating the dryness in the atmosphere.
The clear skies due to the absence of any cloud influencing synoptic conditions add to the mix resulting in higher than temperatures during the day. The same clear skies and the land oriented wind pattern also plays a role in reducing the night time temperatures as well. When the winds are from the land it brings the cool conditions as land cools down faster and is much cooler than the sea during nights.
Numerical Models indicate the next 3 / 4 days is likely to see fairly cool nights across Tamil Nadu with North Interior Tamil Nadu to see abnormally cool nights. Places like Vellore, Dharmapuri, Krishnagiri are likely to see nearly 3 / 4 degrees below normal while Chennai is likely to also cool nights around 22 degrees in the absence of the modulating Easterlies during the late nights.