Why in news
A shear zone runs over the south peninsular India, and a cyclonic circulation lies over the southeast Arabian Sea off south Kerala in the middle troposphere level.
Strong westerly winds are also prevailing along the Kerala coast.
Under its influence, the State is likely to experience widespread rainfall accompanied by thunderstorms, lightning, and gutsy winds with a speed of 30–40 kmph during the next seven days, says IMD
Westerlies & Impact on India
Westerlies are wind patterns that move from the West to the East
In both hemispheres, westerlies blow from the mid-latitudinal high-pressure belt to the subpolar low-pressure belt.
They go from the southwest to the northeast in the Northern Hemisphere.
They blow from the northwest to the southeast in the Southern Hemisphere.
Compared to the westerlies in the Northern Hemisphere, the westerlies in the Southern Hemisphere are stronger and more reliable.
On the onset of the South-West Monsoon, The location of ITCZ shifts north and south of the equator with the apparent movement of the Sun.
During the month of June, the sun shines vertically over the Tropic of Cancer and the ITCZ shifts northwards.
The southeast trade winds of the southern hemisphere cross the equator and start blowing in southwest to northeast direction under the influence of Coriolis force.
These winds collect moisture as they travel over the warm Indian Ocean and rains over India
Shear Zone
A shear zone is a monsoon weather feature that is an area filled with opposing winds concentrating heavy rain in that zone.
An east-west shear zone located 10 degrees north over the southern peninsula is a vertical zone.
It can prevail either in the lower, middle or upper atmospheric levels — allows active winds of high speeds to interact.
This zone also allows monsoon winds to remain active, thus causing intense rainfall over the area under its influence.
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