Signs of Seasonal Shift – Peeping Westerlies

Weather Update

Time & Tide waits for None, goes the proverb, similarly seasons also wait for none though it runs at its own pace coming early a few years & coming late a few years but they do check in as expected every year. As April gives way to May the weather bloggers of Indian Sub continent start looking for cues that could indicate the arrival of Southwest Monsoon. In some ways the person who possibly started this trend was Mr. Rajesh Kapadia, Godfather of the Indian Sub Continent, who started tracking monsoon progress for his Vagaries Weather Blog.

His staggered Monsoon updates were pretty much a milestone driven monsoon progress charting various factors like Mascarene High, Pressure Gradient over North India etc. Though Southwest Monsoon as such does not provide direct rains to places like Chennai, being a rain shadow region, it is always exciting for weather bloggers to track the progress. One of the first things which we look forward in the short term is to see the arrival of Cross equatorial Westerlies which is a key component of the Southwest Monsoon Jigsaw. Wind charts indicate cross equatorial westerlies are slowly showing up near the Horn of Africa and is expected to strengthen in the days to come.

With the influence of ITCZ now seen extending north of Equator its only a matter of time the rainfall events over Peninsular India will improve in both spatial nature & also intensity. The Kingmaker, Maden Julian Oscillation, is also expected to arrive over the western parts of Indian Ocean in a couple of days. This will further enhance the conditions not only for rainfall events but also the strengthening of Cross Equatorial Westerlies thereby setting up the platform for Southwest Monsoon to reach the Andaman Islands in a couple of weeks time.

On the short term front rains are expected to continue along the Western Ghats with with places in South Karnataka likely to see heavy spell of rains today evening. As the westerlies strengthen the LWD will shift further East bringing thunderstorms over the interior parts of Tamil Nadu before the arrival of Southwest Monsoon.