Monsoon is a seasonal circulation of winds that creates long lasting thunderstorms and heavy rains with significant rainfall totals. Monsoons occure during the summer, when the land is warmer than the ocean. This causes air to rise over the land and air to blow in from the ocean to fill the void left by the air that rose.
Because of its effect on agriculture — among other effects — the monsoon is one of the most anticipated, tracked, and studied weather phenomena in the region.
Here’s the perfect monsoon circulation. 3 main components clearly seen (watch the video below).
- Heat low over northwest India
- Typical monsoon trough
- Mascerene high over south Indian Ocean.
Pressure gradient between Mascerene high and Indian land mass is the main driving force for Monsoon.
Easterly flow south of equator becomes southwestrly along Somalia coast carrying copious amount of moisture from Arabian sea over land.
While another branch of the monsoon flow over Bay of Bengal becomes northeasterly forming monsoon trough.
There are so many factors affecting monsoon. This current situation just so perfect but doesn’t guarantee what’s in future.
One more important component of the Monsoon is Tibetan anticyclone at 200 hPa.
Now you’ve got an idea why forecasting monsoon is so difficult.
Scientist (Retired), Center for Climate Change Research, IITM. Follow me on Twitter