The onset of southwest monsoon over south Andaman Sea last (Saturday) night was masterminded by raging super typhoon Dolphin in the northwest Pacific.
The super typhoon is now the predominant weather system under the command area of the larger Asian monsoon and has been instrumental in ratcheting up wind speeds over not just the northwest Pacific but also the Indian Ocean.
What it does is pull the monsoon winds off the equator and guide them in as they turn in from a southwesterly direction off the Somali coast (Arabian Sea arm of the monsoon) and south Bay of Bengal (Bay arm).
Large Pacifc and Indian ocean basins spanning tens of thousands of sq km form apart form an extended area of influence under a single monsoon system for all practical purposes.
This is why the southwest monsoon is considered a planetary phenomenon, the largest and most spectacular arm of which is the one that plays over the Indian subcontinent.
The onset phase in the Bay is forecast to hold strong over the next two to three days in tandem with the peaking of the super typhoon.
The system would start weakening to the south of Japan when the activity over the Bay of Bengal is forecast to peak over.
Wind speeds in the central Bay of Bengal would have touched beyond 50 km/hr before this happens, forecast outlook says.
During this phase, heavy to very heavy rains over south peninsular India would have shifted to northeast India and adjoining east India, Bangladesh, Myanmar and adjoining western Thailand.
Winds are forecast to wind down over the Bay by May 23/24 and heavy rain over south peninsula would lift by that time.
The cross-equatorial monsoon flows that turn off the Somali coast and those in the Bay may start picking up again post May 25, as per these forecasts.