Tropical waves govern Monsoon intra seasonal oscillations across the globe. In this MJO plays a very key role modulating the strength of the monsoon. Additionally MJO along with ER many a times is the trigger for cyclogenesis during post monsoon periods. Over the past few months there has been a battle royale between MJO and the Base state. As we transition from El Nino to La Nina MJO has been struggling to put together a cohesive movement. Often we have seen a break down of MJO as it tries to propagate towards the Western Hemisphere.
For the first time in two months a fresh MJO pulse has emerged over the Indian ocean passing through Africa. Late June we saw MJO emerge over Indian Ocean from Africa but struggled against the base state eventually collapsing over over the Maritime Continent. The next couple of months has seen MJO confined to a weak state as it tried to move across the Western Hemisphere. Initially weather models were expecting a strong amplitude MJO to move across Indian Ocean. Over the past few days gradually the amplitude forecasts are showing a reduction in intensity. It remains to be seen is a sign of one more collapse of MJO over the Maritime Continent. In the interest of a robust NEM it may be essential MJO completes one global circuit before SWM gives way to NEM.
After a couple of weeks of above active thunderstorms monsoon it is now time to look back to monsoon dynamics. The last couple of days the daily rainfall over TN & PDC is near normal after 10 days of excess rains. With the arrival of MJO over Indian Ocean gradually monsoon dynamics will pick up in pace. Wind charts indicate a transition from the chaotic state to a more streamlined Westerlies gradually from today. This in turn will bring about a slow return of rains over the west coast. At the same time it will also reduce thunderstorm possibilities over the leeward areas of Tamil Nadu.
We will take one week at a time and see how much can Monsoon push up the seasonal average with this phase of active monsoon dynamics.Wind charts indicate southern parts of Kerala may see stronger westerlies from today. Parts of South Kerala and Kanyakumari district in Tamil Nadu may see widespread rains with few places coming under very heavy rains. The persisting cyclonic circulation over interior Peninsular India is likely to bring about another day of thunderstorms over the region. Parts of North Karnataka, adjoining areas of AP & TS states and interior Maharashtra may benefit from these thunderstorms.
With westerlies gradually coming in we may see better chances for thunderstorms over coastal areas like Chennai. Towards the end of the week there is a high chance North Coastal TN including Chennai may see one or two days of moderate thunderstorms. Afternoons though will continue to remain hot under clear skies.