Early Kerala Monsoon Onset Likely, Bay of Bengal May Spawn A Storm

MAY 18, 2017, THURSDAY

Monsoon has already arrived in Andaman Nicobar islands. Conditions are favourable for it to reach Kerala 2-3 days before it's due gate, that is June 1. Forecast models are predicting that after hitting the state, it will progress rapidly northwards and cover Karnataka, Goa by June 2, 2017.

Meanwhile rainfall activity is going to intensify in the Bay of Bengal and southern Arabian Sea post May 20. Especially the Arabian Sea branch of the monsoon is going to go into overdrive. This will be partly because of MJO passing through the Indian Ocean presently. More on MJO later.

Though the US agency Climate Prediction Center believes the eastern Indian Ocean is going to see stormy weather in the second half of May as the Madden Julian Oscillation (MJO) is passing through the Bay of Bengal. Do not be surprised if the Bay spawns a tropical storm by month end.

You may wonder what on earth is MJO? The Madden-Julian Oscillation (MJO) is the major fluctuation in tropical weather on weekly to monthly timescales. The MJO can be characterised as an eastward moving 'pulse' of cloud and rainfall near the equator that typically recurs every 30 to 60 days. This definition is courtesy the esteemed Bureau of Meteorology.

The thumb rule is whenever MJO passes by the Indian Ocean, it throws out tropical cyclones. Or there is heavy precipitation. That is why an Arabian Sea cyclone is becoming less probable, and a Bay of Bengal cyclone more likely. Because MJO is going to pass through Bay of Bengal (part of southeastern Arabian Sea also) till May 31.

Says the CPC in it's May 15 bulletin.......

• During Week-1, the MJO may play a role in a tropical cyclone over the Bay of Bengal. During Week-2, the convective signal from the MJO is likely to be centered over the Maritime Continent. 
  

MJO will pass through Bay of Bengal till May 31. Good chance of a tropical depression/cyclone developing by May end.

MJO is currently passing through Northern Indian Ocean. Hence possibility of a Arabian Sea (low) or Bay of Bengal (high) cyclone.