Brick by Brick is a phrase often used when a certain thing is done steadily and in a step by step manner. Weather dynamics also works often in a similar manner considering the complex nature of how a lot of factors interact with each other and events that happen many hundreds of kilometers away influence completely what appears to be unconnected events. For e.g. Cyclones dont develop overnight, though one could argue they might undergo a rapid change in characteristic when least expected like how Hurricane Otis underwent rapid intensification becoming the strongest landfalling Pacific hurricane on record. Large scale dynamics like Monsoon also happens in phases with things gradually falling in place over time before one sees a crescendo leading to a peak phase and a gradual decline towards withdrawal.
Though the onset of Northeast Monsoon for this year was announced by IMD on 21st October things have been weak overall so far. To give a context the deficit for Tamil Nadu & Pondicherry subdivision as on 18th October was 11% which has climbed up to 44% as of yesterday. If one were to look at Chennai district the deficit has climbed up from 65% to 77% indicating how poor NEM has been during the time onset has been announced by IMD. For the week ending 25th October only Kanyakumari was the only district to record positive anomaly with the TN & PDC sub division recording an 88% deficit during the week when NEM onset was announced. 9 districts in the state recorded nil rainfall during this week making the onset declaration even more questionable.
The good news though is Northeast Monsoon 2023 is possibly reaching the nadir of its season with the next few days likely to be the last phase of suppressed monsoon conditions. There is clear indication NEM is building its season brick by brick with support from favorable passage of a weak amplitude MJO over the Indian Ocean. Unlike the past years this year the behavior of MJO has not been text book style for the past few months with most of Southwest Monsoon period seeing MJO fight against the base atmospheric state driven by El Nino and off late Positive IOD. There is a fair possibility the upcoming couple of weeks could see similar behavior as a weak amplitude MJO passes through Indian Ocean before collapsing over parts of Maritime Continent and adjoining areas of West Pacific. In a way MJO is likely to sacrifice itself to kickstart NEM 2023 season during the middle of November.
The best example of the changing trend towards a positive phase of Northeast Monsoon is the positive anomaly rainfall chart from long term ensemble weather models during the second week of November. For the first time during this NEM season we are seeing a weekly positive anomaly chart for large parts of Peninsular India including North Coastal Tamil Nadu. This is also corroborated by the tropical disturbance probability chart which indicates reasonable activity over Bay of Bengal starting from next week when the a possible Low Pressure Area / Trough of Low could bring the first active spell of NEM 2023. Influenced by the MJO this could be followed by a couple of more disturbances during the rest of November keeping the monsoon dynamics going.
In the meanwhile for the next few days as Easterlies strengthen slowly and push away the drier winds from North we could see scattered rains over Tamil Nadu with many places over coastal areas including Chennai seeing light to moderate rains today. Places closer to the Ghats and South Tamil Nadu may continue to see rains influenced by wind instabilities along with parts of South Kerala which has seen NEM2023 compensate for the extremely poor SWM 2023.
There is no better way to summarize what is ahead for us than this Thirukural couplet from Thiruvalluvar.
கெடுப்பதூஉம் கெட்டார்க்குச் சார்வாய்மற் றாங்கே
பெய்யாமல் வாழ்வைக் கெடுக்க வல்லதும் மழை; மழையில்லாமல் வளம் கெட்டு நொந்தவர்க்கும் துணையாய் அவ்வாறே காக்க வல்லதும் மழையாகும். Rain by its absence ruins men; and by its existence restores them to fortune
எடுப்பதூஉம் எல்லாம் மழை.