During the 1st fortnight of February the weather discussions in Peninsular India mostly revolve around winter. Some parts of Peninsular India start looking at the first hint of Summer to come in. But it is indeed rare for discussions to move towards a potential tropical disturbance. But that is exactly what we looking at this year. In yesterday’s All India Weather Bulletin IMD has indicated a LPA is likely to form over SE Bay on 15th February.
The UAC currently seen over the Equatorial waters and adjoining SE Bay is expected to deepen into an LPA. The rare development of a tropical disturbance in February in part is under the influence of a pair of tropical waves. An ER Wave has been traversing across Indian Ocean from East to West. After a long time we are seeing a fresh pulse of MJO traversing across Indian Ocean as well.
This West to East movement of MJO across Indian Ocean towards maritime continent has provided a window for a rare LPA during February. Off season disturbances are a challenge for weather forecasters across the globe. The absence of adequate historical data is a handicap for decision making. This also makes it difficult for ML weather models that lean a lot on historical data. Physics based models face a different struggle of trying to estimate the factors and its respective influences.
At this point in time there is a good agreement in the LPA forming over the next 48 hours. Ensembles are in agreement about a westward drift from SE Bay to SW Bay in the next 120 hours. Subsequently there is a very high degree of divergence in intensity estimates. This divergence is also reflecting in track forecasts as well. The role of MJO and whether presence of remnant influence of ER is going to influence events during this period. Keeping this in mind it may be wise to wait for a couple of more days before looking at impact.
In all this talk about the LPA it is easy to miss out on something else sneaking in. Summer is all set to check in over parts of South and interior areas around West and Northwest TN. Irrespective of the LPA developing in the coming days afternoon temperatures are likely to increase over South TN. Already Peninsular west coast has started seeing summer conditions with increasing afternoon temperatures.
Places in Kanyakumari, Tirunelveli, Tenkasi districts may start seeing afternoon temperatures increase from today / tomorrow. This will herald the onset of summer over these areas. Gradually interior areas of TN may also start seeing an increase in afternoon temperatures. Coastal TN between Chennai and Delta need not worry yet about summer. These places join the party much later.