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Sanjeev Kumar Patro

Bhubaneswar: When Odisha has been witnessing the initial moments of  Covid-19 second wave, the IMD's Regional Specialised Meteorological Centre (RSMC), the niche cyclone tracking agency for the entire north Indian Ocean, has today hoisted an alert of low-pressure area (LOPAR) in the south-east Bay of Bengal (the Andaman seas).

For people in Odisha, the LOPAR has only revived the ghastly memories of the last two consecutive years when the State witnessed the fury of devastating cyclones - Fani and Amphan - during the peak summer month of May in 2019 and 2020.

Given that context,  how the new low-pressure area that has been predicted to take shape by around April 4 in Andaman seas, will pan out for Odisha? Will 2021 join the list of cyclonic years of 2019 and 2020?

WILL BAY OF BENGAL SEED A CYCLONE IN 2021?

While the IMD's latest bulletin reveals that a cyclonic circulation persisting over the Southeast Bay of Bengal (BoB) and adjoining Andaman Seas, and the system has the important weather feature of vertical extension, the country's lead met agency, therefore, made a forecast that by April 4, a LOPAR will take shape in the region.

The moot point is will this LOPAR grow up to become the first tropical cyclone of 2021? And If it's so, what threat it will hold for Odisha and India?

As per the data available with Indian National Centre for Ocean Information Services (INCOIS), while the sea Surface Temperature (SST) for the whole of BoB is remaining above 26 degree Celsius, the SST in the LOPAR area has been measured high at around 32 deg C.

Moreover, the Madden Julian Oscillation (MJO), which is in the weak phase now, will enter into the strong phase from April 1. An IITM (Indian Institute of Tropical Meteorology) MJO analysis says the coming phase of MJO will aid convective activity and may aid the low pressure to gain strength. The rain-bearing phase of MJO will remain till April 7.

As the LOPAR will take shape by April 4, the strong phase of MJO till April 7 may help the LOPAR to become well marked, says the analysis.

A CYCLONE THEN A REALITY SOON?  

As per US-GFS model data available, a LOPAR will come into existence at around midnight of April 1 and the central pressure of the system has been estimated to remain at around 1002 millibar.

There has been a rare unanimity among all models - IITM's (India) CGEPS (Climate Forecast System-based Grand Ensemble Prediction System), US-GFS (Global Forecast System) and ECMWF (European Centre for Medium-Range Weather Forecast).

All the models give a very low probability of the LOPAR growing into a tropical cyclone.

THE MODEL PREDICTION

As per the US-GFS model, there is a high probability that the system will grow up to a tropical depression only. Moreover, the prediction is the system will head towards Myanmar. The system is unlikely to chart towards the Indian mainland, the model predicts.

Similarly, the ECMWF prediction clearly mentions that the system will not grow up to become a cyclone. The model of this top-rated global met agency predicts the system to grow into a well-marked low pressure or a depression. It predicts with over 70 per cent probability that the system will chart the Myanmar way. (see the image below)

The CGEPS model of IITM, a peer Indian agency, also assigns a very low probability to the system getting developed into a cyclone. It assigns a probability of 30 per cent only, which is considered very low.

WILL APRIL SEED ANY MORE CYCLONE?   

As per the long-range model forecast of ECMWF and IITM's CGEPS, there is nil probability of any cyclone genesis in the Bay of Bengal (BoB) till April 22.

However, what needs to be mentioned here is Odisha faced the cyclone fury in the month of May for two consecutive years. Though the prediction on sea surface temperature has no such cyclonic clues, still the scenario will become crystal clear by mid-April only.

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