Low Forms Over Bay, But Flood-Hit North Odisha Gets a Breather; Heavy Rain Shifts to Mahanadi Belt| Exclusive

Bhubaneswar: A fresh Low Pressure Area (LPA) formed over Northwest Bay of Bengal and its neighbourhood on Sunday morning. The national weather forecaster further added that the associated cyclonic circulation extends upto 7.6 km above mean sea level tilting southwestwards with height.

The big concerning factor here is how the low pressure area will impact Odisha, especially the flood-battered zone of northern Odisha – Baleswar, Keonjhar, Bhadrak, Jajpur and Mayurbhanj.

An analysis of the IMD'sdescription of a southwest tilt with height drops the big hint on how it is going to pan out on flood-hit zone of the State.

Though it signifies that a mature, developing monsoon low-pressure system in the Bay of Bengal, it also drops big hints on exactly where the heaviest rainfall will hit.

What Hints It Drop?

As the IMD describes that the cyclonic vortex leans toward the southwest as it go higher into the atmosphere (up to 7.6 km), it also suggest that the strongest cloud development, moisture convergence, and upward vertical motion are displaced.

The consequence: the heaviest rainfall will not fall directly over the Northwest Bay; it will be pushed southwest of the center – directly into central and southern of flood-battered districts of Odisha. More so, the tilt suggest that system is strong enough to sustain. It explains that the system is drawing on two distinct air masses to keep itself alive and growing:

• The Hot/Dry Air aloft coming from the northwest (north India/Pakistan).

• The Cool/Moist Monsoon Current coming from the southwest (Arabian Sea).
  The boundary between these two types of air creates temperature and moisture gradients fueling the system, helping the cyclonic circulation extend deep into the upper atmosphere.

• Also, it suggests that as it matches the broader upper-level winds, the system is embedded in a strong easterly/southeasterly jet, which in turn will be steering the system on a west-northwestward path across Odisha and into Chhattisgarh over the next 24 to 48 hours.

Measuring The Impact

Going by the configuration of the low prssure system, the rainfall footprint of the LPA is expected to remain south of the flood-hit belt of Baleswar, Mayurbhanj, Keonjhar, Jajpur and Bhadrak, sparing these districts from another spell of intense rainfall.

Instead, the weather system is likely to concentrate its rain over central and coastal Odisha before shifting westwards, bringing heavy rainfall to districts including Puri, Bhubaneswar, Cuttack and the Mahanadi basin in western Odisha.

This is an important distinction at a time when north Odisha is already grappling with the aftermath of flooding.

A low-pressure area over the Bay would normally raise fears of another deterioration in the flood scenario. But the projected track and rainfall distribution suggest that the current system will pass too far south to load the flood-hit northern river basins with another major spell of rain.

Forecast inputs show the heaviest rainfall footprint over the downstream and central Mahanadi belt, including the coastal-central districts, before the system moves inland towards western Odisha and the upstream Mahanadi catchments extending into Chhattisgarh.

The immediate weather impact is therefore likely to be felt more strongly over Puri, Khordha, including Bhubaneswar, Cuttack, Jagatsinghpur and adjoining central districts. As the low moves west-northwest, the heavy rainfall zone is expected to shift towards Sambalpur, Jharsuguda, Bargarh, Subarnapur, Deogarh and parts of Sundargarh, bringing the Mahanadi catchment into focus.

IMD has also hoisted a red warning till Morning hours of August 24. It predicts, “Heavy to Very Heavy Rainfall at a few places with Extremely Heavy Rainfall at one or two places very likely to occur over the districts of Kataka, Anugola, Dhenkanal, Kalahandi, Nabarangpur.”

Breather for North Odisha

For north Odisha, however, the current system could offer a temporary weather window. The forecast places Baleswar, Mayurbhanj, Keonjhar, Bhadrak and Jajpur on the northern periphery of the low, where rainfall intensity is expected to be substantially lower than over central and western Odisha.

That means the current Bay low is unlikely to trigger a fresh deterioration in the flood conditions over the northern Odisha districts that have already witnessed rising rivers and inundation.

Point To Be Noted

The concern instead shifts to the Mahanadi system, where rain could arrive first over the downstream central-coastal plains and then over western Odisha and the upstream catchments.

The weather system, therefore, presents a different kind of flood equation for Odisha. North Odisha may escape the heaviest rain, but the Mahanadi catchment will have to absorb a two-stage rainfall spell – first over the downstream belt and then over the western and upstream catchments.

In short, it is a low over the Bay, but not another direct weather blow for flood-hit north Odisha. The heavier rain threat this time is expected to shift towards central coastal Odisha and western Odisha, particularly the wider Mahanadi basin.
Also Read: Fresh Low Pressure Around Aug 24 Threatens More Rain; North Odisha May Remain in Flood Grip Till August-End| Exclusive