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Low over Bay of Bengal triggers six-day rain outlook
A fresh low-pressure area formed over the north-west Bay of Bengal on Sunday, extending a chain of tropical disturbances. The IMD has issued a six-day heavy rainfall outlook across many states.
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A fresh low-pressure area formed over the north-west Bay of Bengal on Sunday, extending what is shaping up as an unbroken chain of tropical disturbances feeding into India's monsoon trough. The system sits at the downstream end of a conveyor belt running deep into the western Pacific.
Satellite imagery Sunday morning showed three tropical systems arranged across that basin. Typhoon Saudel headed toward the east China coast. Tropical Storm Narra lingered off Vietnam. Tropical Depression 19 spun east of the Philippines. All three have tracks with a westerly or north-westerly component, the kind of movement that sends waves of atmospheric energy across Indochina and into the Bay, where the monsoon circulation can give them a second life.
The immediate suspect behind the new Bay low is Narra. Forecast to hover near the Vietnam coast until Wednesday, it could help shepherd further inbound circulations through the coming week, the India Meteorological Department said. Saudel briefly showed ambitions of becoming a category-5 super typhoon over the central Pacific before weakening to a category 3 on approach toward the Taipei-east China coast sector. Its associated atmospheric pulse also contributed.
The larger backdrop is a Pacific that remains exceptionally warm. The heat, associated in part with the El Niño pattern in the equatorial and eastern Pacific near the South American coast, has extended across the central Pacific and deep into the western Pacific, which appeared particularly warm on Sunday. Farther west, sea-surface temperatures have cooled closer to the east China coast, a likely factor in Saudel's weakening as it nears land.
The monsoon trough Sunday morning stretched from Ferozpur through Karnal, Bareilly, Lucknow and Ranchi, then passed through the centre of the new low over the north-west Bay and ran south-eastward into the east-central Bay. That alignment leaves the door open for disturbances arriving from across Indochina to plug directly into the monsoon circulation. A predecessor low over north-east Madhya Pradesh, which has been carrying much of the monsoon workload in recent days, has weakened and ceded centre stage to the newborn Bay system.