With monsoon having ramped up itself to being vigorous over the past few days, weather watchers have started wondering if there is a La Nina signature embedded into it.

About one in two La Nina events (the latest in the series being the strong event witnessed last year) are expected to redevelop the following year.

LA NINA REPEAT?

Last year had seen flooding rains spread over northwest India and into Pakistan as the cooling phenomenon in the equatorial east Pacific peaked.

The event has been known to drive up the performance of an ongoing Indian monsoon but with no direct cause-effect relationship.

The Australian Bureau of Meteorology (BoM) has said in the latest update that a rain-friendly Madden-Julian Oscillation (MJO) wave is in the process of transiting the Indian Ocean from west to east.

A periodic perturbation of atmospheric pressure in the higher levels, the wave has alternating wet and dry phases with concomitant impact on ground weather.

MJO WAVE

The BoM has said that over the past week, the MJO event has developed in the Indian Ocean, and has tracked east towards South China Sea/northwest Pacific.

Guidance from climate models suggest that the MJO will continue to track east, but weaken as it crosses the Bay of Bengal.

The ongoing heavy to very heavy rains can directly be attributed to the MJO wave, with a low-pressure area being freshly thrown up over Saurashtra and Kutch on Tuesday.

This is even as predecessor ‘low' persisted over northwest and adjoining west-central Bay of Bengal persisted from overnight off the Orissa and Andhra Pradesh coasts.

LIKELY CONVERGENCE

Both the formations are heading to converge and set up a combined trough across west and central India over the next day or two while sustaining the rainfall.

The trough is forecast to be gulped up by a bigger westerly trough approaching in from across the northwest border and could sustain the rain until Monday next subsequent to which the rains could relent.

A weather warning issued by India Meteorological Department on Tuesday said that isolated heavy to very heavy rainfall would occur over Gujarat, Konkan, Goa, Madhya Maharashtra, coastal Karnataka and Kerala during the next two days.

Isolated heavy rainfall has been forecast over Orissa, north coastal Andhra Pradesh, south Chhattisgarh and Vidarbha during this period.