Tuesday, December 08, 2009

‘Suppressed rain phase' may lift in South later this week

A suppressed phase of the periodical Madden-Julian Oscillation (MJO) wave, a weather-maker or -breaker alternatively, is just about preparing to leave equatorial Indian Ocean and the adjoining southern Indian peninsula.

The MJO wave travels in the upper level of the atmosphere and suppresses rainfall during its dry phase, as is being concurrently witnessed over the region.

According to international weather models, an MJO-neutral phase would set in next ahead of the wet MJO phase associated with raised convection of the seawater, cloud-building, condensation and precipitation.


This phase would see weather activity being triggered on the surface of the sea, which would be propagated to the mainland in phases. Cyclonic circulations, low-pressure areas and easterly waves would get activated during this phase.

In its update on Monday, the India Meteorological Department (IMD) said that isolated showers were recorded over Tamil Nadu and Kerala during the 24 hours ending in the morning.

This trend is forecast to hold over the next few days before shifting gear from Thursday, according to an IMD outlook.

Sunday's cyclonic circulation over southwest Bay of Bengal in lower levels persisted and a trough from this extended up to east-central Bay of Bengal.

This cyclonic circulation over southeast and adjoining southwest Bay of Bengal is now expected to move west-north-west.

The IMD outlook until Thursday spoke about the possibility of isolated rainfall over extreme south peninsular India the next two days, before scaling up thereafter.

An outlook for the North-East States said isolated rain or thundershowers are likely over the region during next the next two days.

Satellite cloud imagery showed convective clouds over parts of south Bay of Bengal and southwest Arabian Sea.


The US National Centres for Environmental Prediction has maintained its outlook for isolated to moderate showers over the southern peninsula during the week ending December 14.

But the rains are forecast to become widespread the following week (December 15 to 23), presumably supported by the wet phase of the MJO wave that would have entrenched itself over the equatorial Indian Ocean and the adjoining peninsular seas by that time.

The European Centre for Medium-Range Weather Forecasts (ECMWF), too, did not see any reason to make any drastic change to its forecast for weather for the southern peninsula, which could make gains in terms of recorded rain as the week wore on.

Presence of a western disturbance has warmed up the northwest region a bit, but this is normal weather to be expected of the season. Another western disturbance is expected to affect the western Himalayan region Wednesday, according to the IMD.

This would deny cold north-westerlies the needed space to invade the region and trigger a fall in mercury. In the bargain, warm, moist and even wet conditions are to be expected over northwest India for another three to four days, according to international models.

Rains have been indicated for northwest and adjoining central India as per this forecast.

On Monday, low to medium-high clouds were seen over parts of Jammu and Kashmir, Himachal Pradesh, Arunachal Pradesh and south peninsular India.

Maximum temperatures were near normal over most parts of the country except Assam and Meghalaya.

Minimum temperatures were above normal over many parts of Madhya Pradesh, Rajasthan and the North-East States. They were below normal over parts of Himachal Pradesh. The lowest minimum temperature of 4 deg Celsius was recorded at Amritsar.

No comments:

Post a Comment