|
|
|
  |
| Sunday, 1 May 2005 |
 |
|
 |
News |  |
| News Business Features Editorial
|
Meteorologists promise monsoon comfort by K. R. Abhayasingha, Director, Department of Meteorology The disaster that occurred on 26th December last year is the worst in the history of Sri Lanka when the intensity and the resulted damage are concerned. It claimed for more than 40,000 lives and property damage of billions of rupees in a short time like two hours. Tsunamis come once in a century or so. But natural hazards like Monsoons, cyclones, thunderstorms, tornadoes, easterly waves an depressions are common weather events in a year's cycle of weather in Sri Lanka. Therefore, with the bad memories of the last tsunami, we should be ready to face possible natural disasters that come with other weather phenomena. Southwest monsoon rains are to come within a few weeks easing off the warmth that made us very uncomfortable during the first inter monsoon season in March-April. The southwest monsoon may come as a burst under the influence of a low-pressure area or a depression or instead it may establish over our country quietly, usually during the third week of May. It is normal for the southwest monsoon to stay with us for nearly four months, June to September, moisturizing the island with monsoon rains. Most of the monsoon rains experience in the southwest quarter. Weather is the most blamed in the world, as it does not behave the way we want it to and it has extremes, which are disruptive and hazardous. Even though the monsoon weather, particularly the rains, is vitally wanted and expected, monsoon weather has its bad and hazardous effects too. Most of the southwest monsoon rain will be confined to the south west quarter of the island. But under influence of a low-pressure area or a depression in the Bay of Bengal, rains may widespread over many parts of the country while a major part of the precipitation falling in the southwest quarter. During this monsoon, southwesterly wind streams that usually start from the high-pressure regime in the Madagascar region will blow across Sri Lanka towards low-pressure areas in North Indian landmass. Southwesterly wind profile up to a vertical height of about 6-8 km will bring a lot of moisture from the Indian ocean to make the lower atmospheric levels well moist to form rain bearing clouds covering the southwest quarter of the island. With a good monsoon wind flow with speeds exceeding 40 kmph, the moist air is dragged to central hilly region to form not only shallow clouds but also huge clouds called cumulonimbus as a result of the orographic effect over the hills. Under such situations showers or thundershowers are experienced over the hill country bringing fairly heavy rain to hydro catchment areas. Under certain circumstances, prevailing wind sometimes pushes the thunderstorms to the eastern side of the hills making Uva and eastern provinces wet with evening/early night thundershowers. The monsoon blowing is so strong that the wind shear between surface and
upper levels will result in mixing the atmosphere around us. This makes the
atmosphere a little cooler and comfortable unlike the uncomfortable stagnant
atmosphere in March-April season with high moisture concentration. |
|
| News | Business | Features
| Editorial | Security
| Produced by Lake House |
