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Archive for the ‘Weather & Climate’ Category

Still chilly

Cold weather (relatively colder than before) is prevailing since the beginning of the week. Strong winds accompanied by intermittent rainy periods are causing a sensation of chill, especially on high grounds. Temperature has fallen below normal.

In the western parts of the island as we move from the centre towards Port Louis and the vicinity, it’s much better. I just came back from Domaine les Pailles where the Infotech 2007 event (an annual expo of the IT sector) is being held. It was quite warm with a pleasant sun. Here in the central plateau, where I am, it’s still kind of chilly.

The meteorological services say two strong anticyclones to the south of the mascarenes will maintain the cold weather and gusts of the order of 60 km/h. Seas will be rough and people are advised not to venture in the high seas. The weather should improve as from Monday.

So keep your pulls and blanket handy till then.

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Wind chill

Everybody’s shivering since yesterday. True it’s winter time; but it’s not that cold. The lowest temperature recorded last night was 13.7 deg C on the central plateau (middle and higher region of the island). It was hardly one degree below normal. Night temperature has often dipped to 10 degrees C in the past.

Day temperatures recorded yesterday varied from 21 to 27 deg C, about 2 degrees below normal during this period. However, south easterlies are blowing at an average speed of 25 km/h peaking at 50 or 60 at times, bringing in cold air from the South Pole. And the sea is rough beyond the reefs with waves of the order of 3 meters high.

This is a typical situation due to a strong anticyclone to the south east of the mascarenes. Anticyclones are common in winter and they bring along strong winds, rainy and cold weather most of the time. Although temperatures may be within the range of normal for the period, you feel colder than expected. It’s a sensation of cold due to what is called wind chill or often referred to as wind chill factor.

Wind chill relates to a condition of enhanced feeling of cold due to the combined effect of temperature and wind speed in a relatively dry air. It is usually lower than the actual air temperature. For instance, for an actual temperature of 15 deg C together with a dry wind of 40 km/h, you may have a sensation of 10 deg C. The reason why you can see everybody draped in loads of woolen pulls, coats, scarves, caps and huge jackets. No way can you have a good night’s sleep without double blankets. And while I’m at my keyboard my fingers are virtually numb.

It will become more comfortable by the end of the week as the anticyclone moves away eastwards. That’s what the local meteorological services are forecasting.

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Temperature slightly above normal during the day; normal during the night in the first half of the season; and below normal during the night in the second half of the season. Minimum temperature may on some occasions reach 8 to10 degrees Celsius in conditions of light wind and clear sky.

Rainfall slightly below normal. Ditto for average wind speed.

Temporary wet and chilly conditions giving rise to a sensation of extreme cold with strong anticyclones causing fresh South Easterly trade winds to blow over the mascarenes in July and August.

Those are the forecasts for Mauritius and Rodrigues as indicated by the Mauritius Meteorological Services in its 2007 Winter Seasonal Outlook released last week. They are based on various meteorological conditions prevailing on global, regional and local scales, like El Nino and La Nina oscillations, pressure pattern, jet stream location and intensity, sea surface temperature, and the Indian monsoon; and on model forecasts from Global Long Range Forecast Centres.

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The phenomenal waves that hit our island last weekend are expected to subside. Among the six missing, four were found dead. They were pushed ashore by the waves. One body was found partly eaten by sharks.

In view of the occurrence of unfamiliar and unexpected natural phenomena these days, the government has decided to review measures to mitigate consequences. A warning system similar to that for cyclones will be established to alert people on the likelihood of waves of such magnitude as was experienced last week. The communications system will be enhanced for a more effective collaboration and coordination among such authorities as the Meteorological Services, the Police and the National Coast Guard.

In the meantime coastal dwellers are requesting aid from the Government for compensation of loss of their housing and belongings.

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An unprecedented tidal wave hit the mascarene islands on Saturday night. Waves with average height of 5 to 6 metres and peaks of 10 to 11 metres caused considerable damage to coastal habitations. These coincided with the high tides at 10.30 pm. Eight persons are reported missing, one in Mauritius, five in Rodrigues and two in Reunion Islands.

Information from the Meteorological Services reveal that these waves have been caused by an extra-tropical storm some 2000 km to the South of the Mascarenes. With a central pressure of 950 hPa it may be compared to intense tropical cyclone Gervaise which hit Mauritius in 1975 when a maximum gust of 175 km/h was recorded. Extra-tropical depressions are common during this transition period to winter which is also characterized by strong anticyclones to the south. The southern coasts have been mainly affected.

Some people thought it was a tsunami. But tsunami is a different phenomenon. It is triggered by earthquakes in the deep seas. Its waves travel over very long distances. They can enter several meters inland with devastating effects. Tidal waves occur at the surface of the sea as a result of strong sustained winds.

Although this time the waves have been phenomenal, tidal waves have been observed in the past in 1915, 1976, 1987 and 1995 during similar periods of the year. It is therefore not a new phenomenon as some people tend to believe.

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Will it chill?

We are now in the transition period to winter, here in Mauritius. Nice period; getting cooler as we plunge into the middle months of the year, although on some days it’s like in summer. The cyclone season will be officially over on 15 May. The next will start on 01 November.

In winter we have strong anticyclones with central pressure of the order of 1040 hPa. When this occurs it’s chilly; time for the loads of furry blankets, jackets and pull-overs. The temperature may fall to a minimum of 10 to 11 deg C at certain places in the central plateau. While the normal minimum turns around 15 to 18 deg C. OK it’s not like what others in the higher latitudes would experience. But when you are used to an average temperature varying between 20 to 30 deg C, a drastic fall below 15 is something.

Strong south easterly winds blowing from the south poles may gust to 50 km/h, even higher at times. The period is often characterized by deficient rainfall.

It’s also the sugar cane harvest season. But nowadays the amount of sugar cane plantation has considerably decreased with the end of the Sugar Protocol which guaranteed a quota on the European market. Several acres of land have been converted into commercial undertakings. Huge buildings are mushrooming in areas where sugar canes sprung. A considerable number of sugar cane employees have been made redundant with the Voluntary Retirement Scheme (VRS). This scheme provides for enhanced compensation and a plot of land in return for loss of employment. Redeployment is not always possible due to ageing.

It seems that the remaining sugar plantation will be used to produce ethanol. There’s already a test going on in the south with a big factory.

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Human health is vulnerable. It becomes even more vulnerable when climate and weather change. The effects of such change are becoming more evident. Reports indicate that the mean surface temperature of the earth has risen by nearly 1oC over the last century. And the rise is expected to progress, with definite impacts on sea-level rise, weather behavior and ozone layer; which means greater vulnerability to life on earth.

Extremes of temperatures and weather events are known to give rise to high risks of heat and cold-related illnesses, even deaths, and to imbalances in the ecological systems. They lead to high incidence of vector-borne diseases, diarrhoeal and other infectious diseases, injuries, psychological disorders and deaths, and damage to infrastructure. Resulting biological impacts of air pollution including pollens and spores cannot be underestimated. Their incidence on conditions of asthma, allergic and respiratory disorders can have fatal consequences. Studies show that dust mite growth is optimal at a temperature of 25oC and a humidity of 75%.

In Western Europe the heat waves of summer 2003 caused some 35 000 extra deaths. France alone counted 15 000 fatalities. The most affected population included older people above 70, mainly women.

Change in precipitation will bring about water-related health issues. Natural disasters like floods and droughts; diet and nutrition problems; increase in plant pests resulting in increase in pesticide use and pesticide intoxication are some of the concerns that would need to be addressed.

Sea-level rise will inevitably provoke displacement of population and damage to infrastructure thereby increasing the risks of infectious diseases and psychological disorders with precarious hygiene and habitation conditions.

Ozone hole has already been identified in the Antarctic and ozone depletion in the Arctic region. This will lead to increased exposure of people to ultraviolet radiation with dangerous consequences. Skin diseases and cancer, eye diseases and cataract, and immune system suppression are likely to threaten the human health to a greater extent. Reports from the World Health Organization (WHO) indicate that every year some 60 000 people are killed around the world as a result of excessive exposure to the sun. Out of this figure malignant melanomas and skin carcinomas account for about 48 000 and 12 000 respectively

With this background the socio-economic dimensions of climate change are multifold. Public health consequences including mental health, nutritional impairment, and civil strife are but a few issues that will polarize more and more attention. Action needs to focus on effective prevention strategies integrated into well-designed preparedness planning systems. Accurate and timely weather forecasts, a sound understanding of the health effects, information and advice to the population, and targeting the most vulnerable groups are vital in order to be able to mitigate the far-reaching consequences of global climate and weather change.

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