Cyclones ahead - Be prepared
It is not too long after the second inter-monsoon, 2006 which
recorded tremendous amount of weather-related natural hazards in Sri
Lanka. With the beginning of the second inter monsoon season in the
second week of October, 2006 the country experienced the typical
hazardous weather conditions.
Torrential rain and lightning associated with thunderstorms ended up
with a calamity; death and property damage.
Weather-related natural hazards are recurrent yearly as the seasonal
climate patterns repeat every year.
We are reaching the last quarter of the year 2007. The rains fell so
far (May-Mid August) during the Southwest Monsoon season seems to be
lower than the average for the relevant period. But even with such
weather situation natural hazards were reported from a number of places.
Evolution of the earth has been undergoing long processes through
billions of years and there is no reliable proof yet to witness the
completion of the evolution. As it happened yesterday, is happening
today the evolution will continue in future.
This is common to any location or any country on the globe and as a
result, many parameters including those related to weather and weather
systems are continuously changing and fluctuating.
In addition to the natural changes, the influences of the cruel human
activities have added significant changes to the global temperature and
the climate. Global warming has already resulted in changes of climate
and increase of intensity and frequency of extreme weather events like
cyclones, Warm climate conditions, snowstorms, thunderstorms, tornadoes
and El Nino.
The large number of cyclones developed in 2005 in the Pacific and
severe cyclones which caused significant hazards in a number of parts of
the world in 2006 and 2007 signals us about the bad results of the
Meteorologists have already warned the world of development of severe
cyclones in the Pacific Ocean in coming cyclone season. Unfortunately no
one has so far disclosed the weather in the Bay of Bengal in coming
months. But we are to revise our own understanding of the weather
systems that influence weather in Sri Lanka during the second inter
monsoon season and early part of the North east monsoon.
Statistics has shown us that this is the period with high probability
of cyclones in the Bay of Bengal.
Changes of weather parameters and the extreme events were there from
the beginning of our atmosphere and they are not new. Droughts, floods,
warm climate episodes, cold episodes, cyclones, snowstorms, tornadoes
and lightning have been common and natural events on the globe in
different scales in different parts of the world in different seasons
throughout the history.
Fluctuations of weather, climate and extreme weather events have also
affected the globe during the history.
As there are clear evidences of global warming and climate change
during last few decades, the environmental scientists and meteorologists
are organizing all types of awareness programs to bring the message of
the rising trend of frequency and the intensity of hazardous weather
systems as a result of unusual warming of the globe.
It is the right of all nations to understand the real situation and
also the normal climate and weather conditions in climate seasons
leading to natural hazards. Such understanding is required in order to
mitigate those natural hazards.
Climate change is certainly not responsible for all observed
developments of extreme weather systems and their fluctuations. There
are many occasions with extreme weather situations occurring under
normal environmental circumstances. Significant changes of climatic
parameters in all time scales are normal and natural for any place or
any country on our earth.
Weather conditions expected during the coming second Inter monsoon
season and the early part of the North East Monsoon include
thunderstorms, tornadoes, low level disturbances, depressions and
Therefore we should be prepared for all the effects, preferably the
bad effects, of them. There are a number of precautionary steps that
help to, reduce or mitigate the possible Natural Disasters.
Cyclones are hazardous and they have been responsible for
considerable damage to property and life in the world and our country as
well. The severe cyclones that swept many parts of Sri Lanka in November
1978 and December 2000 are good examples.
These systems have enormous energy, more powerful than an atomic
bomb, and hazards are caused in a number of ways by strong winds, heavy
rains, storm surges and lightning.
The paths of the cyclones also show peculiar characteristics. The
cyclonic systems developing in the Northern Hemisphere move initially in
a westerly to northwesterly direction while aging and tend to re-curve
For this reason, meteorologists in the region, particularly those in
India and Sri Lanka, show a special interest to watch the cyclones that
develop in the Bay of Bengal because they move towards us while
intensification. Many parts of the Indian ocean have high probability of
giving birth to the low-pressure areas but only those develop in the Bay
of Bengal considerably influence (direct or indirect) on weather over
Diameter of a well intensified cyclone is in the order of 1000
kilometres (km) but the dimensions of the area affected by such a system
may be very much larger than 1000 km. Cloudy skies with fairly strong
winds, gusty at times, and continuous rain or thundershowers are the
normal weather conditions that prevail over many parts of the country
when we are under the influence of a cyclones centred over, or in the
vicinity of, Sri Lanka.
Coastal areas are affected by the storm surges, which are caused by
the interaction of the winds associated with a cyclone and the surface
water of the ocean. This interaction will increase the wave heights to
values of about 5 - 6 meters and such waves cross the coast into the
land. It is obvious that such waves will wash the property on the
coastal regions away to the sea on their way back.
When a cyclone is close to the island, say about 500km from eastern
coast, it may show significant influence on weather parameters like wind
and rain over the island and on waves over the adjoining sea area
Under such situations, fishermen are warned to refrain from going to
the seawaters for fishing. With the movement of such a system towards
the island the intensity of the hazardous effects will definitely
increase and all under the threat have to take all possible protection
and precaution in order to reduce hazards.
The eastern parts of the island are the most vulnerable to cyclones
that cross over or pass close our island because the strongest winds and
storm surges influence directly the eastern coastal areas. But depending
on the intensity of a cyclone and its position, other coastal areas also
may have effects of storm surges.
Many low-lying areas are directly affected by strong winds, heavy
rains and lightning and indirectly by floods. Those living in hilly
areas have to face the hazards caused by small-scale or large-scale
landslides and damages caused by fallen and uprooted huge trees.
Therefore, we should launch the precautionary steps to minimize the loss
of life and damage to property well in time.
It is our duty to take all precautionary measures that can be taken
before such an event in order to reduce and/or minimize hazards. Also we
have to be ready for cyclones and get organised to launch all necessary
steps to reduce hazards during and after a cyclone.
Since natural weather events cannot be stopped or avoided, we have
nothing other than considering and practising precautionary steps to
mitigate the hazards.
Winds, particularly strong and gusty wind streams, are associated
with low level disturbance, depressions, cyclones, thunderstorms and
tornadoes. Winds are capable in lifting and blowing off the roots of
buildings and braking and uprooting trees.
Fallen trees and their branches are responsible for most of the
tornado damages. Simple remedy is cutting the branches of vulnerable
trees and cutting or trimming the inclined and old trees to make them
resistive to strong blowing.
This is important matter to be thought seriously as the trees around
and close by buildings (preferably houses) are concerned. It is
important to note that such precautions should be and can be
successfully launched in fair weather days.
Sheet-roofs (asbestos and aluminium) have to be protected. This can
be done by clipping the sheets, bonding them properly and/or tying them
tightly with strong and heavy parts of buildings.
Hazards caused by rains
Rain has direct and indirect effects. Soil erosion, collapse of
low-grade buildings and damage to crops, particularly those in
agricultural sites, and mild earthslips are common direct effects of
heavy rains. Improper irrigation systems and blocking of canals in both
rural and urban areas have been already understood as main reasons for
this. Therefore the precautionary steps are obvious, and the remedial
steps have to be thought of during the fair weather periods.
Floods, landslides, epidemics are indirect or after effects of the
heavy and intermittent rains. Individuals and the relevant authorities
are aware of the types of precautionary steps of which majority of them
should be performed during the fair weather periods.
Hazards caused by tornadoes
Tornadoes, also products of Cumulonimbus clouds, are responsible for
a bigger percentage of the physical damages resulted by thunderstorms in
Thunderstorms with vigorous up draft and spinning winds are capable
of giving birth to tornadoes. The ultimate stage of concentration of
both cyclonic spin and energy of atmospheric motion is reached in the
If the air is particularly humid, water vapour may condense in the
core and a funnel cloud then projects down from the main cloud base.
Fresh energy is released by this condensation and the cloud may then
extend to ground level to form the tornado; the cloud column is usually
twisted hence the name 'twister' sometimes given to the phenomenon. The
intense twisters suck up small objects like dust, leaves and debris and
therefore, the twister or the funnel is seen from distant places like a
dark column stretching towards the ground.
Tornadoes average about 100 metres across. Their destructive power is
caused both by their tremendous winds, which may exceed 200kt (400 kmph),
and by the great radial gradient of pressure, which causes explosive
destruction of buildings etc., in their path. Their duration is very
variable, about 10 to 15 min on average.
The life of a tornado is as short as 10-15 min. During this time it
moves very fast, does the damage and dissipates. Therefore those who
have a close threat of a tornado should have to take precautions very
quickly in order to minimize the tornado-caused hazards. Tornadoes are
common during the inter-monsoon periods (March - April and October -
November). But their development under any circumstances with unstable
atmosphere during any season cannot be ruled out.
A number of tornadoes may be embedded within a cyclonic system too.
We have had enough natural hazards in the past and causes of such
hazards are well understood. Therefore it is not genius thing to spend
money and time unnecessarily to analyze the causes of the natural
hazards and write research papers and lengthy articles to media after
We have enough experience of fatal hazards of extreme weather events
experienced in the past. And it is dead sure that the events will
develop and affect our country in future too. What we have to do is
taking all precautionary steps in time to get prepared for the