Elements for Life

[

] 140

XTREME WEATHER EVENTS

exert tremendous stress on

societies and economies worldwide. Civilizations have

learnt throughout the years how best to cope with their

specific, average climate. Deviations from climatic means or

average weather conditions can bring loss of life and destruc-

tion of property, in proportion to the severe or extreme

meteorological phenomena that occur. For example, extreme

rainfall (high or low) values can cause flooding or drought,

causing tremendous losses to society, agriculture and energy

production. However, it is also possible that ‘good’ weather and

climate will bring beneficial rainfall, favourable to the suste-

nance of water supplies, hydroelectricity or irrigation.

A recent example is the massive impact of hurricane Katrina

on the New Orleans population. There were immense losses

to local and national economies, as well as significant social

and political ramifications. Another example is the sudden and

swift polar air movements over California and San Antonio,

Texas, in mid January 2007. These caused large losses to citrus

fruit production in California, interruption to power lines in

several areas and the closure of airports due to freezing rain.

In South America, ‘hurricane’ Catarina (so called because it

landed over the State of Santa Catarina, Brazil) brought tremen-

dous loss of life and significant material and architectural

damage. It also raised the concern that Catarina might indi-

cate the first regional impacts of global warming as a result of

forest burning, as well as increased fossil fuel usage in indus-

trial activity and transportation. In addition, areas of southern

Brazil vital to grain production (soybean, wheat, corn, rice)

for export and for internal consumption suffered recurrent

droughts, which brought huge losses to the local and national

economy as well as to the insurance companies.

‘Hurricane’ Catarina on the Brazilian coast

Between 27 and 28 March, 2004 a hurricane-like phonome-

non developed in the South Atlantic. This was the first

‘hurricane’ recorded over the South Atlantic basin since the

initiation of geostationary satellite imagery during the mid

1960s. The storm hit the coast of southern Brazil at Santa

Catarina on 28 March. Even though no direct measurement

was made (the nearby radar was non-operational at the time)

the intensity of the winds was estimated by models and satel-

lite imagery to the order of 90 kilometres per hour, with winds

of up to 150 kilometres per hour.

Usually, hurricanes do not form in the southern Atlantic due

to greater wind speeds at high altitude, which prevent storms

from gaining height and strength. Catarina started from a cut-

off low in the mid South Atlantic. In almost all observed cases,

these lows move towards the south-eastern Atlantic and dissi-

pate. Catarina however, moved towards the coast of Brazil and

changed structure and dynamics in a very unusual manner,

building up strength and forming a hurricane-like phenome-

non that became known as ‘hurricane Catarina’. The inaccurate

prediction of Catarina’s intensity, development and impact

generated a high level of media and public criticism of the

meteorological institutions involved.

The need for an integrated regional operational project

In the wake of Catarina, the National Meteorological Services

(NMS) of several countries in southern South America began

discussions and activities aimed at the mitigation of such disas-

ters. Since severe weather phenomena over the region usually

have their genesis in higher latitudes in the south, intensifying

as they move from Argentina to Uruguay to Paraguay and Brazil,

it is obvious that a joint effort is needed for maximum effec-

tiveness.

The region is large and requires improved data (in-situ, satel-

lite and radar derived) on land, and on the south-western South

A virtual centre for disaster reduction in

South America: monitoring, prediction and

early warning of severe weather events

Antonio Divino Moura, Instituto Nacional de Meteorologia, Brazil

Satellite picture, taken on 27 March 2004, of the ‘hurricane’ Catarina

Photo: Jacques Descloitres – NASA/GSFC – MODIS satellite