Definitions and names of meteorological
phenomena of particular interest to Malawi
Chiperoni: Malawian name for influx of cool moist air
from the south east, bringing overcast conditions with drizzle on
windward slopes along the Northern lakeshore and in particular to
many areas in the South of Malawi. This phenomenon can persist for
up to a week but the usual duration is two to three days.
Mwera: Strong SE ly winds occur immediately before and
occasionally during a Chiperoni outbreak. Lake Malawi is
particularly affected by the Mwera due to the flat and obstruction
free nature of its surface, allowing winds of considerable strength
to develop. The onset of a Mwera can be quite sudden causing a rapid
deterioration in the condition of the late itself. Amateur and
weekend sailors are urged to pay particular attention to this
The Inter-Tropical Convergence Zone (ITCZ): The zone where
air streams from both hemispheres converge oscillates with the sun
from season to season and lies South of the equator, usually across
or near Malawi between November and March. It is the main factor
governing the increased convergence, which is responsible for Malawi
s rainy season.
Technical meteorological terms, processes
High Pressure System, Anticyclone: An atmospheric
pressure area where the highest pressure is in the centre,
decreasing outwards. Winds flow around the high pressure in an
anti-clockwise direction in the Southern Hemisphere. These systems
are not regular in shape and occasionally bulge out to form Ridges
of High Pressure.
Tropical Revolving Storms or Cyclones: Intense low
pressure areas, which form over oceans such as the Indian Ocean
during the Summer months, usually December to April. These
disturbances have gale force winds blowing inwards and clockwise
around the centre. Weather in association wit cyclone is usually
violent with torrential rain. They occasionally move inland.
Cyclones can cause severe flooding and disruption of public
services, infrequently reaching disaster proportions.
Air Mass: A fairly homogenous mixture of air, in respect
of temperature and humidity, covering a large area, which may extend
over thousands of miles.
Fronts: In temperate climates air mass discontinuities are
demarcated by Fronts . These are not featured on the Malawi weather
Surface convergence: An upwelling of excess air as air
streams from different directions converge.
Convection: The over turning process which results when
air which is warmer than its surroundings and therefore less dense
rises, allowing colder air to take its place. This colder air may,
in its turn, be heated by contact with ground causing the whole
process to be repeated.
Clouds and their development: Clouds are formed when air
is cooled sufficiently for invisible water vapour to be deposited
out as visible water droplets. When these droplets are big enough
they become heavier than their surroundings and fall as rain. The
initial cooling is usually the result of air that has been forced to
Forced ascent over higher ground or mountain ranges
Convergence of different air streams at the surface.
Low, Low Pressure Systems, Depression: opposite of high
pressure system with the centre having the lowest pressure. Bulges
and elongation in the circular pattern are known as Troughs of Low
Pressure. The flow of wind around a depression is clockwise in the
Economic Benefits of Meteorological Information
There are many economic benefits that users of meteorological
data and information can realise such as:-
Fuel saving in aircraft operation Increased crop yield by
utilising correct planting dates. Saving lives by use of Mwera
warnings over the lake. Saving lives and property by using tropical
cyclone warnings. Food security through the use of rainy seasonal
rainfall forecasts. Man-day savings in construction through use of
rainy days information.
If you are interested in past weather and climate data and
Information, you can obtain these only from the Meteorological
Headquarters at Chileka at the address below:
Department of Climate Change and
P. O. Box 1808
Tel: +265 1 822 014
Fax: +265 1 822 215
Remember to remember: The
weather is such a natural force t reckon with that it can
not and should not be ignored in man s day to day operations
because in any tussle between weather and man, the weather
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