This document provides an overview of tropical cyclones, including: 1. Definitions of tropical cyclones from scientific organizations emphasize they are low-pressure systems that form over warm tropical oceans and rotate due to coriolis force. 2. Formation of tropical cyclones in the southern hemisphere requires specific conditions like sea surface temperatures over 27°C and location between 5-25° south latitude. 3. Climate change has led to increased ocean temperatures, making conditions more favorable for stronger and more frequent tropical cyclones in recent decades in regions like southern Africa.

1. 2023
PETER KOPANO MAPHALLA
220144291
5/25/2023
Tropical Cyclone Assignment

2. 1
Introduction.
It is always important to firstly understand a phenomenon before discussing some of
its deeper concepts and related processes. With that being said, the aim of this essay
is to look at the weather phenomenon of tropical cyclones. In general, tropical cyclones
are known to many people as dangerous clouds that bring devastating rain causing
severe flooding and strong winds that destroy vegetation and property. This means in
general many people just know them as dangerous phenomena that can place their
lives at risks but not fully understanding their physical nature and processes. As such,
it is important to look at the scientific meanings of these weather phenomenon in detail
to understand them. According to Singh, Pillay and Chandrabhaon (2015) a tropical
cyclone is a weather phenomenon that is characterized by a small, intensely
developed low pressure system associated with severe storms and heavy winds. The
National oceanic and atmospheric administrations (NOAA) explain a tropical cyclone
as a low-pressure system with a warm center and developing in the warm water
oceans at the tropical regions (2023).
In addition, the World Meteorological Organization (WMO) refers to tropical cyclones
as continuous rotating storms with a low pressure at the center originating from the
tropic warm oceans where they draw energy for their development (2022). The aim of
mentioning all these definitions from more than one scientific scholar or organization
is to bring forth different meanings of tropical cyclones and find common concepts to
help in understanding them. With the mentioned explanations one can see that the
low pressure is a common word used in all of them. These gives an idea that a tropical
cyclone in its physical nature is a low pressure with its associated characteristics.
Furthermore, it is stated that these low pressure weather systems are referred to with
different names in different parts of the world, for instance in North America they call
them Hurricanes, in Eastern Australia they call them Willy Willies, in South East Asia
they call them Typhoons, in India Cyclones, lastly Madagascar and South Africa call
them Tropical Cyclones (NOAA, 2015). The World Meteorological Organization
mentions that these weather systems are classified based on the maximum wind
speed, for example, when the recorded speed is less than 63 km/h it is classified as a
tropical depression, when the speed it at 63 km/h to 110 km/h it is classified as a
tropical storm and when the maximum speed is 110 km/h+ it is now a tropical cyclone,
hurricane or typhoon depending at the region (2022). It also mentions that when they

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are classified as tropical storms, they are now given a name. These names are given
according to the regional rules for instance in the Southern hemisphere and Atlantic
(Indian and south pacific oceans) the cyclones are named in alphabetical order with
women and men’s names being alternated, all for the purpose of avoiding confusion
since they can occur frequently (WMO, 2022). The organization importantly mentions
that if a tropical cyclone is dangerous and severe, its name is no longer used. With
what has been said, one now has an idea of what are these weather systems called
tropical cyclones. It is the purpose of these research essay to dwell more on the
phenomenon of tropical cyclones. As such, the essay will look at the formation of
tropical cyclones in the southern hemisphere, their frequencies, their history and lastly
it will closely look at the well-known cyclone named Freddy to bring more
understanding of these extreme weather systems.
Formation of Tropical cyclones in the southern hemisphere.
These weather systems have certain requirements for their effective formation. To give
a context to these, Gray (2010) mentions that tropical cyclones develop effectively in
the southern hemisphere on the eastern side of the continents due to the warm oceans
in those parts. He further states the following characteristics for formation :1. Sea
surface temperatures of 27 degrees Celsius or over, as this will increase high
evaporation rates because high temperatures are necessary for the formation of a low
pressure (convectional lifting). The water vapor will release latent heat that will act as
a fuel of the tropical cyclone. 2. It needs to be between 5° and 25° south of the equator
at tropics, because at less than 5° closer to the equator the Coriolis force is weak to
promote the creation of the vortex or spiral rotation of air. Therefore, at 5° to 25°
latitudes south of the equator is a good place because there is the required Coriolis
force, and the temperatures are much higher. 3. Calm conditions are also required
because strong winds or strong wind shear will prevent the development of the vortex,
therefore calm conditions are required for effective convergence air and formation of
towering cumulonimbus clouds to take place. Fourthly, upper divergence is needed to
maintain the continuous powering of the low pressure on the surface and increase
surface convergence.

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In terms of the formation process, Christopherson & Birkeland (2015) explain the full
formation process with an inclusion of the aforementioned characteristics needed for
the development of a tropical cyclone. They mention that firstly, at 5° to 25° south of
the equator, the developing cyclone will have to accumulate heat and energy from the
warm ocean beneath it. These oceans have a warm temperature of about 27° Celsius
(+) which cause the evaporation process to place in higher rates, with intense humidity
and unstable rising air. This unstable ascending air would then cause a low-pressure
system to develop above the surface of these warm ocean in the southern
hemisphere. They further state that the upper jet stream in the higher altitudes will lead
to the development of a low-pressure system which would rapidly power the low
pressure at the surface. Because these will be taking place a bit 5° further from the
equator, this will allow the present Coriolis force to cause the air to spiral towards the
center of that low pressure.
Figure 2: The clockwise rotation of the air causing the eye of a tropical cyclone (WMO,2022)
With reference to figure 2, Christopherson and Birkeland further state that as the
Coriolis force is causing a clockwise spiral rotation, this will cause the air to be drawn
towards the centre and as such a feature that is channel like called the eye is formed
(2015). Furthermore, as the high evaporation rates are taking place, latent heat is
released, and this acts as energy that power this weather system to intensify even
more. This released latent heat leads to even more unstable air conditions which lead
to more ascending of air. Immense condensation will now take place causing
tremendous development of towering cumulonimbus clouds that produce torrential
rain with strong winds. Because of this low pressure, some of the air is rapidly drown
to the eye where there is calm, warm, and clear type of weather conditions. Lastly,
Christopherson & Birkeland state that this moving cyclone will dissipate when it starts

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coming across friction such as on land where there will not be the presence of moisture
to act as energy and when this weather system may be approaching cold waters.
To expand more on these, Sign, Pillay & Chandrabhaon (2015) state that the formation
of tropical cyclones in the southern hemisphere takes place in stages from the initial,
immature, mature and dissipating stage.
Figure 1: Stages of Tropical Cyclone Development in the Southern Hemisphere (Excel in Geography, 2015)
With reference to Figure 1, during the initial stage (Stage 1) the pressure is above
1000 millibars, isobars are far part (gentle pressure gradient), the eye begins to form
as warm air meets towards the center of the storm, cirrus, cumulus clouds produce
light rain and gale force winds occur up to 50Km from the eye (WMO, 2022). In the
immature stage (stage 2) with further reference to figure 1, the pressure at the center
drops below 1000 millibars, the eye intensifies as the air continues to meet and rise
spirally at the center. The winds are at a tropical storm level (60-110km/h) and
cumulonimbus clouds forming around the eye with a diameter of about 100 km (Sign,
Pillay &Chandrabhaon, 2015). In the mature stage (stage 3) which is when the system
is now a fully developed tropical cyclone, the pressure at the center is way below 1000
millibars and stops dropping. The isobars are close together to show a steep gradient
causing strong winds of about 120km/h speed. The eye is fully developed, and
towering cumulonimbus clouds form around. There is a semi-circle dangerous

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quadrant on the left of the system which experiences the severe weather conditions.
Lastly, it is the dissipating stage (stage 4) which the tropical cyclone reaches when it
encounters land where there is high friction affecting wind speed and less moisture.
When it reaches cold water bodies there is less or no moisture and the pressure rise
to above 1000 millibars then it dies (Sign, Pillay & Chandrabhaon, 2015).
Climate change, frequency, and intensity in relation Tropical Cyclones.
According to Christopherson & Birkeland Climate change is the long-term weather
conditions that affect regions such as oceans for periods of over 30 years (2015). In
research conducted by Bengtsson, he states that Climate change can never be
separated from the phenomenon of tropical cyclones because these weather systems
flourish over warm oceans where they receive energy (2007). For over the years,
Climate change has led to an increase of global temperature with oceans becoming
increasingly warmer and this is a favorable factor for the formation of tropical cyclones.
These high temperatures caused by climate change over the years has led to an
increase in sea surface temperatures which has led to high evaporation rates than
before (Bengtsson, 2007). And it is known that rapid evaporation is critical factor in the
formation of intense low-pressure systems which are the foundation of tropical
cyclones. The research has shown that it is these climate change that has led to an
increase at the rate at which ice or glaciers have been melting which has led to an
increase in sea levels. These has made it worse with regards to the impact of these
tropical cyclones because these has led to the rate at which storm surges impact
coastal areas. According to Potts (2021) The frequency and intensity of tropical
cyclones has been increasing by five percent per decade since 1979, with category
three to five being the most frequent in the cyclone prone regions such as the eastern
side of Mozambique. Further model research studies aided by the theory of potential
intensity of Cyclones anticipate an average intensity increase of about five percent for
every 2° Celsius of global warming. In summary, these researchers argue and indicate
that with these further global warming levels in the coming decades, tropical cyclones
of about category four to five will increase associated with extreme wind speeds and
rain. These means that indeed Climate change has a greater influence because it has
caused global increase of temperatures which are creating favorable conditions for the
formation of tropical cyclones. With this kind of large-scale favorable characteristics,
a family of tropical cyclones can be formed, and they might move slowly for many days

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while exerting wide scale damage on areas they would be passing and because of the
increase in seal levels many areas would be prone to more flooding due to the level
of storm surges.
Southern Africa History of Tropical Cyclones.
According to the World Meteorological Organization (2022) there has been many
tropical cyclones occurring in the southern east coast of africa with some of them not
been detected and officially listed because some dissipated in their early stages. The
organization mentions that to date there has been thirty tropical cyclones which have
affected the interior parts of southern africa such as South Africa, Malawi, Zimbabwe,
Eswatini, Lesotho, Mozambique. Madagascar is regarded an African country and it
has been hit hard by these severe weather systems than any on that eastern part of
Africa.
To mention the few, the World Meteorological Organization tropical cyclone timeline
show that in the year 2000 on the 25th of February Tropical cyclone Eline made a
devastating landfall onshore in Beira, Mozambique. Eline is said to be the most
catastrophic in a century to hit that area, making the water levels of the Limpopo River
rise to 12 meters and 16-Kilometer-wide covering. These Cyclone is said to have left
approximately three hundred thousand people homeless and about seven hundred
accounted deaths.
Figure 3 People left homeless after Cyclone Eline Hit Mozambique (The Guardian, 2000)
Figure 3 shows people on top of a house and a wide scale flood after tropical cyclone
Eline made landfall in Mozambique. The United Nations (UN) and other humanitarian
organizations such as the United States Agency International Development (USAID)

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had to spend close to 12 million Dollars to help in the revamping of the infrastructure
in Mozambique. During the incident, it is said that other countries and organizations
sent helicopters and medical experts to help in the evacuation of people as a way of
trying to reduce number of fatalities (The Guardian, 2000).
In 2003, December 13th Tropical cyclone Delfina made landfall in Mozambique where
it killed about 47 people, with flooding and winds damaging about 20000 houses
leaving people homeless. This cyclone caused floods that reached Malawi killing at
least fourteen people. Due to the residual outbreak caused by flooding, a cholera
outbreak was recorded affecting about four hundred people. About 3.1 million was
used to help provide people with shelter, drinkable water and food supplies and mass
evacuations (WMO, 2003). In 2004, January 26th Tropical Cyclone Elita made her
landfall in Madagascar hitting it three times as it was busy moving back and forth
between Eastern Mozambique and Northwest Madagascar loosing and regaining
intensity (WMO, 2008). It is also worth mentioning the trio Tropical cyclones that hit P
in 2012, Dando, Cyclone Funso and cyclone Irina which affected parts of Mozambique,
South Africa and Malawi killing close to 100 people via floods in total (WMO,2012)
In 2015, January 14, Tropical disturbance Chedza emerged and when it was passing
over the Mozambique channel it intensified due to the warm waters into a tropical
cyclone. This cyclone came along with devastating winds and folds killing 13 people,
destroying about three thousand homes, and forcing about nine thousand people out
of their homes. This storm flooded the Tsiribihina river which overflooded and
submerged some of the areas on the riverbanks and it also cased floods in the
neighboring Malawi. According to the National Aeronautics and Space Administration
(NASA) at the early stages of these storm, warnings were issued, and people were
evacuated in some parts that were predicated for the storm to hit (2015).
The World Meteorological Organization (2017) reported that in 2017, 15th of January
Tropical Cyclone Dineo made landfall in central Mozambique. It formed into a
disturbance on the 13th when the RSMC La Reunion the issued warnings about it.
when it reached the Mozambique channel it intensified to become a tropical cyclone
and the RSMC then named it Dineo. These Cyclone reached maximum wind speeds
of 140km/h and pressure drops of about 949 hPa. About 200 mm of rain fell in
Inhambane, with winds damaging about twenty thousand houses, hundred and thirty

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people being directly displaced. About 250 fatalities in total were recoded and a budget
of about two hundred and seventeen million was spent for disaster relief purposes. It
received widespread media attention and reports because it affected South Africa,
Mozambique, Zimbabwe, and Malawi before it dissipated on the 17th of January 2017.
Furthermore, Tropical Depression made a landfall in Mozambique in March 2019 on
the 4th later it migrated to the Mozambique channel where it developed into a Tropical
Cyclone called Idai as shown below on Figure 4. It made a severe landfall in Beira and
become weaker as it migrated towards Zimbabwe. It is reported that it is the second
deadliest after it killed about one thousand three hundred people in Malawi, Zimbabwe
and Mozambique combined (UNICEF, 2019).
Figure 4 The erratic path map of Tropical Cyclone Idai (UNITAR, 2019)
According to Pillay & Rumney Tropical Cyclone Eloise made landfall in Mozambique
north of Beira (2021) in the date of January 22nd in 2021. This Cyclone migrated
Southwestward brining severe rainfall where in its path until it reached its dissipation
stage in South Africa. At least Eleven people were killed in Mozambique, 10 in South
Africa Limpopo, 2 in Malawi and 4 in Zimbabwe. In the recent years, World
Meteorological organization reports that later in 2021 Tropical cyclone Jobo made
landfall east coat of Tanzania, in 2022 Tropical Cyclone Ana and Dumaku made
landfall in Mozambique (2022).

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Cyclone Freddy.
Tropical Cyclone Freddy was the most terrifying and amazing weather system as
described by many weather reporting and research institutions because of its erratic
path and days of survival no matter the frictions it came across.
According to the US Joint Typhoon Warning Center and Australian Bureau of
Meteorology This weather system developed on the 6th of February 2023. It emerged
on this date at the Northwest coast of Australia in the warm Indian ocean. Then it
started migrating west from its origin with winds of about 167 Km/h at the epicenter
(Myronets, 2023).
Freddy’s Path.
According to many reports Freddy travelled a very rare and erratic path in the history
of Tropical Cyclone. From Where Freddy developed in the Northwest coast of
Australia, he started moving west crossing the whole south Indian warm ocean
towards the east coast of Africa. In total distance Freddy travelled about eight
thousand kilometers from where he developed. It travelled through the Mauritius
channel, La Reunion, and attacked Madagascar on the 21st of February. But Freddy
did not stop, he continued to migrate until he reached Mozambique on the 24th of
February. Then migrated back to the ocean and regained power. Then on the 11th of
March Freddy returned and struck Mozambique again. This time around on the 13th of
March, Freddy persevered and migrated in land of Mozambique bringing heavy down
pours of rain even to the southern parts of Malawi Regardless being a tropical
depression (Myronets, 2023)

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Figure 5 The erratic path of Cyclone Freddy (Meteo France) by (Watchers News.com, 2023)
With Reference to Figure 5, one can see that indeed Tropical Cyclone Freddy was
terrifying as reported. The path was so unpredictable and the levels of its intensity
fluctuating from high to low and high till he dissipated. In a general analysis, the fact
that tropical Cyclone Freddy travelled a very long distance, crossed inland
Madagascar, struck East coast Africa and returned tells a lot about its intensity being
very high.
Countries Struck and damaged by Tropical Cyclone Freddy
As the most ever recorded travelling weather system, Tropical Cyclone affected
Countries; Madagascar, Mozambique, Mauritius, Zimbabwe, and Malawi (ISS, 2023).
According to Mbiyozo & Maunganidze (2023) Tropical Cyclone Freddy caused severe
damage In the Southern Parts of Malawi. At the date of 29 March, about seven
hundred and seven (707) people died due to intense flooding and about five hundred
and eleven of those people were accounted in Malawi. The local authorities in Malawi
also reported that about one thousand three hundred people were injured, five
hundred and fifty-six missing and others not known where they are. Approximately
Five hundred and eight thousand (508 000) people were left without homes after five
hundred and eight sites (508) were affected creating a higher humanitarian need of a
situation (Mbiyozo & Maunganidze, 2023).
Furthermore, severe flooding has affected the supply of power in Malawi almost
country wide, eroded critical infrastructure such as toilets, eroded and polluted water
supply channels. This was causing lack of clean water after there was a cholera

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outbreak reported even in other Countries which Cyclone Freddy Caused severe
flooding (Mbiyozo & Maunganidze, 2023). Other infrastructure damaged in Malawi
were schools which others were used as shelter for people who were displaced and
about four hundred and four thousand (404 000) children were not able to return to
school. Lastly, it is also known that Tropical Cyclone Freddy affected about 1 million
people in total when counting in Mozambique, Mauritius, Zimbabwe and Madagascar
and displaced about hundred and sixty thousand people. With about forty percent of
people who were displaced taking refuge in Countries that are vulnerable to climate
change (Mbiyozo & Maunganidze, 2023).
What makes Tropical Cyclone Freddy similar or different to other events.
This weather system is more unique less similar to other natural weather systems.
One of the similar things is that Tropical Cyclone is one of the four cyclones to have
crossed the entire Southern Indian Ocean, with the early previous being Leon-Eline
and Hudah in the year 2000 (ISS, 2023).
According to the World Economic Forum (2023) Tropical Cyclone Freddy is unique
due to the following aspects, it has hit Mozambique twice in its life span after surviving
thousands of kilometers Journey across the Indian ocean. Secondly, It Survived more
than the highest number of days ever recorded, which was 31 days and Freddy
reaching 34 days. Freddy is also unique as it has breached the record of number of
rapid intensifications in a single lifetime. The way in which Tropical Cyclone Freddy
travelled was unique, amazing to watch on a satellite and the most ever unpredictable
as it hit a single country Twice. Lastly, it is said that it has surpassed the highest
accumulated cyclone energy (ACE) and created a new record in the Southern Indian
Ocean and possibly Globally (WEF, 2023).
Conclusion.
It was the purpose of this research essay to look at a wider scale of understanding
tropical cyclones along with their frequencies, relationship with climate change,
history, and intensities in the Southern Hemisphere. The research explained an
understanding of the weather system of tropical cyclone by referencing from both
general and scientific perspectives. With regards to climate change, it was found that
based on several researches and models the increase in global temperatures caused
by global warming indeed influence the frequency and intensity rates of these terrifying

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weather systems. Looking at the history of tropical cyclones, it was found that about
thirty tropical cyclones have hit the main land parts of southern africa. The core of the
research discovered a lot about the famous tropical cyclone Freddy which was unique.
Tropical Cyclone Freddy remains the most studied tropical cyclone worldwide due to
its unique stances such as crossing the entire South Indian Ocean, striking
Mozambique twice and lasting for over 34 days. This indeed has been evidence of
how it is of importance to scientifically study these weather phenomena as a way of
coming up with preventative and precautionary measures to avoid severe human
fatalities.
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