How hurricanes come to be.
Since the beginning of the hurricane season – June 1st 2021 – Dominican residents, and those living throughout the Caribbean, Southern US and Central America, have been monitoring weather systems that leave West Africa and move out across the Atlantic Ocean, on a 3,000-mile journey towards the Americas.
They travel along the very same trade wind paths that brought the ancestors of Afro-American peoples in bondage, propelling the sails of European slave ships towards the Americas – carrying the labour ‘at the edge of the hurricane….at the end of the slave trade winds’, as Brathwaite once described it (1993: 260-61). These very same alizés (as the winds are known to francophone islanders) carry Saharan dust to the Antilles, bringing beautiful hazy sunsets and particulate deposits on vehicles and windows. This dust is said to curb the formation of cyclones.
These alizés, and all that they carry, invite the Caribbean to look eastwards, towards weather disturbances born as far away as East Africa. To vigilantly track them via satellite images on TV and online, to follow their development on inter-island WhatsApp and Facebook groups, where citizen weather watchers exchange reports, forecasts and observations along the island chain. And this is not to mention that most trusty medium, the FM radio. During storm events Dominicans call in to DBS (Dominica Broadcast Service) Radio to describe conditions in their local areas – the heaviness of rain, strength of winds, nearby damage, and status of utilities (i.e., water and electricity outages). Separated by steep ridges, deep valleys and mountains, Dominican weather patterns may differ radically between enclaves in the north, south, east, west or interior of the island. Yet, in this sharing there’s a kind of crowdsourcing of live weather information; a triangulated conversation between individual observations, communally gathered reports and official met office information.
With the recent passage of category-1 Hurricane Elsa (2nd of July 2021) this tracking came alive. Elsa was the first hurricane to make landfall in 2021, and the 5th storm of the year (‘E’ being 5th in the alphabet). In fact, Elsa was the earliest 5th named storm on record, with storms beginning with ‘E’ typically arriving in August.
Atlantic cyclones are named using a rotating roster, where a name can be recycled after 6 years. This year the 2015 list is being reused. However, during August of 2015 Erika struck Dominica, causing death, destruction and widespread flooding. Hence it was retired, and this year Elsa has been inserted in its place.
Elsa spared Dominica, where it was felt only as a tropical storm with minimal damage. But the hurricane caused more severe damage elsewhere: killing one person in St Lucia, two people in The Dominican Republic, and causing one confirmed death in Florida. On top of this, 9 Cubans aboard a 22-person vessel on a migratory journey to America were also presumed dead after the US coastguard ended a week-long air and sea search for survivors (the remaining 13 were rescued and taken into US immigration custody). Elsa also caused some flood and wind damage to homes, infrastructure, and crops across the Lesser and Greater Antilles; and was the first hurricane to make landfall in Barbados in 66 years (damaging over 800 homes).
Although causing minimal destruction in Dominica, Elsa was ‘a wakeup call’, as a friend put it. A reminder to be prepared for the season. To store food and water (for drinking and washing), locate local shelters, cut branches near homes, clear drains (to avoid flooding), to buy batteries, candles and store spare bottles of cooking gas.
The memory of hurricane Maria, just four years ago – referred to in Dominica as simply ‘the hurricane’ – and tropical storm Erika two years before that, offer painful reminders to prepare for storms that can so rapidly organise themselves into cyclones. Moving from…
- a wave (non-cyclone)
- to a depression (cyclone, winds <38mph)
- to a tropical storm (cyclone, <39-74mph)
- and then up through the categories (1-5) of a hurricane (cyclone, 74mph+)
…in the space of a few days.
For a hurricane do develop within the main development region (MDR), between west Africa and the Caribbean, at such an early stage in the year portends to a highly active hurricane season (NOAA 2021).
How Atlantic Hurricanes form?
Hurricanes begin as tropical waves. A tropical wave is an atmospheric system of low pressure that typically moves in a westward direction. They originate as ‘African Easterly Waves’, undulating weather patterns that travel across the Sahara out to the Atlantic. Some sixty waves may be generated throughout a single 6-month hurricane season (June 1st to November 30th), with roughly one in ten forming into cyclones.
Their power is generated by the contrasting temperature of the hot arid Sahara Dessert and the cooler moist tropical conditions of the Gulf of Guinea in West Africa and central African rainforests. These weather systems continue westwards as they gather energy. With small atmospheric disturbances they can become unstable, rising higher into the atmosphere, and gaining moisture as they move out over the Atlantic – into an area close to Cape Verde. Here they can develop into clusters of thunderstorms (NOAA).
All this unfolds within a thin tropical band called the Intertropical Convergence Zone (ITCZ, see lines below) where trade winds meet and move the weather systems out further towards the Americas. As NASA Earth Observatory note:
The intense sun and warm water of the equator heats the air in the ITCZ, raising its humidity and making it buoyant. Aided by the convergence of the trade winds, the buoyant air rises. As the air rises it expands and cools, releasing the accumulated moisture in an almost perpetual series of thunderstorms.
A feature of this convergence zone is its rising warm air currents called ‘updraughts’, which pull moisture high into the atmosphere, where it forms energised and rain-filled thunderclouds. Places located along this strip receive some of the heaviest annual rainfall on the planet.
The location of the ITCZ moves throughout the year, bringing seasonal shifts in the location of heavy rainfall – resulting in the wet and dry seasons of the tropics (rather than the cold and warm seasons of northern countries, for instance). Most of the Caribbean receives its wet season during June to August; whilst Brazil’s is December to February; and Guyana experiences both (see the lines meeting below).
Out in the Atlantic, tropical waves are energised by warm ocean temperatures, they are moved by converging trade winds and spun counter-clockwise by the rotation of the planet – this is how they form into cyclones.
The indigenous Kalinago of Dominica were able to foretell the arrival of hurricanes, perhaps owing to their ability to anticipate the clear weather and drop in pressure that tends to precede their landfall. They were so accurate at such forecasting that they warned English settlers in St Kitts of hurricanes that made landfall in ‘1657, 1658, 1660, 1665, and 1667 … [E]very time the Caribs [Kalinago people] on Dominica and St. Vincent sent a warning ten or twelve days in advance’ (Dunn in Yarde 2012: 77). Kalinago people knew the hurricane as Ioüallou, calling their wet season – from May to October – Ioü llouo yourou. They planned their planting, raiding, trading and house building with the hurricane in mind. And so too European seafarers, colonial settlers and slavers, began to map the winds and seasonal storms.
To return to Elsa, island residents in the Eastern Caribbean tracked the wave carefully to see how fast it was developing, whether it would become organised into a cyclone – depression, storm, or hurricane – and whether/where it might make landfall. Many Caribbean governments placed their islands on ‘hurricane watch’, issuing advisories to send staff home from work, avoid seacraft operations and avoid all river or sea bathing.
In the end, the hurricane just passed from east to west across the south of the Dominica, causing minimal wind damage and outing water and electricity for a day. The storm then moved on through the Greater Antilles and southern US.
How Hurricanes Die
Cyclones ‘die’ as a result of making landfall or entering cooler waters. ‘Striking an island’, NOAA note,
especially a mountainous one, could cause its circulation to break down. If it hits a continent, a hurricane will be cut off from its supply of warm, moist maritime air. It will also… draw in dry continental air, which combined with increased friction over land leads to the weakening and eventual death of the hurricane. Over mountainous terrain this will be a quick end.(NOAA 2021)
Such knowledge is popularly held in Dominica too. As one interviewee told Therese Yarde in her PhD research on Dominican understandings of nature:
According to where the hurricane is coming, you find the mountains can be very helpful in breaking down the wind force and that kind of thing(Yarde 2012: 379)
Having moved over multiple islands Elsa slowed to a tropical storm as it continued to arc upwards along the east coast of the US.
With the start of August, as we enter the most active period of the hurricane season (the vast majority of hurricanes form after August 1st), islanders continue to look vigilantly to the east for more storms to come. During this time many will recall that timeless childhood nursery rhyme:
June to soon
July stand by
August come you must
October all over(thanks to Genny Seaman for the reminder; originally an old mariners poem)
For a detailed and accessible introduction to the science hurricane formation, tracking, effects + routes see this article by Morsink on the Smithsonian Institute website