Understanding typhoons, hurricanes, cyclones

A tsunami wave

The super typhoon Haiyan has been in the news a lot recently. As the media runs stories on the death, destruction and desperation it has left in its wake, we almost feel we have heard the word typhoon too much.
But do we know what it means? Can we answer an inquisitive child why a typhoon is different or not different for that matter from a hurricane, a tornado, a cyclone or a tsunami?

Cyclones, hurricanes and typhoons

According to Khalid Muwembe, a senior meteorologist and spokesperson of the department of Meteorology at the ministry of water: “A cyclone, hurricane and typhoon are the same thing.”

He says they are tropical storms that form over the ocean and gain strength of over up to 119 kilometres per hour. And whether such a storm will be called a hurricane, cyclone or a typhoon depends on the ocean it comes from. “If the storm is from the Indian Ocean it is a cyclone, if it is in the Atlantic Ocean it is a hurricane and those on the Pacific Ocean are called typhoons,” he says. Generically all of them are called tropical cyclones.

How they happen
“A precondition for them to happen is warm water about 25.3 degrees centigrade, which is only found in the tropics,” he continues. He adds that usually the tropical cyclones occur far from the tropic lines, not more than 10 degrees north or south of them.

According to the Nasa website, the tropical storm comes about as a result of warm air over a part of the ocean rising. And as it rises, it creates a vacuum that cooler air rushes to fill. This cool air also heats up and rises as well and more air moves in to occupy that vacuum, and cycle goes on. The site also says the storms north of the equator spin anti-clockwise while those south of the equator spin clockwise.

On Monday, a cyclone hit the coast of Somalia reportedly killing about 100 people. The Philippines is still reeling from the shock of Haiyan and who can ever forget Katrina and the havoc it wrecked on New Orleans in the US. Whatever place they occur, hurricanes, typhoons or cyclones are reported to leave destruction of epic proportions.

However, not all tropical cyclones are as strong or as destructive. “Their strengths depends on weather conditions in the area. If there are strong winds, for instance, they fan them along,” says Muwembe. The storms are also able to gather energy as they cover long distances over open water making their landfall (which is when a tropical cyclone hits the land), a violent affair with strong wind accompanied by heavy precipitation (rainfall, sleet, hail or snow). This explains the deluge we witness after a cyclone hurricane or typhoon.

Haiyan for instance was a category 5, which is the strongest type of storm we have. “Normally, when you find this type of storm the wind at the centre can be travelling at 150 kilometres per hour,” he explains.

How long a tropical cyclone takes from when it is formed over water to make a landfall depends on a lot of factors. If energy is persistent as the tropical cyclone moves over the ocean the tropical storm will make a big landfall. “Sometimes they make a landfall, sometimes they lose energy and are too weak to cause significant impact on land,” says Muwembe.

The landfall is also the death of the typhoon or hurricane or cyclone. Much as it is destroying anything in its path, the friction with those obstacles like houses, hills and mountains, trees and so forth weaken it and it loses strength,” elaborates the meteorologist.

This is probably why they do not make it that far inland on large land masses like continents. But islands in a tropical storms path will be little deterrent and as we have seen in the Philippines, the typhoon can sweep right across a whole island.

Tsunami

When one hears tsunami, memories of Fukushima or the 2005 Indonesian tsunami come to mind. But that was the aftermath mainly. A tsunami is in essence an unusually large wave caused by a huge displacement of water in a waterbody.The dictionary says it is also caused by a quake or a volcanic eruption.

As such, a tsunami is preceded by a disturbance like an underwater quake, or the eruption. However, the tsunami may reach coastlines far from the place the quake or eruption happened or was felt. For instance, the 2004 Boxing Day tsunami was triggered by an earthquake on Sumatra Island in Indonesia but the waves travelled as far as the Seychelles, Reunion islands and the East African coast.

As the explanation points out, most of these are threats for mostly people living on coastlines. Still we are not completely excluded. For example Uganda could see a tsunami in the event of an underwater quake in Lake Victoria for instance or one of the many inland lakes.

Why some areas are always are more prone to storms

Khalid Muwembe, a meteorologist, explains that tropical cyclones have very definite paths which they follow year in year out. “In the Atlantic Ocean, the hurricanes form off the West African coast around Cape Verde and move towards the East coast of the North America,” he says. This explains why despite Africa and America both having a coastline on the Atlantic, the American east coast experiences hurricanes while the West African coast hardly ever does.
The same applies for the Indian Ocean, where the cyclones form off the southeastern part of the continent and move towards the islands in southern Africa. “That is why cyclones always devastate Madagascar and Mauritius. They are in the path of the tropical cyclones that happen over the Indian Ocean,” he explains.

Uganda’s mini tornados

According to Muwembe there is also a version of tornado closer to home than we thought. “We call it a waterspout and it forms like a tornado dropping from the clouds over the lake. A water spout also damages whatever is in its path,” he says.

The last one happened early this year on March 14 and destroyed structures on Lujjabwa Island in Lake Victoria. Thankfully, there were no fatalities or serious injuries. Also, the island is mainly a fishing village and the structures were not permanent. But over 75 shelters were flattened,” he shares.

The waterspouts happen quite often over the open lake several times a year. Muwembe says there is at least one every season. The frequency means the fishermen who mostly live and carry their trade around the lake know how to tell the signs and often move to safety when they see it forming.

“To them, this small tornado is also a blessing in disguise. After the water calms they rush to its path to collect fish because it kills so many fish,” says Muwembe.
It may seem like a thing of fear, but it is overall not very destructive.

Definitely not in the class of the Haiyans and Katrinas of this world. Makes you thankful to be here in landlocked high altitude Uganda doesn’t it?

Extent of destruction by Super Typhoon Haiyan

Here is a snapshot of the dire situation on the worst-hit islands of the Philippines after Super Typhoon Haiyan – one of the strongest storms ever recorded – left tens of thousands dead, missing or homeless:

Leyte Island
Around 1.7 million people live on the hard-hit island, whose provincial capital Tacloban was shattered by Friday’s category-five storm. Vicious winds and waves up to five metres (16 feet) high flattened homes and left countless bodies strewn across the city.
United Nations humanitarian chief Valerie Amos said there were fears that some 10,000 of the city’s 220,000 people were killed. An earlier estimate by a regional police chief said 10,000 may have died in the whole province.
Tacloban has been the focal point of relief efforts. On Monday about 90 US marines arrived aboard two US military C-130 transport planes packed with relief supplies.

Samar Island
Aerial photos of Samar, where Haiyan first made landfall packing winds of 315 kilometres (195 miles) an hour, show whole stretches of coast reduced to matchwood.
The governor of the island has said 433 people were known to have died, although that number was almost certain to rise.
Guiuan, the first place to experience the full brunt of Haiyan, was last week a bustling community of 47,000 people but late Monday a grim picture began to emerge, with one resident telling an AFP journalist that armed men were threatening to kill fellow survivors for food.

Cebu Island
At least 56 people died when the typhoon hit the northern edge of the central island of Cebu, which is popular with foreign holidaymakers.
The urbanised capital of Cebu City, considered the country’s second most important trading centre, was not badly affected, but there are fears for other parts of the island, which has a population of around 866,000.

Malapascua Island
A small island of about 3,000 people popular among divers. The typhoon smashed houses, resorts and restaurants. One woman recalled “the winds were so strong. The roofs went flying, the boats were thrown into the trees”. Authorities say they do not know if there were any casualties.

Panay island
Around 200 people are known to have died on Panay, home to more than 3.9 million people, many of whom work in the fishing industry.

Boracay Island
The popular resort island of Boracay, near Panay, suffered extensive damage with debris from shattered beachfront stalls scattered all over its powdery-white sands.

Palawan Island
Much of Palawan, a largely unspoilt wilderness, escaped the worst of Haiyan but the island’s northern edge was hit, including Coron town, a high-end tourist spot. The town’s mayor Clara Reyes said nine people had been killed and that the town would run out of food in two days.
The storm destroyed 90 per cent of Coron, knocking out power, contaminating the water supply and damaging the airport, leaving about 400 tourists stranded.

Negros Island
The sugar-growing centre of the Philippines prepared extensively for the storm, evacuating over 89,000 people from their homes in case of flooding. The island, home to four million people, escaped relatively unscathed and no deaths have so far been reported.