US forecasters have upgraded tropical storm Isaias to a Category 1 hurricane. The weather system is headed for the Bahamas and the US after unleashing floods and landslides in the Dominican Republic and Puerto Rico.
Emergency workers clear trees toppled by Tropical Storm Isaias in the Dominican RepublicImage: AFP/E. Santelices
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Storm Isaias strengthened into a hurricane on Friday as it moved towards the Bahamas and the US East Coast, the National Hurricane Center (NHC) announced on Twitter.
The Miami-based agency said the hurricane was packing maximum sustained winds of 130 kilometers (80 miles) per hour as it tracked northwest across the Atlantic Ocean at a speed of around 30 kph (18 mph).
Hurricane warnings were in place for the northwestern, central and southern Bahamas, where Isaias was expected to make landfall on Friday before reaching Florida's coast on Saturday. The southern US state is currently grappling with one of the worst coronavirus outbreaks in the US, with more than 6,500 deaths from the disease.
How do tropical storms form?
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No evacuations have been ordered yet in Florida or the Bahamas. But authorities have warned people to prepare for heavy rains, flooding and storm surges.
Bahamas Prime Minister Hubert Minnis announced late Thursday that he was relaxing a coronavirus lockdown due to the impending storm, but that an overnight curfew would apply from Friday. He said supermarkets, pharmacies, gas stations and hardware stores would be allowed to stay open as long as weather permitted.
"These are especially difficult days,'' he said during an online news conference. "We need at this time the spirit of love and unity.''
Before it was upgraded to a hurricane, Tropical Storm Isaias caused power outages, toppled trees and triggered flooding and landslides across the Dominican Republic and Puerto Rico on Thursday. At least one person was killed in the Dominican Republic, while hundreds of thousands of people were without power and water in Puerto Rico.
Cyclones, typhoons, hurricanes - the power of devastation
Cyclones, typhoons and hurricanes pack a devastating punch: wherever they go, they leave a trail of destruction. But how do these powerful tropical storms arise?
Image: AFP/D. Sarkar
Social distancing impossible during Cyclone Amphan
Residents along Bangladesh's coast are being moved to safety as one of the strongest cyclones in years strikes the region. Millions of people had to be evacuated from low-lying regions along the Bay of Bengal on May 19. But plans are complicated by the coronavirus precautions. Maintaining social distancing is nearly impossible.
Image: AFP/District Administration of Bhola
Typhoon season amid the COVID-19 pandemic
On May 14, Typhoon Vongfong slammed the Philippines with strong winds and heavy rains, destroying the city of San Policarpo in the eastern province of Samar. At least five people died and more than 91,000 people were forced to leave their homes. Typhoons are not unusual in the Philippines at this time of year. But the COVID-19 outbreak lockdown measures are exacerbating the situation.
Image: AFP/A. Beronio
Three names - one phenomenon
Hurricane, typhoon, and cyclone are actually three names for the same phenomenon. Along the North American coast they are called hurricanes, in East and Southeast Asia they are called typhoons, and near India and Australia they are called cyclones. But despite the different names, they develop in the same way.
Image: Reuters
A cyclone is created
Tropical storms develop over oceans when the water temperature is at least 26 degrees Celsius (79 degrees Fahrenheit). As the warm water evaporates and condenses, the air around it heats up and drags cooler air upwards, creating powerful winds.
The eye of the storm
The Earth's rotation causes the air stream to move around the eye of the storm, which can be up to 50 kilometers wide. This area is nearly completely free of clouds and wind.
Image: picture-alliance/dpa
A storm hits land
When a tropical storm hits a coastline, it becomes weaker due to the lack of warm water. In Australia, "Marcia" was soon downgraded to a category one storm, while "Lam" weakened after striking near Brisbane. Masses of water from the sea often cause the worst damage - as seen here in China after Typhoon Nanmadol in August 2011.
Image: picture-alliance/dpa
Chaos ensues
Hurricane Sandy was one of the strongest hurricanes ever recorded over the Atlantic Ocean. It caused waves of up to 4 meters high, fires, power outages and broken dykes. Sandy arrived with winds at speeds of more than 145 kilometers per hour. Cuba, New York and New Jersey were particularly affected.
Image: Reuters
Destructive vortex
Tornadoes however, are non-tropical whirlwinds that can occur anywhere a storm is brewing. Local temperature differences force warm air upwards and cold air down, and a column of warm air rotates upwards at an increasing velocity. Tornadoes are usually only a maximum of 1 kilometer in diameter.
Fastest storms
As the warm air rises, it forms a funnel, the main characteristic of a tornado. Inside the funnel, the speed of the air can be tremendous - up to 500 kilometers per hour. Tornadoes are the fastest whirlwind type of weather phenomenon.
Image: Fotolia/Daniel Loretto
Trail of destruction
A tornado can leave a trail of destruction several kilometers long. In the US Midwest, tornadoes occur several hundred times a year, as dry, cold air from the north hits damp, warm air from the Gulf of Mexico. It's different in other countries - in Germany, for example, tornadoes occasionally occur along the coast.
