Cyclone Chapala flooded the coastal cities of Yemen with at least five years worth of rain when it made landfall early Tuesday morning. (NOAA/EUMETSAT)

Cyclone Chapala made landfall in Yemen early Tuesday, becoming the first hurricane-strength storm on record to do so. Though photos and video on social media depict disastrous flash flooding in coastal cities, the actual damage and death toll in the war-torn country may never actually be known.

Tropical cyclones are not uncommon in the Arabian Sea — on average a few weak to moderately strong storms spin up each year. However, cyclone landfalls in this region are rare. Cyclone Chapala is the first known hurricane-strength storm to make landfall in Yemen since modern records began there in the 1940s, and just the third hurricane on record to make landfall across the entire Arabian Peninsula.

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Chapala took the worst possible path for Mukalla, a port city on the central coast of Yemen that’s home to about 300,000 people. Chapala made landfall about 25 miles to the southwest of this city, which put Mukalla in the storm’s strongest winds and its highest surge and waves.

But the storm’s rainfall ended up being the most dangerous impact to coastal Yemen, and the city of Mukalla in particular. The amount of moisture in the storm just prior to landfall, measured in precipitable water, was a full 10 times as high as it was just west of the storm over the Arabian Peninsula. And the rains would have been made worse as the air flowed over the mountains, wringing even more moisture out over Mukalla.

The port city of Mukalla in Yemen is surrounded by dry, vegetationless mountains. (Google Earth) The port city of Mukalla in Yemen is surrounded by dry, vegetationless mountains. (Google Earth)

The torrential downpour was well-forecast by global and hurricane models, which suggested as much as 20 or even 30 inches could fall in the higher elevations around Mukalla and run down the hillsides into the vulnerable port city.

According to the U.K. Met Office, this region typically gets less than 4 inches of rain per year, meaning Chapala would have delivered at least five years’ worth of rain to parts of Yemen.

When that rain fell on the dry mountainsides it poured down into coastal communities, unimpeded by vegetation, and overwhelmed the manmade canal that runs through the center of Mukalla.

But we will probably never know exactly how much rain fell or how strong the winds gusted in Mukalla, which has been governed by tribal council and al-Qaeda since April after the government and military withdrew.

Reuters reports that the seafront promenade and homes were destroyed, and that around 6,000 people fled the cyclone to higher ground:

“The wind knocked out power completely in the city and people were terrified. Some residents had to leave their homes and escape to higher areas where flooding was less; it was a difficult night but it passed off peacefully,” said Sabri Saleem, who lives in Mukalla.

There were no initial reports of injuries.

An al-Qaeda militant on Twitter prayed for deliverance from the storm and said that a U.S. pilotless drone was flying especially low over the city, where the militant group’s deputy leader was killed in an air strike in June.

“May God cause it to crash,” said the man, going by the name of Laith al-Mukalla.

Farther south in Hadhramaut, where the center of Chapala made landfall, local media reports that at least 25 people are injured, 21 are missing and more than 50 homes have been destroyed.

But no such official reports have come from the port city to the north. “There is no state in Mukalla,” Iona Craig, a freelance reporter in Mukalla, told Mashable. “There was basically no preparedness. Al-Qaeda posted pictures in the hours before landfall of a team of rescue vehicles. In practice those won’t have been much help in floods.”

The World Health Organization says they are making efforts to provide relief to the hardest-hit areas. In a news release on Monday, the organization said they delivered trauma kits to 1,000 patients in Mukalla, 20,000 liters of fuel to eight hospitals to ensure they can keep power, and 2,500 liters of fuel for 16 ambulances.