Why was Typhoon Yolanda so deadly?

When Typhoon Yolanda (International Name: Haiyan) struck in 2013 it was the disaster-prone Philippines' worst storm on record, with 7,350 people dead or missing.

Several factors caused the staggering death toll:

Strongest storm

With gusts exceeding 305 kilometers (190 miles) per hour at first landfall, Yolanda was the strongest ever to hit land at the time. Typhoons more commonly reach peak velocity while still traveling over oceans.

The powerful front drove a giant wall of seawater called a storm surge, estimated to be 7.5 meters (24.6 feet) high, into coastal towns like Tacloban, a city of 240,000 people.

Overall, Yolanda tore across a group of islands with a combined area the size of Portugal.

Low-lying islands

The Philippines is the first major landmass on the Pacific Ocean's typhoon belt. A wall of mountains on the coast of the main island of Luzon dampens some of the blows, but the smaller, flatter islands -- such as those that lay in Yolanda's path -- are more exposed.

Much of Tacloban sits less than five meters above sea level. The town and others nearby were defenseless against the storm surge that funneled through a shallow bay sandwiched between Leyte and Samar islands.

Inadequate warnings

Even though the hardest-hit areas received early warnings, the weather service and other officials later admitted that the victims were unfamiliar with the term "storm surge".

The last deadly storm surge in Tacloban had hit in 1887, more than a century before Yolanda. In a country with scores of regional languages, the government also did not have local terms to be able to communicate the phenomenon to everyone.

After the disaster, the government agency worked with linguists to craft simpler meteorological terms to ensure the danger posed by typhoons, floods, landslides and other adverse events would be fully understood by all.

Extreme poverty

In a nation where one in five people earn less than two dollars a day, the people in Yolanda's path stood out for their deep poverty. Many of the victims built their homes on the islands' narrow coastal plains and lived off subsistence fishing and farming.

Yolanda destroyed or damaged 1.14 million houses, many of them made of cheap, flimsy materials that stood no chance against nature's wrath.

Failure to evacuate

The national government, through a geohazard mapping program begun in 2006, had flagged most of the areas that were prone to the impacts of natural disasters.

However, local governments failed to evacuate many of the vulnerable population away from the danger zones, partly because they did not fully appreciate the threat and partly because they had not built enough shelters.

In the town of Hernani on Samar island, where Yolanda made the first of many landfalls, several families were wiped out by a storm surge when they left their flimsy shacks to ride out the storm at a low-lying school built along the coast, neighbors told AFP. — Agence France-Presse