Experts say Typhoon Haiyan was about as strong as it could theoretically get when it swept through the Philippines, killing thousands of people and driving hundreds of thousands from their homes. But intensity limits have been rising over decades past — and climate models suggest they will keep rising over the decades to come, with the potential for bigger and more devastating storms.
"The tragedy of this particular storm is that it reached its limit just about the time it made landfall," Kerry Emanuel, a climate scientist at the Massachusetts Institute of Technology, told NBC News.
Based on satellite imagery, the U.S. military's Joint Typhoon Warning Center estimated that Haiyan's winds reached a sustained peak as high as 195 mph shortly before it made landfall, with gusts rising to 235 mph. Estimates from Philippine weather officials were lower, suggesting that the storm packed sustained winds of 147 mph and gusts of 170 mph when it hit land. Either way, the typhoon ranks among the world's strongest tropical storms and appears to have been more powerful than Hurricane Katrina in 2005.
If the higher estimates are correct, the warning center said Haiyan's maximum strength would exceed that of its previous record-holder: Hurricane Camille, which hit the northern Gulf Coast in 1969 with sustained winds of 190 mph.
"This is at the top end of any tropical system that we've seen on our planet," said Bryan Norcross, The Weather Channel's hurricane specialist.
The tale of Typhoon Haiyan's destructive power has turned the world's attention from the Atlantic hurricane season, which has been much weaker than average, to the less understood Pacific front. Here are answers to a few of the most frequently asked questions:
Satellite imagery from NASA's Tropical Rainfall Measuring Mission shows Typhoon Haiyan's structure as the storm made its way across the Philippines on Nov. 8.
What's a typhoon?
Typhoons, hurricanes and cyclones are just different names for the same type of storm. "The ingredients for these storms include a pre-existing weather disturbance, warm tropical oceans, moisture and relatively light winds," the National Oceanic and Atmospheric Administration says. "If the right conditions persist long enough, they can combine to produce the violent winds, incredible waves, torrential rains and floods we associate with this phenomenon."
Such storms are called hurricanes when they're in the Atlantic and Northeast Pacific, cyclones in the South Pacific and Indian Ocean, and typhoons in the Northwest Pacific. A "super typhoon" like Haiyan has maximum sustained surface winds of at least 150 mph, according to the Joint Typhoon Warning Center. That's equivalent to a Category 4 or 5 hurricane.
What factors made Typhoon Haiyan so deadly?
Some experts have said Haiyan was skimming so quickly across the Pacific that it didn't suck up the deeper, cooler ocean water that might otherwise have reduced the storm's energy before landfall.
Another factor is that Haiyan followed a track that was outside the typical "Typhoon Alley" for the Philippines. "The high pressure to the north was a little farther south," Norcross explained. "That pushed the storm track farther to the south, into the central Philippines, as opposed to the northern Philippines where they get most of the storms. The central Philippines are much more vulnerable, because people haven't moved to places that are safe from typhoons."
When the storm passed over the hard-hit coastal city of Tacloban, the area's funnel-shaped bay turned the storm surge into a 20-foot-high wall of water. Norcross said some U.S. coastal areas could suffer similar effects during a hurricane. "Around the coast in the U.S. — the Florida Keys, the western coast of the state of Florida, up in the panhandle, Louisiana — all are susceptible to this kind of storm surge," he told NBC News.
How frequently do storms like Typhoon Haiyan come along?
"In the current climate, a storm of this intensity is probably a once-in-a-decade thing," Emanuel said, "but a storm of that intensity hitting land would be a much rarer thing." That coincidence might occur once in a century, he said. Climate models suggest that the landfall-at-maximum phenomenon may occur more frequently in the future — but to verify that hypothesis, Emanuel said you'd have to collect data over the next 100 years or so. "I hope it's at least 100 years," he said.
Why is it so hard to be precise about the storm's strength?
Both Emanuel and Norcross bemoaned the fact that Pacific typhoons aren't being studied as closely as Atlantic hurricanes. The U.S. military discontinued up-close typhoon monitoring in 1987, and the Joint Typhoon Warning Center now relies primarily on satellite and radar data. That's why it was so hard to pin down precisely how strong the storm was as it headed for the Philippines.
"Was it better developed than Hurricane Wilma in 2005, or Katrina at its peak? We really can't say, because we didn't have any hurricane hunters flying in this to actually measure the winds," Norcross said.
In addition to the Hawaii-based warning center, China, Japan and Taiwan have typhoon-monitoring agencies, "but there's no coordinated effort," Emanuel said. He recommended setting up an international center and using typhoon-hunting airplanes — or robotic drones, for that matter — to keep track of the typhoons of the future.
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