by Richard Harris
The deadly typhoon that swept through the Philippines was one of the
strongest ever recorded. But storms nearly this powerful are actually
common in the eastern Pacific. Typhoon Haiyan’s devastation can be
chalked up to a series of bad coincidences.
Typhoons — known in our part of the world as hurricanes — gain their
strength by drawing heat out of the ocean. Tropical oceans are
especially warm, which is why the biggest storms, Category 4 and
Category 5, emerge there. These storms also intensify when there’s
cool air over that hot ocean.
“The Pacific at this time of year is very ripe and juicy for big
typhoons,” says Kerry Emanuel, a climate scientist at the
Massachusetts Institute of Technology. “Once or twice a year we get a
Category 5 typhoon out there.”
“But it’s a great rarity, fortunately, that a storm just happens to
reach peak intensity when it’s making landfall. And that’s what
happened in this case.”
As it approached one large island in the Philippines, the storm pushed
up into a broad bay. That created a 13-foot storm surge that caused
widespread devastation at the head of that bay, in the city of
Tacloban.
Mountains also wring rainwater out of storms like these. And then
there’s the wind.
“So we had a triple whammy, of surge, very high winds and strong
rainfall,” Emanuel says.
Super Typhoon Haiyan could be the strongest on record, but scientists
can’t say for sure because they don’t have direct measurements of the
wind speed. Hurricane scientists usually fly into storms heading
toward the United States to measure wind speed and barometric
pressure. And the U.S. Navy used to do that for storms in the western
Pacific. But Emanuel says budget cuts ended that practice decades ago.
“Since then, we’ve had to rely on satellites, mostly, to estimate
typhoon intensity,” he says. “And satellites are very good at
detecting the presence of typhoons but they’re not so great when it
comes to estimating how strong they are.”
Scientists at the U.S. Navy/Air Force’s Joint Typhoon Warning Center
infer that Haiyan produced sustained wind speeds of around 190 or 195
mph at its peak. John Nielsen-Gammon, the Texas state climatologist at
Texas A&M University, says gusts blew up to 230 mph, which is as fast
as a speeding race car.
“Imagine instead of having just one car, imagine millions of raindrops
and debris moving at the same speed past you, and you’re trying to
stand in the middle of it,” Nielsen-Gammon says. “That’s the kind of
force such a hurricane can generate.”
The strongest hurricane or typhoon winds on record were from Camille,
which struck the U.S. Gulf Coast in 1969. But its 190 mph winds don’t
tell the whole story. The diameter of the storm matters as well.
“Camille was a very small storm, maybe about one-fifth the size of
Haiyan,” he says. “So it caused a lot of devastation but over a
relatively limited area.”
To find out whether Haiyan had record-breaking winds, scientists may
turn to amateurs for information.
“Any major storm will attract storm chasers, and Haiyan was no
different,” Nielsen-Gammon says. “So there were people who traveled to
Tacloban specifically to get footage of the storm, and they took along
some instruments. So we’ll probably get some data out of that.”
Of course, that number is only one way to measure the overall severity
of a typhoon. The mounting death toll will be another.
And climate scientists like Nielsen-Gammon and Emanuel say that as the
planet continues to heat up, so will the oceans. And that means there
will be more energy available for storms — and likely more Class 4 and
5 typhoons. – NPR via ENN
