With sustained winds of an estimated 195 miles per hour, steady intensification, and a prolonged Category 5 classification, Haiyan – the typhoon that killed thousands of people in the Philippines when it made landfall on Nov. 8 – was about as intense as a storm gets. But was it an anomaly? Indicative of a “new normal” of super storms? Evidence of climate change?
Not necessarily, according to Daniel Stern ‘05, an NSF postdoctoral fellow at the NCAR Earth System Laboratory in Boulder, Colorado, who was on campus on Wednesday to deliver two lectures hosted by the Department of Earth and Atmospheric Sciences.
Conditions in the Pacific are ripe for strong storms, year-round. Typhoons – similar to hurricanes that originate over the Atlantic – gain their strength by drawing heat out of the ocean, forming when sea surface temperature rise above 79F (26C). The temperatures near the Philippines tend to hover around 86F (30C).
In the case of Haiyan, the conditions were particularly favorable, Stern said.
As storms move along the ocean, they churn up the water, which often causes cooler water to rise to the surface and ultimately slow down the storms’ progress. Vertical wind shear – the change of winds with height - can also slow down a storm. High shear is considered anything above 23 miles per hour (20 knots.
The warm water in the Pacific went pretty deep as Haiyan was forming, and the wind shear was only 6-12 mph (5-10 knots), meaning the typhoon didn’t meet much resistance as it hurtled westward, Stern said.
Yes, Haiyan is one of the strongest typhoons ever recorded, and its 13ft storm surges caused extra devastation to the islands’ coastal communities. But storms nearly as powerful are actually quite common in the Philippines, which has already been pelted by 9 tropical cyclones this season. Haiyan is the fourth Category 5 storm in the Western Pacific this year, and according to the Accumulated Cyclone Energy index, which incorporates the number, strength and duration of all the tropical storms in a season, the region has had a slightly below-average season.
Are storms getting stronger, and is manmade global warming to blame?
Stern said the scientific literature seems to suggest a slight increase in the maximum intensity of tropical storms – between 2 and 10 percent by 2100. But we probably won’t be observing much change in the near future.
“I don’t think this is an anomaly or evidence of a new pattern of storms, or the new normal,” he said. “I don’t think it’s indicative of the effect of climate change.”
Another alumnus, Owen Shieh ‘07, also presented a TEDx talk about typhoons and other hazardous weather events in Honolulu on Nov. 16.
And extension specialist Keith Tidball, coordinator of the New York State Extension Disaster Education Network, offered his tips for how to support recovery efforts in this article, as well as the Cornell Disaster Relief and Outreach blog, which is also compiling information about how Cornellians can contribute to relief efforts.
