The ability of the Atlantic Ocean to churn out destructive hurricanes might create the impression that the majority of the world’s major tropical storms occur in that region.
Anyone harboring this perception would be mistaken.
“There’s loads of hurricanes in the western Pacific (Asian half), more than in anywhere else in the world,” said Cliff Mass, a professor of atmospheric sciences at the University of Washington.
“We don’t hear about them because they don’t hit the United States.”
All rotating storms are called cyclones, according to the National Hurricane Center in Miami. In one of the oddities of the weather business, those generated in the Atlantic and eastern Pacific — nearest North America — are called hurricanes and those in the western Pacific Ocean are called typhoons.
From 1981 to 2011, an average of about 30 cyclones sprung up every year in the Pacific, compared with only 6.4 in the Atlantic, according to a chart compiled by the National Oceanic and Atmospheric Administration. These storms are defined as having sustained winds greater than 33 meters per second, or about 74 mph.
Most of the typhoons are in the western Pacific because that half of the ocean is warmer, Mass said. Warmer currents tend to run up the western half of the oceans, in the Atlantic as well, he said.
As to why the Pacific is warmer than the Atlantic, it’s not clear, Mass said.
“It’s probably due to the size of the ocean. But (we’re) not sure,” he said.
Hurricanes don’t happen on the West Coast of the United States because the ocean water is too cold, Mass said.
Even farther south, such as in California and Mexico, the water is not warm enough for hurricanes, he said.
Hawaii doesn’t often get hit by hurricanes but did get a large one in 1992, Iniki. Six deaths were attributed to the storm and damage estimates ranged up to $2 billion.
The storm occurred during a strong El Nino year, in which the ocean temperature is higher than usual.
Storms that move into the Pacific Northwest are “cold-core” storms and generated by a contrast in temperatures — warmer to the south and cooler to the north, Mass wrote in his weather blog. While these can be destructive, they’re not marked by the tight spiral pattern of cyclones, and they start farther north.
Sometimes, a storm will start out as a cyclone and, as it moves north, becomes a cold-core storm — as has happened with Sandy, according to Mass.
“Many tropical storms weaken when they go through this transition, but for a small subset the opposite occurs,” he wrote in his blog on Sunday. “The two energy sources work synergistically for a while, resulting in a strengthening and expanding system … such is the forecast fate of Sandy.”
The Columbus Day storm of 1962, which killed about 50 people on the West Coast from California to British Columbia, started out as Typhoon Freda in the Pacific. By the time it came ashore, its gusts reached as high as 150 mph and the storm caused the equivalent of more than $1 billion in today’s money.
Still, the Columbus Day storm is not exactly the same type as Sandy, though the result was similar, Mass said.
“It started way away, weakened and got strong again,” he said.
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Glossary
Cyclone: A closed-circulating storm rotating counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
Tropical cyclone: A warm-core cyclone, originating over tropical or subtropical waters, with wind circulation around a well-defined center. Once formed, a tropical cyclone is maintained by pulling heat from the ocean at high temperature. They differ from extratropical cyclones, which derive their energy from temperature contrasts in the atmosphere.
Hurricane or typhoon: A tropical cyclone with winds of 74 mph or more. The term “hurricane” is used for Northern Hemisphere tropical cyclones east of the International Dateline to the Greenwich Meridian. The term “typhoon” is used for Pacific tropical cyclones north of the equator west of the International Dateline.
Source: National Hurricane Center
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