Weather and Natural Disasters

The reason Hurricane Patricia grew so strong so quickly

Strongest storm in history

If you think the strongest hurricane ever recorded appeared all of a sudden and out of nowhere, you're in good company.

Hurricane Patricia intensified on Thursday and Friday, and data from Air Force planes measured record-breaking sustained wind speeds of about 175 knots (over 200 miles per hour), and gusts of up to 247 miles per hour, according to the National Hurricane Center.

The monster hurricane weakened to a Category 2 storm early Saturday, after making landfall in Mexico, but those initial numbers made Patricia the strongest storm ever measured.

The storm's rapid intensification shocked researchers and confounded models. So how did Patricia get so intense, so suddenly?

Kerry Emanuel, an atmospheric scientist at MIT, told CNBC that Patricia's sudden intensity may have been due to the unusually warm water in the part of the Pacific where Patricia had been developing.

"Usually, when hurricanes try to intensify up to that speed limit, they begin to churn up cold water, and that starts to slow them down," Emanuel said. "That is particularly true in the Eastern Pacific."

Ocean water has different layers of temperature; it tends to be warmer toward the top, and colder at lower depths. The warmest water forms a thin layer at the top, and Emanuel said that layer of warm water at the surface is much larger than it usually is.

It also is a bit less salty than the deeper water, which means it is lighter, and it is mixing less with the colder, saltier water below.

We have set a record number of category 4 and 5 hurricanes in the Northern Hemisphere, and it is the consistent consensus that warming is contributing to the intensity of storms. We expect the frequency of high intensity events to increase.
Kerry Emanuel
atmospheric scientist, Massachusetts Institute of Technology

In short, then, the colder water that would normally inhibit a hurricane simply is not there.

Emanuel said the unusually warm water might be the result of the El Niño climate pattern, which warms water in this region of the Pacific Ocean. An especially powerful El Niño is expected this autumn and winter.

While all of that could explain what is happening, more data are needed, Emanuel said. He added that none of the models used for forecasting hurricanes, including his own, "got Patricia right," and it may be some time before researchers have clear answers.

NBC News reported that the hurricane was "rapidly weakening" on Saturday morning, citing the U.S. National Hurricane Center in Miami. The storm was downgraded after its maximum sustained winds decreased to near 100 mph as of 1:15 a.m ET.

Authorities said early Saturday there were reports of flooding and landslides, but no word of fatalities or major damage, according to NBC.

Emanuel has studied the effect of warming on hurricanes, and he said there is a connection between warming climates and the intensity of storms.

"We have set a record number of category 4 and 5 hurricanes in the Northern Hemisphere, and it is the consistent consensus that warming is contributing to the intensity of storms," he said. "We expect the frequency of high-intensity events to increase."

Extreme weather viewed from space.
Hurricane Patricia strengthens to Category 5 as it nears Mexico

A band of water that stretches from Mexico all the way up to Alaska is 1 to 2 degrees warmer right now than its average, said Scott Braun, a research meteorologist at NASA's Goddard Space Flight Center. The warmer water acts as a source of energy for the hurricane — evaporation off the water allows the storm to keep forming clouds at higher temperatures, and direct heat off the ocean heats the storm from underneath.

Atmospheric conditions around Patricia are the other half of the recipe, and they also favorable for Patricia, Braun told CNBC. The air is very moist, and there is very little vertical wind shear — the differences in wind speeds at different heights that typically would weaken the storm by tilting it or tearing it apart. The dry air and the lack of vertical wind shear means there is very little that can stop the storm from building intensity.

"This is a combination of extreme ocean conditions with favorable atmospheric conditions," Braun said. "You have very warm sea surface temperature, a deep warm water layer, very moist air, and very little vertical wind shear."

Braun said that the storm seemingly came out of nowhere in part because rapid intensification events are hard to predict.

"Conditions [around Patricia] were certainly ripe for rapid intensification, but it was on the extreme side of rapid intensification," Braun said. "Wind speed increased by about 95 knots in 24 hours, about 70 knots higher than the forecast."

"It is the type of event you can almost never forecast, because while we know that these rapid intensification event occur, they are so extreme that if you are wrong, you are 'the boy that cried wolf,'" he said.