A 'Cool' Anomaly

As indicated by this satellite-generated map, sea-surface temperatures in the Atlantic are currently the coldest on record since 1982. Map courtesy of NOAA/NESDIS.
By Robert C. Jones Jr.

As indicated by this satellite-generated map, sea-surface temperatures in the Atlantic are currently the coldest on record since 1982. Map courtesy of NOAA/NESDIS.

A 'Cool' Anomaly

By Robert C. Jones Jr.
Colder Atlantic temperatures could change hurricane season forecasts, but the trend isn't expected to last.

With subtropical storm Alberto forming in the northwestern Caribbean Sea in late May, the 2018 Atlantic hurricane season was off to hot—and early—start, stoking fears that we could be in for a repeat of last year’s destructive storms.

But it’s a cool trend, in the form of below-average water temperatures, which at least for now may help to allay our anxiety over a busy six-month period of storms.

Warm water at the ocean’s surface that is at least 80 degrees Fahrenheit is the fuel that powers hurricanes. But with the area off the coast of Africa near the Cabo Verde Islands, where the majority of intense hurricanes develop, now averaging in the low 70s, mid-June is seeing some of the coldest Atlantic sea surface temperatures on record since 1982, raising hopes among Hurricane-weary citizens that a below-average storm season may be in the cards.

“The cooling in the Atlantic now is suggestive of a somewhat weaker hurricane season than perhaps was originally forecast,” said Ben Kirtman, a professor of atmospheric sciences at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science.

Scientists at the National Oceanic at Atmospheric Administration’s Climate Prediction Center have forecast a near or above-normal hurricane season, with a 70 percent likelihood of 10 to 16 named storms, of which 5 to 9 could become hurricanes, including 1 to 4 major storms.

“What we’re seeing are cool sea-surface temperature anomalies in the deep tropics, warm in the subtropics, and then cool again in the high latitudes,” said Brian McNoldy, a senior research associate and tropical cyclone specialist at the Rosenstiel School. “The pace of this anomalous cooling in the deep tropics has actually been increasing. We’re already into mid-June, so if it’s this way in another two months, I would think it would have quite an impact on the hurricane season.”

But what’s causing the cooler Atlantic temperatures, and, more importantly, how long will they last?

“Any sea-surface temperature anomaly that you see in the Atlantic or in the Pacific is due to all kinds of processes. At the moment, there’s a warm structure in the Pacific. I wouldn’t call it an El Niño type of thing,” explained Kirtman, referring to the climatic event characterized by unusually warm ocean temperatures in the Equatorial Pacific. “But it’s definitely warmer than normal in the tropical Pacific. So I think part of what we’re seeing in this cooling in the Atlantic is a remote response that’s coming from the Pacific.”

Kirtman, who is also director of NOAA’s Cooperative Institute for Marine and Atmospheric Studies based at the Rosenstiel School, is one of the first to develop an El Niño/La Niña prediction system using sophisticated climate models. He leads a team of government laboratory researchers, academicians, and operational climate forecasters in developing the North American Multi-Model Ensemble prediction system, which has been issuing forecasts in real-time since August 2011 and became an official NOAA operational system two years ago.

What recent forecast models two months out are showing, Kirtman said, is that the “cooling in the Atlantic seems to be decaying—going towards normal. So the chances of it remaining cooler are pretty slim.”

Which is the reason not to delay preparing for a potential storm strike.

Said McNoldy, who has maintained a blog on tropical Atlantic activity since 1996, a Hurricane Hub portal on the Rosenstiel School website, and is the tropical weather expert for The Washington Post’s Capital Weather Gang blog, "Within any hurricane season, even a quiet one, you can still have a strong hurricane or two or even three. And if they hit us, it's a big deal."


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