New forecast projects milder than predicted storm season

The British Virgin Islands was among the Caribbean islands that suffered catastrophic damage in Hurricane Irma. Several Caribbean islands were hit by Hurricanes Irma and Maria last summer and are still recovering from the storms. - PHOTO: U.K. Ministry of Defence

Forecasters at Colorado State University’s Department of Atmospheric Science have updated their projections for the 2018 hurricane season, and they now believe that conditions are ripe for a mild spate of storms over the next few months.

The new projection, updated on July 2, puts the odds for at least one major hurricane tracking into the Caribbean at 31 percent, 11 percent lower than the average for the last century.

Also, the Colorado State researchers believe there will be 11 named storms, four hurricanes and one major hurricane this season, reductions from their earlier projections of 14, seven and three, respectively, in April.

For perspective, the median for the period between 1981 and 2010 was 12 named storms, 6.5 hurricanes and two major hurricanes per storm season.

The main drivers of this year’s projections are colder ocean temperatures and a weakened El Nino, said Michael M. Bell, an associate professor at Colorado State University’s Department of Atmospheric Science.

“There’s a large high-pressure system that sits over the Atlantic at this time of year. That drives the trade winds which keep you guys nice and cool there in the Caribbean,” said Mr. Bell, one of the co-authors of the study. “When those trade winds are stronger than normal, that tends to cool the waters. In this case, the pressure is stronger than typical, and that’s what’s leading to those colder ocean temperatures. It’s an atmosphere/ocean interaction that’s causing the ocean to cool down.”

The study also found that the probability for a major hurricane making landfall on the entire coastline of the United States is 39 percent, down from an average of 52 percent for the last century.

Colorado State University’s researchers have plotted in the current data and compared it to assembled data-sets for the last 36 years to make their projections, and they will have a final detailed forecast on Aug. 2.

Mr. Bell said that two seasons that closely resemble the current conditions took place in 2009 and 2014, and both of those years featured lower than average storm activity.

“We’ve been monitoring the situation closely since our first forecast came out in April,” said Mr. Bell. “It’s interesting how things have changed from that initial forecast where we thought an above-average season was more likely. I think the two biggest things that have changed is that ocean temperatures have cooled a lot more than expected off the coast of Africa, which is surprising to some degree, and the other big factor that caused us to reduce our forecast is the El Nino conditions.

“It looks more likely that it will be a weak El Nino, and that I think is a little less surprising.”

Mr. Bell said that ocean temperatures reached a near-record warmth last season, which makes it a little more surprising to see them plunge to a near-record cooling this time around.

The first month of hurricane season resulted in just one named storm – Alberto – in the Atlantic, but Mr. Bell cautioned that the heaviest storm activity usually does not take place until August and September. That is why the final projection – the one on Aug. 2 – will have the highest expected degree of accuracy.

The July 2 edition of the study also projected that the east coast of the U.S. – including peninsular Florida – will have a 22 percent chance of a major hurricane making landfall, as opposed to the average of 31 percent for the last century. The probability of a major hurricane making landfall in the United States is just 75 percent of the long-term average, but Mr. Bell cautioned that people need to be prepared for any contingency if they live in the potential path of a major storm.

“All it takes is one and we always try to emphasize that,” he said.

“Even at 31 percent [for the Caribbean], we’re talking about essentially a 1/3 chance for a major hurricane to track through that region. We certainly hope we don’t see any landfall impacts this year, especially after last year. But we’ll just have to wait and see.”

 

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