WASHINGTON — The Atlantic Hurricane Season officially begins June 1, and forecasters, doomsayers and intense weather watchers have been releasing their predictions for the coming season for months. I will take you through the roughly 150 years of Atlantic hurricane history and our current thinking for an outlook for the coming season.
WHAT IS AN AVERAGE SEASON?
An average season is characterized by a landfall of a hurricane in the United States, minimum annual probability of 4.75 percent and 17 named storms.
WHAT DOES A 90 PERCENT CHANCE MEAN?
“Normal” generally means at least one hurricane category. However, since there is no statistical expectation of high or low hurricane activity, the term average can mean nearly anything a week out from the official start of hurricane season.
Since records have been kept, there have been some years where there were fewer named storms, but no hurricane warnings. With a normal season, this is likely an anomaly of the statistics. The average is based on the standard deviation of numbers. Since 1970, Hurricane Devastation Zones have centered on the following regions:
The nation’s hurricane zones have also been more widespread recently. This year, parts of the upper Midwest are in the Hurricane Impact Zone, and this is occurring on average.
RELATED: Weather map looking at upcoming hurricane season
WHY WE PREDICT HEAVY HURRICANES
Hurricanes are associated with warm sea surface temperatures, but there are a number of other factors that also are important. These include surface currents, the convection processes within the deep Earth’s atmosphere, topographic gradient and vertical motion of the oceanic surface.
So, to reiterate, there is no statistical expectation of more than one hurricane in the U.S. per year. However, given the warming of the ocean, there is a higher chance that the area between Florida and Bermuda will see six or more hurricanes per season by 2050.
WHAT HAPPENS IN THE MAJOR HURRICANES?
Category 1 hurricanes have winds between 39 mph and 74 mph. Storms with winds between 74 mph and 111 mph are categorized as hurricanes, and those with winds over 111 mph are Category 3 hurricanes.
Category 4 storms have winds between 111 mph and 138 mph.
Category 5 storms have winds of 140 mph or higher.
Category 6 storms have winds of 151 mph or higher.