From the start, there was something pretty odd about Hurricane Bertha.
The storm formed just before Independence Day last week, and immediately showed plenty of it. Bertha developed from a tropical wave almost immediately as the disturbance came off the coast of Africa, and so became the most easterly forming July tropical storm known to us, as well as the most easterly forming Atlantic tropical storm period.
In this, Bertha was aided along by warmer than average ocean temperatures, which could sustain the storm's development so early in the season. As hurricane expert Greg Holland of the National Center for Atmospheric Research put it to me by email, Bertha was "one for the record books" and the storm was just getting going.
As Bertha moved steadily westward, she intensified, first becoming a hurricane and then exploding into a powerful Category 3 major hurricane Monday with 120 mile per hour winds and possibly, for a brief while, a Category 4. It's the earliest we've seen such an intense Atlantic hurricane since the year 2005, when hurricanes Dennis and Emily were Category 4 and 5 storms, respectively, in July. Dennis reached Category 4 strength on July 7 of that year ... the same day on which Bertha exploded three years later.
That's a particularly worrisome precedent because in 2005, the hurricane year only got worse after Dennis featuring Category 5s Katrina, Rita, and Wilma.
But perhaps even more worrisome is this recent appearance of very intense hurricanes in July, a month that traditionally has not featured many of them. Says Holland: "It is notable that we have had a remarkable run of July storms, which over the past decade have been running more than 50% above the previous average." Technically, given her origins so close to the African coast, Bertha is categorized as a Cape Verde-type hurricane, and those tend to be the most powerful and destructive of them all. But they don't generally form until later in the hurricane season ... or, at least, that's how it used to be.
As global warming occurs, it's quite possible that the tropical Atlantic will itself warm up enough to sustain hurricanes earlier in the year and, at the same time, will stay warm enough to sustain them later in the year. This would suggest a gradual lengthening of the hurricane season on both ends, thanks to an expansion of what scientists call the Atlantic region's "warm pool."
Bertha may or may not affect any land areas at present, it could affect the island Bermuda, or it could stay in the open ocean. But either way, we can only consider it bad news.
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