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Wednesday, October 9, 2013
Tropical Storm Karen proved to be another in a long series of tropical flops for the United States last week — not that anyone on the coast is complaining.
Originally projected to be a strong tropical storm or weak hurricane at landfall along the Gulf Coast, the strong shearing winds of a jet stream trough over the U.S. mainland ripped Karen’s convection away from its circulation center, and the storm weakened into a barely discernible swirl of low pressure.
Karen is gaining something of a second life this week that will have some effects on our weather, which we’ll get to in a minute, but first let’s marvel at the amazingly sparse tropical period the U.S. is experiencing not just this season, but arguably for the past eight years.
It has been eight years since a major hurricane came ashore in the United States, the longest such period in recorded U.S. weather history.
The first objection that some may raise about this is “What about Sandy?” Well, technically, Sandy wasn’t a hurricane at landfall in New Jersey last October, but a post-tropical cyclone, as its tight, warm inner core had been largely replaced by a broader, cold circulation.
Even if Sandy had been a hurricane at landfall, it lacked the 111 mph or greater sustained winds (not just gusts), or Category 3 level, necessary to be considered a major hurricane.
Another one that could come into question would be Hurricane Ike, which caused extensive damage in Galveston, Texas, in 2008. While Ike has peaked as a Category 4 hurricane with winds of 145 mph, it came ashore with 110 mph winds, just barely within Category 2 range. Its storm surge, however, was more like that of a major hurricane.
One lesson from Sandy and Ike: It doesn’t take a major hurricane to cause major damage.
But it’s still a remarkable streak that no Category 3 or greater hurricanes have hit the U.S. since Wilma in late October 2005, which was the last of seven such major hurricanes (and 10 total hurricanes) to do so over two seasons.
Since hurricanes Dolly, Gustav and Ike hit different parts of the western Gulf Coast in 2008, there have been only two hurricanes of any strength that have made landfall in the United States: Irene in 2011 (North Carolina) and Isaac in 2012 (Louisiana).
The lull in hurricanes hitting the U.S. does not appear to be correlated to a reduction of overall tropical activity in the Atlantic. In fact, the last few seasons have been busy, when looking at the ocean as a whole.
The last three Atlantic tropical seasons have averaged 20 named storms, 10 hurricanes and four major hurricanes, compared to norms of 10, six and three, respectively. The bulk of those just haven’t affected the U.S., for various reasons.
This season appears to be different than those, as it has produced only two hurricanes and no major hurricanes so far anywhere in the Atlantic. If this trend continues, it will be the first Atlantic tropical season without a major hurricane since 1968.
Karen’s new life
Karen was a flop as a tropical system, but its circulation is being reconstituted into a different animal, a coastal low, that will slowly drift northward along the Eastern seaboard the next few days.
While coastal areas will get wind-driven rain and some high surf, Southwest Virginia will get cool, clammy weather with some drizzle and light rain, as the counterclockwise circulation around the low banks cool, damp air against the mountains.
Highs will struggle to get above 60 in much of our region today and Thursday. Those summer-like 80s of last week are already a memory as we move deeper into the autumn battle between the tropics and the tundra.
Weather Journal runs on Wednesdays.
Weather JournalMidday update: More ice likely later