Hurricanes keep avoiding U.S., will it continue?
Hurricanes Igor and Julia at Category 4 intensity
With the 2010 season producing tropical cyclones in rapid succession now, the United States coastline continues to remain nearly immune from the realistic threat of a direct hurricane strike. Not a single storm from this year's basket of 13 systems (11 named) has come within 75 miles of our shores at hurricane strength. In fact, only one of those 13 tropical cyclones, tropical storm Bonnie, actually made a U.S. landfall. And that was at minimal tropical storm status (40mph) near Homestead, FL, 27 miles south of Miami on the morning of July 23. One can only hope the steering currents will continue to be so kind.
In the near term, with three named systems on the active roster (Igor, Julia, and Karl), it appears the "0-for" streak will continue. Igor, the most ferocious system of the year, remains a powerful category 4 hurricane with maximum sustained winds estimated at 135 mph. Its spectacularly beautiful satellite presentation belies the tempestuous maritime conditions surely ongoing underneath its eyewall.
The variance in the track guidance is relatively small with Igor. It will very likely remain far off the mainland U.S. coast, though not before agitating the seas enough to produce large swells near the mid-Atlantic Coast over the weekend. Interests in Bermuda, however, should closely monitor the progress of Igor, as the large hurricane-force wind field may closely approach the island in a couple of days.
Julia, yet another category 4 hurricane, is the slightly disheveled looking feature on satellite imagery well to the east of Igor. With maximum winds estimated at 135 mph, Julia is expected to strengthen a little more during the next several days as it too curves northward over the central Atlantic.
According to meteorologist Jeff Masters at wunderground, it is only the second time on record there have been two category 4 hurricanes at the same time in the Atlantic. He also said Julia's 135 mph winds make it the strongest hurricane on record so far east. And hurricane researcher Phil Klotzbach at Colorado State University told CWG (Capital Weather Gang) that between August 27 and September 15 there have been four (Danielle, Earl, Igor, and Julia) category 4 hurricanes -- the most on record in such a short period.
Tropical storm Karl, the most recent addition to the season, is closer to home. Yet its proximity to Mexico, and projected track over the Yucatan, should prevent the storm from intensifying much beyond its present state (estimated at 65 mph as of Wednesday morning).
But will the steering currents for the storms later this season continue to spare the U.S. from a direct hit?
If the underlying shape of the atmosphere continues to feature an upper-level ridge of high pressure over the Southern Plains (shaded in orange above), as it basically has for the last month, then the answer is probably so. Many of this year's systems that have migrated westward across the tropical Atlantic have found a 'soft spot' in the upper flow over the Atlantic, between the Southern Plains high pressure and another high pressure system over the eastern Atlantic (also shaded in orange on the right side of the picture). In this zone, between roughly 75W and 45W, the winds aloft have seldom been directed toward North America.
The clockwise circulation around each of the high-altitude high pressure ridges has combined to create a northwesterly (offshore) wind and a southerly wind over the western and central Atlantic that has effectively shoved approaching Cape Verde storms (that develop off the west coast of Africa) back out to sea. In addition, the clockwise circulation around the Southern Plains system has also helped to block storms that formed in the Caribbean (like Alex, Hermine, and Karl) from turning northward in time to cross the U.S. Gulf Coast.
But if the pattern shifts just a little, toward one that moves the'weakness' in the upper-level ridging closer to Eastern North America, then the path will be cleared somewhat for a landfall. In this case, instead of a northward turn over the Central Atlantic, the recurvature could take place at a longitude much closer to home. Some of the global weather models are hinting that this might indeed occur in the next 1-2 weeks. We will be watching this for you closely.
(CWG's Jason Samenow contributed to this post)
Capital Weather Gang
| September 15, 2010; 10:29 AM ET
Categories: Tropical Weather
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