BLOG: Hurricane season now underway, likely below average

BLOG: Hurricane season now underway, likely below average

Pre-season Tropical Storm Ana notwithstanding, as I first blogged about from the National Hurricane Conference held in Texas earlier this spring, the 2015 Atlantic Hurricane Season may tend to be on the quiet side.

But frankly, that's nothing new.

Not since 2005 has a major hurricane last made landfall on U.S. shores.

Major hurricanes - categories 3 - 4 - 5 with winds of 111 mph or more - are the most intense and account for roughly 80% of all hurricane damage.

Considering it's been a decade since Wilma - the most intense hurricane on record in the Atlantic basin - lashed South Florida, you might think we're due for a big season.

Probably not.

Seasonal forecasters say several key factors are coming into play now that may keep a lid on tropical activity.

Dr. Phil Klotzbach, a hurricane research scientist from Colorado State University, leads a team that's been producing seasonal forecasts since 1984. His most recent, released on Monday, calls for a "well below-average season," stating key signals are in place nearly insuring as such. "Sea-surface temperatures in the Atlantic basin are the coldest since the early 1990's; that coupled with higher than normal pressure over the basin and a building El Nino tell us 2015 will likely be on the quiet side."

A developing strong El Nino means much warmer water in the equatorial Pacific Ocean. In connecting the dots, that causes very strong westerly winds to blow across from the Pacific into the Atlantic, right over the favored zones for tropical cyclone generation.

The one thing that hampers tropical cyclone growth more than anything is strong, upper-level shear. Shear, the twisting of wind with height simply blows off the tops of the thunderstorm clusters in and around the cyclone.

Another big player looks to be the persistent ridge of high pressure over the western U.S. and the seemingly locked-in east coast trough. Ridges generally promote hot and dry weather during the summer months, and that's a concern for drought stricken states such as California and Nevada.

In the East, it's just the opposite: a big, semi-permanent dip in the jet stream means a continuation of cooler weather along the east coast and likely wetter too (think New England snows this past winter).

A "U" shaped jet along and just off the east coast generally keeps storms tracks offshore, which bodes well for coastal communities hoping to escape a major land-falling hurricane this season.

But be warned, even in "quiet" seasons, big storms can fire up. Hurricane Andrew - still the costliest hurricane on record - was a category 5 at landfall in South Florida late in the summer of 1991.

It was also the lone hurricane that year.

As a meteorologist for nearly 30 years, I can't stress enough to always be prepared. If there's only one hurricane this season, but it plows through your neighborhood, it will have been a very busy season!

- Al Conklin

Notes of interest:

Hurricane season runs from June 1 through November 31.

1915-1964: 23 major hurricanes directly struck the U.S east coast.

1965-2014: Only 9 major hurricanes made a U.S. east coast landfall

In any given year, there is a 52% chance of a major hurricane making landfall somewhere along the U.S. east coast.

In North Carolina, there is a 28% of a land-falling hurricane in any given year and an 8% risk of it being a major storm.

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