LSU AgCenter Climatologist Eyes New Norm To Measure Hurricane Season

John Grymes  |  7/2/2005 2:12:27 AM

News You Can Use For July 2005

The predicted number of hurricanes for the 2005 season is well above the norm for a single season. A look at the past 10 years, however, shows active seasons have become more common than unusual, according to LSU AgCenter climatologist Jay Grymes.

The nation's foremost hurricane prognosticators, including scientists from the National Hurricane Center, are expecting another busy storm season. Forecasters are calling for up to 15 named storms, with as many as nine of those storms achieving hurricane strength.

Grymes says about half of those hurricanes are expected to become "major" hurricanes, reaching category 3 or higher intensities on the Saffir-Simpson hurricane scale.

"These numbers are well above the norm, with long-term records indicating about 10 named storms, including six hurricanes, on average," Grymes says, but adds, "The past 10 years have been anything but average." He notes that storm counts have been above the norm for all but one season since 1995, with 15 or more named storms reported in 1995, 2001, 2003 and 2004.

This same 10-year period has seen a very active run of tropical weather for the Bayou State as well - nine storms have made landfall in Louisiana over the last 10 years, including last year's landfall by Tropical Storm Mathew.

In addition, Louisianians have watched nervously as a number of big, destructive storms came uncomfortably close. Among them were1995's Opal, 1998's Georges and two near misses by last year's Ivan. The last 10 years included "direct hits" by 1997's Danny, flooding rains delivered by 2001's Allison and the record year of 2002, with four landfalls along Louisiana's coast from Bertha, Hanna, Isidore and Lili.

"Of greater concern to interests along the Gulf Coast is the fact that most tropical weather scientists believe that this recent run of elevated storm counts may continue for another 10, 15, even 20 years or more," Grymes says, noting, "Evidence is mounting that there may well be a cycle of roughly 50 to 60 years with regard to tropical activity over the Atlantic Basin."

The climatologist explains that multi-decadal periods occur when surface water temperatures and atmospheric conditions are "in phase" and enhance the likelihood of storms to develop and intensify. These periods of increased storm counts are then followed by an extended run of years when storm activity is somewhat depressed.

Grymes points out that individual years within this long-phase cycle of elevated/depressed storm activity may deviate from the pattern, but the overall effect is to produce extended clusters of "stormy" years followed by prolonged runs of "quieter" tropical seasons.

For information on related topics, visit the AgCenter Web site at www.lsuagcenter.com/. For local information and educational programs, contact an extension agent in your parish LSU AgCenter office.

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On the Internet: LSU AgCenter: www.lsuagcenter.com/
Source: Jay Grymes (225) 578-6870, or JGrymes@agcenter.lsu.edu

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