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'VERY ACTIVE' Still the Watchword
The 2006 Hurricane Season is expected to be above average.
In its early April update, the Colorado State University (CSU) forecast
team has maintained its earlier prediction for the 2006 hurricane
season: the U.S. Atlantic basin will likely experience another very
active season, but most likely with fewer landfalling intense
hurricanes than in 2005, the costliest, most destructive hurricane
season ever (see HP, Spring 2006, page 15).
The team’s forecast for the 2006 hurricane season
anticipates 17 named storms forming in the Atlantic basin between June
1 and November 30. Nine of the 17 storms are predicted to become
hurricanes, and of those nine, five are expected to develop into
intense or major hurricanes (Saffir/Simpson Category 3, 4, 5) with
sustained winds of 111 mph or greater.
"We have maintained our forecast from our early
December prediction as the Atlantic Ocean remains anomalously warm and
tropical Pacific sea surface temperatures have continued to cool," said
Phil Klotzbach of the CSU hurricane forecast team based in Fort
Collins, CO. "We expect either neutral or weak La Niña
conditions to be present during the upcoming hurricane season."
BY THE NUMBERS
The hurricane forecast team predicts tropical
cyclone activity in 2006 will be 195 percent of the average season. By
comparison, 2005 witnessed tropical cyclone activity that was about 275
percent of the average season with 27 named storms, 15 hurricanes and
seven intense hurricanes. Long-term averages are 9.6 named storms, 5.9
hurricanes and 2.3 intense hurricanes per year.
"Even though we expect to see the current active period of
Atlantic major hurricane activity to continue for another 15 to 20
years, it is statistically unlikely that the coming 2006-2007 hurricane
seasons, or the seasons that follow, will have the number of major
hurricane U.S. landfall events as we have seen in 2004-2005," said CSU
Professor William Gray.
The hurricane forecast team reiterated its
probabilities for a major hurricane making landfall on U.S. soil:
• 81 percent chance that at least one major hurricane
will make landfall on the U.S. coastline in 2006 (the long-term average
probability is 52 percent).
• 64 percent chance that a major hurricane will make
landfall on the U.S. East Coast, including the Florida Peninsula (the
long-term average is 31 percent).
• 47 percent chance that a major hurricane will make
landfall on the Gulf Coast from the Florida Panhandle west to
Brownsville, TX (the long-term average is 30 percent).
The team also predicted above-average major
hurricane landfall risk in the Caribbean.
"In any one season, most U.S. coastal areas will not
feel the effects of a hurricane no matter how active a season,"
Klotzbach said. "The probability of landfall for any one location along
the coast is very low. However, low landfall probability does not
ensure that hurricanes will not come ashore, so coastal residents
should always be prepared."
Probabilities of tropical storm-force,
hurricane-force and intense hurricane-force winds occurring at specific
locations along the U.S. East and Gulf Coasts within a variety of time
periods are listed on the CSU’s Landfall Probability Web site:
www.e-transit.org/hurricane. It is the first publicly accessible
Internet tool that adjusts landfall probabilities for regions,
sub-regions and counties based on the current climate and its projected
effects on the upcoming hurricane season. Klotzbach and Gray update the
site regularly with assistance from the GeoGraphics Laboratory at
Bridgewater State College in Massachusetts.
NOT MAN-MADE
The hurricane team’s forecasts are based on the
premise that global oceanic and atmospheric conditions—such as El
Niño, sea surface temperatures and sea level pressure—that
preceded active or inactive hurricane seasons in the past provide
meaningful information about similar trends in future seasons.
For 2006, Gray and the hurricane forecast team
expect continued warm tropical and north Atlantic sea-surface
temperatures, prevalent in most years since 1995, as well as neutral or
weak La Niña conditions: a recipe for greatly enhanced Atlantic
basin hurricane activity. These factors are similar to conditions that
occurred during the 1964, 1996, 1999 and 2003 seasons. The average of
these four seasons had well above-average activity, and Klotzbach and
Gray predict the 2006 season will have slightly more activity than the
average of these four years.
Gray does not attribute changes in recent and
projected Atlantic hurricane activity to human-induced global warming.
"Seasonal and monthly variations of sea surface temperature within
individual storm basins show only very low correlations with monthly,
seasonal and yearly variations of hurricane activity," Gray said.
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