With two months still to go before the official start of the 2011 Atlantic hurricane season, the prognosis appears to be for a season featuring above-average activity, according to the outlooks from a couple of highly respected forecasters.
The Colorado State University (CSU) forecast team -- in its 28th year of issuing predictions -- predicted on Wednesday an above-average 2011 Atlantic Basin hurricane season featuring a 72% chance that at least one major hurricane will make landfall on the U.S. coastline. While the team, which is headed by William Gray and Phil Klotzbach, slightly reduced its early December prediction, it still called for an active season based on current La Nina conditions that are expected to transition to near-neutral conditions during the heart of the hurricane season.
The CSU team, known as the CSU Tropical Meteorology Project, now calls for 16 named storms instead of 17 forming in the Atlantic Basin between June 1 and Nov. 30. Nine of those are expected to turn into hurricanes with five developing into major hurricanes (Saffir/Simpson category 3-4-5) with sustained winds of 111 mph or greater.
"We expect that anomalously warm tropical Atlantic sea surface temperatures combined with neutral tropical Pacific sea surface temperatures will contribute to an active season," said Klotzbach. "We have reduced our forecast slightly from early December due to a combination of recent ocean warming in the eastern and central tropical Pacific and recent cooling in the tropical Atlantic."
Klotzbach and Gray made this early April forecast based on a new forecast scheme that relies on 29 years of historical data. The hurricane team's forecasts are based on the premise that global oceanic and atmospheric conditions -- such as El Nino, sea surface temperatures, sea level pressures, etc. -- that preceded active or inactive hurricane seasons in the past provide meaningful information about similar conditions that will likely occur in the current year.
"We remain -- since 1995 -- in a favorable multi-decadal period for enhanced Atlantic Basin hurricane activity, which is expected to continue for the next 10-15 years or so," said Gray. "Except for the very destructive hurricane seasons of 2004-2005, United States coastal residents have experienced no other major landfalling hurricanes since 1999. This recent nine of 11-year period without any major landfall events should not be expected to continue."
Late last month AccuWeather.com forecasters predicted that the 2011 Atlantic hurricane season would not produce as many tropical storms as in 2010 but would still be "active," and the storms it creates will probably cause more trouble for the U.S. coastline than last year (see Daily GPI, April 1).
AccuWeather.com's extended forecast called for 15 named storms -- including eight hurricanes, three of them intense -- to form in the Atlantic Basin this year.
The CSU team noted that there have been five years since 1949 that exhibited characteristics most similar to the oceanic and atmospheric features observed during February-March 2011: 1955, 1996, 1999, 2006 and 2008. All years but 2006 had either neutral or La Nina conditions during the hurricane season, and all years but 2006 were very active hurricane seasons, the team said.
The hurricane forecast team's probabilities for a major hurricane making landfall on U.S. soil:
The team also predicts a 61% chance of a major hurricane tracking into the Caribbean (the long-term average is 42%).
A total of 19 named storms formed in 2010, with 12 of them becoming hurricanes, including five intense hurricanes. The long-term (1950-2009) averages for the Atlantic hurricane season are 10 named storms, six hurricanes and two intense hurricanes; the 1995-2009 averages are 14, eight and four, respectively.
The CSU team said it will issue forecast updates on June 1 and Aug. 3.
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