Hurricane activity in the Atlantic basin this year is projected to be near or below average, though forecasters urge preparation and stress the uncertainty of their estimates.
According to the National Oceanic and Atmospheric Administration’s (NOAA) forecast, there is a 50-percent chance of a below-normal season, a 40 percent chance of a near-normal season and a 10-percent chance of an above-normal season. The six-month hurricane season began June 1, and NOAA predicts a 70 percent likelihood of eight to 13 named storms, those with winds of greater than 39 mph, and three to six of those could become hurricanes, achieving winds of 74 mph or higher, including one or two major hurricanes, with winds of 111 mph or higher.
These numbers are near or below the seasonal averages of 12 named storms, six hurricanes and three major hurricanes, based on the average from 1981 to 2010. The Atlantic hurricane region includes the North Atlantic Ocean, Caribbean Sea and Gulf of Mexico. The 20013 hurricane season was the first since 1994 in which there were no major storms, and losses for the global insurance industry from natural catastrophes and man-made disasters fell 44 percent to $45 billion from $81 billion in 2012, according to Swiss Re.
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"The risk of a landfalling hurricane is a serious threat for any tropical season, regardless of seasonal outlooks for the Atlantic Basin at large," said James Waller, PhD, research meteorologist for GC Analytics. "While there is indeed a weak correlation between hurricane counts in the Atlantic Basin and the number of U.S. landfalls, statistical significance is the subject of some debate in the scientific community. Warmer waters in the West Atlantic and Caribbean coupled with the uncertainty surrounding the strength and placement of the impending El Niño, warrant a moment of pause for the 2014 season."
The forecasts fall below the short-term mean, attributable to the expected onset of an El Niño and cooler than normal sea-surface temperatures (SSTs) in the Atlantic Main Development Region (MDR), both of which suppress hurricane formation and severity, Guy Carpenter said.
“Atmospheric and oceanic conditions across the tropical Pacific are already taking on some El Niño characteristics,” said Gerry Bell, Ph.D., lead seasonal hurricane forecaster with NOAA’s Climate Prediction Center. “Also, we are currently seeing strong trade winds and wind shear over the tropical Atlantic, and NOAA’s climate models predict these conditions will persist, in part because of El Niño. The expectation of near-average Atlantic Ocean temperatures this season, rather than the above-average temperatures seen since 1995, also suggests fewer Atlantic hurricanes.”
The transition to El Niño recently had slowed prior to June, according to “Extended Range Forecast Of Atlantic Seasonal Hurricane Activity And Landfall Strike Probability For 2014,” by Philip J. Klotzbach and William M. Gray of the Tropical Meteorology Project at Colorado State University. And, the tropical Atlantic has warmed, an anomalously that caused them to increase their forecast slightly, though they still expect a below-average probability for a major hurricane landfall in the United States and the Caribbean.
El Niño is signaled by warmer than normal SSTs in the tropical East Pacific, which enhances wind shear in the tropical Atlantic and disrupts tropical cyclone formation. Conditions in the tropical Pacific indicate that an El Niño is forming, according to the NOAA Climate Prediction Center. The existence of an El Niño doesn’t preclude the possibility for a damaging hurricane season, Guy Carpenter said, and its location and strength are important factors. For example, 2004 was a weak El Niño year, with the warm waters located closer to the Central Pacific, but nine hurricanes formed and five made landfall in the United States; 1969 also was a weak El Niño season that saw twelve hurricanes and two landfalls, including the second strongest landfall in recorded U.S. history, Hurricane Camille. Cooler than average SSTs in the tropical Atlantic also factor into predictions of a quiet season.
“SSTs in the Atlantic MDR indicate moderately cool SSTs over a sizeable area,” Guy Carpenter said. “However, upon closer inspection, above normal SSTs are found in an area adjacent to the U.S. East Coast and Florida. This implies that while tropical cyclone development may be suppressed for much of the Atlantic, disturbances adjacent to the U.S. mainland and northern Caribbean could find conditions that enable development into hurricanes. This, coupled with weaker suppression effects of the El Niño and its location away from the southern U.S. and northern Caribbean, indicates an environment that could still allow storm production and U.S. landfalls."
The strength and placement of the El Niño is uncertain and the effects of the disruptive, hurricane suppressing wind shear may be displaced, according to the report. And, in the waters adjacent to the eastern U.S. and the northern Caribbean, SSTs are not cooler than average, presenting an environment that could enable hurricane development and landfall.
"As history has shown more than once, proper preparation is necessary regardless of basin activity," said Waller. "Preparation for hurricane impacts and the resulting disruption to infrastructure should be an ongoing and essential process for homeowners, businesses, government agencies and the (re)insurance industry. We continuously emphasize that hurricane landfalls are influenced by large-scale weather circulation at the time of the event, which can surprise even the world's best forecasters. The landfall of one or two hurricanes cannot be ruled out for any season, regardless of predictive models."
