James Waller, Ph.D, Research Meteorologist
The risk of a landfalling hurricane is a serious threat for any tropical season, regardless of seasonal outlooks for the Atlantic Basin at large. In fact, sea-surface temperatures (SSTs) along the U.S. coast and northern Caribbean are trending above average, and tropical cyclone development in these areas close to the mainland is cause for concern. Such development depends on short-term weather patterns at the time of occurrence, not on how many hurricanes are expected in the Atlantic basin at large.
For the North Atlantic Basin, seasonal outlook providers are expecting tropical activity to fall below the long-term average of 1954-2013. Common factors noted by these providers include a probable warm or “El Niño” phase of the El Niño Southern Oscillation and cool SSTs in the Atlantic Main Development Region (MDR) (the area of the tropical Atlantic between Africa and the Gulf of Mexico, specifically 10 degrees north to 20 degrees north longitude and 20 degrees west to 85 degrees west latitude). Indeed tropical waters of the Central and Eastern Atlantic are cooler than average, but warmer waters in the West Atlantic adjacent to the coast are still cause for a moment of pause.
It is also accepted that El Niño conditions tend to suppress hurricane development in the Atlantic basin, but scientific research reveals that this effect is strongest in the deep tropics. Also, the strength, placement and onset date of the El Niño and its suppressing effects are still subject to some uncertainty. The 2004 hurricane season was a weak El Niño year, which brought five landfalling U.S. hurricanes, four of which affected Florida. The 1965 season was a strong El Niño year, with four hurricanes in the Atlantic Basin, and a single landfalling U.S. Hurricane named Betsy, that rendered severe impacts to the Florida Keys and the Northern Gulf Coast. The 1992 season was a decaying El Niño year, and a quiet season with only four hurricanes in the basin, and a single U.S. landfall - Hurricane Andrew. That storm is among the strongest U.S. landfalling hurricanes on record and brought long-lasting impacts to the insurance industry, not to mention the residents of Homestead, Florida.
It is clear that the proportion between basin activity and hurricane landfalls has been historically very volatile. Basin activity does not consistently relate to landfalls (or their severity) - these are determined by weather patterns at the time of occurrence, not pre-season estimates of hurricane frequency.
We know that unexpected events can and do happen, with examples like Charley (2004), Betsy and Andrew. Warmer waters in the West Atlantic and Caribbean, and the uncertainty of the strength and placement of the oncoming El Niño especially warrant a moment of pause for the 2014 season.
As with any hurricane season, a review of response plans and procedures is essential for property owners and the (re)insurance industry alike.
The year-to-year volatility warrants preparation for any season. The 2010 season saw 19 named storms and 12 hurricanes without a single U.S. landfall. In 1985 there were seven hurricanes in the basin, and six of these made U.S. landfall (some of which were very impactful). We in the industry are also well aware of the 1992 season that produced only four hurricanes, including one historic U.S. landfall (Andrew), not unlike 1965 with Betsy and the severe impacts to southern Louisiana.
Seasonal activity predictions for the basin are valuable, but the impacts of even a single landfall (quiet season or not) can be quite severe. Historical experience warrants proper review and preparation of hurricane plans by all interests from individual homeowners to businesses to the insurance industry at large.
In light of this reality, seasonal outlook providers expect 2014 counts to fall near or slightly below the long-term mean of 1954-2013. The forecasts also fall clearly below the short-term 1995-2013 mean.
Factors of greatest influence include:
1. The expected onset of an El Niño.
2. Cooler than normal temperatures in the Atlantic MDR.
The predictions of seasonal outlook providers, including the Colorado State University team of Professors William M. Gray and Phillip J. Klotzbach, are included in the table below.
Another key theme for seasonal tropical outlooks this year is uncertainty. Seasonal outlook providers such as Gray and Klotzbach emphasize such uncertainty and note factors such as the strength and placement of the expected El Niño for the upcoming summer.