Storm & Security

SEASONAL/FORECAST | by Howard Shingle | Early Warning Three key factors converge for a season with the potential for extreme activity. Two words that might best describe the 2013 Atlantic hurricane outlook would be "active" and "threatening." Active in that all pre-season forecasts anticipate this season to be above normal, once again. Threatening in that stronger storms are expected with a high probability of at least one making landfall. By the numbers, forecasters expect between nine and 18 named storms this season with six to 11 hurricanes of which three to six will be major. A closer look at the forecasts reveals similar reasons for high activity: unusually warm Atlantic Ocean surface temperatures this spring and the expectation that El Niño, which would dampen storm formation, will not develop. The forecast team at Colorado State University's (CSU) Dept. of Atmospheric Science anticipates "enhanced activity" for 2013 compared to 1981 to 2010 climatology, mainly due to the combination of "an anomalously warm" tropical Atlantic Ocean and a relatively low likelihood of El Niño. The National Oceanic and Atmospheric Administration (NOAA) adds a third factor: the continuation of a climate pattern that began in 1995 and is responsible for an era of high activity for Atlantic hurricanes. These three climate factors strongly control Atlantic hurricane activity, NOAA states, and are expected to come together to produce an active or extremely active 2013 hurricane season. AccuWeather.com warns that stronger storms (Cat. 2 or higher) could be in the offing because of less wind shear and because Saharan dust, which tends to stifle storm development, could be less frequent this year. While landfall is nearly impossible to predict accurately this far ahead of any storm, two forecasts put the probability for at least one U.S. landfalling hurricane this year at around 70 percent. The biggest concerns for a landfall are along the East Coast—those areas impacted last year by Sandy. With many of the coastal sand dunes damaged or destroyed, and with rebuilding activities farther inland still ongoing, the potential for destruc- 10 STORM & SECuRITY PROTECTION / FORECAST 2013 tive flooding is higher there this season than normal should another storm surge occur. An impact on Florida is another concern. "Florida is long overdue for a direct hurricane hit," says AccuWeather.com Expert Senior Meteorologist Dan Kottlowski. "Though they have been impacted by named tropical storms in the last couple of years, a direct hit by a hurricane has not occurred since Hurricane Wilma in 2005." Trend Analysis The CSU forecast is based on a new April statistical scheme, being used now for only the third time, and an analog-based model. The statistical scheme is a combined measure of the year-to-year mean of six indices of hurricane activity, which then is compared to the 1950 to 2000 average. The analog model records current oceanic and atmospheric trends and matches them to previous seasons with similar trends. "There were five hurricane seasons since 1900 with characteristics most similar to what we observed in February-March 2013," writes CSU research scientist, Philip J. Klotzbach. "We anticipate that the 2013 hurricane season will have more activity than the average of our five analog years … due to a likely increase in the number of weaker storms being detected today because of advancements in satellite and aircraft technology," he adds. For 2013, the CSU analog model calls for an active season, while the statistical scheme calls for a very active season. AccuWeather.com meteorologist Jillian MacMath states a key point to watch is the possibility that this season will get off to a quick start with the potential of storms developing in the Caribbean in June. AccuWeather.com points out that in 2012, two named storms formed before June 1, the official start of hurricane season. Last year became the third straight Atlantic hurricane season to have had 19 storms, and already this year we've had an early warning this trend could continue. "One of the side effects of the anomalous weather pattern during March was a sharp increase in sea surface temperatures in the tropical North Atlantic," says Todd Crawford, chief meteorologist for Weather Services International (WSI), a part of The Weather Company. "While it [occurred] three months before hurricane season officially begins, this early warming of the tropical waters is an indication that an active season is in store, and our statistical forecast models confirm this hypothesis. Our current forecast … may be a bit conservative if the warm tropical ocean temperatures persist heading into the season." Landfall The CSU team notes that whereas individual hurricane landfall events cannot be accurately forecast months in advance,

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