Climate Number: 19 Named Storms
The official 2012 Atlantic Hurricane Season is now over. Compared to the 30-year average of 12 named storms per year, 2012 was above-normal with 19 named storms, but not an exceptional year. Ten of these storms became hurricanes (annual average is six hurricanes). Only one storm, Michael, became a major hurricane (annual average is three major hurricanes), reaching category three strength. Michael formed in the open Atlantic Ocean where it also dissipated. 2012 marked the second year in a row that the Mid-Atlantic and Northeast were hit by a named storm, with Post-tropical Cyclone Sandy making landfall at New Jersey and bringing record storm surge levels to New York’s Battery Park, among other locations. The NOAA 2012 Atlantic Hurricane Season Outlook released in late May gave a 50 percent chance of a near normal season, a 25 percent chance of an above normal season and a 25 percent chance of a below normal season. The variable conditions in the tropical Pacific Ocean constitute a big source of uncertainty in the Atlantic hurricane seasonal outlooks. In May, warm El Niño conditions looked to be developing there. The El Niño never came, however, nor did the associated vertical wind-shear over the Atlantic, which discourages tropical cyclone formation. The lack of vertical wind-shear may have contributed to the above average season. Uncertainty in the outlooks also comes from the potential different combinations of storm types that can arise given the same conditions. For example, conditions favorable to hurricane formation can spawn several smaller storms or one or two big storms. Besides the tropical Pacific, there are other less predictable sources of variability that affect the vertical wind shear over the Atlantic. Other important variables for hurricane formation, such as sea-surface temperatures, atmospheric moisture, disturbances and dominant weather patterns are also difficult to predict several months in advance.
The 2012 Atlantic Hurricane Season in 4.5 Minutes from NOAA
Source: NOAA. “Busy 2012 hurricane season continues decades-long high activity era in the Atlantic.” 29 November 2012. Accessed Online 2 December 2012 < http://www.noaanews.noaa.gov/stories2012/20121129_hurricaneseasonwrapup.html > and National Oceanic and Atmospheric Administration. “NOAA 2012 Atlantic Hurricane Season Outlook.” 24 May 2012. Accessed Online 2December 2012