2011 Hurricane SeasonDecember 29th, 2011 at 3:22 am by Bill Steffen under Bill's Blog, Weather
Click on the pictures to enlarge (from Wikipedia, Hurricane paths and Hurricane Irene). The 2011 Atlantic Hurricane Season featured an above normal number of tropical storms, a near normal number of significant hurricanes and a below number of tropical storms that significantly impacted land. While the tornadoes in 2011 tended to strike highly populated areas (Joplin, Tuscaloosa, Birmingham, Springfield MA), most tropical storms in the Atlantic seemed inclined to mostly avoid land. None of the hurricanes reached Category 5 (on the Saffir-Simpson Scale). The lone hurricane to hit the U.S. was Irene (the only hurricane to directly hit the U.S. since 2007 (the longest period without a hurricane hit since the Civil War). Irene was the first hurricane of the season. It was preceded by 8 mostly lackluster tropical storms. Irene briefly reached Category 3 with 120 mph winds, but was only a Category 1 with 85 mph winds when it hit the Outer Banks of N. Carolina. It continued north to New England as a tropical storm. Despite the relatively low winds (for a hurricane), Irene caused 10.1 billion dollars in damage (the majority from flooding) and took 55 lives in the Caribbean and the U.S. I got a couple of tweets last night from the famous hurricane climatologist and West Michigan native, Dr. Ryan Maue. He says “Tropical cyclone numbers globally for 2010 (#of tropical storms/number of hurricanes/number of major hurricanes): 69 / 39 / 20 vs. 2011 77 / 39 / 21. Total of 146 global tropical cyclones during past 24-months is fewest in the historical record for a 24-month period since 1970. Cyclone Thane will impact India — and make a total of 10 hurricane-force global TC landfalls in 2011. That ties 2002 for lowest since 1978. Out of 77 global tropical cyclones in 2011, 3 made landfall at major strength (96 knots+). Yasi (Oz), Typhoons Nanmadol & Nalgae. 4%. The National Oceanic and Atmospheric Administration (NOAA) uses Accumulated cyclone energy (ACE) to give a measure of the combined number and strength of individual tropical cyclones and entire tropical cyclone seasons. Click here for full screen ACE graph from Dr. Maue. It uses an approximation of the energy used by a tropical system over its lifetime and is calculated every six-hour period. The ACE of a season is the sum of the ACEs for each storm and takes into account the number, strength, and duration of all the tropical storms in the season. As you can clearly see in the graph, tropical cyclone ACE values increased from the mid 1970s to the mid 1990s, and have been declining for the past 15 years. Global accumulated cyclone energy has been near a historic minimum over the last several years. ALSO, tweet from Joe Bastardi of Weatherbell: “By the way, La Nina to fall apart by summer, El Nino (weak to mod) likely next winter. El nino after double nina means wild winter 12/13.” La Ninas generally do weaken in the spring/summer. I can’t say I know where we will be next winter. Winters with a neutral to slightly positive El Nino tend to be cold and/or snowy in the Great Lakes. The coldest back-to-back winters of the 20th century (1976-1979) were preceded by the long La Nina of 1973-1975. The La Nina year of 1974 (2nd year) brought the famous Super Outbreak of Tornadoes on April 3rd. Michigan has not had an EF4 rated tornado since 1977 and unfortunately, we are overdue.