Tropical cyclones in 2011

During 2011, tropical cyclones formed within seven different tropical cyclone basins, located within various parts of the Atlantic, Pacific and Indian Oceans. During the year, a total of 131 tropical cyclones had formed this year to date. 71 tropical cyclones had been named by either a Regional Specialized Meteorological Center (RSMC) or a Tropical Cyclone Warning Center (TCWC). Thirty-nine of these named systems eventually intensified into hurricane-equivalent tropical cyclones. The most active basin in the year was the Western Pacific, which documented 21 named storms. North Atlantic basin documented 19 named storms, continuing the consecutive third-most active season trends from the previous year, due to the 2010–12 La Niña event. Conversely, the Eastern Pacific basin featured slightly more activity than the previous season, with 11 named storms. The least active basin in the year was the North Indian Ocean basin which documented only 2 named storms, the lowest since the 1993 season. Activity across the Southern Hemisphere were almost evenly spread, with the South-West Indian Ocean basin recording 10 tropical cyclones, the Australian region recording 17 tropical cyclones, and the South Pacific basin also recording 10 tropical cyclones, respectively. Twenty-one Category 3 tropical cyclones formed in the year, including three Category 5 tropical cyclones. The accumulated cyclone energy (ACE) index for the 2011 (seven basins combined), as calculated by Colorado State University was 573.8 units.

The strongest tropical cyclone of the year was Typhoon Songda, with a minimum central pressure of 920 hPa (mbar). The costliest tropical cyclone of the year was Hurricane Irene, which caused $14.2 billion worth of damage. The deadliest tropical cyclone of the year was Severe Tropical Storm Washi, which killed 2,546 people.

Global atmospheric and hydrological conditions
The strong La Niña from the previous year continued into 2011, whereby it peaked in January. Afterwards, it began weakening considerably, to the point where in May it was determined that a transition to neutral conditions took place. By the end of Summer, this neutral state continued to persist, although there were still remnants of the La Niña evident. Due to continued cooling of the Pacific, it was determined that the La Niña redeveloped, albeit in a weak state, which would then continue into the next year.

January
During January 2011, a total of 12 tropical cyclones, all of them, formed within the southern hemisphere. No tropical cyclone was observed in the northern hemisphere. Of the systems, 7 further intensified to become named. Out of the systems, Wilma was the most intense tropical cyclone, with a minimum barometric pressure of 935 mbar/hPa.

February
10 systems formed and 5 named storms during February.

March
March was a relatively inactive month in which 11 systems formed, and only 3 received names.

May
May was a mostly inactive month in which only 4 tropical cyclones formed, in which 2 received names.

August
August was the most active month of 2011, with 18 systems forming in the month.

September
September was a below-average month, with only 16 tropical cyclones forming in that month.

November
November was inactive with only 7 tropical cyclones forming, as well as Rolf, a system that formed in the Mediterranean sea.