The 2009 Atlantic hurricane season was an event in the annual tropical cyclone season in the north Atlantic Ocean. It was below-average Atlantic hurricane season with nine named storms, the fewest since the 1997 season. The season officially began on June 1, 2009, and ended on November 30, 2009, dates that conventionally delimit the period of each year when most tropical cyclones develop in the Atlantic basin. The first storm to form was Tropical Depression One on May 28, 2009 (one of three in 2009 that did not become a tropical storm), while the last storm, Hurricane Ida, dissipated on November 10.
Of the year's nine named storms, three became hurricanes with two intensifying further into major hurricanes. The inactivity throughout the basin was linked to the formation of an El Niño, which increased wind shear. The two most significant storms of the season, in terms of loss of life and damage, were Hurricanes Bill and Ida. Hurricane Bill was an unusually large storm and was also the season's strongest, attaining winds of . Tropical Storm Claudette was the only storm during 2009 to make landfall in the United States; Hurricane Ida became extratropical shortly before coming ashore in Alabama.
This timeline includes information that was not operationally released, meaning that data from post-storm reviews by the National Hurricane Center, such as a storm that was not operationally warned upon, has been included. This timeline documents tropical cyclone formations, strengthening, weakening, landfalls, extratropical transitions, and dissipations during the season.
By convention, meteorologists use one time zone when issuing forecasts and making observations: Coordinated Universal Time (UTC), and also use the 24-hour clock (where 00:00 = midnight UTC). The National Hurricane Center uses both UTC and the time zone where the center of the tropical cyclone is currently located. The time zones utilized (east to west) prior to 2020 were: Atlantic, Eastern, and Central. In this timeline, all information is listed by UTC first with the respective regional time included in parentheses. Additionally, figures for maximum sustained winds and position estimates are rounded to the nearest 5 units (knots, miles, or kilometers), following the convention used in the National Hurricane Center's products. Direct wind observations are rounded to the nearest whole number. Atmospheric pressures are listed to the nearest millibar and nearest hundredth of an inch of mercury.
Timeline of events
May
May 28
1 a.m. EDT (0600 UTC) – Tropical Depression One develops from an area of low pressure roughly east-northeast of Cape Hatteras, North Carolina. 1 p.m. EDT (1800 UTC) – Tropical Depression One attains its peak intensity with winds of and a barometric pressure of 1006 mbar (hPa; ). May 29 7 p.m. EDT (0000 UTC on May 30) – Tropical Depression One degenerates into a non-convective remnant low-pressure area roughly south-southeast of Halifax, Nova Scotia.
June
No tropical cyclones formed during the month of June. June 1 12 a.m. EDT (0400 UTC) – The 2009 Atlantic hurricane season officially begins.
July
No tropical cyclones formed during the month of July, making the 2009 season one of fourteen since 1944 in which no tropical storms developed during June and July.