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Tropical Storm Sean was a tropical cyclone that affected the island of Bermuda in November of the 2011 Atlantic hurricane season. The nineteenth tropical system and the eighteenth named storm of the 2011 season, Sean developed from a non-tropical low pressure area on November 8. Initially subtropical, the system displayed gale-force winds over a portion of the Atlantic Ocean. However, several hours after classification, the storm began to display tropical characteristics, and it was noted by the National Hurricane Center that Sean had transitioned into a fully tropical storm. Moving in an erratic motion to the southwest of Bermuda, Sean steadily strengthened to reach a peak intensity of 65 mph (100 km/h) before curving towards the north and eventually the northeast. On November 11, Sean passed by the island of Bermuda, bringing tropical storm force winds and heavy rainfall before becoming extratropical early on November 12, and was absorbed by a neighboring extratropical storm, soon afterwards.

Meteorological history

The origins of Sean were from an extratropical cyclone that formed over the central United States on November 3 along a cold front, which moved into the Atlantic Ocean the following day. On November 6, the system became nearly stationary between Bermuda and the Bahamas after separating from the front. The circulation became better-defined while the convection increased.[1] By November 8, the system developed gale force winds near the center,[2] and at around 0600 UTC that day, the National Hurricane Center (NHC) classified it as Subtropical Storm Sean. By that time, the convection and wind field had become more symmetric,[1] although it was classified as a subtropical cyclone due to the proximity of an upper-level low.[3] Within 12 hours, Sean separated from the low and transitioned into a tropical cyclone,[1] after developing a warm core.[4]

After becoming tropical, Sean developed outflow and was able to intensify due to light wind shear and warm enough water temperaturess. With a ridge to the northeast, the storm moved slowly to the west.[1] On November 9, an eye feature developed in the center,[5] which became more pronounced into a ring of convection.[1] The NHC predicted Sean would intensify into a hurricane,[6] although the storm reached peak winds of Template:Convert/mph on November 10; this was based on the lack of strong convection, as well as surface wind reports from the Hurricane Hunters.[1] Subsequently, an approaching cold front increased shear and turned Sean to the northeast, causing Sean to weaken in combination with cooler waters. After passing about 85 mi (Template:Convert/km) west-northwest of Bermuda, Sean became extratropical on November 12. Early the next day, it was absorbed by the cold front.[1]

Preparations and impact

Tropical Storm Sean and its precursor produced light rainfall in outer rainbands for several days in Bermuda.[7] Shortly after the storm formed, the Bermuda Weather Service issued a tropical storm watch at 1200 UTC on November 8, which was upgraded to a tropical storm warning the next day. When Sean passed near the island on November 11, it produced sustained winds of Template:Convert/mph, with gusts to Template:Convert/mph.[1] The storm produced rough seas to the east coast of Florida, which drowned one swimmer in Jensen Beach.[8] Rip currents were also reported in North Carolina, though no fatalities occurred.[9]


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Template:Cite report
  2. Stacy Stewart (November 8, 2011). "Tropical Weather Outlook". National Hurricane Center. Retrieved November 10, 2011. 
  3. Eric Blake (November 8, 2011). "Subtropical Storm Sean Discussion Number 2". National Hurricane Center. Retrieved November 11, 2011. 
  4. Eric Blake (November 5, 2011). "Tropical Storm Sean Discussion Number 3". National Hurricane Center. Retrieved November 11, 2011. 
  5. Eric Blake (November 9, 2011). "Tropical Storm Sean Discussion Number 6". National Hurricane Center. Retrieved November 11, 2011. 
  6. Eric Blake (November 9, 2011). "Tropical Storm Sean Discussion Number 7". National Hurricane Center. Retrieved November 11, 2011. 
  7. Template:Cite report
  8. Template:Cite report
  9. David Horn (November 9, 2011). "Tropical Storm Sean stirs waters off NC coast". National Hurricane Center. Retrieved February 23, 2012. 

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