August 2011 Tropical Cyclones Report

• Atlantic Basin
• West North Pacific Basin
• East North Pacific Basin

Atlantic Basin

Max wind 52 mph Emily first appeared as a strong, yet poorly organized African easterly wave at the close of July. During its approach toward the Lesser Antilles, the system became better defined and produced squalls over the area, including the island of Martinique. By August 1st, Emily had strengthened into a tropical storm–albeit a disorganized one. Inhibited by the entrainment of dry air from the Saharan Air Layer and moderate westerly wind shear which caused an eastward tilt in storm structure, the storm signaled minimal potential for further development. After passing near Puerto Rico, Emily made landfall at Hispaniola on the 4th, bringing periods of prolonged rainfall and triggering extensive flooding and mudslides in Haiti and the Dominican Republic. Up to 21 inches (528 mm) of rainfall was recorded in the city of Neiba. Weakened by the mountainous terrain, Emily was declassified to a tropical wave on the 5th. During subsequent hours, the storm regenerated to a weak tropical cyclone and brought rains in excess of 8 inches (200 mm) to the Bahamas before permanently dissipating on the 7th. Overall, the storm claimed a total of four lives.

Tropical Storm Emily Satellite Image

Tropical Storm Emily Forecast Track Saffir-Simpson Scale Color Legend

A short-lived system, Franklin was the 6th named storm within the Atlantic basin. (Climatologically, the 6th named storm typically occurs near September 8th during a given Atlantic hurricane season.) Franklin developed on the 10th as a disorganized area of convection off the east coast of Florida, strengthened to a tropical storm during the early morning hours of the 13th and dissipated by day’s end. The fact that the storm tracked toward progressively cool waters and encountered increasing vertical shear and dry air at mid-levels greatly contributed to its brevity. Steering westward into the North Atlantic for the duration of its course, Franklin posed no threat to life or land.

Tropical Storm Franklin Satellite Image

Tropical Storm Franklin Forecast Track Saffir-Simpson Scale Color Legend

On August 14th, Gert became the 7th named storm of the season. This marks the fourth earliest date on which a 7th storm has been named. (Season-years with earlier 7th named storms include 2005, 1995, and 1936.) Within 15 hours of becoming a tropical depression, Gert intensified to a tropical storm just southeast of Bermuda. Because Gert tracked roughly 90 miles (150 km) to the east of the island territory, only modest rains and winds were felt onshore.

Tropical Storm Gert Satellite Image

Tropical Storm Gert Forecast Track Saffir-Simpson Scale Color Legend

After propagating westward into the waters of the western Caribbean, the tropical wave from which Harvey arose organized into a tropical storm on August 19th just offshore of Honduras. This date marks the fourth earliest occurrence of the 8th storm within a season. In addition, being the 8th named storm to remain below hurricane strength, Harvey qualifies 2011 as the first Atlantic hurricane season since record keeping began since 1851 to have more than six consecutive tropical storms that failed to reach hurricane strength. On the afternoon of August 20th, the storm made landfall in Belize. Honduras, Guatemala, and portions of Mexico’s Yucatan Peninsula received as much as 6–7 inches of rainfall. In Mexico, landslides were responsible for three fatalities. As it continued inland, the high terrain of the Sierra Madre Mountains contributed to the storm’s weakening.

Tropical Storm Harvey Satellite Image

Tropical Storm Harvey Forecast Track Saffir-Simpson Scale Color Legend

Irene – the first hurricane of the 2011 Atlantic hurricane season and the first landfalling U.S. hurricane since 2008–emerged off the Cape Verde Islands on August 15th as a well–defined tropical wave. On August 20th, the storm attained tropical storm status, becoming the 9th named storm of the season. This is the second earliest date at which nine storms have occurred; the last time this record was met was in 1936. Tracking westnd–northwestward, Irene made its first landfall in Puerto Rico, reaching hurricane strength while passing over. After crossing the Turks and Caicos Islands, Irene underwent rapid cyclogenesis, strengthening to a category 3 storm just prior to passing through the Bahamas. (It is reported that roughly 90& of structures on the Acklins and Crooked Islands were destroyed.) The storm then curved north–northeast, and made landfall in the Outer Banks region of NC on the morning of August 27th. In Harlowe, NC, a storm surge of 8.5 feet was reported, and in Onslow Bay, wave heights reached 27 feet. A total of 20” of rainfall fell both in Jacksonville, NC and Virginia Beach, VA. In the days following, Irene tracked towards the Northeast, making its second U.S. landfall in New Jersey and its third and final U.S. landfall in Brooklyn, NY. This marks the second hurricane to hit the state of New Jersey in 108 years. Torrential rain and storm surges of 3–4 feet caused significant river flooding across eight states, including NY, VT, and NJ. The flood waters are considered to be one of the Northeast’s worst flood disasters.
The storm itself was unusually large, boasting an expansive 500 mile (805 km) diameter, and tropical force winds which extended nearly 300 miles (483 km) from its center. It was also slow moving – traveling at a top speed of 20 mph (32 km/h) compared to speeds of 30–40 mph (48–64 km/h) for similarly sized storms. Irene claimed at least 48 lives and caused an estimated $7 to 10 billion dollars in damages in the U.S. and $3.1 (USD) in the Caribbean. This total ranks it among the top 10 costliest disasters in U.S. history. In addition, it qualifies 2011 as the year having the greatest number of billion-dollar weather disasters within the United States. (Prior to Irene, 2011 tied 2008 with 9 disasters.) Due to the storm’s widespread socio–economic impacts, it is expected that the storm name "Irene" may be retired from future use.

Tropical Storm Irene Satellite Image

Tropical Storm Irene Forecast Track Saffir-Simpson Scale Color Legend

Jose initially developed as a tropical wave off the west coast of Africa on August 17th. Over the following weeks, the system fluctuated in intensity before reaching and maintaining tropical storm strength on the 28th. Within 27 hours, the storm was blown apart northeast of Bermuda by the vigorous upper-level winds created in the wake of hurricane Irene.

Tropical Storm Jose Satellite Image

Tropical Storm Jose Forecast Track Saffir-Simpson Scale Color Legend

Hurricane Katia was the 11th named storm and 2nd hurricane and major hurricane of the 2011 Atlantic season. Characteristic of a Cape Verde hurricane, the storm developed south of the Cape Verde Islands on August 29. It became a tropical storm on August 30 and then a hurricane the next day. In subsequent days, Katia danced around hurricane intensity until September 4 when it finally strengthened from a tropical storm to a Category 2 hurricane within six hours. After upgrading to a Category 4 storm–the first of the season–on September 5, Katia’s intensity fluctuated yet again, and by the close of September 6 the storm had weakened back to a Category 1 hurricane. On the morning of September 10, Katia became a strong extratropical cyclone and its remnants accelerated east-northeast across the North Atlantic toward the British Isles. Over September 11-12, Ex-Katia brought hurricane-force winds and heavy rains to Scotland, Ireland, and Great Britain–some of the worst since Hurricane Lili of 1996. In addition to a maximum wind gust of 98 mph (158 km/h) at Cairngorm Summit, Scotland, significant tree damage and power outages as far east as Saint Petersburg, Russia were reported. Katia caused a total of 3 high-seas related deaths along the U.S. East Coast. In addition to causing one fatality in the U.K., the equivalent of $157 million U.S. dollars in damages was reported. Since 1851, only 10 extratropical storms have hit within 200 miles (322 km) of Ireland.

Tropical Storm katia Satellite Image

Tropical Storm Katia Forecast Track Saffir-Simpson Scale Color Legend

West North Pacific Basin

Tropical Storm Merbok Satellite Image

Tropical Storm Merbok Forecast Track Saffir-Simpson Scale Color Legend

Tropical Storm Nanmadol Satellite Image

Tropical Storm Nanmadol Forecast Track Saffir-Simpson Scale Color Legend

Tropical Storm Talas Satellite Image

Tropical Storm Talas Forecast Track Saffir-Simpson Scale Color Legend

East North Pacific Basin

Fernanda developed from a small low pressure system near the ITCZ, centrally located between the southern tip of Baja California and the Hawaiian Islands. By the 16th, it had entered the Central Pacific as a strong tropical storm. Fernanda continued on its westward track and remained well away from land. Cyclolysis soon overtook the storm, and it downgraded to post-tropical on the 20th near Hawaii’s Big Island.

Tropical Storm Fernanda Satellite Image

Tropical Storm Fernanda Forecast Track Saffir-Simpson Scale Color Legend

Around the time Fernanda was tracking into the Central Pacific, tropical depression Greg was spinning up off the southern coast of Mexico. Less than 48 hours later, the storm, which underwent steady intensification, became the 6th hurricane of the 2011 Pacific season. After attaining peak winds of 85 mph (137 km/h) –consistent with category 1 strength–Greg began to gradually weaken, and reverted back to a tropical depression by August 20th. As a result of traversing cooler waters, the storm deteriorated further into a remnant low. Although Greg’s west-northwestward track steered it away from the coastline, the storm remnants, which continued to drift for several days, did manage to bring cloudy conditions to parts of Southern California.

Tropical Storm Greg Satellite Image

Tropical Storm Greg Forecast Track Saffir-Simpson Scale Color Legend

Citing This Report

Metadata