Tropical Storm Don (2011)
Encyclopedia
Tropical Storm Don was the fourth named storm
of the 2011 Atlantic hurricane season
and the first tropical cyclone to make landfall
in the United States
during the 2011 season. Forming from an area of low pressure along a tropical wave
, Don was operationally upgraded straight to tropical storm intensity on July 27, after a reconnaissance aircraft
noted the presence of tropical-storm-force winds. It tracked across the Gulf of Mexico
and reached a peak intensity of 50 mph (85 km/h) before moving ashore in Texas
on July 30 as a tropical depression. Initially, Don was a possible catalyst for relief to the drought-stricken state, but the system dissipated rapidly after making landfall, providing very little in the way of help to the state.
first identified off the west coast of Africa
on July 16. Preceded by a surge of deep tropical moisture
, it tracked westward over the open Atlantic for several days, with minimal convection
confined to the monsoon trough
. The National Hurricane Center
(NHC) first mentioned the potential for gradual tropical cyclogenesis
on July 21, when it was positioned about 750 mi (1200 km) to the east of the Windward Islands
. As the system moved through the Lesser Antilles on July 23, it produced tropical-storm-force winds in Puerto Rico. The combination of vertical wind shear
and proximity to land impeded further development. Convection increased along the northern portion of the wave on July 24, although by the following day no significant redevelopment was expected.
Early on July 26, the thunderstorms became more concentrated to the south of Cuba, in association with a low pressure area
. The system continued to organize, and by 0600 UTC
on July 27, the surface circulation
organized enough to be classified a tropical depression about 60 mi (95 km) northeast of Cancún
, Mexico. Within twelve hours, the depression intensified into a tropical storm. Operationally, the system was not known to be a tropical cyclone until 2100 UTC on July 27, after a reconnaisance aircraft flight into the system confirmed the presence of a closed albeit elongated circulation center. At that point, the NHC classified it as Tropical Storm Don. Upon forming, the storm moved to the west-northwest along the southern periphery of a low- to mid-level ridge
over the northern Gulf of Mexico
. The NHC predicted steady intensification to at least 65 mph (100 km/h) owing to generally favorable conditions including warm waters and light to moderate wind shear. However, none of the tropical cyclone forecast models anticipated much strengthening.
Initially, Don failed to intensify significantly due to a misalignment between the lower and mid-level circulations. The wind shear in the region further exposed the circulation from the convection late on July 28, although the winds increased slightly. Early on July 29, Don attained peak winds of 50 mph (85 km/h) as reported by the Hurricane Hunters, and the storm maintained that intensity while moving across the Gulf of Mexico. As Don approached the Texas coast early on July 30, the thunderstorms rapidly diminished, due to the combination of wind shear, drier air, and cooler water temperatures just offshore. The winds decreased as the convection dissipated, and Don made landfall
on Padre Island National Seashore
as a tropical depression. About three and a half hours later, Don degenerated into a remnant low, and the circulation dissipated six hours after that.
warned that the tropical wave from which Don formed was capable of dropping 80 to 150 mm (3.1 to 5.9 in) of rainfall over the state, while producing sustained winds of 35 to 45 km/h (21.7 to 28 mph) and gusts up to 65 km/h (40.4 mph). After Don was designated as a tropical storm, the Yucatán
state government issued a green-level alert. The alert indicated that although the tropical storm was located close to the state, it was only considered to be slightly dangerous. Late on July 27, the National Hurricane Center issued a tropical storm watch
from Port Mansfield, Texas
to San Luis Pass, Texas. Six hours later, the tropical storm watch was extended southwards to the international border.
After the storm was named, officials in Texas
began making preparations for Don. The University of Texas Medical Branch
in Galveston
issued a level one alert for Don, and city officials began preparing for a possible evacuation. On July 27, oil companies throughout the western Gulf of Mexico began removing non-essential personnel from their rigs and platforms in preparation for the storm. The next day, BP
, Royal Dutch Shell
, Anadarko
and Apache
announced the evacuations of some of the oil facilities in the area, while Exxon-Mobil began preparing the Baytown Refinery
for a possible strike from the storm. Several oil companies stopped oil production as a result of Don; by midday on July 28, 6.8% of oil production and 2.8% of natural gas production in the Gulf had been shut in
ahead of the storm.
Due to its abrupt weakening prior to landfall, Don produced minimal rainfall, with totals of less than 1 in (25.4 mm). However, Bay City, Texas
, located well northeast of where the storm made landfall, reported 2.56 in (65 mm). In southern Texas, the rains resulted in slippery roads and some ponding. Cotton farmers benefited from what rains that did fall as they harvested their crop. Winds during the storm's passage were minimal, with a peak wind gust of 41 mph (66 km/h) at Waldron Field. In addition, Don moved ashore with a storm surge
that peaked at of about 1.89 ft (0.576072 m) at Bob Hall Pier. There were no reports of damage.
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
of the 2011 Atlantic hurricane season
2011 Atlantic hurricane season
The 2011 Atlantic hurricane season is tied for the third most active season on record with 1887, 1995 and 2010. It began on June 1, 2011, and ended on November 30, 2011, however these dates conventionally delimit the period of each year when most tropical cyclones develop in the Atlantic basin...
and the first tropical cyclone to make landfall
Landfall (meteorology)
Landfall is the event of a tropical cyclone or a waterspout coming onto land after being over water. When a waterspout makes landfall it is reclassified as a tornado, which can then cause damage inland...
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
during the 2011 season. Forming from an area of low pressure along a tropical wave
Tropical wave
Tropical waves, easterly waves, or tropical easterly waves, also known as African easterly waves in the Atlantic region, are a type of atmospheric trough, an elongated area of relatively low air pressure, oriented north to south, which move from east to west across the tropics causing areas of...
, Don was operationally upgraded straight to tropical storm intensity on July 27, after a reconnaissance aircraft
Hurricane Hunters
The Hurricane Hunters are aircraft that fly into tropical cyclones in the North Atlantic Ocean and Northeastern Pacific Ocean for the specific purpose of directly measuring weather data in and around those storms. In the United States, the Air Force, Navy, and NOAA units have all participated in...
noted the presence of tropical-storm-force winds. It tracked across the Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
and reached a peak intensity of 50 mph (85 km/h) before moving ashore in Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
on July 30 as a tropical depression. Initially, Don was a possible catalyst for relief to the drought-stricken state, but the system dissipated rapidly after making landfall, providing very little in the way of help to the state.
Meteorological history
The genesis of Tropical Storm Don was from a tropical waveTropical wave
Tropical waves, easterly waves, or tropical easterly waves, also known as African easterly waves in the Atlantic region, are a type of atmospheric trough, an elongated area of relatively low air pressure, oriented north to south, which move from east to west across the tropics causing areas of...
first identified off the west coast of Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
on July 16. Preceded by a surge of deep tropical moisture
Moisture
Humidity is the amount of moisture the air can hold before it rains. Moisture refers to the presence of a liquid, especially water, often in trace amounts...
, it tracked westward over the open Atlantic for several days, with minimal convection
Atmospheric convection
Atmospheric convection is the result of a parcel-environment instability, or temperature difference, layer in the atmosphere. Different lapse rates within dry and moist air lead to instability. Mixing of air during the day which expands the height of the planetary boundary layer leads to...
confined to the monsoon trough
Monsoon trough
The monsoon trough is that portion of the Intertropical Convergence Zone which extends into or through a monsoon circulation, as depicted by a line on a weather map showing the locations of minimum sea level pressure, and as such, is a convergence zone between the wind patterns of the southern and...
. The National Hurricane Center
National Hurricane Center
The National Hurricane Center , located at Florida International University in Miami, Florida, is the division of the National Weather Service responsible for tracking and predicting weather systems within the tropics between the Prime Meridian and the 140th meridian west poleward to the 30th...
(NHC) first mentioned the potential for gradual tropical cyclogenesis
Tropical cyclogenesis
Tropical cyclogenesis is the term that describes the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which mid-latitude cyclogenesis occurs...
on July 21, when it was positioned about 750 mi (1200 km) to the east of the Windward Islands
Windward Islands
The Windward Islands are the southern islands of the Lesser Antilles, within the West Indies.-Name and geography:The Windward Islands are called such because they were more windward to sailing ships arriving in the New World than the Leeward Islands, given that the prevailing trade winds in the...
. As the system moved through the Lesser Antilles on July 23, it produced tropical-storm-force winds in Puerto Rico. The combination of vertical wind shear
Wind shear
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...
and proximity to land impeded further development. Convection increased along the northern portion of the wave on July 24, although by the following day no significant redevelopment was expected.
Early on July 26, the thunderstorms became more concentrated to the south of Cuba, in association with a low pressure area
Low pressure area
A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
. The system continued to organize, and by 0600 UTC
Coordinated Universal Time
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...
on July 27, the surface circulation
Atmospheric circulation
Atmospheric circulation is the large-scale movement of air, and the means by which thermal energy is distributed on the surface of the Earth....
organized enough to be classified a tropical depression about 60 mi (95 km) northeast of Cancún
Cancún
Cancún is a city of international tourism development certified by the UNWTO . Located on the northeast coast of Quintana Roo in southern Mexico, more than 1,700 km from Mexico City, the Project began operations in 1974 as Integrally Planned Center, a pioneer of FONATUR Cancún is a city of...
, Mexico. Within twelve hours, the depression intensified into a tropical storm. Operationally, the system was not known to be a tropical cyclone until 2100 UTC on July 27, after a reconnaisance aircraft flight into the system confirmed the presence of a closed albeit elongated circulation center. At that point, the NHC classified it as Tropical Storm Don. Upon forming, the storm moved to the west-northwest along the southern periphery of a low- to mid-level ridge
Ridge (meteorology)
A ridge is an elongated region of relatively high atmospheric pressure, the opposite of a trough....
over the northern Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
. The NHC predicted steady intensification to at least 65 mph (100 km/h) owing to generally favorable conditions including warm waters and light to moderate wind shear. However, none of the tropical cyclone forecast models anticipated much strengthening.
Initially, Don failed to intensify significantly due to a misalignment between the lower and mid-level circulations. The wind shear in the region further exposed the circulation from the convection late on July 28, although the winds increased slightly. Early on July 29, Don attained peak winds of 50 mph (85 km/h) as reported by the Hurricane Hunters, and the storm maintained that intensity while moving across the Gulf of Mexico. As Don approached the Texas coast early on July 30, the thunderstorms rapidly diminished, due to the combination of wind shear, drier air, and cooler water temperatures just offshore. The winds decreased as the convection dissipated, and Don made landfall
Landfall (meteorology)
Landfall is the event of a tropical cyclone or a waterspout coming onto land after being over water. When a waterspout makes landfall it is reclassified as a tornado, which can then cause damage inland...
on Padre Island National Seashore
Padre Island National Seashore
Padre Island National Seashore is a National Seashore located on Padre Island off the coast of South Texas. In contrast to South Padre Island , PINS is located on North Padre Island and consists of a long beach where nature is preserved...
as a tropical depression. About three and a half hours later, Don degenerated into a remnant low, and the circulation dissipated six hours after that.
Preparations and impact
The state civil protection agency in Quintana RooQuintana Roo
Quintana Roo officially Estado Libre y Soberano de Quintana Roo is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 10 municipalities and its capital city is Chetumal....
warned that the tropical wave from which Don formed was capable of dropping 80 to 150 mm (3.1 to 5.9 in) of rainfall over the state, while producing sustained winds of 35 to 45 km/h (21.7 to 28 mph) and gusts up to 65 km/h (40.4 mph). After Don was designated as a tropical storm, the Yucatán
Yucatán
Yucatán officially Estado Libre y Soberano de Yucatán is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 106 municipalities and its capital city is Mérida....
state government issued a green-level alert. The alert indicated that although the tropical storm was located close to the state, it was only considered to be slightly dangerous. Late on July 27, the National Hurricane Center issued a tropical storm watch
Tropical cyclone warnings and watches
Warnings and watches are two levels of alert issued by national weather forecasting bodies to coastal areas threatened by the imminent approach of a tropical cyclone of tropical storm or hurricane intensity. They are notices to the local population and civil authorities to make appropriate...
from Port Mansfield, Texas
Port Mansfield, Texas
Port Mansfield is a census-designated place in Willacy County, Texas, United States. The population was 415 at the 2000 census.-Geography:Port Mansfield is located at ....
to San Luis Pass, Texas. Six hours later, the tropical storm watch was extended southwards to the international border.
After the storm was named, officials in Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
began making preparations for Don. The University of Texas Medical Branch
University of Texas Medical Branch
The University of Texas Medical Branch is a component of the University of Texas System located in Galveston, Texas, United States, about 50 miles southeast of Downtown Houston...
in Galveston
Galveston, Texas
Galveston is a coastal city located on Galveston Island in the U.S. state of Texas. , the city had a total population of 47,743 within an area of...
issued a level one alert for Don, and city officials began preparing for a possible evacuation. On July 27, oil companies throughout the western Gulf of Mexico began removing non-essential personnel from their rigs and platforms in preparation for the storm. The next day, BP
BP
BP p.l.c. is a global oil and gas company headquartered in London, United Kingdom. It is the third-largest energy company and fourth-largest company in the world measured by revenues and one of the six oil and gas "supermajors"...
, Royal Dutch Shell
Royal Dutch Shell
Royal Dutch Shell plc , commonly known as Shell, is a global oil and gas company headquartered in The Hague, Netherlands and with its registered office in London, United Kingdom. It is the fifth-largest company in the world according to a composite measure by Forbes magazine and one of the six...
, Anadarko
Anadarko Petroleum Corporation
Anadarko Petroleum Corporation is one of the world’s largest independent oil and gas exploration and production companies, with approximately 2.3 billion barrels of oil equivalent of proved reserves and production of 206 million BOE as of December 31, 2008. Anadarko employs a worldwide...
and Apache
Apache Corporation
Apache Corporation is an American independent oil and gas corporation. It is headquartered in 1 Post Oak Central in the Uptown district of Houston, Texas....
announced the evacuations of some of the oil facilities in the area, while Exxon-Mobil began preparing the Baytown Refinery
Baytown Refinery
ExxonMobil's Baytown Refinery in Baytown, Texas is the largest oil refinery in the United States, with an input capacity of per day as of June 1, 2010. The site first opened in 1919 and was originally operated by the Humble Oil Company. Today, it is the largest employer in the city...
for a possible strike from the storm. Several oil companies stopped oil production as a result of Don; by midday on July 28, 6.8% of oil production and 2.8% of natural gas production in the Gulf had been shut in
Shut-in (oil drilling)
In the petroleum industry, shutting-in is the implementation of a production cap lower than the available output of a specific site. This may be part of an attempt to constrict the oil supply or a necessary precaution when crews are evacuated ahead of a natural disaster....
ahead of the storm.
Due to its abrupt weakening prior to landfall, Don produced minimal rainfall, with totals of less than 1 in (25.4 mm). However, Bay City, Texas
Bay City, Texas
Bay City is a city in Matagorda County, Texas, United States. The population was 18,667 at the 2000 census. It is the county seat of Matagorda County. The current mayor is Mark Bricker.-Geography:Bay City is located at...
, located well northeast of where the storm made landfall, reported 2.56 in (65 mm). In southern Texas, the rains resulted in slippery roads and some ponding. Cotton farmers benefited from what rains that did fall as they harvested their crop. Winds during the storm's passage were minimal, with a peak wind gust of 41 mph (66 km/h) at Waldron Field. In addition, Don moved ashore with a storm surge
Storm surge
A storm surge is an offshore rise of water associated with a low pressure weather system, typically tropical cyclones and strong extratropical cyclones. Storm surges are caused primarily by high winds pushing on the ocean's surface. The wind causes the water to pile up higher than the ordinary sea...
that peaked at of about 1.89 ft (0.576072 m) at Bob Hall Pier. There were no reports of damage.