Tropical Storm Bret (2011)
Encyclopedia
Tropical Storm Bret was the second named storm
of the 2011 Atlantic hurricane season
. It developed along the southwestern periphery of a weather front
to the north of the Bahamas on July 17. At first, Bret moved little and gradually strengthened in response to favorable upper-level conditions, reaching peak sustained winds
of 65 mph (100 km/h). Steering currents subsequently became better established in the area, and the storm turned toward the northeast only to encounter a substantial increase in vertical wind shear
. Despite the shear, Bret maintained a well-defined cyclonic
wind circulation for several days, with intermittent bursts of thunderstorm
s occurring near the center. By July 22, it had been devoid of strong thunderstorm activity for several hours, prompting the National Hurricane Center
to discontinue advisories when the storm was located about 375 miles (605 km) north of Bermuda
.
Since Bret remained over the open Atlantic for most of its duration, its effects on land were limited. While it was moving little, the storm produced inclement weather and widespread cloudiness over much of the north-central Bahamas. Squalls off the coast of Florida
generated rough seas along coastlines, injuring a number of people. Although it remained well offshore, the storm enhanced moisture that caused beneficial rainfall in Bermuda.
dropped southward over the northwest Atlantic, supporting a cold front
that extended westward across Bermuda
to inland over Georgia
. The front produced a large area of light showers to its north, as the westernmost component remained quasi-stationary over northeastern Florida
. On July 16, a surface low developed just off the coast along the decaying boundary
, producing an area of sporadic convection
just to the north of the Bahamas. Although a circulation was initially absent and surface pressures remained relatively high, the low later became better organized under abating shear conditions
. At 2100 UTC on July 17, the National Hurricane Center
(NHC) declared it a tropical depression about 100 mi (160 km) northwest of Great Abaco Island
, after reconnaissance
confirmed the presence of a closed circulation center. It strengthened into Tropical Storm Bret just three hours later, owing to a quick increase in winds and deep central convection.
Situated along a weakness in the subtropical ridge
, the cyclone drifted very slowly southward during the initial stages of its existence. Though traces of dry air were noted to its west, Bret continued to strengthen; prominent band
s of deep thunderstorms tightened around the eastern semicircle of the storm. Satellite images
displayed a disorganized eye-like feature
on July 18, suggesting a rather sharp increase in strength. Indeed, an additional reconnaissance flight into the cyclone found peak surface winds of around 65 mph (100 km/h), confirming the increase. Following its peak, Bret initiated an accelerating motion toward the northeast in response to building high pressure. It fluctuated little in intensity for several hours, although a combination of high wind shear over the storm and a lack of tropical moisture
inhibited further development. By July 19, the circulation center had become exposed and devoid of deep convection, and the storm weakened to 50 mph (85 km/h) winds upon moving through an increasingly hostile environment. Despite the unfavorable conditions, Bret retained this intensity for the next couple of days as it briefly slowed, with a distinct low-level circulation and a few patches of persistent thunderstorms located over the southwestern quadrant
.
Early on July 20, the sheared cyclone began to reaccelerate within the deepening southwesterly wind flow. Over the next day, Bret continued to deteriorate in organization; however, a brief weakening of the upper winds allowed intermittent bursts of convection to redevelop south of the exposed center. It eventually weakened to a tropical depression over cooling waters
early on July 22, once again lacking significant convection while increasing in forward speed. Forecasters at the NHC noted that Bret remained "a maverick tropical cyclone by refusing to dissipate despite experiencing very hostile wind shear conditions," with ship data
indications of prevailing strong winds. By 1500 UTC, however, the circulation had become ill defined, prompting the NHC to declassify it as a tropical system about 375 mi (605 km) north of Bermuda
.
and Andros Island
, and authorities urged small craft operators to secure their vessels. The warnings were discontinued later that day as Bret turned away from the territory.
Since it initially moved little, Bret brought prolonged overcast conditions to much of the northern Bahamas, with most activity occurring over the Abaco Islands and Grand Bahama
. An estimated 3 in (75 mm) of precipitation fell in Abaco over the weekend of July 16–17. In addition, a weather station on the island reported gale
-force gusting of up to 48 mph (77 km/h) at the height of the storm. The rains lead to the cancellation of a local Little League
baseball match. Outer rainbands spawned a waterspout
that touched down on eastern Paradise Island
, accompanied by lightning strikes and torrents. In all, locals considered the storm's impact to be generally positive, as its rains aided in alleviating mild drought
conditions across the nation.
. Strong rip current
s swept dozens of people out to sea, but all remained unharmed and were quickly rescued. Additionally, the waves washed ashore venomous jellyfish that stung more than 200 people near coastal beaches. Scattered funnel cloud
s and waterspouts were reported overseas, though the phenomena dissipated soon thereafter without affecting land. Onshore, its effects were minimal; weak morning showers and breezy winds briefly brushed Brevard and Volusia Counties
. As Bret lifted out of the area, it drew in a large mass of dry air, limiting chances of much-needed rain to subdue a large wildfire
in the Okefenokee Swamp
.
Light showers from the precursor front skirted Bermuda prior to tropical development, with 24-hour precipitation totals of no more than 0.87 in (22 mm) recorded on the territory. Moisture brought on by the storm from afar enhanced rainfall that ended months of dry conditions in Bermuda; 1.75 in (45 mm) of precipitation fell at L.F. Wade International Airport on July 18, with an additional 1.6 in (40 mm) recorded the next day. Although the rains proved to be mostly beneficial, minor flooding affected some local businesses in poor-drainage areas.
Tropical cyclone naming
Tropical cyclones have officially been named since 1945 and are named for a variety of reasons, which include to facilitate communications between forecasters and the public when forecasts, watches, and warnings are issued. Names also reduce confusion about what storm is being described, as more...
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...
. It developed along the southwestern periphery of a weather front
Weather front
A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena. In surface weather analyses, fronts are depicted using various colored lines and symbols, depending on the type of front...
to the north of the Bahamas on July 17. At first, Bret moved little and gradually strengthened in response to favorable upper-level conditions, reaching peak sustained winds
Maximum sustained wind
The maximum sustained winds associated with a tropical cyclone are a common indicator of the intensity of the storm. Within a mature tropical cyclone, they are found within the eyewall at a distance defined as the radius of maximum wind, or RMW. Unlike gusts, the value of these winds are...
of 65 mph (100 km/h). Steering currents subsequently became better established in the area, and the storm turned toward the northeast only to encounter a substantial increase in 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...
. Despite the shear, Bret maintained a well-defined cyclonic
Cyclone
In meteorology, a cyclone is an area of closed, circular fluid motion rotating in the same direction as the Earth. This is usually characterized by inward spiraling winds that rotate anticlockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere of the Earth. Most large-scale...
wind circulation for several days, with intermittent bursts of thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
s occurring near the center. By July 22, it had been devoid of strong thunderstorm activity for several hours, prompting 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...
to discontinue advisories when the storm was located about 375 miles (605 km) north of Bermuda
Bermuda
Bermuda is a British overseas territory in the North Atlantic Ocean. Located off the east coast of the United States, its nearest landmass is Cape Hatteras, North Carolina, about to the west-northwest. It is about south of Halifax, Nova Scotia, Canada, and northeast of Miami, Florida...
.
Since Bret remained over the open Atlantic for most of its duration, its effects on land were limited. While it was moving little, the storm produced inclement weather and widespread cloudiness over much of the north-central Bahamas. Squalls off the coast of Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
generated rough seas along coastlines, injuring a number of people. Although it remained well offshore, the storm enhanced moisture that caused beneficial rainfall in Bermuda.
Meteorological history
In mid-July, a broad upper troughTrough (meteorology)
A trough is an elongated region of relatively low atmospheric pressure, often associated with fronts.Unlike fronts, there is not a universal symbol for a trough on a weather chart. The weather charts in some countries or regions mark troughs by a line. In the United States, a trough may be marked...
dropped southward over the northwest Atlantic, supporting a cold front
Cold front
A cold front is defined as the leading edge of a cooler mass of air, replacing a warmer mass of air.-Development of cold front:The cooler and denser air wedges under the less-dense warmer air, lifting it...
that extended westward across Bermuda
Bermuda
Bermuda is a British overseas territory in the North Atlantic Ocean. Located off the east coast of the United States, its nearest landmass is Cape Hatteras, North Carolina, about to the west-northwest. It is about south of Halifax, Nova Scotia, Canada, and northeast of Miami, Florida...
to inland over Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
. The front produced a large area of light showers to its north, as the westernmost component remained quasi-stationary over northeastern Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
. On July 16, a surface low developed just off the coast along the decaying boundary
Stationary front
A stationary front is a boundary between two different air masses, neither of which is strong enough to replace the other. On a weather map, this is shown by an inter-playing series of blue spikes pointing one direction and red domes pointing the other. They tend to remain essentially in the same...
, producing an area of sporadic 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...
just to the north of the Bahamas. Although a circulation was initially absent and surface pressures remained relatively high, the low later became better organized under abating shear conditions
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...
. At 2100 UTC on July 17, 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) declared it a tropical depression about 100 mi (160 km) northwest of Great Abaco Island
Abaco Islands
The Abaco Islands lie in the northern Bahamas and comprise the main islands of Great Abaco and Little Abaco, together with the smaller Wood Cay, Elbow Cay, Lubbers Quarters Cay, Green Turtle Cay, Great Guana Cay, Castaway Cay, Man-o-War Cay, Stranger's Cay, Umbrella Cay, Walker's Cay, Little Grand...
, after reconnaissance
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...
confirmed the presence of a closed circulation center. It strengthened into Tropical Storm Bret just three hours later, owing to a quick increase in winds and deep central convection.
Situated along a weakness in the subtropical ridge
Subtropical ridge
The subtropical ridge is a significant belt of high pressure situated around the latitudes of 30°N in the Northern Hemisphere and 30°S in the Southern Hemisphere. It is characterized by mostly calm winds, which acts to reduce air quality under its axis by causing fog overnight, and haze during...
, the cyclone drifted very slowly southward during the initial stages of its existence. Though traces of dry air were noted to its west, Bret continued to strengthen; prominent band
Rainband
A rainband is a cloud and precipitation structure associated with an area of rainfall which is significantly elongated. Rainbands can be stratiform or convective, and are generated by differences in temperature. When noted on weather radar imagery, this precipitation elongation is referred to as...
s of deep thunderstorms tightened around the eastern semicircle of the storm. Satellite images
Weather satellite
The weather satellite is a type of satellite that is primarily used to monitor the weather and climate of the Earth. Satellites can be either polar orbiting, seeing the same swath of the Earth every 12 hours, or geostationary, hovering over the same spot on Earth by orbiting over the equator while...
displayed a disorganized eye-like feature
Eye (cyclone)
The eye is a region of mostly calm weather found at the center of strong tropical cyclones. The eye of a storm is a roughly circular area and typically 30–65 km in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the second most severe weather of a cyclone...
on July 18, suggesting a rather sharp increase in strength. Indeed, an additional reconnaissance flight into the cyclone found peak surface winds of around 65 mph (100 km/h), confirming the increase. Following its peak, Bret initiated an accelerating motion toward the northeast in response to building high pressure. It fluctuated little in intensity for several hours, although a combination of high wind shear over the storm and a lack of 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...
inhibited further development. By July 19, the circulation center had become exposed and devoid of deep convection, and the storm weakened to 50 mph (85 km/h) winds upon moving through an increasingly hostile environment. Despite the unfavorable conditions, Bret retained this intensity for the next couple of days as it briefly slowed, with a distinct low-level circulation and a few patches of persistent thunderstorms located over the southwestern quadrant
Circular sector
A circular sector or circle sector, is the portion of a disk enclosed by two radii and an arc, where the smaller area is known as the minor sector and the larger being the major sector. In the diagram, θ is the central angle in radians, r the radius of the circle, and L is the arc length of the...
.
Early on July 20, the sheared cyclone began to reaccelerate within the deepening southwesterly wind flow. Over the next day, Bret continued to deteriorate in organization; however, a brief weakening of the upper winds allowed intermittent bursts of convection to redevelop south of the exposed center. It eventually weakened to a tropical depression over cooling waters
Sea surface temperature
Sea surface temperature is the water temperature close to the oceans surface. The exact meaning of surface varies according to the measurement method used, but it is between and below the sea surface. Air masses in the Earth's atmosphere are highly modified by sea surface temperatures within a...
early on July 22, once again lacking significant convection while increasing in forward speed. Forecasters at the NHC noted that Bret remained "a maverick tropical cyclone by refusing to dissipate despite experiencing very hostile wind shear conditions," with ship data
Voluntary observing ship program
Due to the importance of surface weather observations from the surface of the ocean, the voluntary observing ship program, known as VOS, was set up to train crews how to take weather observations while at sea and also to calibrate weather sensors used aboard ships when they arrive in port, such as...
indications of prevailing strong winds. By 1500 UTC, however, the circulation had become ill defined, prompting the NHC to declassify it as a tropical system about 375 mi (605 km) north of Bermuda
Bermuda
Bermuda is a British overseas territory in the North Atlantic Ocean. Located off the east coast of the United States, its nearest landmass is Cape Hatteras, North Carolina, about to the west-northwest. It is about south of Halifax, Nova Scotia, Canada, and northeast of Miami, Florida...
.
Bahamas
Upon the formation of a depression, the government of the Bahamas issued a tropical storm watch for northwestern islands of the nation. It was upgraded to a tropical storm warning on July 18, when the storm showed signs of intensification. Further south, a severe weather warning was in effect for New ProvidenceNew Providence
New Providence is the most populous island in the Bahamas, containing more than 70% of the total population. It also houses the national capital city, Nassau.The island was originally under Spanish control following Christopher Columbus' discovery of the New World, but the Spanish government showed...
and Andros Island
Andros, Bahamas
Andros Island is an archipelago within the archipelago-nation of the Bahamas, the largest of the 26 inhabited Bahamian Islands. Geo-politically considered a single island, Andros has an area greater than all the other 700 Bahamian islands combined...
, and authorities urged small craft operators to secure their vessels. The warnings were discontinued later that day as Bret turned away from the territory.
Since it initially moved little, Bret brought prolonged overcast conditions to much of the northern Bahamas, with most activity occurring over the Abaco Islands and Grand Bahama
Grand Bahama
Grand Bahama is one of the northernmost of the islands of the Bahamas, and the closest major island to the United States, lying off the state of Florida. Grand Bahama is the fifth largest island in the Bahamas island chain of approximately 700 islands and 2,400 cays...
. An estimated 3 in (75 mm) of precipitation fell in Abaco over the weekend of July 16–17. In addition, a weather station on the island reported gale
Gale
A gale is a very strong wind. There are conflicting definitions of how strong a wind must be to be considered a gale. The U.S. government's National Weather Service defines a gale as 34–47 knots of sustained surface winds. Forecasters typically issue gale warnings when winds of this strength are...
-force gusting of up to 48 mph (77 km/h) at the height of the storm. The rains lead to the cancellation of a local Little League
Little League
Little League Baseball and Softball is a non-profit organization in South Williamsport, Pennsylvania, United States which organizes local youth baseball and softball leagues throughout the U.S...
baseball match. Outer rainbands spawned a waterspout
Waterspout
A waterspout is an intense columnar vortex that occurs over a body of water and is connected to a cumuliform cloud. In the common form, it is a non-supercell tornado over water. While it is often weaker than most of its land counterparts, stronger versions spawned by mesocyclones do occur...
that touched down on eastern Paradise Island
Paradise Island
Paradise Island is an island in the Bahamas formerly known as Hog Island. The island is located just off the shore of the city of Nassau, which is itself located on the northern edge of the island of New Providence. It is best known for the sprawling 'Vegas-by-the-sea resort' Atlantis.Paradise...
, accompanied by lightning strikes and torrents. In all, locals considered the storm's impact to be generally positive, as its rains aided in alleviating mild drought
Drought
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
conditions across the nation.
United States and Bermuda
Off the coast of Florida, the storm generated rough sea conditions with waves of up to 5 ft (1.9 m); high surf lightly injured several swimmers and surfers in Brevard CountyBrevard County, Florida
Brevard County is a county located in the U.S. state of Florida, along the coast of the Atlantic Ocean. As of 2007 U.S. Census Bureau estimates, the population is 536,521, making it the 10th most populous county in the state. Influenced by the presence of the John F. Kennedy Space Center, Brevard...
. Strong rip current
Rip current
A rip current, commonly referred to by the misnomer rip tide, is a strong channel of water flowing seaward from near the shore, typically through the surf line. Typical flow is at 0.5 metres per second , and can be as fast as 2.5 metres per second...
s swept dozens of people out to sea, but all remained unharmed and were quickly rescued. Additionally, the waves washed ashore venomous jellyfish that stung more than 200 people near coastal beaches. Scattered funnel cloud
Funnel cloud
A funnel cloud is a funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind and extending from the base of a cloud but not reaching the ground or a water surface. A funnel cloud is usually visible as a cone-shaped or needle like protuberance from the main cloud...
s and waterspouts were reported overseas, though the phenomena dissipated soon thereafter without affecting land. Onshore, its effects were minimal; weak morning showers and breezy winds briefly brushed Brevard and Volusia Counties
Volusia County, Florida
Volusia County is a county located in the state of Florida. The U.S. Census Bureau 2010 official county's population was 494,593 . Its county seat is DeLand, and its most populous city is currently Deltona....
. As Bret lifted out of the area, it drew in a large mass of dry air, limiting chances of much-needed rain to subdue a large wildfire
Wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...
in the Okefenokee Swamp
Okefenokee Swamp
The Okefenokee Swamp is a shallow, 438,000 acre , peat-filled wetland straddling the Georgia–Florida border in the United States. A majority of the swamp is in Georgia and protected by the Okefenokee National Wildlife Refuge and the Okefenokee Wilderness. The Okefenokee Swamp is considered to be...
.
Light showers from the precursor front skirted Bermuda prior to tropical development, with 24-hour precipitation totals of no more than 0.87 in (22 mm) recorded on the territory. Moisture brought on by the storm from afar enhanced rainfall that ended months of dry conditions in Bermuda; 1.75 in (45 mm) of precipitation fell at L.F. Wade International Airport on July 18, with an additional 1.6 in (40 mm) recorded the next day. Although the rains proved to be mostly beneficial, minor flooding affected some local businesses in poor-drainage areas.
External links
- The NHCNational Hurricane CenterThe 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...
's advisory archive on Tropical Storm Bret - The NHCNational Hurricane CenterThe 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...
's graphics archive on Tropical Storm Bret