Hurricane Katia (2011)
Encyclopedia
Hurricane Katia was the eleventh named storm, second hurricane and second major hurricane of the 2011 Atlantic hurricane season
. A Cape Verde-type hurricane
, Katia developed from a tropical wave
south of the Cape Verde Islands on August 29. Tracking west-northwestward, the system gradually strengthened within an area supportive of tropical development
. Late on August 31, Katia was estimated to have attained hurricane status well away from land. On September 1, Katia was downgraded to a tropical storm after wind speeds dropped below hurricane strength. The following day, it was upgraded back to a Category 1
hurricane, then back down to a tropical storm on September 3. In the morning of September 4, it strengthened rapidly to reach Category 2 status. During the course of the day on September 5, it grew in strength to become a Category 4 hurricane. On September 6, it weakened steadily to a Category 1 hurricane, and four days later it became extratropical, while located to the south of Newfoundland.
associated with a tropical wave
moved off the west coast of Africa into the Atlantic Ocean
. As it moved westward into a region favorable for tropical cyclogenesis
, forecasters at the National Hurricane Center
(NHC) expected gradual development of the wave over the following days. The following afternoon, an area of low pressure developed within the wave as it tracked roughly 400 miles (643.7 km) south of the Cape Verde Islands. In light of further convective development and the appearance of curved bands
on satellite imagery, the NHC designated the low as Tropical Depression Twelve early on August 29. Situated south of a subtropical ridge
, the depression maintained a west-northwestward track. Initially, strong wind shear
prevented further organization; however, by the morning of August 30, deep convection formed near the center of circulation and Dvorak technique
intensity estimates rose to T2.5, or 40 mph (64.4 km/h). This prompted the NHC to upgrade the depression to Tropical Storm Katia, the eleventh named storm of 2011. Continuing west-northwestward into a region of lower shear and high sea surface temperature
s, further intensification took place over the following day.
Gradual development of the storm's central dense overcast took place throughout August 31 and microwave imagery depicted a developing banding eye feature
. Later that day, it was estimated that Katia intensified into a hurricane well-away from land. However, increasing wind shear associated with an upper-level low to the northwest displaced convection from the hurricane's center, resulting in temporary weakening on September 1. Over the following few days, Katia's intensity fluctuated between 70 and 75 mph (110 and 120 km/h) as it struggled to maintain convection amidst wind shear and dry air. At times, a mid-level eye developed; however, this feature was displaced to the north of the low-level circulation. On the morning of September 4, Katia strengthened once again and buoy data from a NOAA data buoy confirmed a much stronger storm and Katia was upgraded to a Category 2 hurricane, with winds of 100 mph (160 km/h). Satellite imagery also indicated that the system had a more pronounced eye developing, and the storm was becoming more organized. Strengthening of the cyclone leveled off as the day went on, and while an eye remained visible on visible satellite imagery, infrared satellites were not always able to detect an eye. In the late evening of September 5, Katia strengthened to a Category 4 hurricane with winds of 135 mph (215 km/h); however, it then weakened back into a Category 3 during the early morning of September 6, with winds of 125 mph (200 km/h) due to an eyewall replacement cycle
taking place.
By that evening, Katia had weakened to a Category 1 hurricane, and by the morning of September 7, the hurricane had continued to weaken more. The eyewall replacement cycle that had been taking place was interrupted, and dry air led to the system weakening and becoming less organized. Katia continued to weaken throughout the day, and by late evening, it had begun to turn northward, moving between a subtropical ridge and upper-level low.
In the early hours of September 8, Katia began to strengthen slightly, with winds increasing to 90 mph (150 km/h), and the pressure dropping to 970 mbar (hPa; 28.64 inHg). The hurricane then weakened in the afternoon, but held its intensity in the late evening as the formation of an eye was seen on satellite imagery. Due to the storm turning to the northeast, vertical wind shear decreased, and this decrease was responsible for the Katia being able to maintain its intensity. Katia became a strong post-tropical cyclone on the morning of September 10 as it became embedded in a frontal zone, while still maintaining hurricane-force sustained winds. The remnants of Katia accelerated across the Atlantic, and by September 12, the system crossed Ireland and the United Kingdom, with winds still at hurricane intensity.
, large swells
impacted several islands. Due to this, a yellow alert was raised in Guadeloupe
to warn residents of rough or dangerous sea.
A 37 year old fisherman was swept away by high seas conditions.
Although well away from the storm, Katia's rip current
s resulted in the death of a swimmer in Volusia County, Florida
. A second person drowned off the coast of Maine
on September 9 after being knocked off his boat by large waves. While nearing and moving up the U.S. East Coast, the NHC issued warnings of Katia's rip currents with several public advisories.
during September 11 with hurricane force wind speeds and possible hurricane force wind gusts. On September 9, in preparation for this both the Met Office
and Met Eireann
started to issue alerts and warnings for parts of the British Isles. They warned that parts of the British Isles were likely to experience gale-force and storm-force windspeeds during September 11 and 12 which could be strong enough to uproot trees, create widespread travel chaos, and cause major damage to buildings, with western parts of the United Kingdom
also at risk from localized flooding.
In preparation for the storm, Irish ferries canceled a number of its Swift sailings between Dublin and Holyhead
. Swedish met institute
issued a class 1 warning (certain risks and disturbances) for gale-force winds for the night before September 13.
The maximum wind gust recorded in the United Kingdom at a non-mountain station on the day of landfall was 81 mph (130.4 km/h) at Capel Curig
, Wales. The highest gust overall was 98 mph (157.7 km/h) at Cairn Gorm
Summit, Scotland. In County Durham, a man was killed when a tree fell on a minibus he was driving. Across the United Kingdom, damage was estimated at £100 million ($157 million USD). Large waves also battered the west coast of Scotland.
The remnants of Katia produced damage as far east as Russia
. In St. Petersburg, wind gusts up to 45 mph (75 km/h) damaged buildings and left roughly 1,500 residents without power
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...
. A Cape Verde-type hurricane
Cape Verde-type hurricane
A Cape Verde-type hurricane is an Atlantic hurricane that develops near the Cape Verde islands, off the west coast of Africa. The average hurricane season has about two Cape Verde-type hurricanes, which are usually the largest and most intense storms of the season because they often have plenty of...
, Katia developed from 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...
south of the Cape Verde Islands on August 29. Tracking west-northwestward, the system gradually strengthened within an area supportive of tropical development
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...
. Late on August 31, Katia was estimated to have attained hurricane status well away from land. On September 1, Katia was downgraded to a tropical storm after wind speeds dropped below hurricane strength. The following day, it was upgraded back to a Category 1
Saffir-Simpson Hurricane Scale
The Saffir–Simpson Hurricane Scale , or the Saffir–Simpson Hurricane Wind Scale , classifies hurricanes — Western Hemisphere tropical cyclones that exceed the intensities of tropical depressions and tropical storms — into five categories distinguished by the intensities of their sustained winds...
hurricane, then back down to a tropical storm on September 3. In the morning of September 4, it strengthened rapidly to reach Category 2 status. During the course of the day on September 5, it grew in strength to become a Category 4 hurricane. On September 6, it weakened steadily to a Category 1 hurricane, and four days later it became extratropical, while located to the south of Newfoundland.
Meteorological history
On August 27, 2011, a large area of disorganized showers and thunderstormsAtmospheric 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...
associated with 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...
moved off the west coast of Africa into the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
. As it moved westward into a region favorable for 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...
, forecasters at 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) expected gradual development of the wave over the following days. The following afternoon, an area of low pressure developed within the wave as it tracked roughly 400 miles (643.7 km) south of the Cape Verde Islands. In light of further convective development and the appearance of curved bands
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...
on satellite imagery, the NHC designated the low as Tropical Depression Twelve early on August 29. Situated south of a subtropical ridge
Ridge (meteorology)
A ridge is an elongated region of relatively high atmospheric pressure, the opposite of a trough....
, the depression maintained a west-northwestward track. Initially, strong 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...
prevented further organization; however, by the morning of August 30, deep convection formed near the center of circulation and Dvorak technique
Dvorak technique
The Dvorak technique is a widely used system to subjectively estimate tropical cyclone intensity based solely on visible and infrared satellite images. Several agencies issue Dvorak intensity numbers for cyclones of sufficient intensity...
intensity estimates rose to T2.5, or 40 mph (64.4 km/h). This prompted the NHC to upgrade the depression to Tropical Storm Katia, the eleventh named storm of 2011. Continuing west-northwestward into a region of lower shear and high sea surface temperature
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...
s, further intensification took place over the following day.
Gradual development of the storm's central dense overcast took place throughout August 31 and microwave imagery depicted a developing banding eye 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...
. Later that day, it was estimated that Katia intensified into a hurricane well-away from land. However, increasing wind shear associated with an upper-level low to the northwest displaced convection from the hurricane's center, resulting in temporary weakening on September 1. Over the following few days, Katia's intensity fluctuated between 70 and 75 mph (110 and 120 km/h) as it struggled to maintain convection amidst wind shear and dry air. At times, a mid-level eye developed; however, this feature was displaced to the north of the low-level circulation. On the morning of September 4, Katia strengthened once again and buoy data from a NOAA data buoy confirmed a much stronger storm and Katia was upgraded to a Category 2 hurricane, with winds of 100 mph (160 km/h). Satellite imagery also indicated that the system had a more pronounced eye developing, and the storm was becoming more organized. Strengthening of the cyclone leveled off as the day went on, and while an eye remained visible on visible satellite imagery, infrared satellites were not always able to detect an eye. In the late evening of September 5, Katia strengthened to a Category 4 hurricane with winds of 135 mph (215 km/h); however, it then weakened back into a Category 3 during the early morning of September 6, with winds of 125 mph (200 km/h) due to an eyewall replacement cycle
Eyewall replacement cycle
Eyewall replacement cycles, also called concentric eyewall cycles, naturally occur in intense tropical cyclones, generally with winds greater than 185 km/h , or major hurricanes...
taking place.
By that evening, Katia had weakened to a Category 1 hurricane, and by the morning of September 7, the hurricane had continued to weaken more. The eyewall replacement cycle that had been taking place was interrupted, and dry air led to the system weakening and becoming less organized. Katia continued to weaken throughout the day, and by late evening, it had begun to turn northward, moving between a subtropical ridge and upper-level low.
In the early hours of September 8, Katia began to strengthen slightly, with winds increasing to 90 mph (150 km/h), and the pressure dropping to 970 mbar (hPa; 28.64 inHg). The hurricane then weakened in the afternoon, but held its intensity in the late evening as the formation of an eye was seen on satellite imagery. Due to the storm turning to the northeast, vertical wind shear decreased, and this decrease was responsible for the Katia being able to maintain its intensity. Katia became a strong post-tropical cyclone on the morning of September 10 as it became embedded in a frontal zone, while still maintaining hurricane-force sustained winds. The remnants of Katia accelerated across the Atlantic, and by September 12, the system crossed Ireland and the United Kingdom, with winds still at hurricane intensity.
Preparations and impact
As Katia passed to the northeast of the Lesser AntillesLesser Antilles
The Lesser Antilles are a long, partly volcanic island arc in the Western Hemisphere. Most of its islands form the eastern boundary of the Caribbean Sea with the Atlantic Ocean, with the remainder located in the southern Caribbean just north of South America...
, large swells
Swell (ocean)
A swell, in the context of an ocean, sea or lake, is a series surface gravity waves that is not generated by the local wind. Swell waves often have a long wavelength but this varies with the size of the water body, e.g. rarely more than 150 m in the Mediterranean, and from event to event, with...
impacted several islands. Due to this, a yellow alert was raised in Guadeloupe
Guadeloupe
Guadeloupe is an archipelago located in the Leeward Islands, in the Lesser Antilles, with a land area of 1,628 square kilometres and a population of 400,000. It is the first overseas region of France, consisting of a single overseas department. As with the other overseas departments, Guadeloupe...
to warn residents of rough or dangerous sea.
A 37 year old fisherman was swept away by high seas conditions.
Although well away from the storm, Katia's 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 resulted in the death of a swimmer in Volusia County, Florida
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....
. A second person drowned off the coast of Maine
Maine
Maine is a state in the New England region of the northeastern United States, bordered by the Atlantic Ocean to the east and south, New Hampshire to the west, and the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast. Maine is both the northernmost and easternmost...
on September 9 after being knocked off his boat by large waves. While nearing and moving up the U.S. East Coast, the NHC issued warnings of Katia's rip currents with several public advisories.
Europe
As a post tropical cyclone, Katia moved quickly across the Atlantic, and was expected to start affecting the British IslesBritish Isles
The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...
during September 11 with hurricane force wind speeds and possible hurricane force wind gusts. On September 9, in preparation for this both the Met Office
Met Office
The Met Office , is the United Kingdom's national weather service, and a trading fund of the Department for Business, Innovation and Skills...
and Met Eireann
Met Éireann
Met Éireann is the national meteorological service in Ireland, part of the Department of the Environment, Heritage and Local Government.-History:...
started to issue alerts and warnings for parts of the British Isles. They warned that parts of the British Isles were likely to experience gale-force and storm-force windspeeds during September 11 and 12 which could be strong enough to uproot trees, create widespread travel chaos, and cause major damage to buildings, with western parts of the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
also at risk from localized flooding.
In preparation for the storm, Irish ferries canceled a number of its Swift sailings between Dublin and Holyhead
Holyhead
Holyhead is the largest town in the county of Anglesey in the North Wales. It is also a major port adjacent to the Irish Sea serving Ireland....
. Swedish met institute
SMHI
SMHI is an abbreviation for Sveriges Meteorologiska och Hydrologiska Institut, . SMHI is a government agency in Sweden and operates under the Ministry of Sustainable Development...
issued a class 1 warning (certain risks and disturbances) for gale-force winds for the night before September 13.
The maximum wind gust recorded in the United Kingdom at a non-mountain station on the day of landfall was 81 mph (130.4 km/h) at Capel Curig
Capel Curig
Capel Curig is a village and community in Conwy County Borough, in Wales. It lies in the heart of Snowdonia, on the River Llugwy, and has a population of 226...
, Wales. The highest gust overall was 98 mph (157.7 km/h) at Cairn Gorm
Cairn Gorm
Cairn Gorm is a mountain in the Scottish Highlands overlooking Strathspey and the town of Aviemore. At 1245 metres it is the sixth highest mountain in the United Kingdom...
Summit, Scotland. In County Durham, a man was killed when a tree fell on a minibus he was driving. Across the United Kingdom, damage was estimated at £100 million ($157 million USD). Large waves also battered the west coast of Scotland.
The remnants of Katia produced damage as far east as Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
. In St. Petersburg, wind gusts up to 45 mph (75 km/h) damaged buildings and left roughly 1,500 residents without power
External links
- Public Advisory on Hurricane Katia from the National Hurricane Center
- Forecast Discussion on Hurricane Katia from the National Hurricane Center
- http://www.youtube.com/watch?v=M9CoHiSNElo/Hurricane Katia as seen from the International Space StationInternational Space StationThe International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...
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