Hurricane Katia

Hurricane Katia

Category 4 major hurricane (SSHWS/NWS)
File:Hurricane Katia Sept 5 2011 1700Z.jpg Hurricane Katia as a major hurricane on September 5
Formed	August 29, 2011
Dissipated	September 13, 2011
(Extratropical after September 10)
Highest winds	1-minute sustained: 140 mph (220 km/h)
Lowest pressure	942 mbar (hPa); 27.82 inHg
Fatalities	3 direct
Damage	~ $157 million (2011 USD)
Areas affected	Lesser Antilles, U.S. East Coast, Canada, Europe
Part of the 2011 Atlantic hurricane season

Hurricane Katia was a long-lived and intense tropical cyclone that caused minor damage primarily throughout the Lesser Antilles and Europe during September 2011. It was the twelfth tropical cyclone and eleventh named storm, as well as the second hurricane and major hurricane of the unusually active 2011 Atlantic hurricane season. Originating from a tropical wave southwest of Cape Verde on August 29, Katia tracked generally west-northwest while gradually strengthening. The system intensified to a Category 1 hurricane on the Saffir–Simpson hurricane wind scale on August 31, and further to a Category 3—a major hurricane—by September 5. That afternoon, Katia attained its peak intensity as a Category 4, with sustained winds reaching 140 mph (220 km/h) and a minimum barometric pressure of 942 mbar (hPa; 27.82 inHg), while located several hundred miles north of the Lesser Antilles. The combined effects of higher wind shear from an approaching trough, interaction with a cold front, and increasingly cool sea surface temperatures thereafter gradually weakened the storm as it passed well west of Bermuda, and on September 10, Katia transitioned into an extratropical cyclone while persisting hurricane-force winds.

Due to Katia's forecast track well north of the Leeward Islands, no tropical cyclone watches or warnings were issued for the region; despite this, the government of Guadeloupe raised a yellow alert to notify residents of dangerous seas. A 37-year-old fisherman was swept away and ultimately died as a result of rip currents in the northeastern Caribbean Sea. Strong rip currents also led to the death of a swimmer off the eastern coast of Florida, while a second person drowned after his boat was destroyed by high waves offshore Maine. As a post-tropical cyclone, Katia prompted the issuance of several alerts and warnings for the British Isles. As the cyclone moved through the region on September 13, wind gusts well surpassed hurricane intensity, leaving thousands without power. A man died when a tree fell on his car. In addition, heavy rainfall, peaking at 76.8 mm (3.02 in) in Tyndrum, caused localized flooding. Overall, Katia was responsible for 3 deaths and an estimated $157 million (2012 USD) in damage.

Meteorological history

File:Katia 2011 track.png

Map plotting the track and intensity of the storm according to the Saffir–Simpson hurricane wind scale

On August 27, 2011, a large area of disorganized showers and thunderstorms 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 (640 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 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 temperatures, further intensification took place over the following day.

File:Katia 2011-09-04 1445Z.jpg

Hurricane Katia as it moved away from the Lesser Antilles on September 4

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, on September 1. Over the following few days, Katia maintained its intensity at 75 mph (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 at peak intensity 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, near 70 mph (110 km/h). At 0000 UTC on September 13, Katia's remnant merged with a larger extratropical system, over the North Sea.

Preparations and impact

Lesser Antilles and United States

As Katia passed to the northeast of the Lesser Antilles, 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 currents 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.

Europe

File:Katia post tropical cyclone.jpg

Katia hits the coast of Ireland in the form of a post tropical cyclone.

As a post tropical cyclone, Katia moved quickly across the Atlantic, and was expected to start affecting the British Isles 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 disruption, and cause major damage to buildings, with western parts of the United Kingdom also at risk from localised flooding. In preparation for the storm, Irish ferries cancelled a number of its Swift sailings between Dublin and Holyhead. A group of American students studying in Galway, Ireland were nearly stranded on the Aran Islands when ferries were canceled from Inishmore. Swedish Meteorological and Hydrological 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 km/h) at Capel Curig, Wales. The highest gust overall was 98 mph (158 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.

Katia also caused the cancellation of the second stage of the Tour of Britain cycle race from Kendal to Blackpool due to debris on the road caused by the strong winds across North West England.

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. In Estonia the storm cut off power to approximately 940 households, particularly affecting the island of Hiiumaa and Harju County, with strong winds in coastal areas gusting up to 90 km/h.

See also

• Tropical cyclone effects in Europe
• Hurricane Faith (1966)
• Hurricane Charley (1986)
• Hurricane Katrina

External links

Media related to at Wikimedia Commons