 Hurricane Katia near peak intensity well north of theVirgin Islands on September 5 | |
| Meteorological history | |
|---|---|
| Formed | August 29, 2011 (2011-08-29) |
| Extratropical | September 10, 2011 (2011-09-10) |
| Dissipated | September 13, 2011 (2011-09-13) |
| Category 4 major hurricane | |
| 1-minute sustained (SSHWS/NWS) | |
| Highest winds | 140 mph (220 km/h) |
| Lowest pressure | 942mbar (hPa); 27.82 inHg |
| Overall effects | |
| Fatalities | 3 direct, 1 indirect |
| Damage | $157 million (2011USD) |
| Areas affected | Lesser Antilles,East Coast of the United States,United Kingdom,France,Germany,Poland,Latvia,Estonia,Russia |
IBTrACS | |
Part of the2011 Atlantic hurricane season | |
Hurricane Katia was a strongtropical cyclone that had substantial impact acrossEurope as apost-tropical cyclone. The eleventh named storm, second hurricane, and second major hurricane of the active2011 Atlantic hurricane season, Katia originated as a tropical depression from atropical wave over the eastern Atlantic on August 29. It intensified into a tropical storm the following day and further developed into a hurricane by September 1, although unfavorable atmospheric conditions hindered strengthening thereafter. As the storm began to recurve over the western Atlantic, a more hospitable regime allowed Katia to become a major hurricane by September 5 and peak as aCategory 4 hurricane with winds of 140 mph (230 km/h) that afternoon. Internal core processes, increasedwind shear, an impingingcold front, and increasingly coolocean temperatures all prompted the cyclone to weaken almost immediately after peak, and Katia ultimately transitioned into anextratropical cyclone on September 10.
Although Katia passed well north of theLesser Antilles, a yellow alert was hoisted forGuadeloupe to notify residents of dangerous seas. Strongrip currents along theEast Coast of the United States led to the deaths of two swimmers. After losing its tropical characteristics, Katia prompted the issuance of numerous warnings acrossEurope. Hurricane-force winds impacted numerous locations, downing trees, toppling power poles, and leaving thousands without electricity. The storm was responsible for two deaths in theUnited Kingdom: one when a tree fell on a vehicle inCounty Durham, and another during a multi-car accident on theM54 motorway resulting from adverse weather conditions. The post-tropical cyclone caused approximately£100m ($157 million, 2011 USD) in damage in the United Kingdom alone.
Extratropical cyclone, remnant low, tropical disturbance, or monsoon depressionOn August 27, theNational Hurricane Center (NHC) began monitoring a large mass of convection associated with atropical wave just off the western coast of Africa.[1] An area of low pressure formed in association with the disturbance the following day,[2] gaining sufficient organization to be declared a tropical depression by 06:00 UTC on August 29 approximately 430 miles (690 km) southwest of the southernmostCabo Verde Islands.[3] The depression initially struggled upon designation, with its well-defined center displaced near the northeastern edge of the storm's convection as a result of strong east-northeasterlywind shear.[4] By 00:00 UTC on August 30, however, an increase in the cyclone's convective organization marked its intensification into Tropical Storm Katia.[3][5]
Katia tracked west-northwestward for several days, steered by an expansive mid-levelridge to the cyclone's north. The strong upper-level winds that were affecting the cyclone gradually slackened, allowing for the expansion of acentral dense overcast, the formation of a large curved band in the southern semicircle, and development of a bandingeye on microwave imagery.[6] Satellite intensity estimates increased accordingly, prompting the NHC to upgrade Katia to hurricane intensity at 00:00 UTC on September 1, while the storm was situated about 1,350 miles (2,170 km) east of theLeeward Islands.[3] Although conditions were forecast to remain conducive for further intensification,[6] water vapor satellite and microwave imagery indicated that mid-level dry air began eroding eyewall convection immediately after the storm's upgrade, and upper-level winds eventually became less favorable as Katia approached a sharpupper-level trough. As a result, the storm maintained its status as a minimal hurricane for almost three days, with only a partial eyewall or banding-eye feature appearing on satellite.[3]
Early on September 4, the hurricane moved beneath a large upper-levelanticyclone which provided a reprieve from the strong southwesterly wind shear. Although its convective organization had yet to become fully symmetrical, an eye became increasingly apparent on infrared imagery. The center moved very near the National Oceanic and Atmospheric Administration's buoy 41044—which registered amaximum sustained wind of 90 mph (140 km/h) and a maximum wind gust of 108 mph (174 km/h)—around 12:00 UTC, indicating that Katia had intensified into a Category 2 hurricane.[3][7] Although aneyewall replacement cycle briefly caused the storm's convective pattern to deteriorate,[8][9] Katia attained major hurricane status—a Category 3 or higher on theSaffir–Simpson hurricane wind scale—by 12:00 UTC on September 5. Twelve hours later, the cyclone further intensified into a Category 4 hurricane and attained peak winds of 140 mph (230 km/h) and a minimum barometric pressure of 942 mbar (942 hPa; 27.8 inHg) as its eye warmed, deep convection became much more symmetric about the center, and upper-leveloutflow expanded.[3][10]
Almost immediately after attaining peak intensity, Katia began to rapidly weaken as a second eyewall replacement cycle began; it was quickly stunted as dry air wrapped into the western portion of the circulation and northwesterly wind shear increased.[11] The inner core process was completed by early on September 7, allowing Katia to level off in intensity as a Category 1 hurricane for several days. Increasing southwesterly flow resultant from an upper-level trough pushing eastward across the United States caused Katia to slow in forward motion and recurve northeast or east-northeast through September 9. The hurricane re-accelerated late that day, eventually bringing Katia overocean temperatures near 22 °C (72 °F).[3] Deep convection in association with the storm decreased and its circulation merged with afrontal system,[12] indicating that Katia had completed transition into anextratropical cyclone by 12:00 UTC on September 10 while located about 290 miles (470 km) south-southeast ofCape Race, Newfoundland. Increasingbaroclinic energy fueled the powerful extratropical low,[12] which skirted the northern coast ofScotland on September 12, before being absorbed by a larger extratropical system over theNorth Sea on the following day.[3]
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Although Katia passed well northeast of theLesser Antilles, a yellow alert was hoisted inGuadeloupe for the potential of 3–5 meters (9.8–16.4 ft)swells.[13]Antigua and Barbuda recorded 21.59 millimeters (0.850 in) of rainfall between September 6 and September 7 from an outer band.[14]
On September 4, the NHC noted that large swells likely to cause life-threateningrip current conditions were expected to impact the East Coast of the United States over subsequent days.[15] The increased surf resulted in the death of a swimmer inOrmond Beach, Florida the following day,[16] and a second death offMonhegan, Maine on September 11.[17]
After transitioning into a post-tropical cyclone, Katia moved quickly across the North Atlantic and toward Europe, prompting the Met Office to begin warnings citizens for potential impacts over subsequent days on September 9. Three days later, the organization raised a yellow severe weather alert for all ofIreland and most of theUnited Kingdom, with a more severe amber alert hoisted across Northern Ireland, northern England, and southernScotland; both alerts warned of the potential for gale-force winds.[18] Concurrently,Met Éireann outlined an extreme weather warning across Ireland, alerting residents to the potential for 130 km/h (81 mph) winds, downed trees, damaged buildings, and flooding.[19]Irish ferries cancelled a number of its sails betweenDublin andHolyhead.[20] TheSwedish Meteorological and Hydrological Institute warned of gale-force winds along the coastline ofSweden, although a brunt of the rainfall was expected in neighboringNorway.[21]
A maximum wind gust of 158 km/h (98 mph) was recorded onCairn Gorm, Scotland as Katia impacted the region, with a peak gust of 130 km/h (81 mph) observed at a non-mountain station inCapel Curig, Wales;[18] these observations marked the strongest impact from a tropical cyclone sinceHurricane Lili in1996.[22] Waves up to 15 meters (49 feet) battered the western coastline of Ireland, and fallen power lines temporarily disruptedDART services. Approximately 4,000 households were left without power across the country.[23] A catering marquee was blown into the air on a set for the television seriesGame of Thrones, causing one injury.[24] InCounty Durham, United Kingdom, a man was killed after a tree fell on the minivan he was driving; the passenger sustained non-life-threatening injuries. A second driver was indirectly killed on theM54 motorway after hazardous weather caused a multi-car accident.[3] Farther south inBradford, an 11-year-old boy was injured after he was hit by a portion of a roof blown off a garage. Downed power poles set several fields on fire.[25] The second stage of theTour of Britain was forcefully canceled after strong winds littered the cycle route with debris.[26] The remnants of Katia produced damage as far east asRussia. InSt. Petersburg, wind gusts up to 45 mph (72 km/h) damaged buildings and left roughly 1,500 residents without power.[27][28] InEstonia, the storm cut off power to approximately 940 households, particularly affecting the island ofHiiumaa andHarju County, with strong winds in coastal areas gusting up to 90 km/h (56 mph).[29]
Media related toHurricane Katia (2011) at Wikimedia Commons
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