Top ten weather stories for 2011: story six
6. Good Night, Irene...and, Katia, Maria and Ophelia
Hurricane experts predicted an active Atlantic hurricane season in 2011 and they were right. From Arlene to Sean (plus one unnamed storm), 19 tropical storms formed in the Atlantic basin – well above the long-term average of 11. Only seven became full-blown hurricanes, with three logged as major at Category 3 or higher: Irene, Katia and Ophelia. The busy storm season reflected a continuation of above-normal activity that began in 1995. Since then, all but two Atlantic hurricane seasons (1997 and 2002) have been stormier than normal. Among the factors contributing to the active hurricane season were a continuation of heated ocean waters across the tropical Atlantic, higher ocean heat content, favourable winds, and an upper-air circulation that encouraged easterly winds with lower wind shearing. Additionally, La Niña conditions re-emerged over the tropical Pacific in August after a brief interlude of neutral conditions from May to July.
Irene was the season’s first hurricane and, as it turned out, its deadliest and most devastating. On August 27, Irene made landfall on the Outer Banks of North Carolina. In the following days, the storm moved slowly northeast, making a second landfall in New Jersey and a third in Brooklyn, New York. Up and down the eastern seaboard torrential rains turned streams into gushing torrents, destroying roads and bridges. Storm surges of more than a metre caused significant river flooding across eight states. Irene claimed at least 47 lives and caused an estimated $7 to $10 billion dollars in damage in the United States, making it among the top 10 costliest disasters in that country’s history.
By the time Irene hit Canada on August 28 in the St. Lawrence region of Quebec and northwestern New Brunswick, it had been downgraded to a post-tropical cyclone. The storm centre followed the Appalachian mountain range, crossed the St. Lawrence River near Matane and reached Labrador late on August 29. Although less intense at that point, Irene covered a broader area than a typical hurricane, with strong winds and heavy rains spread well away from the storm’s centre in an expansive 800-km diameter. It was also slow-moving, traveling at a top speed of 32 km/h compared to speeds of 48 to 64 km/h for similarly-sized storms. At one point, its massive rain shield extended from Kingston to Halifax and from New Jersey to Newfoundland-Labrador. And at its worst in Canada, Irene’s winds topped 113 km/h east of Québec City on Île d'Orleans and rainfall amounts approached 150 mm in just a few hours around Montmagny – L’Islet. The north shore of the St. Lawrence River received 40 to 70 mm with the exception of Québec City and Charlevoix, which, because of their proximity to the storm track, received between 100 and 150 mm. Pounding rains falling at the rate of 10 to 15 mm an hour inundated several communities, particularly in the Eastern Townships, the Montérégie and Lac-St-Jean. Fast-moving waters flooded basements, collapsed roads, washed out culverts and triggered landslides and soil slumps. Storm winds also uprooted trees and downed power lines. Nearly one-quarter of a million Quebecers were left in the dark and some 50,000 customers in New Brunswick and 8,000 in Nova Scotia were without power during the peak of the storm. Northeast of Montreal, amotorist drowned after a landslide sent a chunk of roadway tumbling into the Yamaska River, swallowing two cars. Irene’s impact was made worse in southern and western Quebec, where they had already experienced the wettest August on record.
On September 9, Hurricane Katia moved northward between the United States and Bermuda as a Category 1 storm. On the morning of September 10, as it passed south of Newfoundland, Katia became a strong extratropical cyclone. Its effects on Canada were confined to heavy surf and rip currents. Sea swells of two to three metres came ashore along Nova Scotia’s Atlantic coastline, while waves as much as 13 metres were recorded well offshore over the southern Grand Banks off Newfoundland.
Maria made landfall over the southwestern Avalon Peninsula as a Category 1 storm on September 16, but with little impact. St. John’s residents weren’t taking any chances. With memories of Hurricane Igor still fresh almost a year later, they had prepared well for Maria, which helped to cushion the storm’s blow. Preparations began a week ahead of the storm’s arrival. Ditches and drainage areas were cleaned out, tenuous tree limbs were removed, construction sites were checked for proper drainage and schools were closed ahead of the storm’s arrival. Maria brought heavy rain ahead of its centre and strong winds with its passage. Rainfall in excess of 60 mm fell in Burgeo and St. Lawrence and on the Burin Peninsula. While only 13 mm fell at St. John’s, wind gusts reached nearly 80 km/h. At a few exposed locations around the Avalon Peninsula they hit 100 km/h, including a peak wind of 103 km/h at Cape Pine near St. Shotts. The storm surge was not significant, registering around one-half metre at Argentia at low tide early on September 16. According to the National Hurricane Centre in Miami, Maria was the 13th hurricane to make landfall in Newfoundland since 1851. Also of note, 2011 is the second consecutive year a landfalling hurricane has occurred within the province – a first for the record books.
While Ophelia was the strongest storm of the Atlantic hurricane season, its fury was largely played out over the open Atlantic, where it intensified as a Category 4 storm northeast of Bermuda on October 1. The next day it weakened to a Category 1, and on October 3 entered Newfoundland waters. Ophelia ultimately made landfall over the Avalon Peninsula, where it morphed into a post-tropical storm north of Cape Race with heavy rain (up to 65 mm) and a brief period of strong winds (close to 100 km/h). Although it came and went in short order, Ophelia’s presence was definitely felt – particularly on the Burin and Bonavista peninsulas, where rains in excess of 20 mm per hour led to some basement flooding, road washouts and a few home evacuations. Tropical Storm Sean had no direct effect on Canada, however, a weather front that dumped huge amounts of rain on the Maritimes on Remembrance Day tapped into moisture from Sean.
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