Top ten weather stories for 2006: story one
1. B.C. Weather Woes Part I: So Much Rain, So Little Water
It was a wicked November across British Columbia! The coast was hit often and hard with drenching rains, strong winds and high tides. At mid-month, provincial emergency workers were summoned at 4:00 a.m. to deal with a tsunami warning on the West Coast, while the end of the month was marked by heavy snows and bitter cold. Refueled by subtropical (feeds?) from Hawaii, the storms came onshore day-after-day dropping their wet cargoes on the "wet" coast. The huge storm on November 5-6, dubbed the Pineapple Express, was associated with the remnants of Typhoon Cimaron, the strongest storm to hit the Philippines in eight years. What was especially unusual was not the frequency of the storms but the intensity of the rainfalls. In some instances, 10 to 15 mm of rain per hour fell for 15 consecutive hours, creating a huge potential for flooding. There was no doubting the tropical origins of the air mass as temperatures hit a record high of 17°C.
The storm dumped its heaviest load on Chilliwack swelling already brimming rivers. The Chilliwack River was roughly 20 times its normal flow. Every river in the Lower Mainland, the south coast and the southern half of Vancouver Island rose close to or above flood stage - water levels expected only once in 50 years. Intense rains triggered mudslides, washouts and flooding. In turn, highways closed and hundreds of residents along the Chilliwack River had to evacuate their homes. Five days later another storm battered the coast with more rains and strong winds, leading to what was becoming a common occurrence: cancelled BC ferry sailings, grounded aircraft and power outages.
None of the November tempests had the impact of the storm on November 15 - the worst in two years, according to BC Hydro. Before noon, the storm had blocked seven provincial highways, toppled power lines leaving an estimated 200,000 in eight communities without electricity and collapsed a steel-framed building under construction in East Vancouver. Remarkably, there were no serious injuries. In the watersheds around Vancouver, rainfalls in excess of 150 mm in 15 hours soaked already waterlogged soils. Because dozens of the landslides muddied the water in three Vancouver reservoirs, turbidity levels in the water treatment system rose 30 times the target causing drinking water that had never been cloudier. Consequently, two million residents in Canada's third largest city were advised to boil their water, the widest water warning in Canadian history. With an increased risk of bacteria and viruses in the water supply, health officials declared tap water unsafe for drinking, brushing teeth or washing fruits and vegetables. The advisory was partially lifted the next day, but it remained in effect for nearly a million residents in parts of Vancouver, Burnaby and the North Shore for another 10 days. On November 19, another Pacific storm brought an additional 60 to 90 mm of rain and strong winds to coastal British Columbia.
But just when you thought it couldn't get worse, it did! A series of snowstorms on November 25 blanketed the southwest with record snowfalls over six days and a cold Arctic outflow dropped temperatures to -12°C in Vancouver. The biggest storm dropped 40 to 60 cm of snow in the eastern Fraser Valley. Abbotsford Airport broke its one-day snowfall record for November with 44.1 cm of the white stuff. Downed trees and snapped snow-laden branches left thousands without power.
In the final wrap up, November rainfall and snowfall totals at British Columbia's two largest cities were impressive. Snowfall at Vancouver International Airport amounted to 38.6 cm. Victoria had six days of snow with two back-to-back 15+cm days. Its monthly accumulation of 40 cm was the second greatest November total in 66 years of weather record-keeping and 91 per cent of an average year's accumulation.
With 350.8 mm of rain and snowmelt in November, Vancouver tied the record for the wettest November and the wettest month ever set in November 1983. Remarkably, in 2006, Vancouver set two new monthly precipitation records: one in January (283.6 mm) and another in November (350.8 mm). Victoria was even wetter in November! Its monthly total of 351.9 mm surpassed the total for the previous wettest month of 342.6 mm recorded in January 1953.
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