Twostorms caused worst flooding, damage in years

Published on Thu, Nov 23, 2006 by ack Kintner

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Two storms caused worst flooding, damage in years

By Jack Kintner

Last Wednesday’s weather produced some of the worst flooding and long-lasting damage this area has ever seen, knocking out power to more than 15,000 customers in Whatcom and Skagit counties, several thousand of whom were still without power two days later.

In B.C., communities on the west side of Vancouver Island were still isolated from road washouts and without power on Tuesday, and the Greater Vancouver Regional District (GVRD) was unable to supply potable water to most of the city six days after the storm.

The unusually heavy weather came from two large storms with very heavy rain, one from the southwest and a second from the Gulf of Alaska, according to Canadian and American weather experts.

The two disturbances came together just as they hit the mountains on Vancouver Island. That produced several inches of rainfall on Wednesday while the temperature differences between the storms seemed to accelerate their winds.

The night before they hit, Vancouver weather reporter Tamara Taggart pointed out that the rainfall intensity shown on her computer projection “is something we’ve never seen before” as she called for up to an inch of rain overnight and another five inches on Wednesday for central Vancouver Island. Port Alberni’s mayor said the storms caused more damage than the 1964 tsunami following the Anchorage earthquake

Mudslides in the Vancouver watershed made the city’s tap water unsafe to drink for several days, causing a run on bottled water that spread to Blaine and Bellingham by the weekend.

The most intense part of the rain passed to the north of Blaine and up the Fraser Valley, but wind gusts were officially clocked in the 80 mph range on Bellingham Bay. In Blaine a boater who declined to give his name said that he read “sustained wind speeds of over 100 mph” on his mast-top anemometer. The resulting damage was often tornado-like in being localized and violent.

Hundreds of trees fell, making work difficult for the more than 80 repair crews dispatched by Puget Sound Energy. A semi-truck full of beer was nearly hit by a small wooden shelter used by kids to wait for the school bus (but which was unoccupied at the time) that was blown across the Mt. Baker Highway. The truck swerved before being jackknifed by the wind into the ditch, closing the highway for several hours as the truck was hauled out and, presumably, the beer recovered.

A young black bear who stopped to investigate one of many dangling power lines on East Smith Road was electrocuted when a hot wire touched his nose.

Many trees fell on the lower Nooksack River by gusts of wind that whipped the surface into a mist so fine it looked more like dust or smoke. It lifted a 16-foot Avon raft full of equipment that included several oars and a mountain bike high into the air before dumping the contents into the river and setting the raft down gently, right side up, to drift downstream by itself.

In Blaine and Birch Bay power was out for much of Wednesday afternoon and Thursday morning, and in some places east of town was not restored until Saturday due to numerous trees falling across power lines. Power was still intermittent in some parts of Birch Bay until Sunday night.

According to Seattle TV meteorologist Jeff Renner storms are carried into our area by the jet stream’s flow aloft, and the kind of weather they bring depends upon where they come from based on the jetstream’s direction.

So how did these two storms produce this weather? Imagine two figure skaters spinning with outstretched arms, and what would happen if their arms happened to collide.

Low pressure areas also rotate around a center and have pressure fronts extending out like arms, followed by air masses that are warmer or colder than the air they replace.

A strong flow from the southwest produces the so-called “pineapple express,” characterized by very warm temperatures and heavy rain well up into the mountains. The large storms these bring in can last for several days and produce violent winds and flooding.

Meanwhile, a more westerly flow produces smaller and weaker storms that quickly pass, bringing rain and, especially after they move east, snow in the ski areas and passes. A northwesterly flow brings stronger and more rapidly moving storms often generated from a very large and cold low pressure area. These often persist for many days in the Gulf of Alaska, sending stormy weather down the coast as they rotate around a more or less stationary center.

Lastly, a northerly flow aloft produces a “northeaster,” a flow of cold and dry interior air that locally comes out through the Fraser Valley.