Monster storm heading our way
A system to arrive Sunday may prompt Oregon's first hurricane wind warning
Friday, November 30, 2007
STUART TOMLINSON
The Oregonian To the extent forecasting the weather is like playing music, Oregon meteorologists Thursday were cranking up the volume.
Forecasters from the public and private sector, as well as the media, were scrambling to get their arms around a double-whammy of winter weather barreling toward the region. They expect a rare Willamette Valley snowstorm Saturday, followed by what some predict will be a once-a-decade storm packing high winds and heavy rains early next week.
The National Weather Service has said it might issue its first hurricane wind warning for Oregon in advance of the second storm.
"Everything points to this being a very strong, prolonged event," said the weather service's Ira Kosovitz. "We could see sustained winds of 90 miles per hour, if not 100."
The ingredients for snow Saturday at the lower elevations in northwest Oregon and southwest Washington are coming together, with the highest likelihood of accumulations in the area from Salem in the south to Olympia in the north.
"I think we'll see snow starting around 10 or 11 a.m. lasting for a couple of hours but with not a lot of accumulation," said Clinton Rockey of the National Weather Service in Portland. "It should change over to rain by midafternoon, but snow throughout the day in the Columbia River Gorge and the Cascades."
As noteworthy as that forecast is -- snow being rare around here -- the biggest news Thursday at the National Weather Service offices in Portland was the approaching "monster" Pacific storm that's going to bring potentially damaging winds and widespread flooding to the region Sunday into Monday and Tuesday.
The size and scope of the storm -- which has tapped into the energy of typhoons Mitag and Hagibis -- may prompt the first hurricane force wind warning, which would mean sustained winds of 74 mph or higher on the Oregon and Washington coasts.
That's a big deal, but not quite as big as the "first in history" designation might suggest.
Bill Schneider, the science and operations manager for the weather service, said the agency was given the go-ahead by the National Oceanic and Atmospheric Administration only five years ago, in 2002, to issue such a warning "to highlight the extreme nature of rare storms that may only occur once every 5 to 10 years."
Schneider said such storms -- extratropical cyclones -- don't have the structure of a hurricane, and shouldn't be confused with an actual hurricane, but they are, in fact, larger and have a broader impact zone.
After the wind comes the rain. George Taylor of the Oregon Climate Service characterized the looming storm as a "hybrid," with traits similar to the damaging windstorm of December 1995 and the flooding rains of November 1996.
Forecast models show a plume of moisture extending from Oregon to Hawaii by late Sunday, a classic Pineapple Express that's been called an atmospheric river.
"The intensity of the winds followed by intense rains makes it a very significant storm with big-time rain," Taylor said. "We could see three to four inches (of rain) in the valley, and even more at higher elevations."
The storm is expected to combine rising snow levels with heavy rains, a recipe responsible for damaging floods.
Snow levels -- which have been below pass level this week, allowing Timberline to go to full operations, and Mt. Hood Meadows, Mt. Bachelor and Mt. Hood Skibowl to open additional lifts -- will begin to rise Sunday.
Matt Zaffino, meteorologist for KGW (8) in Portland, said the storm's deep area of low pressure is one of the strongest he's seen in recent memory, even stronger than the Columbus Day Storm of October 1962. He predicted that this storm, however, won't be as damaging as that storm because it will stay farther offshore.
Even so, Zaffino said, "This thing is an absolute monster -- it covers the entire Northeast Gulf of Alaska.
"It's huge."
Stuart Tomlinson: 503-221-8313; stuarttomlinson@ news.oregonian.com
