The report, prepared by Weyerhaeuser hydrologist Maryanne Reiter, is based on data gathered by the National Weather Service, the U.S. Army Corps of Engineers, the U.S. Geological Survey, the Oregon Climate Service, the Office of the Washington State Climatologist, NASA, Weyerhaeuser and other private weather data sources.  Various agency personnel reviewed the data underlying the report and the conclusions of the report.

The report was prepared by Weyerhaeuser in order to understand and characterize the magnitude of the storm event and inform its practices going forward.

Some highlights of the report:

• "The December 1-3 storm offered nearly every winter season hazard...snow...strong winds...heavy rainfall...major flooding...landslides...avalanches and high coastal surf and coastal flooding," National Weather Service report, issued Dec.19, 2007
• The National Weather Service issued the first-ever hurricane warning in the Pacific Northwest.
• Record rainfall amounts fell in many areas of southwest Washington and northwest Oregon, in some areas the highest levels recorded in more than a century of reporting.
• In addition to record rainfall, the intensity of the precipitation was extremely high in some localized areas.  In other words, a great deal of rain fell and it fell very quickly.
• Five new, all-time flood records were set on the Chehalis River in southwest Washington.

The report summary concludes:  “This storm produced concurrent extreme magnitude events; hurricane-strength winds along the coast and an estimated 500-year flood further inland in the upper Chehalis River basin.  High winds impacted the coasts of Oregon and Washington from Newport to Hoquiam.  This storm produced a maximum recorded wind gust of 147 mph and was the first ever hurricane force wind warning issued by NWS in the Pacific Northwest.  While maximum speeds may have been higher in the 1962 Columbus Day storm, this event was of longer duration, which led to extensive damage.  The rain portion of the storm produced not only high storm totals, but also 24-hour rainfall intensities that were up to 140% higher than the 100-year amounts for areas in southwest Washington.  Two weather stations with records back to the late 1800s broke all-time records.  This high rain led to extensive flooding with ten rivers in Washington exceeding their flood of record.  In the Chehalis River basin 5 all-time high records were broken.  For the stations in the upper Chehalis River, flood peaks were twice the previous flood of record and estimated to have a recurrence interval of 500-years.  Either one of the events – the windstorm or the flooding, would have been notable individually, but taken together, they compounded the extreme nature of the storm.”

Copies of the report are available at http://www.weyerhaeuser.com/pdfs/company/media/December2007StormEventSummary.pdf.

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