Overview

September was a dry, mild month, with warm days and cool nights. A dramatic cooling occurred mid-month, with Westside temperatures dropping more than 20 degrees in a day or two, but temperatures rebounded again by the end of the month.

Table 1 is a summary of monthly averages and totals at selected stations throughout the state. Table 2 lists daily temperatures and precipitation for most of the locations listed in Table 1. In Table 3, monthly and seasonal precipitation totals throughout the state are listed.

The annual fall-winter forecast is included on pages 3 and 4.

Basin Summary

Here is a summary of water indicators at the end of the month, by river basin:

n.a. Not available
(1) Percent of normal September precipitation, from NOAA Cooperative sites
(2) Percent of normal seasonal precipitation (since Oct. 1), from NOAA Cooperative sites
(3) Percent of normal seasonal precipitation, from Natural Resources Conservation Service (NRCS) SNOTEL sites
(4) Percent of normal September stream flow, from U.S. Geological Survey (USGS)
(5) Percent of normal seasonal stream flow (since Oct. 1), from USGS
(6) Surface Water Supply Index, from NRCS (-4 = very dry, 0 = normal, +4 = very wet)

Forecasts

The Climate Prediction Center forecast for October - December (see maps below) suggests above-normal temperatures and below-normal precipitation for Oregon. Oregon Climate Service predicts above-average temperatures, with precipitation above average west of the Cascades and near-average in central and eastern Oregon.

ENSO Outlook
Australian Bureau of Meteorology, October 11, 2006

Summary: El Niño conditions persist across Pacific

Current Pacific climate patterns are typical for the development phase of an El Niño event. The key indicators include sea-surface temperatures above El Niño thresholds (although there has been some cooling in the past fortnight), sustained negative values of the Southern Oscillation Index (SOI), generally weaker than average Trade Winds since July and increased cloudiness in the central to west Pacific.

However, to qualify as an El Niño event, these key indicators (especially the ocean temperatures) would need to remain at their present levels (the ocean would need to be somewhat warmer) until the end of the year. There is a strong likelihood that this will occur, given what we know from previous events. Furthermore, most computer models indicate continued warming in the Pacific, implying a strengthening of the developing El Niño pattern.

The observed below average rainfall since late autumn across Australia's southern half, especially in the southeast and southwest, is also consistent with the initial phase of an El Niño event, as are the much higher than average daytime temperatures since August. Furthermore, even if El Niño thresholds are not maintained across the range of indicators, a warming Pacific and a low SOI bias the climate towards being drier and warmer than average across eastern and northern Australia for the remainder of 2006. This is reflected in the October-December outlooks for rainfall and temperature.

The Columbus Day Storm – 44th Anniversary
As we near October 12, most Northwesterners remember 1962 – the famous Columbus Day Storm. If you lived here, and were old enough, you remember the effects the storm had; and those who lived elsewhere (or were too young to remember) can recall the stories they have heard about it. If you haven’t heard of it, read along – we have quite a story here!

The “storm” was actually three separate storms that hit the Northwest on consecutive days, but the second, arriving October 12, 1962, was by far the strongest. It roared across the Pacific, then slowed, turned to the north, and moved just offshore of California, Oregon, and Washington, finally coming ashore in British Columbia. As it passed by, it wreaked great havoc.

Trees, houses, and power lines were destroyed throughout the region; in some cases residents were without power for 2 to 3 weeks. Giant towers holding the main power lines into Portland (over 500 feet high) were knocked down. The Red Cross estimated that 84 homes were completely destroyed, 5000 severely damaged, and 50,000 moderately damaged. 23 people died in Oregon alone, and damages were estimated at $170 million. It was estimated that 11.2 billion board feet of lumber was felled by the storm in Oregon and Washington combined.

In central California, the storm was a major rain-maker. The 1962 World Series between the New York Yankees and San Francisco Giants was delayed for four days due to rain in San Francisco (more than 8 inches in four days at San Francisco Airport). I was a Yankee fan at the time (I have since come to my senses!) and remember waiting impatiently for the Series to recommence. In the Northwest, we had lots of wind and not much rain.

The most complete articles I have seen on the Columbus Day Storm are Bob Lynott and Owen Cramer’s "Detailed analysis of the 1962 Columbus Day windstorm in Oregon and Washington" in the journal Monthly Weather Review of February 1966; and Wolf Read’s “The "Big Blow" of Columbus Day 1962,” available to anyone at http://oregonstate.edu/~readw/October1962.html

Wolf is back in Corvallis after living in Washington and near Portland for awhile, and always does great investigative work and publishes beautifully-illustrated documents. Worth a look!

Wolf reminds us that the Columbus Day Storm originated as a Super Typhoon in the western Pacific, becoming a strong mid-latitude storm when it reached cooler northern latitudes. He says, “this tropical influence suggests that the storm of 1962 be placed in its own category. A lone, dark overachiever whose closest cousins may be those powerful extra-tropical storms experienced on the East Coast, such as post-landfall hurricane Hazel of 1954.” He then goes on to compare wind speeds for the two memorable storms, and they match up very closely: our 1962 storm and the onshore portion of what had been a Category 4 hurricane.