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.

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 October precipitation, from NOAA Cooperative sites
(2) Percent of normal October precipitation, from Natural Resources Conservation Service (NRCS) SNOTEL sites
(3) Percent of normal October stream flow, from U.S. Geological Survey (USGS)
(4) Surface Water Supply Index, from NRCS (-4 = very dry, 0 = normal, +4 = very wet)

Forecasts

The Climate Prediction Center’s (CPC) forecasts for November-January appear below. Temperatures for Oregon (and all of the West) are likely to be above normal, while precipitation probabilities show equal chances of above-, near-, and below-normal in the southern half of Oregon and an increased chance of below-normal precipitation in the northern half.

Oregon Climate Service predicts above-normal temperatures and above-normal precipitation for the next three months, as we have since August. We predict above-normal temperatures and normal precipitation for the second half of winter.
ENSO Update
Australian Bureau of Meteorology, November 1, 2006

There was a general strengthening of all ENSO indicators during October. What will become known as the 2006/07 El Niño, has now developed and is primed to enter the maturing phase, which is characterised by self-sustaining feedback between the Pacific ocean temperatures, winds and cloud patterns. Computer model guidance indicates that Pacific Ocean temperatures are likely to peak around January or February 2007.

Noteworthy features of the Pacific climate during October were (a) weaker or much weaker than average Trade Winds over most of the basin for most of the month; (b) warming of 0.5 to 0.7°C near South America and by about 0.2°C elsewhere along the equatorial Pacific; (c) a marked drop in the SOI to around -15 or slightly lower; (d) an increase in cloudiness over the western to central Pacific; and (e) further warming of the Pacific sub-surface.

In Brief:
* Pacific climate patterns show an intensifying El Niño.
* Equatorial Pacific SSTs have been warming and are over El Niño thresholds.
* Subsurface temperatures have remained warm and have increased in response to a strong westerly wind burst.
* The SOI has fallen to a current (30th October) 30-day value of -15.
* Trade Winds remain much weaker than normal in the western to central Pacific.
* Cloudiness near the date-line has been increasing since late May and was much higher than average in October.
* Computer models are nearly unanimous in predicting El Niño conditions for the rest of 2006 and early 2007.

The U.S. Climate Prediction Center, in an update in early November, said

Equatorial Pacific SST anomalies greater than +0.5†C were observed in most of the equatorial Pacific, with anomalies exceeding +1.0†C between 170†E and 145†W and between 130†W and the South American coast. The latest SST departures in the Niño regions are all near +1.0. Beginning in February the basin-wide upper ocean heat content increased, and since early April positive anomalies have been observed. Since early July weaker-than-average low-level equatorial easterly winds have been observed across most of the equatorial Pacific. In October the Southern Oscillation Index (SOI) was negative for the sixth consecutive month. Collectively, these oceanic and atmospheric anomalies are consistent with the early stages of El Niño in the tropical Pacific.

Over the past several months most of the statistical and coupled model forecasts have trended towards warmer conditions in the tropical Pacific through the Northern Hemisphere winter. The latest NCEP climate forecast system (CFS) predictions indicate El Niño conditions for the remainder of 2006 and into the NH spring (SH fall) 2007. More than two-thirds of the other statistical and coupled model predictions also indicate El Niño conditions during the same period.

The Columbus Day Storm – A Look Back
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 a while, 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.