Overview

This is really getting old! A third consecutive dry month brought back memories of the dry winter of 2000-01. Some Oregon ski areas were forced to shut down due to lack of snow. Water supply folks are getting very anxious. And to top it off, the inland valleys have had a very foggy winter. As a “mild and wet weather” fan, yours truly is “truly disappointed.”

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 precipitation, water supply, and snow pack as of the end of the month, by river basin:

	Precipitation			Snow	Stream Flow		SWSI
BASIN	(1)	(2)	(3)	(4)	(5)	(6)	(7)
OWYHEE	18	113	85	72	27	70	-1.2
MALHEUR	34	101	74	57	66	68	-1.7
GRAND RONDE, POWDER, BURNT	61	76	68	48	61	72	-2.0
UMATILLA, WALLA WALLA, WILLOW	34	56	62	26	57	69	-1.3
UPPER JOHN DAY	25	70	70	52	37	51	-0.9
UPPER DESCHUTES, CROOKED	26	71	62	56	35	51	-0.8
LOWER DESCHUTES, HOOD RIVER	44	57	56	19	47	54	-1.2
WILLAMETTE	38	58	56	32	29	50	-1.0
ROGUE, UMPQUA	45	74	74	51	40	51	-1.0
KLAMATH	57	85	72	52	52	67	-1.9
LAKE COUNTY, GOOSE LAKE	56	141	88	90	28	47	-0.9
HARNEY	43	98	79	61	49	78	-0.6
NORTH COAST	61	67	56	0	61	63	-0.7
SOUTH COAST	56	76	n.a	n.a.	57	65	0.0

n.a. Not available
(1) Percent of normal January 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 snow water equivalent, from NRCS SNOTEL sites
(5) Percent of normal January stream flow, from U.S. Geological Survey (USGS)
(6) Percent of normal seasonal stream flow (since Oct. 1), from USGS
(7) Surface Water Supply Index, from NRCS (-4 = very dry, 0 = normal, +4 = very wet)

Forecasts

The Climate Prediction Center’s (CPC) forecasts for February-April appear below. Temperatures for Oregon (and all of the West) are likely to be above normal, while precipitation probabilities are below normal.

Oregon Climate Service predicts above-normal temperatures and above-normal precipitation for the next three months.

ENSO Update (Australian Bureau of Meteorology, February 5, 2005)

Summary

Surface temperatures have continued to cool over most of the tropical Pacific during the past fortnight, with only the western areas to near the dateline remaining above El Niño thresholds. Other indicators are all neutral: the monthly SOI is positive for the first time since May 2004, central Pacific cloudiness is close to average and the Trade Winds continue to fluctuate about their long-term mean.

As far as El Niño is concerned, the important question is what will happen during the southern autumn and winter. To this end, the most recent survey of computer model guidance had an 8 to 4 majority with central to eastern Pacific temperatures in the neutral range in June. By September the split was 5 to 3 in favour of neutral, and nearly all the models indicate temperatures continuing on the warm side of average. So the general message from the models is for central Pacific temperatures to be warmer than average in winter and spring, with the current risk assessment for El Niño conditions being roughly the same as what would normally be expected early in the year. March to June is known as the "predictability" barrier and model skill is at its lowest predicting across this span of months.

In Brief

* Sea surface temperatures across much of the tropical Pacific have cooled since the beginning of the year, particularly in the eastern Pacific, indicating a return to a neutral (as opposed to borderline warm-neutral) ENSO pattern.
* Subsurface data for January shows that there has been a general cooling across the basin since December.

* The SOI for January was +2, the first positive monthly value since May 2004.

* Trade Winds in the tropical Pacific were mostly near, to above average during January.

* Cloudiness around the dateline continues to fluctuate about the long-term average.

* Eight of twelve computer models predict neutral eastern Pacific conditions in June 2005.

Looking Ahead to Spring
George H. Taylor, February 2005

This winter has been rather mild (except for November), partly due to a couple of winter “heat waves” that I’ve written about. But what’s really unusual about this winter is not the temperatures but the amount of precipitation we’ve received – it’s shaping up as one of the driest winters ever.

In an average year, the Willamette Valley gets about 24 inches of precipitation (rain plus melted snow – but mostly rain) between October and January. This year we received only about half of that. October was wetter than average, but since November the storms have mostly gone north of us (British Columbia has gotten hammered) or south of us (ditto southern and central California). And here we’ve been, sitting under a “ridge” of high pressure, high and dry.

Meanwhile, in the mountains, the snow pack is abysmal. As of mid-February, the “snow water equivalent” (the amount of water in the snow if it were melted) is only about 35 percent of average for this time of year – that’s for the Willamette Valley drainage as a whole. Most of the rest of the state is doing somewhat better than that, with Lake County topping everyone at 91 percent of average.

In fact, Lake County, and the rest of southeast Oregon, is an interesting story. For the past several years that area has been in a “drought designation” because of low snowfall and lack of spring rains. Ironically, the highest percentages of normal in the state occur there now. Maybe that’s nature’s way of evening things out?

But back to the topic—skimpy rainfall and a low snow pack. Put those two things together and you get a lot of unhappy skiers and snowboarders, and some other folks really worried about summertime water conditions. Dry winters seem great to those who hate rain, but sooner or later we “pay the piper.” Empty reservoirs, shallow rivers, wells that fail, increased fire danger – all these are summer consequences of dry winter conditions.

Our saving grace in situations like this is a wet spring. If we get abundant (or even average) spring rain, we are much less likely to experience summer water problems. But how likely is that? I looked back at other dry winters too see what happened in the following spring. The following figures are for Corvallis (yeah, I live here, so I can pick the station to use!).

The six winters that were drier than this winter, and their October-January totals, were 1977 (5.10 inches), 1891 (9.42”), 1979 (10.92”), 2001 (11.75”), 1931 (11.81”), and 1960 (11.88”).

In five of the six years, spring was near average or well above; the only exception was 2001, which had a really dry spring. The next four years in the “dry winter” list, all slightly wetter than this year, were 1926, 1945, 1944 and 1937. Only one of the four (1944) had a truly dry spring.

The other clue here is the wet late summer-early fall we had. The dry winters that were preceded by a wet fall were very likely to be followed by wet springs.

The federal Climate Prediction Center doesn’t think that will happen, however. Their February-March-April forecast is for above average temperatures and below average precipitation. If that happens, this place will be dry as a bone, come summer! And perhaps we should listen to CPC – they did a better job than I did predicting this winter’s. My forecast called for above-average precipitation. I did much better on temperatures: below average in the first half and above average in the second. But that’s small consolation.

I’m starting to get bombarded with questions from the media, and many are asking about fire danger. My standard answer:

“ Nearly every summer it’s dry enough in Oregon for fires. By some definitions of drought, we have one every year. The wild card is ignition: if we get a fire beginning in the wrong place at the wrong time, we’ll get a fire. If the winds are blowing from the wrong direction, it will get big. And that can happen in any year, regardless of whether the winter was dry or wet.

“ What DOES change in dry winters is the length of the fire season. The drier the winter, the earlier the start of the season.

“ The two most common types of ignition are careless people and dry lightning. Both are really hard to forecast. On average, we get a bad “dry lightning summer” about once every 5 years. 2002 was really bad, even though the winter was pretty wet, and the result was the Biscuit Fire, Oregon’s biggest ever.”

So now our hopes rest on three things: a wet spring, few lightning storms, and careful people!

Oregon Climate Service

George H. Taylor, Oregon State Climatologist

Wayne P. Gibson, Programmer/GIS mngr.

Eileen Kaspar, Research Assistant/Manager of Data Services

Melanie Mitchell, Undergraduate Assistant

Wolf Read, Undergraduate Assistant

Emily Gibson, Student Assistant

Cadee Hale, Publications Assistant

Kelsey Kuykendall, Undergraduate Assistant

Sara Joos, Student Assistant

Sean Daly, Student Assistant

Kirk Borgerding, Undergraduate Assistant

Oregon Climate Service, Strand 326,                             	     Phone: (541) 737-5705  
Oregon State University                                                      Fax: (541) 737-5710   
Corvallis, Oregon  97331                                                     E-mail: oregon@coas.orst.edu   
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