Overview

After a promising start to the Water Year, November was a big disappointment, but early December looked very promising. But by the middle of the month The Ridge Was Back. A strong ridge of high pressure brought generally dry conditions, and very little snow. Many of the basins are facing possible shortfalls, and some folks are beginning to use the “D” word: drought.

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	64	136	93	63	154	110	-0.9
MALHEUR	70	127	84	65	70	90	-1.2
GRAND RONDE, POWDER, BURNT	75	85	74	58	73	78	-1.6
UMATILLA, WALLA WALLA, WILLOW	73	63	70	44	76	77	0.1
UPPER JOHN DAY	85	84	78	87	53	63	0.3
UPPER DESCHUTES, CROOKED	108	84	68	75	68	59	-0.3
LOWER DESCHUTES, HOOD RIVER	66	65	59	21	50	58	0.2
WILLAMETTE	68	65	62	37	56	61	0.4
ROGUE, UMPQUA	107	84	80	52	65	58	-0.5
KLAMATH	106	97	80	63	72	75	-1.9
LAKE COUNTY, GOOSE LAKE	166	140	98	109	64	62	-0.8
HARNEY	113	119	86	87	115	93	0.1
NORTH COAST	67	69	53	28	66	63	0.6
SOUTH COAST	95	85	n.a	n.a.	98	69	0.8

n.a. Not available
(1) Percent of normal December 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 December 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 January-March 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 (CPC, January 6, 2005)
“Positive sea surface temperature (SST) anomalies greater than +0.5°C (~1°F) persisted across most of the central and western equatorial Pacific during December 2004. By the end of the month, positive equatorial SST anomalies greater than +1°C (~2°F) were found from 160°E eastward to 155°W and locally in the region near 110°W. During December SST anomalies exceeded 0.5°C in the Niño 4, Niño 3.4 and Niño 3 regions, while anomalies remained near zero along the West Coast of South America (Niño 1+2 region). The pattern of anomalous warmth in the equatorial Pacific in recent months and the most recent 5-month running mean value of the Southern Oscillation Index (-0.6) indicate that a weak warm (mid-Pacific El Niño) episode has developed. However, through December there has been a lack of persistent enhanced convection over the anomalously warm waters of the central equatorial Pacific, which has limited El Niño-related impacts on the global pattern of precipitation. (Note: The recent pattern of heavy precipitation in California has been associated with 1) a persistent high-latitude blocking ridge in the vicinity of the Gulf of Alaska and an associated trough along the West Coast, and 2) a weaker than average jetstream across the central and eastern Pacific. These circulation features are not consistent with El Niño, which would favor a stronger-than-average jet stream over the central and eastern Pacific and a reduced tendency for blocking in the Gulf of Alaska.

“Based on the recent evolution of oceanic and atmospheric conditions and on a majority of the statistical and coupled model forecasts, it seems most likely that weak warm episode (El Niño) conditions will persist for at least the next three months. However, there is considerable uncertainty concerning future developments in the extreme eastern equatorial Pacific (the classical El Niño region).”

Blue Moons

Blue Moon, you saw me standing alone
Without a dream in my heart
Without a love of my own.

“Blue Moon,” by Lorenz Hart and Richard Rodgers

“Blue Moons” don’t happen often, but we’re in for one this year – in August. By definition, Blue Moon is the second full moon in a calendar month. Most months have only one full moon, but once in awhile (“once in a blue moon”) a second one occurs. Since the lunar cycle is 29 days, but most months have 30 or 31 days, so it is possible to have two full moons in a single month. This occurs on average once every two and a half years.

In 2004, July had one full moon on the 2nd, so the following one, on July 31st, qualified as a Blue Moon.
Of course, the moon wasn’t really BLUE. But from time to time the moon has taken on very different colors, even blue.

In 1883, for example, Krakatoa, a volcano in Indonesia, exploded violently. The sound was heard several thousand miles away. Ocean waves created by the blast were detected in the English Channel. And ash rose to the upper levels of the atmosphere.

The moon turned blue.

Some of the ash particles were just the right size to scatter red light, while allowing other colors, such as blue and green, to pass through. White light from the moon emerged from the clouds as blue (and sometimes green).

The blue moons lasted for years after the eruption. Some people reported lavender suns and "such vivid red sunsets that fire engines were called out in New York, Poughkeepsie, and New Haven to quench the apparent conflagration," according to volcanologist Scott Rowland at the University of Hawaii. NASA’s web site has an interesting article describing this (that’s where I found Rowland’s quote):
http://science.nasa.gov/headlines/y2004/07jul_bluemoon.htm?list656723

Other volcanoes, though less significant than Krakatoa, have also turned the moon blue. This includes the 1980 eruption of nearby Mt. St. Helens. The 1991 Pinatubo eruption was the most recent, and you may remember the colorful sunrises and sunsets that lasted for many months.

A somewhat similar light scattering phenomenon occurs in association with severe storms in the Midwest and Eastern U.S. This is the legendary “green sky,” which causes great concern among many sky watchers – or, in some cases, excitement! Not every green sky portends severe weather, and not every sever storm is preceded by green sky, but the two happen often enough that folklore suggests “green skies precede tornadoes.” This phenomenon is rather mysterious, but many scientists believe that water vapor in the air causes enough light scattering to remove all but the green.

More common though, is red sky (as in “red sky in morning, sailor take warning”). This occurs most often near sunrise and sunset, as the sun shines at an angle though the atmosphere. At these times, the sun’s path is very long (think about looking almost horizontally through a swimming pool, versus looking straight down; in the latter case, you’re looking through much less water). Blue and green light are scattered more effectively by air molecules, and during their long transit of the atmosphere they are removed, leaving only the red. Thus, red sunrises and sunsets!

Sky and Telescope had an interesting piece on blue moons, which included the following:

“ Several clues point to a strong connection between the [Main Farmer’s] almanac's Blue Moons and the four seasons of the year. All of the listed Blue Moons fall on the 20th, 21st, 22nd, or 23rd day of November, May, February, or August. These dates fall about a month before the Northern Hemisphere winter and summer solstices, and spring and fall equinoxes, respectively, which occur on similar day numbers.

“ Although the idea of a seasonal pattern suggested itself to us immediately, verifying the details required a lot of detective work. We found that the Blue-Moon definition employed in the Maine Farmers' Almanac is indeed based on the seasons, but with some subtle twists.

“ Instead of the calendar year running from January 1st through December 31st, the almanac relies on the tropical year, defined as extending from one winter solstice ("Yule") to the next. Most tropical years contain 12 full Moons — three each in winter, spring, summer, and fall — and each is named for an activity appropriate to the time of year (such as the Harvest Moon in autumn). But occasionally a tropical year contains 13 full Moons, such that one season has four rather than the usual three.”
(http://skyandtelescope.com/observing/objects/moon/article_127_1.asp)

The same article describes a different definition of a blue moon: not the second full moon in a month, but “the "Maine rule" for Blue Moons: Seasonal Moon names are assigned near the spring equinox in accordance with the ecclesiastical rules for determining the dates of Easter and Lent. The beginnings of summer, fall, and winter are determined by the dynamical mean Sun. When a season contains four full Moons, the third is called a Blue Moon.”

And even under that definition, the second August full moon qualifies!

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

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   
                                                                             Web: http://www.ocs.oregonstate.edu