Overview
May was a wet month, especially in eastern sections of Oregon (where the rains were really needed!). Maximum temperatures were generally below normal due to persistent cloud cover, while minimum temperatures were mostly above normal (for the same reason).
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. Figure
1 shows
the percentage of seasonal precipitation statewide.
Basin Summary
Here is a summary of precipitation, water supply, and snow pack as of the end of the month, by river basin:
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Snow |
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| BASIN |
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| OWYHEE | 118 | 77 | 100 | 0 | 23 | 66 | -1.0 |
| MALHEUR | 167 | 103 | 100 | 0 | 35 | 37 | 0.0 |
| GRAND RONDE, POWDER, BURNT | 190 | 111 | 103 | 81 | 84 | 81 | -0.6 |
| UMATILLA, WALLA WALLA, WILLOW | 137 | 160 | 110 | 0 | 166 | 110 | 1.4 |
| UPPER JOHN DAY | 227 | 114 | 103 | 0 | 98 | 88 | 0.7 |
| UPPER DESCHUTES, CROOKED | 147 | 109 | 95 | 84 | 64 | 60 | 0.3 |
| LOWER DESCHUTES, HOOD RIVER | 116 | 100 | 90 | 60 | 83 | 74 | -0.6 |
| WILLAMETTE | 100 | 93 | 93 | 75 | 81 | 84 | 0.0 |
| ROGUE, UMPQUA | 106 | 90 | 88 | 57 | 76 | 81 | 0.3 |
| KLAMATH | 137 | 100 | 84 | 11 | 48 | 65 | -1.7 |
| LAKE COUNTY, GOOSE LAKE | 164 | 91 | 87 | 11 | 55 | 62 | -0.2 |
| HARNEY | 140 | 84 | 103 | 55 | 63 | 73 | -0.3 |
| NORTH COAST | 103 | 91 | n.a | n.a | 65 | 79 | -0.6 |
| SOUTH COAST | 61 | 98 | n.a | n.a. | 51 | 87 | -1.6 |
Forecasts
The Climate Prediction Center’s (CPC) forecasts for June-August appear
below. Temperatures for all of Oregon are likely to be above normal. Precipitation
probabilities suggest an increased chance ofbelow-normal precipitation. CPC
also says:
“
A consolidation forecast of in-house tools indicates that Niño 3.4 SST
anomalies will rise from its current near zero state to slightly above the
+0.5C threshold [by the end of the year] and then decline slowly thereafter.
The probability spread for cold - neutral - or warm ENSO conditions increases
with the greatest likelihood shifting from near normal in summer to about equal
chances for neutral or warm ENSO conditions by fall. There is little chance
for a cold event to develop.” Translation: there might be a weak El Niño
event later this year, but probably no La Niña.
“
Beginning next winter - the consensus is near the neutral/warm event border
but then declines slowly. Since weak warm events do not exert strong forcing
on the atmosphere... should one develop... we expect that transient atmospheric
circulation patterns will continue to be forced primarily by intra-seasonally
varying phases of the MJO... And the higher latitude patterns will be determined
by varying phases of the AO and NAO that are not currently predictable at seasonal
ranges.” Which means that we’re all clueless about what will happen
next year!
Oregon Climate Service predicts near-normal temperatures and above-precipitation
for June. For the three-month period June-August we predict normal temperatures
and normal precipitation.
Severe Weather, June, 2004
It was quite a week.
In the span of three days, the mid-valley received more than a month's worth
(for June, anyway) of rain. There was lightning and thunder, and some hail.
And even several funnel clouds. The unsettled weather was spread throughout
Oregon.
Barney Lerten of bend.com reported, “Central Oregon's stormiest spring
in some time brought lightning that knocked out power to thousands of residents
Wednesday afternoon, and also triggered a rare funnel cloud sighting in the
Crooked River Ranch area - one of two tornadoes spotted in the state from
the latest bout of unsettled weather.
“
A pilot reported the funnel cloud about 14 miles north of Redmond at 11:35
a.m., dissipating rapidly as it moved south at around 20 mph, the National
Weather Service reported.” The bend.com web site shows a nice picture
of the funnel cloud as it passed near Crooked River Ranch.
Meanwhile, 12 miles north of Eugene, a pilot and observers at the Eugene Airport
spotted a funnel cloud, about 12 miles north of Eugene, the NWS reported. It
showed little movement and also didn't touch ground before dissipating about
two minutes later, observers said. And another funnel cloud was spotted crossing
the Columbia River from Oregon into Washington.
The cause of all this? A “cold core low” that lingered over the
Northwest for several days before moving eastward on Thursday. This is an upper-atmosphere
phenomenon in which a low pressure storm, with very cold air near its center,
moves over us. If air near the ground is fairly warm, there will be significant
movement of air upward and downward: cold air sinks and warm air rises. And
any time air moves vertically, significant (or even sever) weather can result.
In winter, we get plenty of cold-core lows but the air near the ground is usually
quite cool. In summer, we get warm air near the ground but usually don't see
cold core lows. In late spring we can get both. Thus, May and June are the
most common months for funnel clouds and tornadoes in Oregon.
And this is especially true when humidity is high, because moisture (in the
form of water vapor) acts as “fuel” for storms. Following the rainy
weather, there was plenty of moisture available to power the storms and bring
wild weather.
Last year was very different. Warm, dry weather began in mid-May and persisted
until October; we had heat waves but very little severe weather (except for
a few mountain thunderstorms). But in other years, wet conditions in May and
June helped trigger similarly “interesting” weather conditions.
The one I remember best was 1993. I was coaching my son John's baseball team
that year and on three different occasions we had to end practice and hurry
our players under shelter because of lightning strikes nearby. There were plenty
of funnel clouds spotted.
And probably the strongest Oregon tornado ever reported occurred in the month
of June (6/11/1968). A very strong thunderstorm formed over Wallowa County
in extreme northeastern Oregon. The tornado spawned by this storm touched down
in mountainous, forested areas which were mostly uninhabited. For that reason,
there were virtually no eyewitnesses to this tornado, but its status as a tornado
seems certain because of the sheer size of its path and the degree of destruction.
A swath of destruction one half to two miles wide and 8 to 10 miles long was
created by this storm, and destruction along the path was very significant.
About 1800 acres of prime timber was destroyed and another 1200 acres were
badly damaged. It was estimated that over 40 million board feet of lumber were
blown down by the tornado. Hail stones that accompanied the tornado were reportedly
of golf ball size in some cases. It was estimated that the tornado was an F2
on the Fujita scale (F0-F5).
Let's hope something like that never strikes populated areas, or we'll be in
a heap of trouble!
George Taylor, June 2004
Plankton may influence climate change says UCSB scientist
(Santa Barbara, Calif.) -- Plankton appear to play a major role in regulating the global climate system, according to new research.
David Siegel, professor of geography at the University of California, Santa
Barbara, and director of the Institute for Computational Earth System Science,
made the discovery with his former Ph.D. student Dierdre Toole, who is now
based at Woods Hole Oceanographic Institute.
In an article in the May 6 issue of the journal Geophysical Research Letters,
the scientists explain their research in the Sargasso Sea, approximately 50
miles southeast of the island of Bermuda. Siegel's research group has been
making observations at this location since 1992.
Phytoplankton are tiny, single-celled floating plants. They inhabit the upper
layers of any natural body of water where there is enough light to support
photosynthetic growth. They are the base of the ocean's food web, and their
production helps to regulate the global carbon cycle. They also contribute
to the global cycling of many other compounds with climate implications.
One of these compounds is a volatile organic sulfur gas called dimethyl sulfide
or DMS. Scientists had previously theorized that DMS is part of a climate feedback
mechanism, but until now there had been no observational evidence illustrating
how reduced sunlight actually leads to the decreased ocean production of DMS.
This is the breakthrough in Toole and Siegel's research.
They describe how the cycle begins when the ocean gives off DMS to the lower
atmosphere. In the air, DMS breaks down into a variety of sulfur compounds
that act as cloud-condensing nuclei, leading to increased cloudiness. With
more clouds, less sunlight reaches the Earth and the biological processes which
produce DMS are reduced.
According to their research, it appears that phytoplankton produce organic
sulfur compounds as a chemical defense from the damaging effects of ultraviolet
radiation and other environmental stresses, in much the same way as our bodies
use vitamins E and C to flush out molecules that cause cellular damage.
Siegel and Toole found that ultraviolet radiation explained almost 90 percent
of the variability in the biological production of DMS. They showed that summertime
DMS production is "enormous," and that the entire upper layer of
DMS content is replaced in just a few days. This demonstrates a tight link
between DMS and solar fluxes.
" The significance of this work is that it provides, for the first time,
observational evidence showing that the DMS-anti-oxidant mechanism closes the
DMS-climate
feedback loop," said Siegel. "The implications are huge. Now we know
that phytoplankton respond dramatically to UV radiation stresses, and that
this response is incredibly rapid, literally just days."
He explained that the findings give new impetus for scientists to re-examine
the DMS-climate feedback hypothesis. And the DMS-climate feedback may also
play out under possible global warming and climate change scenarios.
As the Earth's ozone shield thins and greenhouse gases increase, higher ultraviolet
radiation will reach the surface layer of the oceans. The findings indicate
that phytoplankton will then produce more DMS in response to this increased
ultraviolet radiation, causing increasing cloudiness and mitigating the effects
of global warming. However, Siegel is careful to note that while the process
may mitigate global warming it will not reverse the trend.
The project was funded by NASA. NASA's Earth Science Enterprise is dedicated to understanding the Earth as an integrated system and applying Earth System Science to improve prediction of climate, weather, and natural hazards using the unique vantage point of space.
Oregon Climate Service
George H. Taylor, Oregon State Climatologist
Wayne P. Gibson, Programmer/GIS mngr.
Mandy Matzke, 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
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
