[env-trinity] CBB: 'La Nina' Now Reigns PNW Weather; Colder Ocean Should Be Boost To Basin Salmon Survival
sari at sisqtel.net
Fri Aug 13 15:59:12 PDT 2010
'La Nina' Now Reigns PNW Weather; Colder Ocean
Should Be Boost To Basin Salmon Survival
An already chilled northeast Pacific Ocean and
rapidly cooling equatorial sea surface
temperatures likely bode well for Columbia River
basin salmonids that start and end their lives in
freshwater but spend most of their lives at sea.
The late winter and early spring saw a fading of
"El Nino" conditions -- elevated sea surface
temperatures in the central and eastern
equatorial Pacific -- that had prevailed over the fall and winter.
El Nino conditions can affect climatic conditions
worldwide as well as ocean conditions outside the
equatorial zone. El Nino's presence tilts the
odds toward warmer and drier conditions in the
Pacific Northwest during the fall and winter.
The reverse is true when La Nina conditions
reign. And they do now reign, according to meteorologists.
"During July 2010 La Nina conditions developed,
as negative sea surface temperature anomalies
strengthened across the central and eastern
equatorial Pacific Ocean," according to an ENSO
(El Nino/Southern Oscillation) alert issued Aug.
5 by the National Weather Service's Climate Predictions Center.
All indicators in the Pacific Ocean show that we
are now in the early stages of a La Niña event.
Computer models predict the central Pacific will
continue to cool in coming months, indicating
some further strengthening of the event is
likely, according to the Aug. 4 ENSO Wrapup
produced by the Australian government's Bureau of Meteorology.
"Signs of an emerging La Niña event have been
apparent in the equatorial Pacific for several
months," the Australian agency says. "Pacific
Ocean temperatures have cooled steadily
throughout the year, the Southern Oscillation
Index (SOI) has increased in value and is
currently around +21, trade winds continue to be
stronger than average and cloudiness has remained
suppressed over the central Pacific. All of these
key indicators have now reached or exceed La Niña levels."
"Given the strong cooling observed over the last
several months and the apparent ocean-atmosphere
coupling (positive feedback), the dynamical model
outcome of a moderate-to-strong episode is
favored at this time," the CPC alert says.
"Therefore, La Niña conditions are expected to
strengthen and last through Northern Hemisphere Winter 2010-11."
"All indications are that surface and subsurface
water is cooling" to establish La Nina
conditions, said Kyle Dittmer, the Columbia River
Inter-Tribal Fish Commission meteorologist. "All
signs of El Nino have gone away."
The signs of El Nino began eroding in March and
La Nina signs have been growing since May to the
point this month of an official CPC declaration.
"La Nina conditions are likely to continue through early 2011," the CPC says.
Coincidentally, or maybe not, water temperatures
off the coasts of Washington and Oregon turned
very cold this late spring and summer. And the
upwelling of nutrients that feed plankton that
feed young fish began, though belatedly, in early
July in strength. The upwelling can begin as early as April.
"It's looking pretty vigorous," Dittmer said of the upwelling indices.
NOAA Fisheries oceanographer Bill Peterson said
that during a mid-July data collection cruise out
of Newport, Ore., surface water near-shore (1
mile from shore) was the coldest ever measured
over 15-year course of an ongoing ocean
indicators study and the deep water at the
study's five mile station was the fourth coldest
in 15 years. Both are very positive indicators for fish, he said.
The researchers sample the coastal waters off
Newport at biweekly intervals during the ocean
upwelling season in spring, summer, and fall. The
Northwest Fisheries Science Center crew samples
various physical ocean conditions, such as
temperature and salinity, as well as biological
conditions such as the productivity of the food
web and availability of food for salmon.
"The ocean's very cold. Typically that's been
very good for the food web," said Nathan Mantua,
an atmospheric research scientist at the
University of Washington and co-director for the
school's Center for Science in the Earth System.
"Survival for chinook and coho tends to be very
high when conditions are like this," Mantua said.
He said that the cooled coastal ocean is probably
not La Nina linked but more likely the result of
winds and other atmospheric phenomenon. It does
give the ocean that welcomes young Columbia River
salmon outmigrants a head start. A cool northeast
Pacific is, eventually, a consistent end product
of El Nino. So an early start means those
favorable conditions for a longer period.
The fact that the northeast ocean is already
chilled and the negative (cool) sea surface
anomalies at the equator show a continued
strengthening "give us some confidence that that
these conditions will persist into next summer," Mantua said.
The CPC says that the earliest that the Northwest
can expect to experience impacts from the newly
developed La Nina is this fall. The center's
October-December long-range forecast is for a
greater than 33 percent chance of above normal
precipitation throughout the region, with the
chances of the same exceeding 40 percent in north
and central Idaho, western and northern Oregon,
and all of Washington state. The temperature
forecast for that period is for equal chances of
below, near, and above normal weather in the region.
A wet winter would mean that an ample snowpack
would build in the mountains that ring the
Northwest and its Columbia River basin. That
stored water is a precious resource for fish,
hydro producers, irrigators and other.
A big snow would be particularly valuable
following an El Nino year. The Columbia River
basin's water supply for the April-September
period, as measured at The Dalles Dam, is only 79
percent of normal, according to the Northwest
River Forecast Center's July 8 final forecast.
Bonneville Power Administration meteorologist
Chris Karafotias says that the transition from El
Nino to La Nino was likely responsible for this
spring's surge of moisture and cool weather in
the Northwest, which was followed by a brief heat
wave. The flip-flopping of weather patterns will
continue to make seemingly unpredictable weather
more common, at least through next winter, he said
"We see this kind of weather pattern about one
every 10 years," Karafotias said. "This summer
has also been reminiscent of what we've seen
before with a transition between El Nino to La
Nina. It typically causes cooler than average
temperatures in western Oregon and Washington
through October, with the exception of September,
which should be warmer than normal. So far, this
is playing out as we expected."
Karafotias also expects some wild weather this fall.
"I expect at least two significant weather events
as the pattern continues to shift further into La
Nina," he said. "I think we'll have a wind storm
into the Willamette Valley this fall or early
winter, and, if history repeats itself, the wind
velocity would exceed 100 miles per hour at the
coast. We could also see western Oregon and
Washington flooding, based on what has happened
in the past with this type of weather pattern."
THE COLUMBIA BASIN BULLETIN:
Weekly Fish and Wildlife News
August 13, 2010
Issue No. 541
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