El Niño Watch, Advisory 2008-05
Coastal Ocean Mean SST (°F) and Deviation from Normal, May, 2008
Several complementary images are now available:
Satellite Chlorophyll a (view image) QuikSCAT Wind Stress Curl a (view image)
Regional Oceanic Conditions
Regional monthly average sea surface temperature (SST) fields for May 2008, derived from NOAA satellites, showed below-average monthly SST in the north Pacific east of 145°. The negative SST anomalies formed a broad coastal band between 25°N and 50°N, in patterns that have persisted since December 2007. This band extends offshore in the north into subarctic areas, and in the south colder SSTs extend west and southwest to include tropical and equatorial regions. This band of negative SST anomalies appears to be weakening and narrowing, offshore between 35°N and 45°N and along the coast of Baja California (23°N - 33°N).
The subtropical high atmospheric pressure system (STH) dominated atmospheric forcing between Cape Flattery (48°N) and Cape San Lucas (23°N). In the monthly mean wind stress field the STH was centered near 34°N, 143°W. Strong southeastward, upwelling favorable, wind stress occurred along the coast between Cape Blanco (43°N) and Point Santa Eugenia (28°N) in patterns also seen in March and April 2008. A particularly strong upwelling episode occurred May 20-24 between 24°N to 45°N, with a maximum intensity at 39°N, as indicated by the NMFS/SWFSC/ERD monthly coastal upwelling index.
May 2008 chlorophyll-a concentration patterns from MODIS satellite imagery showed continued high coastal concentrations. However, chlorophyll-a concentrations decreased in the last month along both coasts of the Gulf of California and the Southern California Bight as warmer water intruded from the south.
Equatorial Pacific Conditions
La Niña conditions weakened in the equatorial Pacific during May 2008. The NOAA Climate Prediction Center is forecasting a possible transition to ENSO-neutral conditions in the tropical Pacific for June-July 2008. For details, see the official NOAA ENSO Advisory bulletin.
Biological and Fisheries Observations
The coast-wide sardine fishery was officially closed by Pacific Fishery Management Council at the end of May due to the success of the fishery in harvesting the first of three harvest allocations. This allocation is about half the first allocation of 2007, but the catch rate was similar in both years. About 170 mt of market squid were landed in May 2008 from waters around the southern California bight and Channel Islands; this was about three times the May 2007 harvest. (California Department of Fish and Game, Marine Region, Los Alamitos, CA) Spring chinook salmon, both hatchery and wild, continued their return to the lower Columbia River and Willamette drainage and other rivers north of 37°N. Thus far, the count of spring chinook at Bonneville Dam is only about 25% of the ten-year average cumulative total for May 31. (Fish Passage Center, Portland, OR ) NOAA NMFS's northbound Gray Whale Survey had observed relatively low numbers of mothers with calves by the end of their annual survey on May 23 2008. However the 171 verified northbound calves is an increase from last year's count of 117 calves.