Climatic Perspective on the fall/winter of

2004-2005

Nathan Mantua, Ph.D.

University of Washington

Climate Impacts Group

http://cses.washington.edu/cig

March 21st, 2005 -- Washington Water outlook

The good news

• The winter of 2004-05 has finally ended!

• It’s been snowing in the Cascades

From the Mt Baker ski area web-cam (10 am, Sunday March 20th)

outline

• Where are we?

• How and why did we get here?

• Where do we appear to be going in the next few months?

Where are we? (climatologically speaking)

• In a lousy snowpack situation - current snow-water for the Washington Cascades ranges from 13% for the Cedar/Tolt/Green to 44% for the Columbia R. above the Methow

How did we get here?

• the low snowpack occurred largely because of warm temperatures during the periods when most of our precipitation occurred: December 6-10 and January 17-19

• Fall and winter storms have generally been too warm to develop this year’s snowpack

35%

76%76%

• White-Green-Puyallup: swe-23%, pcp 53%• Cedar-Snoqualmie-Skykomish Tolt: swe-13%, pcp 64%• Baker-Skagit-Nooksack: swe-23%, pcp 77%

19%

73%73%

• seasonal averages of precipitation and temperature are not exceptional. Most locations in Washington have received 65-80% of normal precipitation since October 1. This is considerably more than in 1977 or 2001. Temperatures also have been only about 1F above normal.

Precip % of normal since Oct 1

• Los Angeles got almost twice as much rainfall as Seattle (~25" versus ~17") since October 1!

Why?

• The proximate cause was a large number of days with a split jet stream around a blocking ridge located over the NW region

• Was it El Niño?– Definitely not “typical” of past

El Niño events

Ocean temperature anomalies

Jet stream wind patterns

RR

Oct 2004-Feb 2005 200mb ht anomalies

The tropical atmosphere has been warm!

Tropical SST indices

• Are we in a situation like the early 1990s with multiyear warmth in the western eq. Pacific?

Oct-Mar 91-95 200mb ht anoms

Oct-Mar 02-05 200mb ht anoms

Oct-Mar 91-95 SST anoms

Oct-Mar 2002-05 SST anoms

\

From NCDC’s 2004 Annual Climate Reporthttp://www.ncdc.noaa.gov

What’s next?

• NOAA’s Climate Prediction Center calls for increased odds for above average spring (AMJ) temperatures, and climatological odds for precipitation (forecast issued March 17th)

Temperature Precipitation

What’s next? (another view)

• The International Research Institute for Climate Prediction (iri.columbia.edu) also predicts a tilt in the odds favoring a warm spring (AMJ)

SST anomalies for the past month

summary

• It has been a warm and dry winter, but not of “record” extremes in either temperature or precipitation

• The tropics have been very warm, yet not in a “classic” El Niño pattern– part of longer term and broader scale atmospheric

warming?

• Official CPC forecast calls for increased odds for a warm spring

CPC forecast for July-August-September 2005

Temperature Precipitation