Climatic Perspective on the fall/winter of Nathan Mantua, Ph.D. University of Washington Climate Impacts Group March 21st, Washington Water outlook

The good news The winter of 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%

White-Green-Puyallup: swe-23%, pcp 53% Cedar-Snoqualmie-Skykomish Tolt: swe-13%, pcp 64% Baker-Skagit-Nooksack: swe-23%, pcp 77% 19% 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 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 R

Oct 2004-Feb mb 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 mb ht anoms Oct-Mar mb ht anoms

Oct-Mar SST anoms Oct-Mar SST anoms

\ From NCDC’s 2004 Annual Climate Report

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) TemperaturePrecipitation

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