Climatic Perspective on the fall/winter of Nathan Mantua, Ph.D. University of Washington Climate Impacts Group April 6, CIG Seminar

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)

Western Snowpack March 1st Northwest snowpack situation was bleak on March 1st

Western Snowpack April 1st The NW snowpack situation has “improved” (as of April 5th)- yet still extremely poor by historical averages

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 22% 52%

(as of April 6, 2005) White-Green-Puyallup: swe-38%, pcp 61% Cedar-Snoqualmie-Skykomish Tolt: swe-29%, pcp 70% Baker-Skagit-Nooksack: swe-45%, pcp 85% 33% 85%

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

Precipitation and Snow- water-equivalent for Seattle City Light’s key watersheds: the Skagit and Pond Oreille ght/ctracks.html

Snowpack update for Seattle’s Water Supply Basins About_SPU/Water_Syst em/Water_Supply/

Seattle Public Utilities Water Supply Update

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!

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

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

SeaTac’s precipitation

Daily temperatures at Sea Tac