View
214
Download
0
Embed Size (px)
Citation preview
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