Climate Review for WY 2004 and Outlook for WY 2005 Philip Mote Climate Impacts Group University of Washington Annual Fall Forecast Meeting October 26, 2004 Boise

Oct Feb 2004 US Climate % Normal Precip Temperature (Deg F)

March 2004 US Climate % Normal Precip Temperature (Deg F)

March-April 2004: a west coast ridge that would not quit 300 mb height anomalies (meters): March-April 2004

Water Year 2004 US Climate % Normal Precip Temperature (Deg F)

NOAA-CPC climate outlook from last fall: climatological odds for fall/winter PNW precip in spring 2004 odds tilted in favor of above average precip. (forecast from August 17, 2003)

NOAA-CPC climate outlook from last fall: climatological odds for fall/winter/spring PNW temperatures (forecast from August 17, 2003)

Summary: NW climate in water year Overall a warm and slightly dry water year; average precipitation from Oct-Feb, then a very warm and dry March. –The water year as a whole was warm/dry throughout most of the western US CPC forecasts from last August called for “climatological odds” for fall/winter/spring precipitation and temperature –The tropical Pacific was just slightly warm, so forecasts called for “ENSO neutral” conditions (neither El Niño or La Niña) in the tropics

A history of ENSO warm cool warm A history of the PDO

tropical ocean temperatures: a weak El Niño is underway

Equatorial Ocean Temperature deviations from the long-term average: 1982-September /83 86/87/88 91/92 97/98 02/03 EN 93 94/95

Multi-model forecast summary

Ocean temperature anomalies August 15-September 11, 2004

The PDO has been less prominent since the early 1990s- present From Bond et al. 2003, Geophysical Research Letters, Vol 30: leading patterns of North Pacific SST since 1950 PDO “Victoria Pattern”

PDO index Victoria pattern index The PDO pattern was strong from 1950s through the 1980s The Victoria pattern was strong from the 1990s through 2003 In the winter of , the North Pacific was warm, yet the pattern of warmth did not resemble either a PDO or Victoria pattern From Bond et al. 2003, Geophysical Research Letters, Vol 30: Phase plot for the 2 leading patterns of North Pacific wintertime SSTs (5 yr avgs) 50s-mid70slate 70s/late 80s

Wintertime SST anomaly patterns

Pacific Ocean Outlook Summary Current forecasts rate a “weak to moderate El Niño” as most likely situation for fall-winter PDO? –A simple forecast with skill relies on “PDO persistence + ENSO influence” Expect weak to moderate warm phase PDO conditions for fall/winter (PDO = +0.5 to +1 st devs for Nino34 =.4 to 1.2) Other? –consistently warm ocean temperatures in the far N. Pacific have not been captured very well by the PDO index in the period from

Nov temp

DJF temp

JFM temp

FMA temp

Nov precip

DJF precip

JFM precip

NOAA/CPC forecasts issued September 16, 2004 FMA precip

Summary and Conclusions Expect a weak to moderate intensity El Niño for this winter NOAA CPC forecast for NW –Increased odds for a warm fall and winter; equal chances wet or dry for Idaho Extreme cold, low elevation snows, and extreme flooding have been less frequent than average in past El Niño winters in the PNW region

Climate information International Research Institute for Climate Prediction Western Regional Climate Center NOAA’s Climate Prediction Center Office of the Washington State Climatologist Idaho State Climate Services