“Pacific Decadal Oscillation” in SST [Mantua et al. 1997] Updated time series available online at: “warm” phase; AK salmon  PNW salmon  “cold” phase; AK salmon  PNW salmon 

Updated North Pacific Index [Jim Hurrell, NCAR] Available online at:

Current Pacific SST anomaly map NOAA Climate Diagnostics Center Available online at

ENSO/PDO/AO effects on US precipitation [Higgins et al. 2000] “ENSO” effect: Strongest along Gulf coast Add “PDO” effect: esp. important across SW? “AO” effect: Ohio River Valley

Current winter precipitation outlook NOAA Climate Prediction Center Available online at

Time series of ENSO/PDO and winter precipitation in New Mexico [Gutzler et al. 2002] Time series of equatorial SST (Niño3) and PDO (Mantua et al.) ending in late summer, Time series of subsequent winter precipitation in Southwest NM (Climate Div 4 and town of Ft Bayard), DJFM 1951/52 – 1997/98

Quantification of seasonal predictability with a “modified” Brier Score Consider the distribution of 16 upper tercile Niño3 years Tercile distribution of precip is 5 / 1 / 10 whereas random distribution would be 5.33 / 5.33 / 5.33 “Modified” 1-tailed Brier Score S: Each annual “hit” = 0 1-bin error = 1 2-bin error = 2 (not 4) Sum annual scores, divide by N … so for 5/1/10, S=11/16=0.69 Perfect skill: S=0.0 No skill: S=1.0 Informally, we find: S>0.9 no utility 0.75<S<0.9 modest utility 0.6<S<0.75 marked skewness S<0.6 forecaster’s dream

ENSO extrema provide significant predictability of SW US winter precip … Predictability of a wet winter following positive JAS Niño3 (better for El Niño than La Niña) Predictability of a dry winter following negative JAS Niño3 [Gutzler et al. 2002] Perfect skill = 0.00 Zero skill = 1.0 or higher Skill  darker shading

… but PDO has a relatively modest effect on SW US winter precip predictability Predictability of a wet winter following positive PDO year Predictability of a dry winter following negative PDO year [Gutzler et al. 2002] Perfect skill = 0.00 Zero skill = 1.0 or higher Skill  darker shading

Decadal modulation of ENSO predictability is the primary influence of PDO Pre-1977Post-1977 Wet winter following JAS El Niño (good predictability post-77; none pre-77) Dry winter following JAS La Niña (good predictability pre-77; none post-77) [Gutzler et al. 2002]

The “climate regime shift” of 1977 profoundly changed ENSO-based predictability … have we changed back to pre-1977 conditions? Characterization of low-frequency variability is extremely difficult to get right the first time At present there is neither a universally accepted index of PDO/NPO nor a satisfactory theory Not all PDO indices show a shift circa 1998 In mid-continent, including SW North America, the ocean is not the whole decadal climate story Decadal climate variability bedevils monitoring of long-term change and prediction of short-term anomalies Nevertheless decadal variability is profoundly important for ecosystems and human society