Climate variations in the Northwest, seasonal climate forecasting, and outlook for winter Nate Mantua Climate Impacts Group University of Washington

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

Effects of PDO and ENSO on PNW average temperature Warm ENSO, warm PDO Warm ENSO Cool ENSO Cool ENSO, cool PDO -½  ½½ ENSO neutral, cool PDO Degrees F Years classified according to

Effects of PDO and ENSO on PNW average precipitation Warm ENSO, warm PDO Warm ENSO Cool ENSO Cool ENSO, cool PDO -½  ½½ Years classified according to Inches

Warm ENSO, warm PDO Warm ENSO Cool ENSO Cool ENSO, cool PDO Annual mean: 50% higher Annual mean: 25% higher ENSO, PDO, and Chester Morse inflow

Summary ENSO, PDO play a modest role in winter and spring climate: zwarm ENSO, warm PDO tilt balance to above- average temperatures and below-average precipitation zcool ENSO, cool PDO tilt balance (less) toward cool wet zENSO and PDO can “cancel” each other zJan-Jun sensitive period for temp, Nov-Mar sensitive period for precipitation

The dry winter of

Nov 2000-Feb mb height

Nov 2000-Feb 2001 temperature anomalies Degrees F

Nov 2000-Feb 2001 precipitation anomalies Standard deviations

Daily Precip: Oct Sep

Monitoring El Niño ENSO Observing Network of 70 buoys

The European Center’s ENSO Forecast Forecast SSTs in the eastern equatorial Pacific, from the European Center for Medium Range Weather Forecasting (

ENSO outlook summary zENSO remains in a near-neutral state zLeading ENSO prediction models are calling for weak El Niño sometime soon zLatest observations support the development of El Niño in next few months

The Pacific Decadal Oscillation

Global SST anomalies: Sept 23-29, 2001

Pacific Decadal Oscillation Update Since fall 1998, PDO index has had mostly negative values PDO Persistence has historically been a skillful forecast (correct ~75% of the time) odds favor “cool/negative PDO” for winter 2002 through August 2001

NDJ FMA MJJ

The Pineapple Express and tropical rainfall: a potential NW link to the tropical Madden-Julian Oscillation

Conclusions zWeak/moderate El Niño is possible for next few seasons zCPC’s forecas for PNW: climatological odds for winter, enhanced odds for a warm spring zwhat about PDO? Cool PDO conditions may favor cool/wet winter and spring yNorth Pacific Ocean situation similar to last year (but atmosphere ignored ocean last year)