Cliff Mass Department of Atmospheric Sciences University of Washington Winter Outlook 2018-2019 Cliff Mass Department of Atmospheric Sciences University of Washington
Last Year: No Major Cyclone Wind Damage Sustained Winds
Gusts
November 13th
Gusts mph
City Light Had Far Fewer Outages than PSE
February 17, 2018
2017-2018 Was a Relatively Boring Storm Season
What About 2018-2019?
The Big Story for this Winter: A Weak to Moderate El Nino Should be in Place
El Nino 101 Neutral La Nina Three Phases
Neutral
La Nina
Why do we care? The Answer: Teleconnections
Moderate to strong El Nino Patterns
Latest Status and Forecast from The NOAA Climate Prediction Center
Niño Region SST Departures from Normal (oC) Last Year We had weak La Nina Now we are slightly above normal…neutral Niño 4 0.4ºC Niño 3.4 0.3ºC Niño 3 0.4ºC Niño 1+2 0.2ºC
Defining El Nino Weak (with a 0.5 to 0.9C SST anomaly from normal in Nino 3.4 area), Moderate (1.0 to 1.4 C), Strong (1.5 to 1.9 C) Very Strong (≥ 2.0 C) events.
Tropical Pacific Ocean Has Warmed Considerably Central and Eastern Pacific Upper-Ocean (0-300 m) Weekly Average Temperature Anomalies Tropical Pacific Ocean Has Warmed Considerably
NOAA Forecast ENSO-neutral is favored through August-October 2018, with El Niño favored thereafter. Chances for El Niño are 65-70% during Northern Hemisphere winter 2018-19.
Weak El Nino
What does a weak to moderate El Nino Imply for the Winter
El Nino Correlation with Our Winter El Nino years (moderate or greater) tend to be warmer and drier in NW. Fewer big storms. Not as much lowland snow. Less than normal snowpack in the mountains. Less windstorms
El Nino, La Nina, La Nada and Major Windstorms Major windstorms appear to avoid El Nino and La Nino years They like neutral winters.
Snow? A bit less in fall
More of a wash after New Years
Latest Climate Prediction Center Forecast for the Upcoming Winter
October through December
January through March
Skill: The El Nino Correlation with Our Weather is Not Perfect: Think of it as weighting some dice
Bottom Line Will probably be in a weak to moderate El Nino near winter. If moderate or stronger, good chance we will be warmer than normal, with less snow or fewer windstorms. Less chance of big snowpack year or major windstorm. If the El Nino is weak—then anything can happen…including big events.
Remember WindWatch: Very useful guidance for the short-term (https://atmos.washington.edu/SCL/)
WindWatch State of the art short-term wind forecasts This year a major new capability: uncertainty information based on ensembles of many forecasts.
The End