Winter Weather Forecast How Windy Will in Be? Professor Cliff Mass University of Washington

What are the chances of getting a major windstorm?

The Most Useful Tool for Predicting the General Characteristics of Northwest Winters: The Connection Between El Nino/La Nina and Northwest Weather

Three Phases La Nina Neutral

An important measure of El Nino/La Nina is the sea surface temperature anomaly in the central tropic Pacific: the Nino 3.4 area El Nino: >.5C La Nina:<-.5C Neutral:.5 to -.5

The Correlations El Nino years tend to be warmer and drier. Fewer big storms. La Nina years tend to be cooler, wetter, and snowier. Neutral (or La Nada) years tend to have normal precipitation and temperature, but are the years with the rare, but damaging, major windstorms and floods.

El Nino, La Nina, La Nada and Major Windstorms Major windstorms appear to avoid El Nino and La Nino years They like neutral winters.

This Year: Weak El Nino Winter

Forecasts by the Climate Prediction Center 65% probability of El Nino Conditions

But How Strong? The effects over the Northwest are greatly influenced by its El Nino/La Nina strength

Central Pacific (Niño 3.4) Sea Surface Temperature Outlook: Weak El Nino El Nino defined as positive temperature anomaly of greater than.5C

SST Outlook: National Weather Service Long- Term Forecast Model The CFS.v2 ensemble mean (black dashed line) predicts ENSO-neutral conditions (warm side of neutral) through spring 2014.

Bottom Line Without a strong El Nino, the potential for strong windstorms will be undiminished.

The seasonal outlooks combine the effects of long-term trends, soil moisture, and ENSO (El Nino/La Nina). TemperaturePrecipitation Climate Prediction Center U. S. Seasonal Outlooks October – December 2014

City Light and its customers can prepare better today for windstorms because short and extended range forecasts have improved

Forecast Models are Now Showing Useful Skill for 7-9 days Out

2012: Hurricane Sandy 125 dead, 60+ billion dollars damage in an area with a population of tens of millions.

Well predicted, more than a week ahead ECMWF 6-day Forecast of Sea Level Pressure

Major Advances in Short-Term Prediction: the High Resolution Rapid Refresh (HRRR)

Best Forecast Next Few Hours: NOAA HRRR Model ( Forecasts made every hour High resolution 15h prediction

Tailored Local Forecast Guidance The UW and the City of Seattle have worked together to produce three web sites with weather guidance for city personnel and citizens: – Rainwatch – Snowwatch – Windwatch

Seattle WindWatch: Upgraded for 2014 by Jeff Baars!

Seattle WindWatch (2014 Edition) Provides access to National Weather Service and UW High Resolution Forecasts. Provides real-time warnings (e.g., , txt message) to city personnel when high winds threaten. Now monitors observed winds. And includes the new HRRR forecasts (out 15 hr)

Warning Capabilities WindWatch electronically warns Seattle Light personnel when observed or forecast winds exceed specified thresholds.

A Now a REALLY Long Wind Forecast Will Global Warming produce stronger winter winds here in the Northwest? City Light has supported the UW to examine the output of long-term regional climate models

The Answer Appears to Be No!

Next Issue Will lightning increase over our area as the Earth warms?

Final Remarks Large uncertainty in seasonal forecasts. Think of dice being weighted A weak to moderate El Nino this winter will probably not weight the meteorological dice heavily. So no reason to expect an atypical wind season Forecast models continue to improve. Seattle WindWatch has substantially enhanced capabilities.

The End