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"The Weather of the Pacific Northwest" by Cliff Mass available from University of Washington Press
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Regional Numerical Weather Prediction

Sponsored by the Northwest Modeling Consortium, we have run the MM5 and now WRF mesoscale models operationally at high resolution since 1995. Currently, the WRF is run at 36 km horizontal resolution over the eastern Pacific, 12 km over the Pacific Northwest, 4 km over Washington, Oregon, and Idaho, and 1.3 km over Washington, northern Oregon, and northern Idaho. The thrust of our work is to determine the benefits of high-resolution forecasting, improve verification approaches, and to identify and address weaknesses in model physics.

Olympex and Evaluation of the Impacts of GPM Satellite Observations

In 2014, NOAA will be launching a new satellite with both active and passive instruments for determining precipitation and microphysics. A ground validation experiment for the satellite, OLYMPEX, will be centered on the Olympic Peninsula. My group will be heavily involved in this field experiment, including data assimilation and assessing model fidelity.

Assimilation of Smartphone Observations and Dense Pressure Observations

We believe it is possible to greatly improve mesoscale analysis and short-term forecasts by assimilation ultra dense networks of pressure observations. Currently, we are experimenting with two sources: a combination of all available mesoscale networks and pressures available from smartphones. Potentially, smartphones could provide millions to hundreds of millions of pressure observations per hour

The West Coast Thermal Trough and Warm-Season Diurnal Circulations

The thermal trough is the most important warm-season mesoscale feature over the U.S. West Coast. We are studying its structure, evolution, and dynamics using observations and high-resolution modeling. In addition, we are documenting the thermally driven diurnal circulations over the western U.S. using high-resolution (1.3 km resolution) WRF simulations.

Assimilation of Lightning in Numerical Weather Prediction

Working with Professor Robert Holzworth of ESS, we evaluating innovative approaches to assimilating lightning strike information into numerical weather prediction. Currently, we are testing nudging and ensemble data assimilation approaches.

Use of Ensembles for Mesoscale Numerical Weather Prediction

We are testing the usefulness of running a high-resolution ensemble predictions using a number of operational initializations and varying physics to test this approach to statistical numerical weather prediction. The UW Ensemble system is one of the highest resolution ensemble systems in the world and we are examining its ability to provide calibrated probabilities and to predict forecast skill. Currently, there are 8 members run twice a day. As part of this project we are working closely with the Statistics department. We are also working with Professor Greg Hakim's group on the development and use of an Ensemble Kalman Filter system for data assimilation and ensemble forecasting.

Regional Climate Simulations

In concert with Eric Salathe of UW Bothell, we are now running the WRF model for ten-year periods (2070-2080, 2045-2055, 2020-2030, 1990-2000) at 45 and 15 km resolutionover the next century using forcing from the PCM and ECHAM a number of global circulation models to determine the regional implications of global warming. We hope to document the effects of regional land-water contrasts and terrain on regional climate change.

Northwest Windstorms

This project is studying the nature of the intense Northwest windstorms associated with deep, synoptic lows that often pass through the Pacific Northwest during winter. Some of these storms have had winds exceeding 125 mph, with the greatest equivalent to Category III hurricanes in wind speed and damage potential. A current issue we are exploring is whether there is any credibility to the popular sting jet hypothesis.

Cooperative Research and Interaction with the National Weather Service

With support from the NWS CSTAR program, we are working to develop mesoscale analysis and prediction tools for operational application. These include ensemble Kalman filter data assimilation and the use of new mesoscale data sources. We also work closely on regional prediction and co-sponsor the Northwest Weather Workshop.

Trends in Heavy Precipitation over Western North America

Examining CMIP-5 GCM runs and several high-resolution dynamically downscaled GCM simulations (using WRF) we are examining whether western U.S. heavy precipitation events will change and the origins of such changes.

Dissemination of Weather Information to the Public

As part of this effort, the PI provides a weekly weather forecast and discussion on KPLU at 9:00 AM on Fridays and a regular blog (, in addition to regular public lectures at schools, fraternal organizations, and other groups.