1. Precipitation in the Olympic Peninsula of Washington State Robert Houze and Socorro Medina Department of Atmospheric Sciences University of Washington Cold-Season Algorithm GV meeting, Fort Collins, 9 Nov 2009

2. The Olympic Peninsula is a natural “precipitation laboratory” Persistent southwesterly flow during the winter provides a reliable source of moisture Extremely large precipitation accumulation produced as the moist SWly flow impinges on coastal terrain Low 0ºC level  rain at low elevations, snow at higher levels

3. The Olympic Peninsula is a natural “precipitation laboratory” Persistent southwesterly flow during the winter provides a reliable source of moisture NCEP long-term mean sea level pressure (mb) for winter (December to January) and topography

4. The Olympic Peninsula is a natural “precipitation laboratory” Extremely large precipitation accumulation produced as the moist SWly flow impinges on coastal terrain Annual average precipitation (PRISM) Maximum

5. The Olympic Peninsula is a natural “precipitation laboratory” Low 0ºC level  rain at low elevations, snow at higher ones Distribution of Nov-Jan 0°C level for flow that is onshore and moist at low levels (KUIL sounding) Mean 0°C level during storms = 1.5 km See this full range in individual storms! Frequency of occurrence 0°C level Plot provided by Justin Minder

6. Resources and experience in the region 1965-2000: Cascade Project, CYCLES, COAST 2001: IMPROVE field experiment 2004-2008: Detailed observing network across a southwestern Olympics ridge 2009: NOAA Mobile Atmospheric River Monitoring System in Westport 2012: NWS Coastal radar expected to be in place Ongoing: Regional Environmental Prediction

7. Resources and experience in the region 2001: IMPROVE field experiment (Stoelinga et al. 2003) Coastline 

8. 2004-2008: Detailed observing network across a southwestern Olympics ridge (Minder et al. 2008) Resources and experience in the region Detailed gauge network SNOTEL RAWS sites COOP site Anemometers Disdrometers

9. Resources and experience in the region 2009: NOAA Mobile Atmospheric River Monitoring System in Westport  Time Height Signal-to- noise ratio Radial velocity Data from vertically-pointing S-band radar

10. Resources and experience in the region 2012: NWS Coastal radar expected to be in place Dark gray areas indicate regions where the 0.5° elevation scans are blocked Example of Olympic Mountain slopes views from coastal radar Current radar coverage Radar coverage with coastal radar

11. Resources and experience in the region Ongoing: Regional Environmental Prediction-- WRF, hydrology, air quality, etc (Mass et al. 2003) Real-time mesoscale numerical simulations dx = 4 kmdx = 36 km

12. Resources and experience in the region Ongoing: Regional Environmental Prediction-- WRF, hydrology, air quality, etc (Mass et al. 2003) Real-time simulations with 1.33 km spatial resolution will be available shortly!

13. Resources and experience in the region Ongoing: Regional Environmental Prediction-- WRF, hydrology, air quality, etc (Mass et al. 2003) Verified by gauges: Minder et al. 2008 Long period of continuous mesoscale simulations provides model climatology e.g., 5-yr MM5 Nov-Jan precipitation climatology (mm)

14. Resources and experience in the region Ongoing: Regional Environmental Prediction-- WRF, hydrology, air quality, etc (Mass et al. 2003) Ensemble forecasting  probabilistic information e.g., probability that the precipitation accumulated in a 3 h period > 0.1in

15. Resources and experience in the region Ongoing: Regional Environmental Prediction-- WRF, hydrology, air quality, etc (Mass et al. 2003) Hydrological prediction: Mesoscale numerical output drives a distributed hydrological model  basin streamflow forecast

16. Possible field experiment configuration NPOL would have an unimpeded view of the Quinault valley and the Olympic mountains Coastal Radar

17. Conclusions The Olympic Peninsula is an ideal natural precipitation laboratory given: –Persistence of moist flow, complex terrain, huge precipitation amounts, and low 0°C level The existing and planned resources and the past experience in this region provide a strong framework for a field campaign

18. Acknowledgment This research was supported by NASA grant NNX07AD59G and NSF grant ATM-08205586