1. Downslope Windstorms in Howe Sound: Two Case Studies Ruping Mo, Paul Joe National Lab for Coastal & Mountain Meteorology, Environment Canada Johnson Zhong, Cindy Yu, Ken Kwok, and Michel Gélinas Pacific Storm Prediction Centre, Environment Canada 15 th Conf. Mountain Meteorology 20–24 August 2012, Steamboat, CO, USA

2. Outline Geography and windstorm climatology Rules of thumb for the freak windstorms Case studies: 1.18 January 2010 – A major event 2.12 February 2010 – A minor event New heuristic rule Conclusions Test test test test

3. Page 3 – February 19, 2016 Howe Sound

4. Where is Howe Sound? Howe Sound Metro Vancouver Pam Rocks

5. Winds in Howe Sound – Climatology Data: Pam Rocks (WAS) – Jan to Mar, 1995 to 2012 (18 years)

6. Winds in Howe Sound – Climatology Sustained winds at Pam Rocks (WAS) Hourly, Jan – Mar, 1995 – 2012

7. Unusual/Freak Southeast Windstorms ???

8. Freak Southeast Windstorms 3014 Hourly, Jan–Mar, 1995–2012 (18 yrs)

9. Heuristic Rule /Rules of thumb Pre-frontal Strong Southeasterlies in the Strait of Georgia P YVR −P YQQ > 6.5 hPa Pressure Difference

10. Case 1: 18 Jan 2010 04:00 PST (12:00 UTC) P YVR −P YQQ > 6.5 hPa (MAX P dif = 11.9 hPa) SE wind warning issued at 20:00 PST 17 Jan

11. Case 1: 18 Jan 2010 Predicted by 1-km model (GEM-LAM-1km) WAS S2S Hwy

12. Page 12 – February 19, 2016

13. Case 1: 18 Jan 2010 Predicted by 1-km model (GEM-LAM-1km) Southwest wind aloft Possible critical layer for wave breaking Induced convective instability over water WAS Possible Critical Layer for SEly

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15. Case 2: 12 Feb 2010 04:00 PST (12:00 UTC) P YVR −P YQQ > 6.5 hPa (MAX P dif = 8.1 hPa) SE wind storm was not predicted. Forecast amended after the fact. (1 st day of 2010 Olympics) Wind dir. unknown

16. Page 16 – February 19, 2016

17. Page 17 – February 19, 2016 First Day of Olympics PYVR−PYQQ > 6.5 hPa (MAX Pdif = 8.1 hPa) SE wind storm was not predicted. Forecast amended after the fact.

18. Case 3: 12 Jan 2010 Predicted by 1-km model (GEM-LAM-1km)

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20. Page 20 – February 19, 2016

21. New rules of thumb Pre-frontal Strong Southeasterlies in the Strait of Georgia P YVR −P YQQ > 6.5 hPa Winds shift to southwest aloft! WSK Wind Profile

22. Page 22 – February 19, 2016

23. Potential hazard on Sea-to-Sky HWY

24. Conclusions Southeast windstorm in Howe Sound is a rare event It has quite an impact on mariners, but is difficult to predict It is likely related to a downslope windstorm due to orographic wave breaking Orographic effect leads to Wind shifting from SE to SW above mountain, which provide a possible critical layer aloft for orographic wave breaking Downslope windstorm could be a hazard on the Sea2Sky Hwy as well The development of LAM-1km model was accelerated for the Olympics and this is a serendipitous benefit of that

25. Thank You! Michael O’Toole’s “Storm Over Howe Sound”