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Bay Effect Snow from the Chesapeake Bay

Explore the unique weather event of bay effect snow in the Chesapeake Bay. Discover the criteria, historical events, and potential impacts of this narrow band of snow. Learn how high-resolution models can enhance forecasting capabilities.

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Bay Effect Snow from the Chesapeake Bay

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  1. Bay Effect Snow from the Chesapeake Bay David F. Hamrick WPC Meteorologist College Park, Maryland

  2. Presentation Overview • Introduction to lake effect, ocean effect, and bay effect snow • Requirements necessary for bay effect snow • November 30, 1999 event • December 25, 1999 event • January 15, 2006 event • January 24, 2013 event • October 18, 2015 mini bay-effect showers • Acknowledgments

  3. Very similar to lake effect snow events Narrow band of snow oriented north to south that affects southeast Virginia Does not happen as often as lake effect Similar processes occur downwind of Delaware Bay, Long Island Sound, and the Great Salt Lake in Utah What is Bay Effect Snow?

  4. Bay Effect Criteria • Occurs during strong cold air advection events when cold air moves over a relatively warm body of water • Must have at least a 13 degree C difference between the water surface temperature and the 850 mb temperature • Must have little directional wind shear and minimal speed shear between the surface and about 900 mb • Must have a long and sustained wind fetch over the Chesapeake Bay with an average wind direction between 340 and 10 degrees • Progressive synoptic scale patterns tend to limit or inhibit these types of events • Land breeze convergence over the bay helps • Usually occurs from late November to January

  5. 29 November 1999 Event • The surface water temperature of the Bay was 14C (57F) and a 850 mb temperature of -10C, and this produced a temperature difference of 24C. • The wind at the Norfolk International Airport was 350 degrees at 15 kts. • This resulted in a wind fetch down entire length of the Bay and created a favorable environment for bay effect snow.

  6. 11/30/99 12Z 850mb Temps

  7. 11/30/99 12Z ETA 500mb Vorticity

  8. 11/30/99 1345Z Visible Imagery

  9. 11/30/99 1347Z Radar Imagery

  10. 11/30/99 1616Z Radar Imagery

  11. Wallops Island Sounding Data from the 30 November 1999 event

  12. Radar Imagery at 13Z 25 December 1999

  13. IR Satellite Imagery and METARS at 16Z 25 Dec 1999

  14. 850mb Temperatures at 12Z 25 Dec 1999 event

  15. Surface Analysis at 12 Z 25 December 1999

  16. Surface Analysis at 15 Z 25 December 1999

  17. Surface Analysis at 18 Z 25 December 1999

  18. Wallops Island Sounding Data from the 25 December 1999 event

  19. January 15th, 2006 ½” at ORF and 1-2” just east of ORF

  20. Surface Analysis at 3Z 15 January 2006

  21. Surface Analysis at 6Z 15 January 2006

  22. Wallops Island Sounding Data from the 15 January 2006 event

  23. Photos from the 15 January 2006 event (Courtesy WFO AKQ)

  24. Satellite and Radar Composite during the 24 January 2013 event

  25. Visible Satellite Imagery at 17Z 24 January 2013 with METARS

  26. Surface Analysis and Satellite Imagery 24 January, 2013 15Z Analysis 18Z Analysis

  27. Wallops Island Sounding Data from the 24 January 2013 event

  28. WPC Winter Weather Forecast prior to the 24 January 2013 event

  29. Bay effect showers 18 October 2015 Early season example that involves showers instead of snow Strong cold air advection down the length of the bay HRRR model captured these showers several hours in advance, even though they were very light

  30. Visible Satellite image at 1430 Z

  31. Radar Imagery at 1417 Z andHRRR Model Guidance Radar valid at 14:17 Z HRRR model valid at 14Z

  32. HRRR Depiction of 850mb temperature and winds at 14 Z -6 -3 0

  33. In Conclusion • Noteworthy events happen on average about every 5 years or so • It is necessary to have a steep lapse rate in the boundary layer with a high to the west and a low to the east • Can be high impact events if the band persists long enough • Bay enhancement is also possible • High resolution model data, such as the HRRR, can give indications to this within 24 hours of the event • WPC meteorologists are paying attention to these types of events

  34. Acknowledgments • Brian Hurley – WPC lead forecaster • Mike Rusnak – WFO Wakefield • Mark Klein – WPC SOO

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