bay effect snow from the chesapeake bay david f. hamrick wpc meteorologist college park, maryland

Bay Effect Snow from Bay Effect Snow from the Chesapeake Baythe Chesapeake Bay

David F. HamrickDavid F. Hamrick

WPC MeteorologistWPC Meteorologist

College Park, MarylandCollege Park, Maryland

Presentation OverviewPresentation Overview

• Introduction to lake effect, ocean effect, and bay Introduction to lake effect, ocean effect, and bay effect snoweffect snow

• Requirements necessary for bay effect snowRequirements necessary for bay effect snow

• November 30, 1999 eventNovember 30, 1999 event

• December 25, 1999 eventDecember 25, 1999 event

• January 15, 2006 eventJanuary 15, 2006 event

• January 24, 2013 eventJanuary 24, 2013 event

• October 18, 2015 mini bay-effect showersOctober 18, 2015 mini bay-effect showers

• AcknowledgmentsAcknowledgments

What is Bay Effect Snow?What is Bay Effect Snow?

•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

Bay Effect CriteriaBay Effect Criteria

• Occurs during strong cold air advection events when Occurs during strong cold air advection events when cold air moves over a relatively warm body of watercold air moves over a relatively warm body of water

• Must have at least a 13 degree C difference between Must have at least a 13 degree C difference between the water surface temperature and the 850 mb the water surface temperature and the 850 mb temperaturetemperature

• Must have little directional wind shear and minimal Must have little directional wind shear and minimal speed shear between the surface and about 900 mb speed shear between the surface and about 900 mb

• Must have a long and sustained wind fetch over the Must have a long and sustained wind fetch over the Chesapeake Bay with an average wind direction Chesapeake Bay with an average wind direction between 340 and 10 degreesbetween 340 and 10 degrees

• Progressive synoptic scale patterns tend to limit or Progressive synoptic scale patterns tend to limit or inhibit these types of eventsinhibit these types of events

• Land breeze convergence over the bay helpsLand breeze convergence over the bay helps• Usually occurs from late November to JanuaryUsually occurs from late November to January

29 November 1999 Event29 November 1999 Event

• The surface water temperature of the Bay The surface water temperature of the Bay was 14C (57F) and a 850 mb temperature was 14C (57F) and a 850 mb temperature of -10C, and this produced a temperature of -10C, and this produced a temperature difference of 24C.difference of 24C.

• The wind at the Norfolk International The wind at the Norfolk International Airport was 350 degrees at 15 kts. Airport was 350 degrees at 15 kts.

• This resulted in a wind fetch down entire This resulted in a wind fetch down entire length of the Bay and created a favorable length of the Bay and created a favorable environment for bay effect snow.environment for bay effect snow.

11/30/99 12Z 850mb 11/30/99 12Z 850mb TempsTemps

11/30/99 12Z ETA 500mb 11/30/99 12Z ETA 500mb VorticityVorticity

11/30/99 1345Z Visible 11/30/99 1345Z Visible ImageryImagery

11/30/99 1347Z Radar 11/30/99 1347Z Radar ImageryImagery

11/30/99 1616Z Radar 11/30/99 1616Z Radar ImageryImagery

Wallops Island Sounding Data Wallops Island Sounding Data from the 30 November 1999 from the 30 November 1999

eventevent

Radar Imagery at 13Z Radar Imagery at 13Z 25 December 199925 December 1999

IR Satellite Imagery and IR Satellite Imagery and METARS at 16Z 25 Dec METARS at 16Z 25 Dec

19991999

850mb Temperatures at 12Z850mb Temperatures at 12Z 25 Dec 1999 event 25 Dec 1999 event

Surface Analysis at 12 Z Surface Analysis at 12 Z 25 December 199925 December 1999

Surface Analysis at 15 Z Surface Analysis at 15 Z 25 December 199925 December 1999

Surface Analysis at 18 Z Surface Analysis at 18 Z 25 December 199925 December 1999

Wallops Island Sounding Data Wallops Island Sounding Data from the 25 December 1999 from the 25 December 1999

eventevent

January 15January 15thth, 2006 , 2006 ½” at ORF and 1-2” just east of ORF½” at ORF and 1-2” just east of ORF

Surface Analysis at 3Z Surface Analysis at 3Z 15 January 200615 January 2006

Surface Analysis at 6Z Surface Analysis at 6Z 15 January 200615 January 2006

Wallops Island Sounding Data Wallops Island Sounding Data from the 15 January 2006 from the 15 January 2006

eventevent

Photos from the 15 January Photos from the 15 January 2006 event (Courtesy WFO 2006 event (Courtesy WFO

AKQ)AKQ)

Satellite and Radar Satellite and Radar Composite during the 24 Composite during the 24

January 2013 eventJanuary 2013 event

Visible Satellite Imagery at Visible Satellite Imagery at 17Z 24 January 2013 with 17Z 24 January 2013 with

METARSMETARS

Surface Analysis and Surface Analysis and Satellite Imagery 24 Satellite Imagery 24

January, 2013January, 2013

15Z Analysis 18Z Analysis

Wallops Island Sounding Wallops Island Sounding Data from the 24 January Data from the 24 January

2013 event2013 event

WPC Winter Weather Forecast WPC Winter Weather Forecast prior to the 24 January 2013 prior to the 24 January 2013

eventevent

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

Visible Satellite image at Visible Satellite image at 1430 Z1430 Z

Radar Imagery at 1417 Z Radar Imagery at 1417 Z andand

HRRR Model GuidanceHRRR Model Guidance

HRRR model valid at 14Z

Radar valid at 14:17 Z

HRRR Depiction of 850mb HRRR Depiction of 850mb temperature and winds at temperature and winds at

14 Z14 Z

0

-3

-6

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

Acknowledgments

•Brian Hurley – WPC lead forecaster

•Mike Rusnak – WFO Wakefield

•Mark Klein – WPC SOO