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Winter Storms and Northeasters

Winter Storms and Northeasters. Robert E. Davis. Dept. of Environmental Sciences. University of Virginia. Email: red3u@virginia.edu. Virginia Mitigation Summit June 17, 2004. Nor’easters and Snowfall in Virginia. Nor’easters. Snow. Nor’easter- generated snowfall.

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Winter Storms and Northeasters

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  1. Winter Storms and Northeasters Robert E. Davis Dept. of Environmental Sciences University of Virginia Email: red3u@virginia.edu Virginia Mitigation Summit June 17, 2004

  2. Nor’easters and Snowfall in Virginia Nor’easters Snow Nor’easter- generated snowfall Many Virginia snow events are not linked to nor’easters

  3. H Cold Air Cold Air Damming WINTER STORM INGREDIENTS Cold Air Damning 1. Sufficient cold air source

  4. WINTER STORM INGREDIENTS Moist Air 2. Sufficient moisture Moist Air

  5. WINTER STORM INGREDIENTS winds L 3. Lifting mechanism (the “storm”)

  6. Cold Air WINTER STORM INGREDIENTS H L Moist Air

  7. Cold Air L TIMING IS EVERYTHING H *Arrival of storm does not coincide with cold air *Warm air from Atlantic decreases vertical thickness of cold air mass

  8. TIMING IS EVERYTHING L L *Forward speed too fast *Low snow accumulations

  9. WINTER STORM INGREDIENTS L L L *Track too far inland *Not enough moisture

  10. THE “SNOWMAKER” TRACK *Ideal track for producing snow in the Mid-Atlantic Heaviest snow frequency * * * Storm Track (Knappenberger and Michaels, 1993)

  11. NOR’EASTERS “A cyclonic storm of the east coast of North America, so called because the winds over the coastal area are from the northeast” (Glossary of Meteorology) L *New England *gale force winds *winter *high waves *beach erosion

  12. “Storms”

  13. FACTORS THAT DETERMINE WAVE HEIGHTS IN DEEP WATER *wind speed *wind duration *fetch Wave height climatologies can be “hindcasted” from historical weather records

  14. Wave Approach Fetch Storm Center

  15. IMPORTANCE OF STORM TRACK

  16. NOR’EASTER FORMATION REGIONS

  17. Nor’easter Type by Class I IV Most Class IV and V storms form near the Bahamas or Florida II V III

  18. 1. New England High • Cold air source • Slows forward motion of storm H • 2. Coastal storm • Atlantic moisture • Lifting mechanism • Slow movement = more snow • Slow movement = bigger waves L L L L NOR’EASTERS AND VIRGINIA SNOW Most major snowstorms in Virginia are caused by large nor’easters

  19. NOR’EASTER SEASONALITY

  20. JET STREAM 1) Boundary between warm, tropical and cold, polar air masses 2) Size and strength vary seasonally 3) Linked to mid-latitude storms at surface 4) Linked to storm tracks

  21. IN WINTER, JET STREAM 1) EXPANDS 2) STRENGTHENS JANUARY JULY

  22. Mid-latitude storms derive their energy from the jet stream

  23. MID-LATITUDE STORM FORMATION REGIONS

  24. JANUARY MIDLATITUDE STORM TRACKS

  25. JULY MIDLATITUDE STORM TRACKS

  26. PREFERRED WINTER STORM TRACKS L L L L L L Continental Track L L Coastal Track L L (After Hayden, 1981)

  27. Golfer’s track “Snowmaker” track (Knappenberger and Michaels, 1993)

  28. H ASH WEDNESDAY STORM March, 1962 • Strong high to north • Storm track off coast • (Bahamas Low) • Slow-moving • Strong northeast winds to the • north of storm • Long fetch, strong winds from same • direction for long duration

  29. ASH WEDNESDAY STORM, MARCH, 1962 Snowfall (inches)

  30. “STORM OF THE CENTURY” March, 13 1993; 7 a.m. EST

  31. “Storm of the Century” Surface weather map 3/13/1993 7 p.m., EST

  32. Mean Annual Snowfall

  33. Record-Holding Snowfall Seasons

  34. EL NINO AND NOR’EASTERS (ALL STORMS)

  35. EL NINO AND NOR’EASTERS (STRONG STORMS)

  36. EL NINO AND VIRGINIA PRECIPITATION LA NINA EL NINO

  37. EL NINO AND VIRGINIA TEMPERATURE LA NINA EL NINO

  38. EL NINO AND VIRGINIA SNOWFALL 35 El Nino La Nina 30 25 20 VIRGINIA SNOWFALL (INCHES) 15 10 5 0 -8 -6 -4 -2 0 2 4 JAN-MAR EL NINO STATUS

  39. Winter Storms and Northeasters Robert E. Davis Dept. of Environmental Sciences University of Virginia Email: red3u@virginia.edu Virginia Mitigation Summit June 17, 2004 Thanks to: Chip Knappenberger Jerry Stenger Pat Michaels

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