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

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

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

5. WINTER STORM INGREDIENTS 2. Sufficient moisture Moist Air

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

7. WINTER STORM INGREDIENTS Cold Air H L Moist Air

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

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

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

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

12. NOR’EASTERS L “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) *New England *gale force winds *winter *high waves *beach erosion

13. “Storms”

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

15. Storm Center Wave Approach Fetch

16. IMPORTANCE OF STORM TRACK

21. NOR’EASTER FORMATION REGIONS

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

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

24. NOR’EASTER SEASONALITY

25. 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 JET STREAM

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

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

28. MID-LATITUDE STORM FORMATION REGIONS

30. JANUARY MIDLATITUDE STORM TRACKS

31. JULY MIDLATITUDE STORM TRACKS

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

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

34. ASH WEDNESDAY STORM March, 1962 H 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

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

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

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

38. Mean Annual Snowfall

44. Record-Holding Snowfall Seasons

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

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

48. EL NINO AND VIRGINIA PRECIPITATION EL NINO LA NINA

49. EL NINO AND VIRGINIA TEMPERATURE EL NINO LA NINA

50. 0 5 10 15 20 25 30 35 -8-6-4-2024 VIRGINIA SNOWFALL (INCHES) JAN-MAR EL NINO STATUS El Nino La Nina EL NINO AND VIRGINIA SNOWFALL

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