2. BACKGROUND RESEARCH

3. FORECASTING CHALLENGES (1)Cold Air Damming (2)Coastal Low Pressures (3)Precipitation Type

4. BUILDING HIGH PRESSURE CONFLUENCE ALOFT SURFACE DIVERGENCE & PRESSURE RISES

8. E-W Elongated High Confluence with little or no ridging at 500mb Cold front just off-shore DIABATICALLY ENHANCED CLASSICAL (SYNOPTIC FORCING)

9. N-S Elongated High Confluence with more ridging at 500mb Cold front far off-shore DRY ONSET CLASSICAL (SYNOPTIC FORCING)

10. HYBRID CAD Equal synoptic/diabatic processes Weak and progressive high IN-SITU CAD Diabatic processes prevail High in unfavorable location Little or no CAA

11. Surface Plot CONTAINS: * Mean Sea Level Pressure Isobars (mb) * 6-hour Total Precipitation (in) * 1000-500 mb Thickness (dm) WHAT DO YOU LOOK FOR? High Pressure ~1030mb in New England U-shaped Isobars east of Appalachians 546 line- Mix 540 line- Snow Timing of Precip (am/pm)

12. 850 mb Plot CONTAINS: * 850 mb Height (dm) * 850 mb Temperature (C) * 850 mb Winds (kts) WHAT DO YOU LOOK FOR? Southerly to easterly winds Temperatures < 0C Snow < 3C Mix Warm Air Intrusion

13. 700 mb Plot CONTAINS: * 700 mb Heights (dm) * Relative Humidity (%) * Omega (mb/s) WHAT DO YOU LOOK FOR? Relative Humidity >70% Negative Omegas Co- located with RH Dry Air Intrusion Westerly Winds

14. 500 mb Plot WHAT DO YOU LOOK FOR? Southwest Winds Tilt of 500 mb Trough Confluent Flow over New England CONTAINS: * 500 mb Heights (dm) * Absolute Vorticity (s^-1) * 500 mb Winds (kts)

15. 300 mb Plot WHAT DO YOU LOOK FOR? Confluent Flow over New England Jet stream and streaks Split Flow/ Dual Jet Structure CONTAINS: * 300 mb Heights (dm) * 300 mb Isotachs (kts) * 300 mb Winds (kts)

16. PRECIPITATION TYPE FORECASTING FEBRUARY 5-6, 2004 Potential SC Ice Storm/CAD Event (1)What is p-type? (2)How do we make an educated guess? (3)PUTTING THE METHOD TO USE…

17. 32 F0C COLD AIR DAMMING & WINTER PRECIPITATION TYPES Warm, moist air COLD, DRY AIR Rain Freezing Rain Sleet Snow WARM NOSE NORTH SOUTH (1) (2) (3)

18. PARTIAL THICKNESS AND GENERAL FORECASTING RULES Partial thickness - the distance between intermediate levels in the atmosphere found in the model output, typically between 1000 and 500 millibars (i.e. 1000-850, 850-700, 700-500) that represent the thermal structure in the atmosphere with increasing height TO DO ON-THE-FLY FORECASTING: For snow to fall: 1000-850 THK < 1290m 850-700 THK < 1540m For sleet/freezing rain to fall: 850-700 THK1540-1555mSleet > 1555mFreezing Rain (larger values of the 850-700 THK indicate warmer air aloft)

19. 5540 1575 3160 5790 Surface850 mb 700 mb500 mb 1000-500 THK & 850 HEIGHT 700 HEIGHT & 500 HEIGHT ???????????????? WILL IT BE…… SNOW, SLEET, OR FREEZING RAIN ????????????????

20. So for the Columbia Area in the Event from Thursday, Feb. 5th… 500mb5790m 700mb3160m 700-500 THK2630m 700mb3160m 850mb1575m 850-700 THK1585m 1000-500 THK5540m 700-500 THK2630m 850-700 THK1585m 1000-850 THK1325m >1540m => no snow, warm nose present >1300m => too warm to freeze

21. P-TYPE FORECASTING NOMOGRAM 1325/1585 1000-850mb THK 850-700mb THK RAIN

22. Actual Observations

23. Related/Future Research CAD Erosion (Stanton 2003, MS Thesis, NCSU) High-resolution modeling (Caldwell 2004, MS Thesis, NCSU) Coastal Frontogenesis (Appel 2002, MS Thesis, NCSU) Quantitative Precipitation Forecasting (QPF)