SNOWIN’ TO BEAT THE BAND

1. SNOWIN’ TO BEAT THE BAND Using Satellite and Local Analysis and Prediction System Output to Diagnose the Rapid Development of a Mesoscale Snow Band Eleanor Vallier-Talbot and David R. Vallee NOAA/NWS Taunton, MA

2. Fast Hitting Snowstorm • Fast moving storm produced swath of 12-16 snows across major metro areas of Southern New England

3. Methodology“Anticipating Mesoscale Band Formation” • WFO Taunton has incorporated the method outlined in Novak, D.R., 2002, for anticipating band formation. • Critical Elements: • Upper Level Divergence • Mid Level Frontogenesis/Instability • Snow Growth and CSI Potential

4. Methodology“Anticipating Mesoscale Band Formation” • Day shift forecasters used the same approach incorporating an updated version of the Local Analysis and Prediction System Output (LAPS) in real time along with Satellite signatures. • Helped diagnose the northwest displacement and resulted in dramatically higher snowfall forecast.

5. Eta Model Guidance • NWP/Eta Model was forecasting cyclogenesis along mid Atlantic coast • Low to pass well south and east of Cape Cod • A track far enough off shore which doesn’t often produce heavy snows far inland

6. Eta Model Guidance • Co-location and placement of upper level divergence, mid level frontogenesis and max upward motion and potential for efficient snow growth were poised to occur along or just off the coast of Southern New England

7. Composite 4-panel - 24 hr fcst valid 12 UTC 7 Feb 03

8. Composite 4-panel - 30 hr fcst valid 18 UTC 7 Feb 03

9. Composite 4-panel - 36 hr fcst valid 00 UTC 8 Feb 03

10. Cross Section – 30 hr fcst valid 18 UTC 7 Feb 03Lebanon, NH to 150 nm south of Martha’s Vineyard, MA

11. Time Height Cross Sections 12 UTC Run for Eta at Norwood, MA -16°C -18°C -12°C -8°C

12. Time Height Cross Section 12 UTC Run for Eta at Nantucket, MA -16°C -18°C -12°C -8°C

13. Composite 4-panel - 12 hr fcst, valid 12 UTC 7 Feb 03

14. Composite 4-panel - 18 hr fcst, valid 18 UTC 7 Feb 03

15. Composite 4-panel - 24 hr fcst, valid 00 UTC 8 Feb 03

16. Cross Section – 18 hr fcst valid 18 UTC 7 Feb 03Lebanon, NH to 150 nm south of Martha’s Vineyard, MA

17. Time Height Cross Sections 00 UTC Run for Eta at Norwood, MA -18°C -16°C -12°C -8°C

18. Time Height Cross Sections 00 UTC Run for Eta at Nantucket Island, MA -18°C -16°C -8°C -12°C

19. RUC40 Model Guidance • 06Z Run of the Eta continued to present a similar solution to the 12z/6th and 00z/6th runs • Winter Weather Experience (WWE) collaborative efforts also placed axis of heaviest snows along the immediate south coast of New England • RUC40 guidance from the 09Z run began to at least hint at a northwest displacement to the major forcing mechanisms

20. Composite 4-panel – 09 UTC RUC40 Valid 12 UTC 7 Feb 03

21. Composite 4-panel – 09Z RUC40 Valid 15 UTC 7 Feb 03

22. Composite 4-panel – 09Z RUC40 Valid 18 UTC 7 Feb 03

23. Reality Check…. • Satellite and LocalLAPS Data tell the tale! • Major Corridor of very heavy snow did develop across the CWA • But did it occur along the south shore where we all thought it would?????

24. Water Vapor Image06 UTC, 7 Feb 03

25. Water Vapor Image12 UTC, 7 Feb 03

26. Composite 4-panel - LocalLAPS Valid 12 UTC 7 Feb 03Frontogenesis is displaced to the northwest!

27. Composite 4-panel - LocalLAPS Valid 16 UTC 7 Feb 03Corridor moving right across the CWA!

28. 16Z Visible ImageNote the “Convective” look to the cloud pattern!

29. WSR-88D Base Reflectivity WFO BOX Valid Time: 14 UTC through 17 UTC