1. The Rapid Evolution of Convection Approaching New York City and Long Island Michael Charles and Brian A. Colle Institute for Terrestrial and Planetary Sciences SUNY at Stony Brook Secondary Author: Jeffrey Tongue NOAA/NWS Upton, NY

2. Probability of Detection (POD) in % – Warned events/total events (Svr tstm/torn.) ALY, BOX, OKX, and PHI Warnings from 1/1/1986 – 10/16/2003

3. False Alarm Rate (FAR) in % – Unverified warnings/total warnings (Svr tstm/torn.) ALY, BOX, OKX, and PHI Warnings from 1/1/1986 – 10/16/2003

4. Motivational Questions What is the thunderstorm distribution over the coastal Northeast? How do severe thunderstorms evolve as they approach the coast? Does the evolution of severe convection change as the sea surface temperatures warm during the summer? How well can mesoscale models forecast these convective events?

5. Outline Climatology: –Severe thunderstorm/tornado reports. –Lightning climatology. Results: –Results of lightning climatology. Case study (18 May 2000): –Squall line evolution. –NWP model simulation of case study.

6. Severe thunderstorm/tornado reports per 100 km 2 per 1 million people Storm reports from 1/1/1950 to 10/31/2002

7. CG Lightning Strike Data National Lightning Detection Network (NLDN) –Global Atmospherics CG lightning to represent convection over NE (similar to Wasula et al 2002) June vs. August convection (2000-2002) 5-7° C difference in sea-surface temp.

8. NLDN sensor locations in the US

9. Sea Surface Temperatures 15 June 200015 August 2000

10. Grid domain

11. Objective Analysis Routine

12. June Density – 2000-2002 - strikes per 100 km 2

13. August Density – 2000-2002 - strikes per 100 km 2

14. June Lightning Hours – 2000-2002

15. August Lightning Hours – 2000-2002

16. Case Study – 18 May 2000 Squall Line Event# of eventsMost severe Lightning5NA Hail91” Wind80126 mph Flash Flood2NA Funnel Cloud1NA Tornado2F2 Total Storm Reports 18 May 2000 through 19 May 2000 Total of 99 storm reports across southern New England The only warned county that didn’t verify was Nassau county, LI. The only damage report in Suffolk county LI was a downed tree.

17. 18 May 2000 1200 UTC Surface Analysis

18. Temperature (every 2° F) Analysis 18 May 2000 18 UTC

19. .5° reflectivity loop – 20 UTC 18 May 2000 to 02 UTC 19 May 2000

20. Above: 21:36 UTC reflectivity indicating cross section. Top Right: Reflectivity cross section showing vertical storm structure. Right: Velocity cross section.

21. Left: 23:33 UTC reflectivity indicating cross section. Above: Cross section showing vertical storm structure.

22. 18 May 2000 Lightning Distribution

23. 18 May 2000 2100 UTC Soundings (9-hr Eta model forecast) KOKX (Brookhaven, NY)KPOU (Poughkeepsie, NY)

24. Eta CAPE – 9-hr forecast valid 21 UTC

25. MM5 description 36, 12, and 4 km domains. Initialized with GFS at 0000 UTC 18 May 2000. Ran 36/12 km MM5 with Grell convective parameterization, explicit only in 4 km domain.

26. Model Verification – Surface Temperature 1800 UTC 18 May 2000 4km MM5 (hr-18) – MSLP and T (°C) Surface Analysis

27. Model Verification – Precipitation 1800 UTC 18 May 2000 Reflectivity Mosaic 12km SBU MM5 – MSLP and 1-hr precip.

28. Model Verification – Precipitation 2200 UTC 18 May 2000 Reflectivity4km SBU MM5 – MSLP and 1-hr precip.

29. MM5 CAPE

30. Future Work Need to better understand the model difficulties in forecasting squall lines over the NE (MM5 rarely has them under weak to moderate CAPE; this is not an Oklahoma environment!!) With a good simulation, one can diagnose three-dimensionally the rapid evolution of severe convection approaching the coast.

31. References NLDN Details: –http://ghrc.msfc.nasa.gov/uso/readme/gai.htmlhttp://ghrc.msfc.nasa.gov/uso/readme/gai.html Wasula, Alicia C., Bosart, Lance F., LaPenta, Kenneth D. 2002: The Influence of Terrain on the Severe Weather Distribution across Interior Eastern New York and Western New England. Weather and Forecasting: Vol. 17, No. 6, pp. 1277–1289.

32. The End

33. Small-scale Interannual Variability June 2000 DensityJune 2001 DensityJune 2002 Density

34. Small-scale Interannual Variability August 2000 DensityAugust 2001 DensityAugust 2002 Density

35. Velocity Cross Section