1 / 35

The Rapid Evolution of Convection Approaching the New York City Metropolitan Region

The Rapid Evolution of Convection Approaching the New York City Metropolitan Region. Brian A. Colle and Michael Charles Institute for Terrestrial and Planetary Sciences SUNY at Stony Brook.

lorie
Télécharger la présentation

The Rapid Evolution of Convection Approaching the New York City Metropolitan Region

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Rapid Evolution of Convection Approaching the New York City Metropolitan Region Brian A. Colle and Michael Charles Institute for Terrestrial and Planetary Sciences SUNY at Stony Brook

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

  3. 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?

  4. Sea Surface Temperatures 15 June 2000 15 August 2000

  5. Severe thunderstorm/tornado reports per 100 km2 per 1 million peopleStorm reports from 1/1/1950 to 10/31/2002

  6. Lightning Climatology using NLDN sensor data (2000-2002)

  7. Analysis Approach

  8. June Density – 2000-2002 - strikes per 100 km2

  9. August Density – 2000-2002 - strikes per 100 km2

  10. June Lightning Hours – 2000-2002

  11. August Lightning Hours – 2000-2002

  12. Case Study – 18 May 2000 Squall Line 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.

  13. 18 May 2000 1200 UTC Surface Analysis

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

  15. .5° reflectivity loop – 20 UTC 18 May 2000 to 02 UTC 19 May 2000

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

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

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

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

  20. MM5 Simulation • 36, 12, and 4 km domains, centered over the Northeast U.S. • Initial and boundary conditions from the GFS run at 0000 UTC 18 May 2000. • Ran MM5 with the Grell convective parameterization (36/12 km), simple ice, and MRF PBL.

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

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

  23. Model Verification – Precipitation 2200 UTC 18 May 2000 Reflectivity 4km SBU MM5 – MSLP and 1-hr precip.

  24. Summary and Future Work • Convection weakens rapidly approaching the NYC metropolitan region during the spring and early summer, resulting in high false alarms rates for the NWS. • The weakening occurs as convection encounters the cool marine boundary layer as evidenced by a lightning composite and case study. • Need to better understand this coastal marine interaction before quantifying localized urban-scale effects. • There are model difficulties in forecasting squall lines over the NE. MM5 rarely has them correct under weak to moderate CAPE.

  25. The End

  26. References • NLDN Details: • http://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.

  27. 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

  28. MM5 CAPE

  29. 18 May 2000 Lightning Distribution

  30. Grid domain

  31. 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.

  32. Small-scale Interannual Variability June 2000 Density June 2001 Density June 2002 Density

  33. Small-scale Interannual Variability August 2000 Density August 2001 Density August 2002 Density

  34. Velocity Cross Section

  35. 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.

More Related