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Evolution of Severe Convection in the New York City Region

Evolution of Severe Convection in the New York City Region. Brian A. Colle, Kelly Lombardo, and John Murray School of Marine and Atmospheric Sciences Stony Brook University - SUNY Bill Goodman, Jeffrey Tongue, and Nelson Vaz National Weather Service, Upton, NY. Photo: 7 July 1976.

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Evolution of Severe Convection in the New York City Region

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  1. Evolution of Severe Convection in the New York City Region Brian A. Colle, Kelly Lombardo, and John Murray School of Marine and Atmospheric Sciences Stony Brook University - SUNY Bill Goodman, Jeffrey Tongue, and Nelson Vaz National Weather Service, Upton, NY Photo: 7 July 1976

  2. What are large-scale conditions favoring severe (tornadic) convective weather? • How does convection evolve in this coastal urban environment? • Importance of Mesonet and radars (TDWRs). *

  3. Tornado climo Sharp Gradient in Severe Convection Near Coast NOWRAD Refl > 45 dBZ counts (1996-2007) for Severe Weather Days for Boxed region Tornado Tracks (1950-2006) * * Source: SPC

  4. Tornado Climatology for NYC and Long Island (1950-2007 – 32 events) Hourly Distribution Monthly Distribution

  5. New York Daily News 1 2 * * * 8 August 2007 NYCEF2 Tornado 1022-1050 UTC (0622-0650 EDT) * * * * * Brooklyn Staten Is.

  6. 0600 UTC 7 August 2007 X RUC 950 mb Winds, potential temps, and frontogenesis K/100km/3hr *10-1

  7. 3: 1300Z 8/7 August 7-8 2007 Storm Reports 4 0600Z 8/7 4: 1600Z 8/7 2 6 7 1 3 1000Z 8/8 1300Z 8/7 5: 2300Z 8/7 6: 0600Z 8/8 7:1000Z 8/8

  8. 1500 UTC 7 August 2007 700 mb Q-vector (shaded = convergence) RUC 950 winds, theta, Frontogenesis Convection over W PA weakens as it moves into a region of subsidence and weak frontogenetical forcing K/100km/3hr *10-1

  9. 0300 UTC 8 August 2007 950 winds, theta, Frontogenesis 700 mb Q-vector Frontogenetical forcing and QG ascent increases during the evening hours over PA K/100km/3hr *10-1

  10. 0700 UTC 0930 UTC 0900 UTC 0800 UTC Surface 06 UTC 8 Aug KDIX dBZ (06 Z 8 Aug) 07 L * L 08 DIX 26 24 25 26 28 09

  11. Surface 10 UTC 8 Aug KDIX dBZ (10 Z 8 Aug) 23 05 06 * 24 DIX * 24 L 09 07 08 25 27

  12. Newark, NJ (EWR) ACARS 1500 J/kg 0830 UTC 8 Aug 0500 UTC 8 Aug RUC 0300 UTC vs 0900 UTC 03Z 03Z

  13. RUC Max CAPE (lowest 180 mb), 925 mb V, ThetaE 0000 UTC 8 Aug 0600 UTC 8 Aug 0900 UTC 8 Aug * * * • Increase in CAPE along the coast and development of a low-level jet.

  14. Evolution From Staten Is. To Brooklyn JFK TDWR 1028 UTC DIX 88-D 1026 UTC *

  15. Vortex Evolution: TJFK (storm rel vel) 2 1 * * * * * * * * * • Tornado develops on north shore of Staten Island, weakens as it crosses Staten Island, and new one develops to NE strengthens after vortex merger and landfall at Brooklyn. * Radar Meso * EF 0-1 * EF2

  16. TJFK 1020Z-1029Z SRV • Intensifying tornadic circulation moves across northern Staten Island • Aliasing in SRV couplet at 1022Z - intense tornadic winds? • First tornado weakens/dissipates over Tompkinsville, then a second tornado develops near the northeast tip of Staten Island by 1027Z and crosses the Narrows toward Brooklyn

  17. TJFK 1030Z-1041Z SRV • Tornado causes EF-2 damage as it moves across Bay Ridge, Kensington, and Flatbush sections of Brooklyn • More aliasing in SRV couplet indicative of intense tornadic winds

  18. Benefit of TDWR Radar TJFK 1030 UTC DIX 88-D 1030 UTC

  19. Composite of 18 LI/NYC Tornado Events (1979-2007) Using NARR (32-km) * 300 mb WindSpeed, 700-mb Z and omega

  20. Composite of 18 Events (1979-2007)1000-mb Z, thetaE, V; sfc CAPE *

  21. Summary • NYC-Long Island tornadoes are most frequent during late summer (August) and can occur from early AM to early evening (1000-0000 UTC). • 7-8 August 2007 NYC tornado event had origins as a MCS over the Plains 30 h earlier along a W-E baroclinic zone. • Convection intensified in a region of large frontogenetical forcing, a nose of higher thetaE along the coast, and development of a LLJ. • Elevated mixed layer and the subsequent diabatic cooling from precipitation was likely important in destabilizing low levels. • There was rapid vortex evolution around Staten Island. (Role of the hills and land-water gradients??)

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