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Nicholas D. Metz and Lance F. Bosart Department of Atmospheric and Environmental Sciences

Synoptic and Mesoscale Conditions associated with Persisting and Dissipating Mesoscale Convective Systems that Cross Lake Michigan. Nicholas D. Metz and Lance F. Bosart Department of Atmospheric and Environmental Sciences University at Albany/SUNY, Albany, NY 12222

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Nicholas D. Metz and Lance F. Bosart Department of Atmospheric and Environmental Sciences

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  1. Synoptic and Mesoscale Conditions associated with Persisting and Dissipating Mesoscale Convective Systems that Cross Lake Michigan Nicholas D. Metz and Lance F. Bosart Department of Atmospheric and Environmental Sciences University at Albany/SUNY, Albany, NY 12222 E-mail: nmetz@atmos.albany.edu Support provided by the NSF ATM–0646907 12th Northeast Regional Operational Workshop Albany, NY 3 November 2010

  2. Motivation 1986 • Great Lakes region is an area of frequent MCS (MCC and derecho) activity • Important to understand MCS behavior upon crossing the Great Lakes MCC Occurrences Frequency of Derechos Johns and Hirt (1987) Augustine and Howard (1991)

  3. NOWrad Areal Coverage ≥45 dBZ III II III I 0

  4. NOWrad Areal Coverage ≥45 dBZ 0

  5. Background 68% 8% 24% Graham et al. (2004)

  6. Purpose • Present a climatological overview of MCSs that encountered Lake Michigan • Examine composite analyses of MCS environments associated with persisting and dissipating MCSs • Describe two MCSs, one that persisted and one that dissipated while crossing Lake Michigan, and place them into context of the climatology and composites

  7. MCS Selection Criteria • Warm Season (Apr–Sep) • 2002–2007 • MCSs in the study: • are ≥(100  50 km) on NOWrad composite reflectivity imagery • contain a continuous region ≥100 km of 45 dBZ echoes • meet the above two criteria for >3 h prior to crossing Lake Michigan 100 km 50 km

  8. Climatology of MCSs n=110 • MCSs persisted upon crossing Lake Michigan if they: • continued to meet the two aforementioned reflectivity criteria • produced at least one severe report

  9. Monthly Climatological Distributions n=110 3.0°C 4.4°C 10.8°C 18.9°C 21.6°C 19.1°C LM LWT Climo

  10. Hourly Climatological Distributions n=110

  11. Synoptic-Scale Composites • Constructed using 0000, 0600, 1200, 1800 UTC 1.0° GFS analyses • Time chosen closest to intersection with Lake Michigan • If directly between two analysis times, earlier time chosen • Composited on MCS centroid and moved to the average position

  12. Dynamic Persist vs. Dissipate 200-hPa Heights (dam), 200-hPa Winds (m s-1), 850-hPa Winds (m s-1) n=17 n=31 m s−1 200-hPa m s−1 850-hPa Persist Dissipate

  13. Dynamic Persist vs. Dissipate CAPE (J kg-1), 0–6 km Shear (barbs; m s-1) n=17 n=31 J kg−1 CAPE Persist Dissipate

  14. 850-hPa Wind Climatology Differences Significant to 99.9th Percentile n=110 Source: NARR

  15. Downstream CAPE/Shear Climatology CAPE Differences Significant to 95th Percentile DTX n=54 Source: UAlbany sounding archive

  16. Case Studies – Bow Echoes 18 June 2010 - persist 24 June 2003 - dissipate 9 out of 13 bow echoes (69%) persisted compared with 47 out of 110 (43%) total MCSs in the climatology

  17. 1800 UTC 18 June 10 - persist MCS Source: UAlbany Archive 1000 UTC 24 June 03 - dissipate Source: NOWrad Composites MCS

  18. 2000 UTC 18 June 10 - persist MCS Source: UAlbany Archive 1200 UTC 24 June 03 - dissipate MCS Source: NOWrad Composites

  19. 2200 UTC 18 June 10 - persist MCS Source: UAlbany Archive 1400 UTC 24 June 03 - dissipate MCS Source: NOWrad Composites

  20. 0000 UTC 18 June 10 - persist MCS Source: UAlbany Archive 1600 UTC 24 June 03 - dissipate Source: NOWrad Composites

  21. 2000 UTC 18 June 10 - persist 04 08 26 20 23 29 32 16 18 12 cold pool boundary SLP (hPa), Surface Temperature (C), and Surface Mixing Ratio (>18 g kg-1)

  22. 1200 UTC 24 June 03 - dissipate 08 20 cold pool boundary 12 18 23 16 20 SLP (hPa), Surface Temperature (C), and Surface Mixing Ratio (>18 g kg-1)

  23. 2200 UTC 18 June 10 - persist 1400 UTC 24 June 03 - dissipate 200-hPa Heights (dam), 200-hPa Winds (m s-1), 850-hPa Winds (barbs; m s-1) Source: 20-km RUC

  24. 2200 UTC 18 June 10 - persist 1400 UTC 24 June 03 - dissipate CAPE (J kg-1), 0–6 km Shear (barbs; m s-1) Source: 20-km RUC

  25. 2-h  differences at 2200 UTC 18 June 10 - persist 975-hPa ∆(K), 0–3-km Shear (m s-1) ∆ (K),  (K), Wind (m s-1) 600 700 800 900 B cold pool cold pool B’ B B’ B B B’ B’ 2000 UTC 2200 UTC

  26. ACARS sounding at 2208 UTC 18 June 10 - persist 975-hPa ∆ (K), 0–3 km Shear (m s-1) B B’ Descent sounding from Madison, WI 900 hPa

  27. Rockford, Illinois meteogram - persist 975-hPa ∆ (K), 0–3 km Shear (m s-1) Source: UAlbany Archive hPa °C T, Td, p

  28. Buoy meteogram - persist 975-hPa ∆ (K), 0–3 km Shear (m s-1) Source: NDBC Buoy 45007 °C Tair,Twater, p hPa T=2.9°C

  29. Lake Interactions 2130 Z 2200 Z T, Td, p LWA – South Haven

  30. 2-h  differences at 1300 UTC 23 June 03 - dissipate 975-hPa ∆(K), 0–3-km Shear (m s-1) ∆ (K),  (K), Wind (m s-1) 600 700 800 900 B cold pool cold pool B’ B B’ 12 Z - GRB B B B’ B’ 1100 UTC 1300 UTC

  31. Oshkosh, Wisconsin meteogram - dissipate 975-hPa ∆ (K), 0–3 km Shear (m s-1) Source: UAlbany Archive T, Td, p hPa °C

  32. Buoy meteogram - dissipate 975-hPa ∆ (K), 0–3 km Shear (m s-1) °C Tair,Twater, p hPa Source: NDBC Buoy 45007 T=3.4°C

  33. Surface-Inversion Climatology Differences Significant to 99th Percentile T5m - TSfc Later Season n=97 Source: NDBC

  34. Conclusions – Climatology/Composite • MCSs persisted 43% of the time (47 of 110 MCSs) upon crossing Lake Michigan during warm seasons of 2002–2007 • MCSs persisted during all months and hours but favored July and August and evening and overnight • MCSs persisted with large downstream CAPE/shear and strong 850-hPa winds and near-surface lake inversions (non-bow echoes) • MCSs persisted with a greater frequency as organizational structure increased

  35. Conclusions – Case Studies • Compared with the MCS that dissipated, the MCS that persisted had: • a deeper, more robust convective cold pool • a near-surface lake inversion of ~equal strength • increased downstream CAPE/shear and a stronger 850-hPa low-level jet stream • In these case studies, (and with other bow echoes in the climatology), persistence/dissipation over Lake Michigan appears to be a function of environmental conditions and NOT interactions with Lake Michigan

  36. Organizational Type n=110 45.7% 33.3% 69.2%

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