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The Effects of Lake Michigan on Mature Mesoscale Convective Systems

The Effects of Lake Michigan on Mature Mesoscale Convective Systems. 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

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The Effects of Lake Michigan on Mature Mesoscale Convective Systems

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  1. The Effects of Lake Michigan on Mature Mesoscale Convective Systems 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 18th Great Lakes Operational Meteorology Workshop Toronto, Ontario 23 March 2010

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

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

  4. Areal Coverage ≥45 dBZ 0

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

  6. Purpose • Present a climatology 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 the lake if they: • continued to meet the two aforementioned reflectivity criteria • produced at least one severe report Dissipate Persist

  9. Intersection Time after Formation n=110 Dissipate Persist

  10. Monthly Distributions n=110 3.0°C 4.4°C 10.8°C 18.9°C 21.6°C 19.1°C Dissipate Persist

  11. Hourly Distributions (UTC) n=110 Dissipate Persist

  12. Synoptic-Scale Composites • Constructed using 0000, 0600, 1200, 1800 UTC 1° 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

  13. Dynamic vs. Progressive Progressive Dynamic Johns (1993)

  14. 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

  15. 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

  16. Progressive Persist vs. Dissipate 200-hPa Heights (dam), 200-hPa Winds (m s-1), 850-hPa Winds (m s-1) n=30 n=32 m s−1 200-hPa m s−1 850-hPa Persist Dissipate

  17. Progressive Persist vs. Dissipate CAPE (J kg-1), 0–6 km Shear (barbs; m s-1) n=30 n=30 n=32 n=32 J kg−1 CAPE Persist Dissipate

  18. Case Studies 7–8 June 2008 - persist 4–5 June 2005 - dissipate

  19. MCS 2105 UTC 7 June 08 - persist Source: UAlbany Archive 1600 UTC 4 June 05 - dissipate MCS Source: NOWrad Composites

  20. 2304 UTC 7 June 08 - persist MCS Source: UAlbany Archive 1800 UTC 4 June 05 - dissipate MCS Source: NOWrad Composites

  21. 0001 UTC 8 June 08 - persist MCS Source: UAlbany Archive 1900 UTC 4 June 05 - dissipate MCS Source: NOWrad Composites

  22. 0104 UTC 8 June 08 - persist MCS Source: UAlbany Archive 2000 UTC 4 June 05 - dissipate MCS Source: NOWrad Composites

  23. 0302 UTC 8 June 08 - persist MCS Source: UAlbany Archive 2200 UTC 4 June 05 - dissipate Source: NOWrad Composites

  24. 2000 UTC 7 June 08 - persist 26 23 26 23 29 20 29 32 04 26 08 MCS 16 18 12 32 Source: UAlbany Archive SLP (hPa), Surface Temperature (C), and Surface Mixing Ratio (>18 g kg-1)

  25. 1800 UTC 4 June 05 - dissipate 20 MCS 23 26 04 12 29 08 16 Source: UAlbany Archive SLP (hPa), Surface Temperature (C), and Surface Mixing Ratio (>16 g kg-1)

  26. 0000 UTC 8 June 08 - persist 2100 UTC 4 June 05 - dissipate 200-hPa Heights (dam), 200-hPa Winds (m s-1), 850-hPa Winds (barbs; m s-1) Source: 20-km RUC

  27. 0000 UTC 8 June 08 - persist 2100 UTC 4 June 05 - dissipate CAPE (J kg-1), 0–6 km Shear (barbs; m s-1) Source: 20-km RUC Source: 20-km RUC

  28. 4-h  differences at 2300 UTC 7 June 08 - persist 975-hPa ∆(K), 0–3-km Shear (m s-1) ∆ (K),  (K), Wind (m s-1) A 600 700 800 900 cold pool cold pool A’ A A’ A A 1900 UTC 2300 UTC Courtesy: M. Weisman Weisman and Rotunno (2004) A’ A’

  29. 4-h  differences at 2300 UTC 7 June 08 - persist 975-hPa ∆(K), 0–3-km Shear (m s-1) A cold pool cold pool A’ A A’ A 2300 UTC 905 hPa

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

  31. Buoy meteogram 975-hPa ∆ (K), 0–3 km Shear (m s-1) Buoy 45007 Source: NDBC °C hPa T=6.2°C Tair,Twater, p

  32. 2-h  differences at 1900 UTC 4 June 05 - 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’ B B B’ B’ 1900 UTC 1700 UTC

  33. 2-h  differences at 1900 UTC 4 June 05 - dissipate 975-hPa ∆(K), 0–3-km Shear (m s-1) B cold pool cold pool B’ B B’ B 935 hPa

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

  35. Buoy meteogram 975-hPa ∆ (K), 0–3 km Shear (m s-1) °C hPa T=2.1°C Buoy 45007 Tair,Twater, p Source: NDBC

  36. 850-hPa Wind Climatology Differences Significant to 99.9th Percentile n=110 Persist Dissipate Source: NARR

  37. Surface-Inversion Climatology Differences Significant to 95th Percentile T5m - TSfc Weak LLJ Later Season n=110 Persist Dissipate Source: NDBC

  38. Phase Space - Warm Season Dissipate Persist All Months n=110 Source: NARR/NDBC

  39. Dissipate Persist AMJ Phase Space - Early Season n=46 Dissipate Persist JAS Phase Space -Late Season n=64

  40. Conclusions – Climatology • MCSs persisted 43% of the time (47 of 110 MCSs) upon crossing Lake Michigan during warm seasons of 2002–2007 • MCSs persisted and dissipated at a wide range of times after formation • MCSs persisted during all months and hours but favored July and August and evening and overnight • MCSs persisted with stronger 850-hPa winds and near-surface lake inversions, especially from April to July

  41. Conclusions – Composites/Case Studies • Compared to MCSs that dissipated, MCSs persisted in environments that contained: • stronger 200-hPa and 850-hPa jet streams • larger amounts of CAPE and 0–6-km shear • similar looking synoptic-scale patterns • stronger, deeper convective cold pools • more stable marine layers

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