the persistence and dissipation of lake michigan-crossing mesoscale convective systems
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The Persistence and Dissipation of Lake Michigan-Crossing
Mesoscale Convective Systems
Nicholas D. Metz* and Lance F. Bosart#
* Department of Geoscience, Hobart and William Smith Colleges# Department of Atmospheric and Environmental Sciences,
University at Albany
E-mail: nmetz@hws.edu
Support Provided by the Provost Office at Hobart and William Smith Colleges
20th Great Lakes Operational Meteorology Workshop
Chicago, IL
14 March 2012
Acknowledge:
Daniel Keyser and Ryan Torn – University at Albany
Neil Laird – Hobart and William Smith Colleges
Morris Weisman – NCAR
Motivation
MCS 1
MCS 2
MCSs Crossing Lake Michigan
Johns and Hirt (1987)Laing and Fritsch (1997)
Frequency of Derechos
MCC Occurrences
MCSs Crossing Lake Michigan
Graham et al. (2004)
68%24%
8%
Purpose
• Present a climatological and composite analysis of MCSs that encountered Lake Michigan
• Describe two MCSs, one that persisted and one that dissipated while crossing Lake Michigan, and place them into the context of the composites
• Discuss two simulations of the persisting MCS to identify the effects of Lake Michigan
MCS Selection Criteria
• MCSs in this study:– are from the warm seasons (Apr–Sep) of 2002–2007– are ≥[100 50 km] on NOWrad composite reflectivity
imagery– contain a continuous region ≥100 km of 45 dBZ echoes – meet the above criteria for >3 h prior to crossing Lake
Michigan
• 47 out of 110 (43%) MCSs persisted upon crossing Lake Michigan
3.0°C 4.4°C 10.8°C 18.9°C 21.6°C 19.1°C
Monthly Climatological Distributionsn=110
LM LWT Climo
12
2121
17
28
11
43% = Persist 57% = Dissipate
Hourly Climatological Distributionsn=110
21
14 1719
12 117 9
Synoptic-Scale Composites
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
Dynamic vs. Progressive
Dynamic Progressive
Johns (1993)
Dynamic Persist vs. Dissipate
Persist Dissipate
200-hPa Heights (dam), 200-hPa Winds (m s-1), 850-hPa Winds (m s-1)
n=17 n=31m s−1
m s−1
200-hPa
850-hPa
Dynamic Persist vs. DissipateCAPE (J kg-1), 0–6 km Shear (m s-1)
Persist Dissipate
n=17 n=31
J kg−1CAPE
Real Data Case Studies
7–8 June 2008 - persist
4–5 June 2005 - dissipate
Case Studies
Source: SPC Storm Reports
MCS 2105 UTC 7 June 08 - persist
Source: UAlbany Archive
1600 UTC 4 June 05 - dissipate
MCSSource: NOWrad
Composites
Source: UAlbany Archive
MCS
MCS
Source: NOWrad Composites
2304 UTC 7 June 08 - persist
1800 UTC 4 June 05 - dissipate
Source: UAlbany Archive
MCS
MCS
Source: NOWrad Composites
0001 UTC 8 June 08 - persist
1900 UTC 4 June 05 - dissipate
Source: UAlbany Archive
MCS
MCS
Source: NOWrad Composites
0104 UTC 8 June 08 - persist
2000 UTC 4 June 05 - dissipate
Source: UAlbany Archive
MCS
Source: NOWrad Composites
0302 UTC 8 June 08 - persist
2200 UTC 4 June 05 - dissipate
23
26
26
23
20
2932
29
26
32
0408
12
1618
2000 UTC 7 June 08 - persist
SLP (hPa), Surface Temperature (C), and Surface Mixing Ratio (>18 g kg-1)
Source: UAlbany Archive
MCS
20
23
26
29
04
08
12
16
02
Source: UAlbany Archive
MCS
1800 UTC 4 June 05 - dissipate
SLP (hPa), Surface Temperature (C), and Surface Mixing Ratio (>18 g kg-1)
0000 UTC 8 June 08 - persist
Source: 20-km RUC
2100 UTC 4 June 05 - dissipate200-hPa Heights (dam), 200-hPa Winds (m s-1), 850-hPa Winds (m s-1)
CAPE (J kg-1), 0–6 km Shear (m s-1)
0000 UTC 8 June 08 - persist 2100 UTC 4 June 05 - dissipate
Source: 20-km RUC
Tair, Twater, p
Buoy 45007
T=6.2°C
Source: NDBC
Buoy meteogram
hPa
20Z/07 22Z/07 00Z/08 02Z/08
14
10
6
18
1006
1008
1010
1012
°C
Tair, Twater, pBuoy 45007
T=2.1°C
Source: NDBC
hPa
12Z/04 18Z/04 20Z/04 22Z/04
14
10
6
18
1006
1008
1010
1012
16Z/0414Z/04
°C
Persist
Dissipate
WRF Modeling Results
Model Configuration
• WRF–ARW v.3.2, initialized at 1200 UTC• NARR initialization and boundary conditions• 4-km domain with explicit convection• MYJ PBL and WSM6 microphysics schemes
Control Run No Lake Michigan
Water converted into land with properties consistent
with surrounding land surface
2000 UTC 07 June 08 – 8-h forecast Surface Temperature (°C) and Wind (m s−1)
Control Run No Lake Michigan
No Marine Cold Pool
2500 J kg−1 4500 J kg−1
MUCAPE
Simulated Reflectivity (dBZ), SLP (hPa), and 2-m Wind (m s−1)
Control Run No Lake Michigan
2000 UTC 07 June 08 – 8-h forecast
1012 10121004 1004
Actual Radar
Control Run No Lake Michigan
2200 UTC 07 June 08 – 10-h forecast
10121012
1004
1004
Simulated Reflectivity (dBZ), SLP (hPa), and 2-m Wind (m s−1)
Control Run No Lake Michigan
0000 UTC 08 June 08 – 12-h forecast
10121012
1004
1004
Enhanced Convection
Actual Radar
Simulated Reflectivity (dBZ), SLP (hPa), and 2-m Wind (m s−1)
Control Run No Lake Michigan
0200 UTC 08 June 08 – 14-h forecast
10121012
1004
1004
Simulated Reflectivity (dBZ), SLP (hPa), and 2-m Wind (m s−1)
Difference between No Lake Michigan and Control Simulations 15-h Total Accumulated Precipitation Difference (mm)
1200 UTC 7 June – 0300 UTC 8 June
Concluding Discussion
• MCS that dissipated progressed into a less favorable synoptic-scale environment and was associated with a weaker near-surface inversion than MCS that persisted
MCS
Concluding Discussion
• MCS that dissipated progressed into a less favorable synoptic-scale environment and was associated with a weaker near-surface inversion than MCS that persisted
• WRF simulations suggest that MCS persistence was primarily a function of the large-scale environment, with Lake Michigan modulating MCS strength within favorable large-scale envelope.
Conclusions – 11 July 11
• 200-hPa jet
• 850-hPa LLJ
• Downstream CAPE
• Over-lake inversion
✔
✔
✔
Buoy air temperature = 21.0°C
Buoy water temperature = 18.9°C
Inversion Strength = 2.1°C
✔
Conclusions – Broader Implications
Walters et al. (2008) Riemann-Campe (2009)
Extra Slides
Areal Coverage >45 dBZ
I II IIIIII
0
Areal Coverage >45 dBZ
0
I II IIIIII
Lake Interactions
LWA – South Haven
2130 Z 2200 Z
T, Td, p
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