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MCS Organization and Development Along Land/Lake-
Induced Thermodynamic Boundaries near Lake Superior
Alan F. Srock and Lance F. BosartDept. of Atmospheric and Environmental Sciences
University at Albany/SUNY, Albany, NY
12th Northeast Regional Operational WorkshopCESTM, Albany, NY3-5 November 2010
Supported by NSF Grant #ATM-0646907
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Motivation
• Intense, warm-season convection often depends on the location of low-level boundaries
• Natural thermodynamic boundaries often occur near the Great Lakes
• Big question: How can boundaries near the Great Lakes affect the formation and evolution of MCSs?
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Lake Breeze Example
Adapted from Keen and Lyons (1978)
Return Flow400-2000 m
LB Inflow 100-1000 m
(water)
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Climatology Results
n=70
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Climatology Results
n=70
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0000 UTC 30 July – 0600 UTC 31 July 2006
Case Study: 30 July 2006
Blue Dots: Wind Reports
Green Dots: Hail Reports
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1-h total precipitation (mm) from Stage IV data ending
0800 UTC 30 July 2006
Precipitation Comparison
6-h Eta forecast precipitation (mm) ending 0900 UTC from 0000 UTC 30 July 2006 run
mm
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1-h total precipitation (mm) from Stage IV data ending
0800 UTC 30 July 2006
Precipitation Comparison
6-h Eta forecast precipitation (mm) ending 0900 UTC from 0000 UTC 30 July 2006 run
mm
W
E
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IR
0915 UTC 29 July
0900 UTC 29 July
Contours every 3 ºC
21 ºC contour
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IR
1200 UTC 29 July
1215 UTC 29 July
Contours every 3 ºC
21 ºC contour
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IR
1500 UTC 29 July
1515 UTC 29 July
Contours every 3 ºC
21 ºC contour
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IR
1800 UTC 29 July
1815 UTC 29 July
Contours every 3 ºC
21 ºC contour
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IR
2100 UTC 29 July
2115 UTC 29 July
Contours every 3 ºC
21 ºC contour
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IR
0000 UTC 30 July
0015 UTC 30 July
Contours every 3 ºC
21 ºC contour
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IR
0300 UTC 30 July
0315 UTC 30 July
Contours every 3 ºC
21 ºC contour
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IR
0600 UTC 30 July
0615 UTC 30 July
Contours every 3 ºC
21 ºC contour
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IR
0900 UTC 30 July
0915 UTC 30 July
Contours every 3 ºC
21 ºC contour
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IR
1200 UTC 30 July
1215 UTC 30 July
Contours every 3 ºC
21 ºC contour
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20–km RUC
250 hPa ‒ 0000 UTC 30 July
Height (m), Wind Speed (m s −1), and Winds (m s −1)
m s −1
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20–km RUC
250 hPa ‒ 0000 UTC 30 July
Height (m), Wind Speed (m s −1), and Winds (m s −1)
m s −1
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20–km RUC
850 hPa ‒ 1200 UTC 29 July
Height (m), Wind (m s−1), θe (K), and θ (K)
K
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20–km RUC
850 hPa ‒ 0000 UTC 30 July
Height (m), Wind (m s−1), θe (K), and θ (K)
K
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MPX ‒ 0000 UTC 30 July
Red – observed Blue – RUC20
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20–km RUC
850 hPa ‒ 0600 UTC 30 July
Height (m), Wind (m s−1), θe (K), and θ (K)
K
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20–km RUC
850 hPa ‒ 1200 UTC 30 July
Height (m), Wind (m s−1), θe (K), and θ (K)
K
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20–km RUC
CAPE/Shear ‒ 0000 UTC 30 July
CAPE (J kg−1) and 1000‒700 hPa Shear (m s−1)
J kg −1
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20–km RUC
CAPE/Shear ‒ 0600 UTC 30 July
CAPE (J kg−1) and 1000‒700 hPa Shear (m s−1)
J kg −1
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20–km RUC
CAPE/Shear ‒ 1200 UTC 30 July
CAPE (J kg−1) and 1000‒700 hPa Shear (m s−1)
J kg −1
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1º GFS
850 hPa ‒ 0000 UTC 30 July
Q-vec, Q-vec convergence, Height (dam), Temperature (ºC)
∙∆
Q
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1º GFS
850 hPa ‒ 0600 UTC 30 July
Q-vec, Q-vec convergence, Height (dam), Temperature (ºC)
∙∆
Q
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1º GFS
850 hPa ‒ 1200 UTC 30 July
Q-vec, Q-vec convergence, Height (dam), Temperature (ºC)
∙∆
Q
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Synoptic Overview
• Large-scale conditions favorable for MCS formation, but eastern MCS did not develop until reaching lake boundary
• Ample low-level moisture advected northeastward throughout the period, likely aided by evapotranspiration
• Thermodynamic boundary persisted over the Northern Plains through the 30th, but not over Wisconsin
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1500 UTC 29 July 2006
Surface Wind (kt), θ (K), Radar (dBZ)
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0000 UTC 30 July 2006
Surface Wind (kt), θ (K), Radar (dBZ)
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0600 UTC 30 July 2006
Surface Wind (kt), θ (K), Radar (dBZ)
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0600 UTC 30 July 2006
Surface Wind (kt), θ (K), Radar (dBZ)
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Temperature (oC)
29/06 29/12 29/18 30/00 30/06 30/12
Wind (kt)
EAU HYR ASX 45006
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Temperature (oC)
29/06 29/12 29/18 30/00 30/06 30/12
Wind (kt)
EAU HYR ASX 45006
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Surface Conclusions
• Two boundaries remained in the wake of the 29 July MCS over central WI:– Southern boundary weakened throughout the
day on cold side of boundary– Northern near-shore boundary remained strong
throughout, aided by natural land/lake temperature gradient
• Eastern part of the next MCS (30 July) organized along northern near-shore boundary at SW edge of Lake Superior
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WRF Modeling Study
• Simulations run to test effect of land/lake boundary on development of convection
• Key details:– Initialized at
0000 UTC 30 July
– 4 km horizontal grid spacing
– Explicit convection
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RUCWRF 6-h forecast
Height (m), Wind (m s−1), θe (K), and θ (K)
850 hPa ‒ 0600 UTC 30 July
K
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RUCWRF
Height (m), Wind (m s−1), θe (K), and θ (K)
850 hPa ‒ 0900 UTC 30 July
K
WRF 9-h forecast
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ObservedWRF
Surface Wind (kt), Reflectivity (dBZ), and θ (K)
Surface ‒ 0300 UTC 30 July
WRF 3-h forecast
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ObservedWRF
Surface Wind (kt), Reflectivity (dBZ), and θ (K)
Surface ‒ 0600 UTC 30 July
WRF 6-h forecast
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ObservedWRF
Surface Wind (kt), Reflectivity (dBZ), and θ (K)
Surface ‒ 0900 UTC 30 July
WRF 9-h forecast
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ObservedWRF
Surface Wind (kt), Reflectivity (dBZ), and θ (K)
Surface ‒ 1200 UTC 30 July
WRF 12-h forecast
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Modeling Conclusions
• WRF simulation resolves key upper-level and synoptic-scale features well
• Near-surface differences between simulation and observations led to differences in reflectivity/precipitation/MCS development
• Better representation of lake-induced near-surface boundaries is likely important for improved forecast of MCS development
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Conclusions
• Near-surface land/lake boundary helped to focus development of the eastern MCS on 30 July
• Eastern MCS did not fully develop until low-level moisture reached near-surface land/lake boundary
• Proper representation of near-surface land/lake boundaries important to improving forecasts of near-lake MCS development
Email: [email protected]