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

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?

Lake Breeze Example

Adapted from Keen and Lyons (1978)

Return Flow400-2000 m

LB Inflow 100-1000 m

(water)

Climatology Results

n=70

Climatology Results

n=70

0000 UTC 30 July – 0600 UTC 31 July 2006

Case Study: 30 July 2006

Blue Dots: Wind Reports

Green Dots: Hail Reports

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

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

IR

0915 UTC 29 July

0900 UTC 29 July

Contours every 3 ºC

21 ºC contour

IR

1200 UTC 29 July

1215 UTC 29 July

Contours every 3 ºC

21 ºC contour

IR

1500 UTC 29 July

1515 UTC 29 July

Contours every 3 ºC

21 ºC contour

IR

1800 UTC 29 July

1815 UTC 29 July

Contours every 3 ºC

21 ºC contour

IR

2100 UTC 29 July

2115 UTC 29 July

Contours every 3 ºC

21 ºC contour

IR

0000 UTC 30 July

0015 UTC 30 July

Contours every 3 ºC

21 ºC contour

IR

0300 UTC 30 July

0315 UTC 30 July

Contours every 3 ºC

21 ºC contour

IR

0600 UTC 30 July

0615 UTC 30 July

Contours every 3 ºC

21 ºC contour

IR

0900 UTC 30 July

0915 UTC 30 July

Contours every 3 ºC

21 ºC contour

IR

1200 UTC 30 July

1215 UTC 30 July

Contours every 3 ºC

21 ºC contour

20–km RUC

250 hPa ‒ 0000 UTC 30 July

Height (m), Wind Speed (m s −1), and Winds (m s −1)

m s −1

20–km RUC

250 hPa ‒ 0000 UTC 30 July

Height (m), Wind Speed (m s −1), and Winds (m s −1)

m s −1

20–km RUC

850 hPa ‒ 1200 UTC 29 July

Height (m), Wind (m s−1), θe (K), and θ (K)

K

20–km RUC

850 hPa ‒ 0000 UTC 30 July

Height (m), Wind (m s−1), θe (K), and θ (K)

K

MPX ‒ 0000 UTC 30 July

Red – observed Blue – RUC20

20–km RUC

850 hPa ‒ 0600 UTC 30 July

Height (m), Wind (m s−1), θe (K), and θ (K)

K

20–km RUC

850 hPa ‒ 1200 UTC 30 July

Height (m), Wind (m s−1), θe (K), and θ (K)

K

20–km RUC

CAPE/Shear ‒ 0000 UTC 30 July

CAPE (J kg−1) and 1000‒700 hPa Shear (m s−1)

J kg −1

20–km RUC

CAPE/Shear ‒ 0600 UTC 30 July

CAPE (J kg−1) and 1000‒700 hPa Shear (m s−1)

J kg −1

20–km RUC

CAPE/Shear ‒ 1200 UTC 30 July

CAPE (J kg−1) and 1000‒700 hPa Shear (m s−1)

J kg −1

1º GFS

850 hPa ‒ 0000 UTC 30 July

Q-vec, Q-vec convergence, Height (dam), Temperature (ºC)

∙∆

Q

1º GFS

850 hPa ‒ 0600 UTC 30 July

Q-vec, Q-vec convergence, Height (dam), Temperature (ºC)

∙∆

Q

1º GFS

850 hPa ‒ 1200 UTC 30 July

Q-vec, Q-vec convergence, Height (dam), Temperature (ºC)

∙∆

Q

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

1500 UTC 29 July 2006

Surface Wind (kt), θ (K), Radar (dBZ)

0000 UTC 30 July 2006

Surface Wind (kt), θ (K), Radar (dBZ)

0600 UTC 30 July 2006

Surface Wind (kt), θ (K), Radar (dBZ)

0600 UTC 30 July 2006

Surface Wind (kt), θ (K), Radar (dBZ)

Temperature (oC)

29/06 29/12 29/18 30/00 30/06 30/12

Wind (kt)

EAU HYR ASX 45006

Temperature (oC)

29/06 29/12 29/18 30/00 30/06 30/12

Wind (kt)

EAU HYR ASX 45006

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

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

RUCWRF 6-h forecast

Height (m), Wind (m s−1), θe (K), and θ (K)

850 hPa ‒ 0600 UTC 30 July

K

RUCWRF

Height (m), Wind (m s−1), θe (K), and θ (K)

850 hPa ‒ 0900 UTC 30 July

K

WRF 9-h forecast

ObservedWRF

Surface Wind (kt), Reflectivity (dBZ), and θ (K)

Surface ‒ 0300 UTC 30 July

WRF 3-h forecast

ObservedWRF

Surface Wind (kt), Reflectivity (dBZ), and θ (K)

Surface ‒ 0600 UTC 30 July

WRF 6-h forecast

ObservedWRF

Surface Wind (kt), Reflectivity (dBZ), and θ (K)

Surface ‒ 0900 UTC 30 July

WRF 9-h forecast

ObservedWRF

Surface Wind (kt), Reflectivity (dBZ), and θ (K)

Surface ‒ 1200 UTC 30 July

WRF 12-h forecast

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

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: srock@atmos.albany.edu