the persistence and dissipation of lake michigan-crossing mesoscale convective systems nicholas d....

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: [email protected]

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


MCS

MCS

Source: NOWrad Composites

2304 UTC 7 June 08 - persist



MCS

MCS





MCS




23

26

26

23

20

2932

29

26

32

0408

12

1618


SLP (hPa), Surface Temperature (C), and Surface Mixing Ratio (>18 g kg-1)


MCS

20

23

26

29

04

08

12

16

02


MCS


SLP (hPa), Surface Temperature (C), and Surface Mixing Ratio (>18 g kg-1)


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)


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)


2000 UTC 07 June 08 – 8-h forecast

1012 10121004 1004

Actual Radar



10121012

1004

1004




10121012

1004

1004

Enhanced Convection

Actual Radar




10121012

1004

1004


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

the persistence and dissipation of lake michigan-crossing mesoscale convective systems nicholas d....

Documents

hpa slide

cape slide

crossing lake michigan

effects of lake michigan

ualbany archive mcs

average position slide

motivation mcs

mcs centroid