Twenty-Three Foot Waves on Lake Twenty-Three Foot Waves on Lake Michigan! Examining Storm Events Michigan! Examining Storm Events

on the Lakeon the LakeMike Bardou and Kevin Birk

Courtesy Mike Bardou

High Impact Wind Events across Lake MI during Fall of 20111. September 29-30th Clipper2. October 20th Ohio Valley Low

Both events produced high end Gale to Storm force winds.

Were “High profile events” as significant waves from these storms caused major impacts to the Chicago area shorelines.

Motivation

1. Increase forecast understanding of these High impact and High Profile wind events across Lake Michigan

2. Better understand and predict the impacts not only to mariners, but also to bystanders onshore.

Low Pressure deepened to 992 mb as it dropped southeastward across the Upper Great Lakes

High pressure around 1028 mb built in across the plains

Rapid increase in Northerly winds across Lake Michigan on the evening of the 29th.

The September 30th Clipper

12 UTC Sep 29th 00 UTC Sep 30th

300 MB Jet and Surface 300 MB Jet and Surface

06 UTC Sep 30th 12 UTC Sep 30th

Big players in rapid onset of Storm Force Winds.oA strong and very fast moving system produced isallobaric pressure rises around 8-12 mb in 6 hours across Lake Michigan oLow Level cold air advection around 5º Celsius in 4 hours.

07 UTC September 30th South Buoy

Water Temp: 15º - 16º C850 mb Temp: 3º C900 mb Temp: 9º C

Forecasts For Sept 29-30th Headlines for Gale watch first issued at 3:00

PM Tuesday 9/27 Gale watch for winds to 40 to 45 kt Waves 15 to 20 ft.

Headlines upgraded to Storm Watch at 3:00 AM 9/28. Storm force winds to 50 kt. Waves 14 to 20 ft.

Storm warning issued at 3:12 PM 9/28. Storm winds to 50 kt increased to 55 kt the morning of the

29th. Waves 14 to 20 ft increased to 20 to 25 ft the morning of

the 29th.

Forecasts For Sept 29-30th Headlines for Coastal Flood Warning

Issued For Porter County Indiana the morning of 9/29 Waves 15 to 20 ft for the Indiana Shores. Waves 12 to 16 ft for the Illinois Shores (No Coastal

Flood product issued other than for rip currents).

Courtesy Mike Bardou

North Half Observations Winds quickly increased to Storm Force during the

evening on the 29th as the surface low passed across the lake.

North winds gusted up to 48 knots from 02 to 05 UTC at the north buoy.

Manistee Harbor, MI peaked at 56 knots a couple hours later.

Winds slowly weakened overnight, but remained near Storm force through the morning on the 30th.

South Half Observations Winds increased to Storm Force during the late

evening on the 29th as the surface low and cold front passed across southern LM.

Northwest winds gusted to 47 knots at the south buoy.

Highest period of winds from 04 to 14 UTC. Total of 19 (9) hours of Gale force (40 kt) and

stronger winds at south buoy. South Haven, MI peaked to 59 knots.

3432

3456

59

62 5246

44

39

34

4038

48

465248

59

47

36

3353

56

44

39

Peak Winds 9/30/2011

49

47

47

Knots

Wave Height Significant wave heights at the south buoy peaked at

23 feet at 08 UTC on the 30th (approximately 6 hours after the onset of north storm force at the north buoy).

*25

*14

* 6 hours of wave data likely above 14 ft missing.

*10

Tug boat reported 24-27 ft waves coming over the Burns Harbor

breakwall 9/30 AM

4-5 ft waves

Courtesy Mike Bardou

Estimated Wave Heights

Courtesy Doug Stukey

Chicago lake front bike path impactshttp://www.youtube.com/watch?v=DP2AfyGMUFE

Calumet Harbor Water Level

Damage in the Chicago Area

October 19th–20th Storm

An energetic upper level trough across the central U.S. produced a strong southerly upper level jet across the eastern states.

Surface low pressure across the southeast U.S. rapidly deepened during the afternoon and evening of the 19th.

As the surface low began to occlude, it moved north northwestward across northern OH and to far southeast MI by the morning of the 20th.

12 UTC Oct 19th 00 UTC Oct 20th

300 MB Jet and Surface 300 MB Jet and Surface

06 UTC Oct 20th 12 UTC Oct 20th

Big players in onset of Storm Force Winds.-The strong pressure gradient (~50 µb/km) that set up as the low retrogressed westward.-1021 mb high across the plains with a 985 mb low across southeastern MI.

09 UTC October 20th South Buoy

Water Temp: 11º C850 mb Temp: 1º C900 mb Temp: 4º C

Forecasts For Oct 19-20th

Headlines for Gale watch first issued at 2:57 PM 10/17 Gale watch for winds to 45 kt Waves 15 to 20 ft.

Headlines upgraded to Storm Watch at 2:44 AM 10/18. Storm force winds to 50 kt. Waves 15 to 20 ft.

Storm warning issued at 2:40 PM 10/18. Storm winds to 50 kt. Waves 20 to 25 ft.

Forecasts For Oct 19-20th

Headlines for Coastal Flood Warning Issued For The Illinois and Indiana shores at 1:58 PM 10/18 Waves 20 to 25 ft for the Indiana Shores. Waves 17 to 22 ft for the Illinois Shores.

Observations Winds increased during the afternoon and evening of

the 19th. Peak winds occurred between 04 and 12 UTC. Total of 24 (15) hours of Gale force (40 kt) and

stronger winds at south buoy. Wave data missing during peak winds at the south

buoy. Peak (recorded) wave heights hit 19 Feet at 1050

UTC – missing data during peak wind period (5th highest on record for LM).

*32

* 11 hours of wave data likely above 10 ft missing

*26

*19

*11

Observations Strong dependency on fetch for significant winds. Near shore observations indicated a significant

decrease in the wind magnitude as the wind direction shifted offshore.

Strong Decrease as winds shifted off land

46

57

5351

54

4654

51

Peak Winds 10/20/2011

39

45

43

Knots

35-40

45-50

6-7 ft

~8 ftShip Reports

History of the Largest Waves on Lake Michigan

Top events by max wave height indicate near storm force winds* in all cases of waves over 16 feet.

All events except one produced favorable fetches for high waves at each buoy.

North Buoy North Buoy

YearYearWind Wind

Direction Direction RangeRange

Max Wind Max Wind Speed (KT)Speed (KT)

Max Wave Max Wave (FT)(FT)

2010 119-246119-246 4848 21.621.61991 MissingMissing MissingMissing 19.419.41979 12/15 205-226205-226 4343 17.717.71979 12/3 194-249194-249 4444 17.117.11993 166-232166-232 4444 17.117.12001 188-216188-216 4343 16.316.3

South Buoy South Buoy

YearYearWind Wind

DirectionDirectionRangeRange

Max Wind Max Wind Speed (KT)Speed (KT)

Max Max Wave (FT)Wave (FT)

Max Max Wave Wave

DirectionDirection2011 9/30 215-351215-351 4747 23.123.1 3583581998 112-266112-266 5454 20.320.3 2282282011 10/20 310-37310-37 4545 19.219.2 0100101989 326-358326-358 4444 18.418.4 MissingMissing2005 176-339176-339 4242 17.417.4 3583581983 340-36340-36 3636 17.417.4 MissingMissing2000 224-40224-40 4343 17.117.1 358358

Fetch only 50 to 60 miles

History of the Largest Waves on Lake Michigan

Top 10 events by max wave height at the south buoy indicate an average of 13.3 hours of Gales and 22.5 hours of waves over 10 Feet.

Gust to Sustained Wind Speed Difference

Wind Gusts in excess of gale force show between 21 and 29 % increase over the sustained wind speed over the Lake.

Over land the percentage increase of gusts is between 43 and 63%.

Lessons Learned

Do not necessarily need tremendously deep low to generate significant wind events on the lake - gradient - isallobaric component – deepening and fast moving

systems - instability amidst strong low/mid level wind field

Are forecast winds ~25% less than your gusts? If not, your wave forecast may be adversely affected.

Gain knowledge of wind/wave thresholds along the shoreline.

These thresholds can be used for warning and decision support services to assess the threat to bystanders and property along the shore.

Questions??

Thank you!

Courtesy Mike Bardou

Courtesy Kevin Birk