Slide 1

Analyzing Channel CurrentsNear the Lake Superior Shoreline in Marquette, MI

Presented By: Keith CooleyNational Weather Service-Marquette1OverviewBackground-channel currents, issues and outreach activitiesArea of concern and terrain featuresObservation PlatformsStudy setup/Methodology/Data Acoustical Doppler Current MeterConclusions/ResultsFuture work2Background

3BackgroundPicnic Rocks-Popular beach destination in eastern Marquette, MI15 total since 19637 drownings since 1996Age range-low 20s to upper 40sDays varied (Not specific to holidays)

4Outreach ActivitiesMarquette Water Safety and Recreation ExpoYMCA, NMU, Sea Grant and Marquette Water Safety Task ForceSigns and pamphlets

5Site Location

6Site Location

7Site Location

KNMUMCGM48View from the Shore

9Swimming Distance

10Acoustical Doppler Current MeterMeasures the shift in frequency to measure velocityMeasures velocity at five different layersEach level is 3 feet deepexcept the top layer

11MethodologyData collectionBinning system for wind directionTwo criteria analyzedCompared wind direction with faster channel current speedCompared wind speed and direction with faster channel current speedNormalized to percent of wind direction

12Wind Events Causing Faster Channel Currents (>.50 ft/s) DirectionTotal Events Layer5Layer4Layer3N5011051039NE68881E2336330SE1286170S442781313SW35531670W30724770NW30060840

13Wind Events Causing Faster Channel Currents Based on Direction in Layer 5 Both Sites14Percent of Wind Events Causing Faster Channel Currents Based on Direction in Layer 5 Both Sites15Wind Events Causing Faster Channel Currents Based on Direction in Layer 4 Both Sites16Percent of Wind Events Causing Faster Channel Currents Based on Direction in Layer 4 Both Sites17Wind Events Causing Faster Channel Currents Based on Direction in Layer 3 Both Sites18Percent of Wind Events Causing Faster Channel Currents Based on Direction in Layer 3 Both Sites19Review of DataLayers 4 and 5 show that North, South, and Northwest winds correlated best with faster currentsNorth and South events consistently maintained greater totals of events through the top three layersLayer 3 maintained very few faster current events overall with only North and South events occurring more frequentlyThe bottom two layers (Layer 2 and 1) had very few events that were greater than 0.5 ft/s20When Normalized to PercentagesNorth and South winds had greatest percentages ranging from 13 to 22 percent in layer 5North, Northwest, West and South maintained the highest percentages in layer 4 ranging from 14 to 30 percentWesterly component possibly due to lag time during frontal passageMost were below 1 percent in layer 3 and below21Events That Create Faster Channel Currents with Less Than 10 Knot Wind SpeedsDirectionTotal Events 5Layer5Total Events 4Layer4Total Events 3Layer3N105921039596NE868611E65333100SE65171500S78311317030SW3120675300W2423777600NW6058848400

22Percent of Events for Each Direction in Layer 5 That Created Faster Currents with Less Than 10 Knot Wind Speeds23Percent of Events for Each Direction in Layer 4 That Created Faster Currents with Less Than 10 Knot Wind Speeds24Percent of Events for Each Direction in Layer 3 That Created Faster Currents with Less Than 10 Knot Wind Speeds25ConclusionsMore events occurred with winds from the north and south directions through each layer Possibly give notice of elevated risks when winds are out of the north or southSouthwest, West and Northwest winds also have higher chances of producing faster channel currentsVery few increased current events were identified in Layer 3 and belowMost events occurred with winds less than 10 knotsexcept for south wind events which had equal chances of producing faster currents for both lower and higher wind speedssimilar to studies by Haines and Bryson (1961)26ConclusionsPossibly look into adjusting the location of the current meter due to low speed measurements

27Future WorkAnalyze lag time between increase/decrease in winds or change in direction compared to the increase/decrease in current flowLook at surface weather patterns to determine if there is a relation of specific setups with stronger currentsDetermine the effect of wave height and direction on the strength of the channel currentCollect more data for analysis and continue outreach activities

28ReferencesDonald, A. H. and R. A. Bryson, 1961, An empirical study of wind factor in Lake Mendota, Limnology and Oceanography, Vol. 6, No. 3, pp. 356 364.29Questions or Comments?

Email: keith.cooley@noaa.gov30