Strong south winds are expected over Lake Michigan Today. Southerly winds of 15 to 30 mph will build waves into the 3 to 7 foot range from South Haven north up the lakeshore. The highest waves will be found from Grand Haven north.
Hazardous Swim Conditions will consist of:
High Waves...3 to 7 foot waves will make swimming hazardous as they will be of short period (occurring every 3-5 seconds) and large by summer standards.
Longshore Currents...the south winds will create strong longshore currents that will sweep up the beach from south to north.
Structural Currents...where the longshore currents run into pier structures, structural currents are expected, sweeping out the pier lakeward. The beaches with particularly dangerous conditions Today will be those located on the south sides of south piers including Grand Haven State Park and Pere Marquette Park in Muskegon.
Rip Currents...occur where breaks or gaps in sand bars allow water to rush back lakeward through the gap. Rip currents will be possible on Thursday due to the high wave action.
The overview graphic shows the multiple threats that can occur during a high wave event on Lake Michigan. Increased winds and waves are the main ingredients to set the others threats in motion. Today, waves of 3 to 7 feet will make swimming hazardous by themselves. The south flow will set the stage for longshore currents that will travel up the beach from south to north. Where these currents encounter pier structures like at Grand Haven and Muskegon, structural currents will form. Breaks or gaps in sand bars move in orientation and location often. It is difficult to know where they will be on a given day. Where gaps occur in sand bars though rip currents are possible on high wave days like Thursday. The wave return itself as it pushes back lakeward can knock smaller children off their feet and pose a hazard.