Gale warnings are in effect for the Great Lakes for Monday, April 21, the National Weather Service said, as strong winds could create hazardous waves up to 10 feet.
“Mariners should alter plans to avoid these hazardous conditions. Remain in port, seek safe harbor, alter course, and/or secure the vessel for severe conditions,” the weather service said of Lake Michigan conditions.
Gale warnings apply to most of Lake Michigan, the northern portion of Lake Huron and all of Saginaw Bay from Monday, April 21, into the morning of Tuesday, April 22.
Small craft advisories are in effect as well for those operating small boats, as strong winds will cause hazardous waves threatening damage. Lake Superior also has posted small craft advisories. All of Michigan is under a hazardous weather outlook.
On lakes Michigan and Huron, winds are forecast to be 15 to 25 knots, with gusts stronger than 30 knots.
The winds are predicted to create dangerous waves from 2-9 feet on Lake Michigan, and 4-10 feet in Lake Huron and Saginaw Bay.
Here’s more on the gale warnings and small craft advisories on Michigan’s Great Lakes:
How strong are predicted winds on Michigan’s Great Lakes?
Here’s a look at the National Weather Service forecast:
Lake Michigan: from St. Joseph up to Manistee, there is a small craft advisory with winds 15 to 25 knots, gusting to 30 knots, and waves 2 to 3 feet. The gale warning says to expect southwest winds 15 to 25 knots, with gusts up to 35 knots, and waves 5 to 8 feet.
Southern Lake Michigan: including waters near Two Rivers and Sheboygan, Wisconsin, and Manistee and Pentwater, there are gale warnings for 15- to 25-knot winds, with gusts up to 35 knots, and waves 6 to 9 feet.
Northern third of Lake Michigan: from Two Rivers, Wisconsin, to Charlevoix, there is a gale warning for winds from 15 to 25 knots, with gusts up to 35 knots, and waves 5 to 8 feet.
Lake Huron: from Alabaster to Bay Port, there are small craft advisories and gale warnings. For small boats, expect winds up to 17-22 knots, with gusts up to 30-32 knots, and 3- to 5-foot waves. The gale warning says to expect sustained winds up to 23 knots, with gusts up to 36 knots, and 4- to 5-foot waves. From the Mackinac Bridge to Presque Isle, there is a gale warning for winds up to 23 knots, with gusts up to 37 knots. The largest waves could reach 10 feet.
What does a gale warning mean?
The warning forecasts sustained surface winds, or frequent gusts, in the range of 34 knots (39 mph) to 47 knots (54 mph), either predicted or occurring, and not directly associated with a tropical cyclone, the NWS glossary explains.
A gale is an extratropical low or an area of sustained surface winds of 34 (39 mph) to 47 knots (54 mph), the glossary says.
A gale watch calls for an increased risk of a gale force wind event for sustained surface winds, or frequent gusts, of 34 knots (39 mph) to 47 knots (54 mph), but its occurrence, location and/or timing is uncertain.
What is a knot in wind speed?
Knots, typically used by aircraft and boats or ships, is a measure of speed. One knot is equal to about 1.15 mph.
The term knot dates from the 17th century, when sailors measured the speed of their ship using a device called a “common log.” The common log was a rope with knots at regular intervals, attached to a piece of wood shaped like a slice of pie, according to NOAA.
Mariners would lower the wood piece into the water and allow it to float freely behind the ship for a specific amount of time (often measured with an hourglass). When the time was up, they would count the knots between the ship and the piece of wood, and that number estimated their speed.
What does a small craft advisory mean?
According to the NWS, a small craft advisory is issued when there are expected sustained winds of 22 knots or frequent gusts of 25 knots or greater, or combined seas of 10 feet or more.
Small crafts include owners of small to medium sized motor and sail boats, affecting fisherman, para-sailors, windsurfers and canoe paddlers.
Is the Mackinac Bridge open?
Yes, the Mackinac Bridge is open as of April 21, though a high wind warning has been issued.
Mackinac Authority will update residents as wind speeds are monitored along the bridge.
“Currently we are experiencing winds of sufficient force in the Straits area (20-34 mph) to issue a warning to all motorists preparing to cross the Mackinac Bridge,” officials said.
Pickup trucks with campers, motor homes, vehicles pulling trailers and enclosed semi-truck trailers and motorists are especially vulnerable to high winds.
They are encouraged to reduce their speed to at most 20 mph, turn on their four way flashers and utilize the outside lane.
What wind conditions result in warnings, escorts, partial closures and full closures?
Here are the speeds that trigger different wind warnings and closures on the Mackinac Bridge:
0-20 mph: No restrictions. Bridge speed limit is 45 mph.
20-35 mph: High wind advisory. High-profile vehicles (RVs, trailers, etc.) should travel no faster than 20 mph across the bridge.
35-50 mph: Escorts required. Any high-profile vehicles must wait to be escorted across the bridge. Escorts ensure that high-profile vehicles travel at speeds of less than 20 mph, depending on conditions.
50-65 mph: Partial closure. The bridge is closed to high-profile vehicles. Passenger vehicles that are not towing anything may cross but at no more than 20 mph.
65 mph and above: The bridge is closed to all traffic.
Contact Sarah Moore @ smoore@lsj.com
This article originally appeared on Lansing State Journal: Gale warnings for the Great Lakes. The weather forecast for Michigan