Last week, as the Jan. 20 storm was working its way from the coast of California to Colorado, I got an email regarding the wind forecast for the Halifax area. In my effort to help people plan for the upcoming storm, I indicated in one of my “Need to Know” boards in the video forecast* that the wind would come around to the south and gust between 70- and 80-km/h Sunday evening.
Darrell wrote: “Enjoy the new format. Can you comment on the discrepancy between your reported wind gust of 70 for Sunday and the forecast by ‘Windfinder’ suggesting wind gusts of 124 km/h? 124 scares me for sure – many black spruce on my property.”
Darrell attached the link to the “Windfinder” forecast. It was a wind, waves and weather forecast for Glen Haven, N.S., a lovely coastal community on the shores of St. Margaret’s Bay.
I should start off by pointing out most public forecasts don’t specify wind direction or speed more than 48 hours out. A meteorologist can project wind patterns and circulation before then, but a slight shift in the track of a storm and the wind forecast can change dramatically. On Wednesday, when Darrell was inquiring, the wind portion of the storm was 96 hours from reaching our region.
To address the discrepancies: “Windfinder” projects wind speeds over the water – for windsurfers and boaters. The site states that “wind, waves, tides and weather reports and forecasts are for wind-related sports like kitesurfing, windsurfing, surfing, sailing or paragliding.
The wind, whether generated by a coastal storm or an afternoon summer sea breeze, blows faster over the ocean than over the land because there is not as much friction over the water. The land has mountains, coastal barriers, trees and man-made structures that cause a resistance to the wind flow. Because the oceans are free of these impediments, the wind can blow at a greater velocity.
My wind forecast, unless otherwise stated, contains wind direction and speed projections over land; marine forecasts deal with wind over the water. There are lots of great forecast sources out there - the key is to find the one that best suits your needs.
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*Can't find your video forecast? Look for your region at WeatherByDay.ca
Cindy Day is the chief meteorologist for SaltWire Network.