In a recent trip report, Alex talked about how he uses Windy to plan his trips, including crossings. I was interested in this strategy, but I had no experience with the Windy app. I decided to keep an eye on some local areas this fall/winter and compare the weather station readings with Windy.
What I found so far is that Windy is good for large-scale predictions, but inaccurate for areas affected by local considerations, as the two models that work in our BC waters, GFS and ECMWF, are global and low-resolution. Supposedly, ECMWF takes into account more local features, but I found that GFS is more accurate at the locations I followed.
Here are three areas I have been watching. The graphs are taken from the Fish Weather app, which collects data from the weather stations. The Windy readings for ECMWF are in my handwriting in red. The GFS readings are green.
1. Solander: the Brooks Peninsula is well known for strong winds, especially on SE blows. Windy fails to predict these large SE winds, as the following graph shows. You can see that Windy’s ECMWF predictions underestimate wind speed by up to 15 knots on this occasion. The biggest difference I’ve seen was on November 16, 2019, when Solander station registered SE 53 knots, whereas Windy had it at SE 27. By contrast, the GFS model is more in the ballpark, but still not super accurate.
2. Sisters Islet
Sisters Islet station often registers the biggest SE winds in the Strait of Georgia. Again, Windy’s ECMWF model fails to register the strength of these winds accurately, with up to a 15 knot discrepancy. GFS is more in the ballpark.
3. Pam Rocks (Howe Sound)
Pam Rocks is an interesting case. In the summer, this area sees pretty regular daily patterns of inflow/outflow. In the winter, there can be arctic outflows of considerable strength. Neither of model predicts these northerly winds very well. In today’s wind event, it even got the direction wrong, predicting wins E or SE winds up to 10 knots, where the station registered N winds of up to 15 knots.
My summary: of the two models, choose GFS for local waters. Even then, areas with known local effects will not be accurately represented, so local knowledge and the shared experience of mariners is essential. Of course, I’ll have to run these comparisons in the summer when different weather patterns prevail.
Cheers,
Andrew
What I found so far is that Windy is good for large-scale predictions, but inaccurate for areas affected by local considerations, as the two models that work in our BC waters, GFS and ECMWF, are global and low-resolution. Supposedly, ECMWF takes into account more local features, but I found that GFS is more accurate at the locations I followed.
Here are three areas I have been watching. The graphs are taken from the Fish Weather app, which collects data from the weather stations. The Windy readings for ECMWF are in my handwriting in red. The GFS readings are green.
1. Solander: the Brooks Peninsula is well known for strong winds, especially on SE blows. Windy fails to predict these large SE winds, as the following graph shows. You can see that Windy’s ECMWF predictions underestimate wind speed by up to 15 knots on this occasion. The biggest difference I’ve seen was on November 16, 2019, when Solander station registered SE 53 knots, whereas Windy had it at SE 27. By contrast, the GFS model is more in the ballpark, but still not super accurate.
2. Sisters Islet
Sisters Islet station often registers the biggest SE winds in the Strait of Georgia. Again, Windy’s ECMWF model fails to register the strength of these winds accurately, with up to a 15 knot discrepancy. GFS is more in the ballpark.
3. Pam Rocks (Howe Sound)
Pam Rocks is an interesting case. In the summer, this area sees pretty regular daily patterns of inflow/outflow. In the winter, there can be arctic outflows of considerable strength. Neither of model predicts these northerly winds very well. In today’s wind event, it even got the direction wrong, predicting wins E or SE winds up to 10 knots, where the station registered N winds of up to 15 knots.
My summary: of the two models, choose GFS for local waters. Even then, areas with known local effects will not be accurately represented, so local knowledge and the shared experience of mariners is essential. Of course, I’ll have to run these comparisons in the summer when different weather patterns prevail.
Cheers,
Andrew