There’s a large fall storm brewing in the North Atlantic that is going to generate some sizable swells. Will they or the southwest wind shift have a major impact here and if so what do we do? The image above is of Playa Francesa on Graciosa Island. Waves generated by northeast winds have no trouble finding their way around the island, albeit in attenuated form. But what about northwest swells?
Here is the line up of the north end of the Canary Islands. Anything coming from the NW has no impediment to reduce their energy.
Now the weather. This is a GFS model for today (Tuesday) at 0600 GMT. We are located at the bottom, about 15 degrees W longitude (right side). That is a powerful system and it is just winding up.
The wind strength here is forecast light, but from the southwest which is almost straight into our anchorage. The Canary Islands are just above the 15W at the bottom of the image.
This is a local detail and we are in the upper right now. Like we said, light winds. If the weather develops in this manner, while we are anchored off what becomes a lee shore, the holding is good and it is deep. So, we can deal with it.
Now the interesting part. This is the WW3 wave model forecast. We are in the NE corner of the island group at the bottom. There are some good sized swells, possibly 16 to 20 feet (five to six meters), headed this way. They will have no trouble partially wrapping around the bottom of Graciosa. The question is how much, and will the proximity of Lanzarote help deflect them south?
A detail of the Saturday forecast (we are in the northeast corner). Three meters, ten feet, sounds pretty big.
Do we stay and see what happens, or go early and park in a marina? We’ll decide tomorrow or Thursday.
Posted by Steve Dashew (October 5, 2010)
October 6th, 2010 at 11:22 am
An excellent topic. In December 2002, we were anchored in 50 feet of water in a bite off central Baja’s Pacific coast. We had decided to wait out large swells coming our way from a very large storm in the Gulf of Alaska. We were getting limited weather info. via satcom, but expected the swells to subside well before they got to us, after all we were 2,000 miles away. Wrong. We woke up to 10 knots of wind and swells of 10 feet. Within an hour, swells were running 15 to 20 feet. As we prepared to leave and run in front of the swells, several 30 footers came into the anchorage, one of which broke and rolled our friends sailboat 50 feet away. He survived, but it was a lesson learned.
A day later the same wave train struck the southern Mexico coastline, 600 miles further south, causing extensive damage to several marinas/boats.