GFS or NAM?

For the last month we have had one of the most dangerous things a sailor could have on a boat – a schedule. We need to be in Annapolis on Friday, September 27th for the start of the job at the boat shows.

We planned on being ready to leave Deltaville on Friday, September, 20th so we would have a big enough weather window to find two days of favorable breezes needed to sail to Annapolis. On Saturday, we made a nice downwind run from Deltaville to Solomons Island, a little more than halfway to Annapolis. But since Saturday night the wind has been dead on the nose for the next leg of the trip to Annapolis.

There are two weather models we have bee watching since leaving Duluth: GFS (Global Forecast System) and NAM (North American Model) via passageweather.com. GFS was the more reliable from Lake Superior to Cape May, but in the Chesapeake NAM seems to have become more reliable. This may be because NAM is a higher definition model, ie: it gives more detail for smaller areas. For more discussion on the models see http://theweatherguy.net/info.html.

gfs

nam

Both models predict unfavorable conditions for sailing to Annapolis by Friday, so we are resigned to a 40 mile motor. But how unfavorable is it going to be today? The GFS model predicts conditions moderating early today with light winds later in the day. The NAM mode predicts conditions moderating late tonight.

Our schedule pushes us towards betting on the GFS model, even though we know that probably is not a great idea and we will probably be motoring into a cold north wind. But the crab boats are going out this morning for the first time in a few days… maybe that is a good sign? Oh well, the sun is coming up, time to get out into the bay and find out!

One thought on “GFS or NAM?

  1. Shane Dennis Post author

    NAM ended up being more accurate. It was light and variable then we beat into a 15kt headwind for a few hours before conditions becomes progressively lighter during the day.

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