Expedition Navigation Software 
1 of 1- Schumann
- Admiral
Offline - Registered: 5/12/2026
- Posts: 15
Which weather model is used when?
Just curious about the mechanics of how expedition uses certain weather models. Let's say I had a race this weekend and wanted to get a sense of our course, and pull GFS, NAM, and ECMWF gribs from saildocs. When I run an optimised route, which of the weather models is it using? If, in this case, GFS and ECMWF have completely opposite predictions for a wind shift half way through the race?
Similarly, day-of and during, which models do people typically prefer? My shallow understanding is that HRRR is the most accurate in a 48 hour window, should one switch to pulling those models for day-of planning? Or is it still helpful to pull multiple?
- Ernie M
- Moderator
Offline
- Registered: 11/05/2015
- Posts: 428
Re: Which weather model is used when?
The first part of your question is for Nick but I think EXP uses the newest model you have selected.
I like to run each modal separately anyway so you know which is advising which action.
I like GFS or as you say HRRR for East Coast US. Maybe if you say what area you;re in will result in someone popping up from there.
Your question points out the challenge of having several choices. If they all align, great! But if they don't, it comes back to the navigator and his experience. You can look for 'clues' if a particular model eg says the windshift will come early vs another model says it will come late. Real time observations will guide your choice.
Hope this helps,
Ernie M
- Schumann
- Admiral
Offline
- Registered: 5/12/2026
- Posts: 15
Re: Which weather model is used when?
Hi Ernie, thanks for the feedback, and good tip!
I'm sailing in coastal New England and the Islands, Long Island Sound, Buzzards Bay, Maine, mostly.
- •
Thread Starter- Ernie M
- Moderator
Offline
- Registered: 11/05/2015
- Posts: 428
Re: Which weather model is used when?
For the New England area the HRRR is pretty good and GFS if you want deeper into the future.
With a little time you can compare those forecasts with real data from
eg plot on EXP the position for buoy 44008 (SE of Cape Cod). You can right click on that spot and click Meteogram to capture the forecast winds for certain times Then as that time arrives check on the NDBC for actual wind recorded at the buoy. (ditto for other large NE buoys)
This will give you a confidence level to plan future races/trips using the Optimization feature.
And, I'm sure you know; make sure you consider the currents!!!
Ernie M
Check out RaceData for iOS and Android. Expedition data in the palm of your hand, or on your wrist! RaceData
Interested in advertising here? Over one thousand active navigators and Expedition users visit this forum. Click here to contact the administrator.