Expedition Navigation Software 
1 of 1- ZeeZee
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Offline - Registered: 3/30/2016
- Posts: 321
Shift wind forecast in time
I noticed that in my area the wind forecast i download in GRIB files is quite good when it comes to wind strength and direction. However, sometimes the timing of a (structural) wind shift is not perfectly forecasted.
Example: the GRIB files expect the wind to shift from 270 to 200 degrees at 4pm, but it turns out the shift already happened at 2pm.
In such cases, wouldn't it be useful to be able to 'shift' the GRIB file data in time within Exp so when you run a Optimal route again it can take into account that the wind has already shifted?
In the example above I would then tell Exp to subtract 2 hours from the times in the GRIB files. So when running an optimal route at 2pm, it will use the wind forecast of 4pm, for the wind at 3pm use the forecast of 5pm etc.
Is this possible in Exp and do you think this can make sense?
- Ernie M
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- Registered: 11/05/2015
- Posts: 411
Re: Shift wind forecast in time
An interesting idea! You could probably accomplish the same by going to Settings/Opt routing and adjusting the Start time accordingly. Of course currents, if significant, wouldn't line up with your hypothetical adjustments so you'd have to deal with that.
In New Englad we often see just what you're talkig about; the fcst is pretty good but just an hour or so off in timing.
Cheers
- Joe Goulet
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- From: Fort Lauderdale, FL USA
- Registered: 9/16/2015
- Posts: 83
Re: Shift wind forecast in time
How is what you guys are asking for / suggesting different from what is provided by time shifting the wind (minutes) in Settings / Opt advanced / Wind?
- ZeeZee
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- Posts: 321
Re: Shift wind forecast in time
Well, that might be exactly what I was asking for. Didn't notice it yet so thanks for making me aware!
Will do some tests with it. If a change happens more quickly than the the GRIB suggests, do I need to enter a positive or negative value in minutes? My test will tell...
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Thread Starter- Joe Goulet
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- From: Fort Lauderdale, FL USA
- Registered: 9/16/2015
- Posts: 83
Re: Shift wind forecast in time
That feature was originally in the "Settings / Opt routing" until "Settings / Opt advanced" was introduced. As your question demonstrated, an experienced user was eventually going to need that capability as it is often the case that the pattern of the grib forecasts "comes true" but not at the time called for.
I should know the answer about plus / minus shifting but, like you, I figure it out every time from scratch using the tooltip at certain points on the grib-loaded chart; then it's another piece of blue tape on my laptop until the race is over.
Last edited by Joe Goulet (9/12/2016 12:59 pm)
- ZeeZee
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- Registered: 3/30/2016
- Posts: 321
Re: Shift wind forecast in time
Thanks Joe.
I tested it and it turned out you need to enter a negative value (in minutes) to 'shift forward' the forcast from the GRIB file. So if at say 2pm you want to apply the forecast as they are contained in the GRIB for 4pm, you need to enter -120.
Great feature and very helpful!
Last edited by ZeeZee (9/13/2016 11:39 pm)
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Thread Starter