Originally Posted by maxingout
In my experience, the Grib files become grib fantasies after three days, and sometimes less than three days.
We use a similar technique to yours but for the general picture I use we-fax. We never rely solely on gribs, unless radio-fax is unavailable.
What I like about gribs is that they better visualise what happens during passage
of fronts - how the wind will behave - general trends - like whether it will veer or back and how much stronger/lighter it will become (not realy telling how strong it will blow but showing the trend).
If you look at model descriptions by each grib source you will notice they promise nothing more than fantasies beyond 3 days. Sure they are educated fantasies, or guesses. The same 'fantasy' effect, however, affects radiofax, text forecast and all the rest of we-stuff.
My observations re gribs are as follows:
- very accurate offshore
within 24 hrs (trends, not values),
- reliable inshore, but local phenomena have to be allowed for.
In any case, since we only have gribs in port, we have them a couple of times a day and so we will use the most recent one to plan departure. We will never use a 3-day-old grib to plan anything, so their accuracy at the 3 day horizon is of no importance (but I am sure you were not talking about this aspect, so this is just a by-comment).
Long live gribs!