Forcast is always unreliable?

[mandlmaunder]

Left ST John 10am Monday for a trip to St Martin, Forcast 15-20knt ene with 6-8 ft wave. Got 10 miles out and it was 25-30knt 10-12ft and very uncomfortable.
Ended up in St Croix for head sail repairs and some rest.
Got the head sail repaired by local guys as it was the webbing tabs at top and bottom that blewout and not easily repaired by hand.
Waited 3 days for a drop in the conditions and left with forcast 8-15knt ne and 3-5 waves , expected and got 15-20knt ne 6-8ft. Not nice for the easterly passage but at least do-able.
Rough ride but nice to arrive and anchor in Simpson Bay after 36hrs for a 90mile rhumline trip, 200miles sailed.
So it just goes to show it aint just the English forcasters that throw leaves into the air then make a guess

[Jobs_a_ good_ un]

Which forecast is it you use is it caribwx ?

[HoratioHB]

Same down the Southern end of the chain - even when they get the changes right the timing is off - like the tropical wave that came through last week 24 hours late when we all thought it had dissappeared. Last season the forecast was 10-15 kts for almost two weeks while we were stuck in Bequia with at least 25 kts blowing. I use caribwx, Gribs, Windguru and the local HF nets but frankly rely on the Mk 1 eyeball most!!

[tri39]

It's the same in the Med. However you have to remember the forecast is for a larger area and local effects may predominate. Also it's easy to underestimate the difference between windward work and running. That is for an actual F4 you will experience F5 upwind and F3 downwind. Also the wave frequency will be faster upwind and slower downwind making upwind work seem much rougher. Additionally the whipping effect at the masthead anemometer will give higher peak readings.
You only have to hove to for a while to realise it's not really as rough as you think. As you follow the weather in your own area you realise it tends to vary in a cyclical pattern and you become quite good at judging whether the wind will rise or fall in the next 24hrs, helping your decision whether to depart or not. The forecast is what a shift worker thinks will happen, whereas the weather is actually what you yourself who may have spent a long time in the area, is actually experiencing!
I trust my own judgement more nowadays altho it can be hard in a protected anchorage to truly judge the outside conditions. If you can see the horizon, scanning it with the binos helps decision making.
As you sensibly did, it's OK to change your mind once out there!