I find magicseaweed to be unaccurate a lot of the time. I use www.windguru.com
and find that to be the best
For good surf you need 2 things to be right -> swell and wind
Generally offshore wind = good, onshore wind = bad
No swell = no waves.
Swell direction is important too so say if you have a swell coming from the west, being on the east coast is no good cos Ireland's in the way.
So say you have a break on the west coast facing west......for there to be good surf here you're going to need winds blowing from the east, northeast or southeast and a swell coming from either west, northwest, or southwest.
So to work out if your chosen spot is going to have good surf on a certain date. Workout which way it faces then go to windguru and check the swell direction and wind direction.....a point to remember with windguru - the predictions up to the 3 day mark are pretty good, for predictions over this there's a good chance something will happen in the meantime which will change the conditions.......so don't go putting all your money on a spot being good in a week based on the predictions.