Does anyone know what area a coastal forecast is supposed to be covering?
I've noticed a big difference in a few of them this week. Example below for Margs but have noticed Lancelin has the same sort for differences.
I think the seabreeze data is pulled from the BoM coastal forecasts/locations. In that case margs would be right at the top of the cape leeuwin coastal forecast, whereas the mainbreak is probably tied into one of the closer onshore weather station locations.
www.bom.gov.au/australia/meteye/?loc=WA_MW009
www.bom.gov.au/places/wa/margaret-river/observations/
Laurie would be the best person to answer that question.
Simply based on my experience comparing the forecast from the actual wind for Perth, the ''coastal'' forecast corresponds to what you'd likely get at Rottnest Island (Approx 20km away from the main land) whereas the local ''surf'' spots give more accurate forecast for what will happen at your local kite spot. This is especially relevant for hot days in Perth when the wind is turning S or SSW at Rottnest Island but struggles to even reach the shore in Perth.