Boating in New Zealand: the best day to go

The forecast has a short shelf life here. A front crosses in an afternoon, the Hauraki Gulf goes from glass to whitecaps inside an hour, and Cook Strait does what Cook Strait does — a funnel between two islands with a tide running through it. In the Marlborough Sounds the water is sheltered and the wind still finds its way down the valleys.

Because the forecast moves, the refresh matters: new model data arrives every two hours and every saved route is scored again with it, ten days out. Tide height at your arrival time and the depth in the anchorage corrected for it come with it, and the route is simulated every half hour, so an afternoon leg is judged on the afternoon rather than on the morning you left in. The warnings for these waters stay the thing you read before you untie.

Depth figures are modelled averages rather than a survey of your bay, and the comfort score is an estimate from weather models rather than a promise. Bonasea does not replace official charts, publications, regulations or the skipper’s judgement. Read the warnings for these waters before you leave, and trust your echo sounder over the app.