What it does
Compares the models
GFS, ECMWF IFS and AIFS, ICON, GEM, UKMO, ARPEGE and JMA are different forecasts of the same weather. When they agree, you can lean on the forecast. When they disagree, that is itself worth knowing before you leave the dock.
Shows the whole field
Wind speed as colour, direction as arrows, and animated streaks that show how the air is moving. Tap anywhere for wind, gusts, sea state and a three-day trace at that point, with every model's answer side by side.
Tells you how old it is
The model run time and its age are always on screen. A twelve-hour-old forecast is a different thing from a fresh one, and you should never have to guess which one you are looking at.
Works offshore
Forecasts are cached automatically, and you can download an area before you leave. With no signal the last forecast is still there, clearly marked as old.
Built for sailing
Knots by default, gusts alongside sustained wind, waves with height, period and direction, and high-resolution regional models where they are available.
Tackwatch shows supplementary weather information. It is not a navigation instrument and must not be relied on for safety of life at sea. Always carry official forecasts and charts.
Status: in development. Tackwatch is not on the App Store yet. This page exists so there is somewhere to point when it is.
Support
Email support@tackwatch.app. It is read by the person who builds the app, so plain descriptions are welcome and there is no ticket system to fight.
If you are reporting something that looks wrong, these help most:
- Which weather model was selected, and the forecast time on the slider.
- Roughly where on the map — a place name or approximate position is plenty.
- What the status chip at the top left said: the run time, the age, and whether it showed an offline or stale marker.
- Your iOS version and device, and a screenshot if you have one.
Why do two models disagree?
Because they genuinely do. Each national weather service runs its own model with its own physics and its own starting conditions. Showing you that spread is the point rather than a defect — a forecast the models agree on is one you can plan around, and one they don't is one to stay flexible about.
Why is there no wind data in some places?
Regional models cover only their own domain, and some models return nothing over open water in certain areas. Gaps are drawn as gaps rather than filled in with a guess. Switching to a global model usually fills them.
Does it work without a signal?
Yes. Whatever was last fetched stays on the device, and you can download an area deliberately before leaving. Anything old is labelled as old.