Departure Planner
The best route is often a different departure
Route optimizers answer "which way?" with the departure you gave them. But shifting the same passage twelve hours can matter more than any routing cleverness, and no amount of clever way-finding fixes leaving into the wrong window. OpenSail solves the whole route for each candidate leaving time and shows you the trade.
Three departures, one honest comparison
Friday 06:00 gets you in fastest on paper, but the squall line has not cleared the Stream yet. Friday 18:00 is 2.6 hours quicker than Saturday and rides a settled gradient breeze on the beam. Saturday morning works, but a following swell builds to 1.8 meters by arrival. Each card is a full route solve, not a point forecast: hours at sea, comfort score, speed score, and the strongest gust anywhere along the track.
The pattern that pays for the feature: the windows where the fast route and the kind route are the same route. When those align, you leave with the whole crew on your side.
Ft. Lauderdale → Freeport · family mode Fri 06:00 27.4 h comfort 62 gust 31 kt squall line clears the Stream by noon Fri 18:00 ★ 24.8 h comfort 88 gust 22 kt beam reach, settled gradient Sat 06:00 26.1 h comfort 79 gust 25 kt following swell builds 1.8 m by arrival
How it works
1. One passage, several clocks
Pick origin, destination, and the departure times you are considering. Each candidate is handed to the same Rust isochrone solver as a full route problem.
2. Score what the crew feels
Every solved window is scored on duration, comfort (heel, slamming, motion), speed, and the maximum gust met anywhere en route, using your vessel and routing mode.
3. Read the trade
Windows are ranked with the trade-offs visible. The best window is marked, and the reason the others lost is a sentence, not a mystery.
The recommendation explains itself
A starred row in a table tells you what to do. The Intelligence Layer briefing tells you why— in the panel on the right, Saturday 02:00 wins on comfort, Thursday's rivals are named along with the reason they lost, and Friday is called out as a shorter passage that costs more than it saves. Every number in that paragraph comes from the computed windows themselves; the briefing never invents weather it wasn't handed.
The confidence pill is the honest part. It is scored from the spread between windows and any arrival caveats: high means a landslide, moderate means close rivals worth a second look, low means wait for the next model run before you commit. A recommendation that admits it was a coin flip is worth more than one that always sounds certain.
And because the runners-up are named — "Thursday is faster but meets more wind" — you can sanity-check the pick against your own judgment, or overrule it with cause. That is the difference between a briefing and a black box.
Recommended departure
Sat 02:00 UTC
37.7 h · comfort 4.6 · max wind 19 kt
Saturday's window gives the best comfort of the set (4.6) with max wind 19 kt, seas to 1.1 m, and a 24° max heel over a 37.7-hour passage. The Thursday slots are close behind at 4.4 and slightly faster, but the earlier one meets more wind and the later one still trails on comfort. Friday pushes wind to 23 kt and heel to 25° — a shorter passage that costs more than it saves. All eight windows are feasible; the trade is an extra hour at sea for the calmest crossing of the set.
Briefing generated from the computed windows — planning aid only, not for navigation.
What it does not do
Honest limitations
- A window is only as good as the forecast that defines it. Past about five days, treat the ranking as a shortlist to re-check, not a decision.
- Windows are model-dependent. Before committing, check the winning window against model agreement; a window the models fight over deserves margin or a pass.
- It ranks the departures you ask about. It does not yet sweep the calendar for you to propose windows unprompted; that is on the roadmap.
- The briefing is a planning aid, not a navigator. It reads the computed windows and nothing else — it inherits the forecast's errors, and your seamanship overrules it.
Frequently asked questions
What is a weather window?
A stretch of forecast time in which a passage can be sailed within your limits for wind, sea state, and comfort. Windows open and close as fronts and gradients move through; the skill is not finding a route through bad timing, it is moving your departure into good timing.
How is this different from just looking at the forecast?
The forecast tells you what the weather does at a point. The departure planner solves your entire route for each candidate leaving time, so a 27-hour passage departing Friday 06:00 is scored against the weather each leg actually meets along the way, not the weather at the dock. Timing effects like arriving at a cape at the wrong tide of wind are exactly what point forecasts hide.
Does it account for my boat and crew?
Yes. Each window is solved with your vessel's polar and draft and your chosen routing mode, so a family-mode comparison ranks windows by the passage your crew will actually experience: comfort score, heel, slamming, and the strongest gust en route.
Does it include currents like the Gulf Stream?
Yes. Ocean currents from Copernicus Marine physics are part of the solve, which matters enormously for Stream crossings where a 3-knot current turns 55 rhumb-line miles into a very different vector problem depending on when you cross.
Why does OpenSail recommend one particular departure?
After the windows are solved, the Intelligence Layer reads the computed results — durations, comfort scores, max wind, seas, heel, and any arrival caveats — and writes a briefing that explains the winner: which windows almost won, why they lost, and what the losing hours would have cost. It works only from your computed windows; it never invents weather, and every claim in the briefing can be checked against the results table.
What does the confidence rating on the briefing mean?
High, moderate, or low — scored from how much daylight there is between the windows and whether any carry caveats like an arrival shortfall or a motor-in finish. A high-confidence pick is a landslide; a moderate one means close rivals worth a second look; low means re-run the planner when the next model run lands before committing.
How far ahead can I plan a departure?
The models carry up to 10 days, but forecast skill decays hard past about day five. The honest workflow: use the planner to shortlist windows early, then re-run it as runs update and check the shortlist against model agreement. A window both GFS and ECMWF agree on is worth more than a marginally better one they fight over.
Keep exploring
Leave on the window, not on the calendar
Solve your passage for every departure you're considering and read the trade in one screen.
Compare your windows