Two step weather routing
Two step weather routing with VRTool
Suppose you want to plan a route with an intermediary point.Say it is not a fixed point like a mark or an island, but an strategic position, close to favourable winds.You don't know where it is yet, but you feel it is in a certain direction where winds are normaly stronger and/or in a suitable direction.
VRTool WR calculator can only work a single segment at a time, from Start to Destination. However you can create a composite route by doing as follow:
Set WR destination far away in the direction you like and do a WR calculation. Plot only the isochrones to the chart. Use the isochrones to choose your strategic intermediary position.
Say you choose a position on the 108h isochrone. Set WR destination to that point and do a calculation up to 108h. Plot the best route.
Now you can do the second step, from that position to the leg final destination. The segment will start from 108h. Set WR start to your chosen 108h position and WR destination to the leg destination.
In the program's main window, in "Track Designer Settings", "Wind Forecast Age" group, select option "[x] a given date/time".
Now you have to figure the date/time of the 108h isochrone. Go to the "Wind grids" and select the current wind grid. The Timestamp will show.
Add 108h to it and convert back to date/time. This time is in UTC. Convert local time by adding the time zone. Input that date/time to the "Start" field in track designer settings. Then you can calculate the second part of the WR track.
Remember to set "Wind Forecast Age" back to "[x] Timestamp+time zone" (the default mode) in the end.