Definition
One sheet per ocean per month, showing wind roses giving the percentage frequency and force of wind from each of eight or twelve directions, prevailing surface currents with mean rates, percentage frequency of gales and fog, mean air and sea temperatures, ice limits and tropical storm tracks. Admiralty issues them as Routeing Charts, the US NGA as Pilot Charts. They present long term climatology, not a forecast, so they inform departure timing rather than daily decisions.
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