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    Re: Gnomonic Charts - Usable Zones
    From: Jeremy C
    Date: 2018 Jan 20, 15:25 -0800

    Frank,

    You make good points, especially about currents. They are a huge factor in how ships sail. For example, I took the GC track from Japan to the PC and if you look at a pilot chart, not only is the weather nice, but the currents are generally helpful along the way.  Take it the other way, and you are fighting the current the whole time.  I wasn't here for the return trip in September, but I know the other captain rode the currents south of Hawaii.

    The issue with weather is that despite the satellites, there are still few surface observations to go by.  One thing that came out of the El Faro was a suggestion to put automated stations on at least US flagged ships to get better observations more often than what sailors can choose to provide, and usually with limited accuracy.  I hope that the weather routing services will improve, especially as data increases in quantity and quality.

    You mention hurricanes but those are lesser concerns for me in routing.  Hurricanes are relatively small and pretty easy to avoid with a bit of planning.  What worries me, especially in high latitudes, are the giant extra tropical lows that form well after you've started your voyage.  I've seen them spread from Iceland down to the Azores on the map and there is no going around that!  You try to stay in the milder areas of the system as you encounter it.  My fear with high latitude sailings is that you can see it coming, but you can't get out of the way, even if you try (reliving my aforementioned 3rd mate experience).  In the end the captain is in a Catch-22 when facing a storm: If there is damage the Master is at fault for not avoiding the storm; and if they take the safe route, and nothing happens, they face the spectre of thought that they could have saved time/money if they had been a bit more daring in the voyage plan.

    A recent news article talked about an LNG tanker that turned around a day from Boston.  The article showed the ship's track out of the Straits of Gibraltar and it was far from a GC track.  I can't say or not if there was a weather routing service employed, but in any case, it was a rhumb line passage because the high latitudes of the N. Altantic in January isn't the place to be, even on a huge tank ship.

    Jeremy

       
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