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Date: 28 Jul 2014 10:43:21
Title: Weather routing

Weather routing is something that commercial shipping as well as long distance sailors do. Not all but many. The idea is that the shortest way can be very costly and actually take longer if you are beating the wind, waves or/and current.

Routing can be done on a paper chart by putting arrows corresponding to the forecasted situation connected to your time at the spot (I have done that).

The other way is to use software that does that for you. We use a program called Meteoviewer from Meteocom. It is probably far from the best on the market when it comes to routing but it is etremely accurate on the forecast.

But there is a third way also to be recommended, especially when doing a passage that is more critical than others. Since we left Sweden (June 2012) we have used this option three times. The first one was when crossing Biscay (we were late according to weather pilots), the second going down to New Zealand ( a well known passage for its notoriously crossing of lows). The third now. The best you can have on board is a meteorologist, right? Who can be better than a pro at analysing the analyses? Computers might do the trick with 10.000 inputs per second, but there is still a lot of experience to be added when it comes to chaos. Weather is chaos. Since it is hard to find a meteorologist that will go across every other week the second best is to have one helping you out from land.

Here in the southern hemisphere the "guru" is  Bob Mc Davitt. He has been working for the New Zealand national weather institution and he has been the forecaster for NZ Americas Cup team when they won. Bob is many yachters weather router and to attend his seminars is a treat.

So when you ask for assistance you mail your meteorologist and if you like the price and the "product" he will set up a departure date for you, and then he will give you a route.

It can look like this:

Pressure reading for your barometer from Whangarei airpot at 5pm Fridy is
1019 hPa

Situation and comments: A burst of cold SW winds and showers moved ovr
Whangarei today/Friday with a passing cold front.
This is the last cold front associated with these SW winds, and forecast is
for a HIGH with light winds in the Tasman sea to mov over Northland this
weekend.

If you depart on Saturday then you should have direct-downwind sailing in SW
winds for Saturday and Sunday and then motoring in light winds of the HIGH
on Monday.
On Tuesday and Wedenesday,the forecast is for NW winds ahead of a front
/trough approaching from the tasman Sea-- go NE in these winds and take a
scenic passgae thru middle of Kermadecs.
On Thursday, more light wind sailing in the sub-tropical ridge
>From next Friday onwards the outlook is for regular trade winds , OK for
sailing north.

Then Bob will give you waypoints and they can look like this:

28-Jul-20:52|31:37S/179:41E|1026|ENE08~10~15|090-02.9-|11|110-0.3|1.7~2.6m|16
29-Jul-01:00|31:37S/179:57E|1026|ENE08~10~15|090-03.0|-19|110
-0.3|1.6~2.4m|16
29-Jul-13:00|31:37S/179:15W|1026|-NE09~11~16|090-03.4|-42|113
-0.2|1.5~2.3m|16
30-Jul-01:00|31:36S/178:23W|1027|NNE09~11~17|090-03.7|-56|138
-0.2|1.4~2.2m|16
30-Jul-13:00|31:36S/177:29W|1028|NNE08~10~15|090-03.8|-65|154
-0.3|1.2~1.8m|17
31-Jul-01:00|31:35S/176:39W|1029|NNE06~07~11|089-03.4|-08|173
-0.2|1.1~1.6m|17

Now the idea of having a good pro on board is that as you give him your positions and observations and he can keep you updated on what's happening.

In our case, the weather pattern changed after departure and we have to sail on further west to have a good angle when the wind veers.

Now having Bob with us does not mean I stop checking my meteoviewer, I'm always in charge and responsible for the safety of the family and therefore I have two sources now.

Routing is not necessary of course, sailors have been doing their things before forecasts, you could just set off and play it by the wind, I guess for us it is a matter of safety and comfort.


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