Route Planning and Weather Forecasting

The next phase of our adventure will take us down the Pacific coast from our home port of Anacortes, WA to San Diego, CA where we will join the CUBAR rally onward to Mexico.  The trip is something like 1200 NM, and we are allowing ourselves about a month to complete it.  Our planned departure is sometime around September 20^th and we want to be in San Diego no later than October 23^rd.  The transit of the coast is considered “downhill” because the prevailing winds and waves are generally from the Northwest, and thus behind us.  However, our departure is late enough in the season that the weather patterns may begin to shift from the relatively mild summer conditions dominated by the East Pacific High to the fall/winter conditions where low pressure systems move through the waters every couple of days.  This has had us become even more serious students of weather forecasting and analysis.

We are thinking about the trip in two phases.  The first is transiting the Washington and Oregon coast to San Francisco, a journey of about 700 NM.  We hope to make this a nonstop passage, which should take about 4 days – at 8 knots we can cover just under 200 miles per day.  The alternative, of course, is to make stops along the coast, making for shorter runs.  However, each of the stops requires making a bar crossing (where a river meets the ocean) which has to be at the right time, considering both tides and time of day.  Furthermore, the route would be nearer to shore, where crab pots are a major navigation hazard.  Making the nonstop passage will allow us to run further offshore (hopefully) avoiding the crab pots and the bar crossings.

The offshore route does require a good four day weather window.  We decided that we would get professional help with the weather by engaging a weather routing service.  Our weather router will meet with us initially to understand our route and look at the optimal departure date, and will then consult with us on a daily or as-needed basis to review conditions ahead.  We have identified some ports along the coast that we might stop at if conditions deteriorate.  These include Newport or Coos Bay along the Central Oregon Coast and Brookings or Eureka along the Southern Oregon/Northern California Coast.  From all that we have heard and read, the major navigation hazard along this section of the coast is Cape Mendocino, just South of Eureka, which can be rough even in periods of settled weather.

Having a weather router will be a huge help for our first big trip down the coast, but we still need to continue to improve our own weather analysis skills.  Last year we took an excellent online weather course offered by the Seven Seas Cruising Association taught by Lee Chesneau, a well known and respected marine weather expert.  The course was a great introduction to marine weather and focused on how to use the many products produced by NOAA in order to plan a safe voyage.  Another resource that I’ve found incredibly helpful is a membership-based site called Attainable Adventure Cruising (https://www.morganscloud.com/), which offers a step-by step guide to collecting and analyzing weather data.

The amount of marine weather resources available on the internet is truly amazing, but of course, it all requires connectivity.  So, from a planning perspective when you have a good connection, everything is good.  When you are at sea or otherwise away from connectivity, things get a bit more complex.  This year we installed an Iridium GO!, which is a satellite modem.  It allows us to communicate, and particularly, retrieve weather data, at sea, although at VERY slow speeds.  We bought that in combination with a weather software package/service called predictwind, which allows us to download and view weather data in a map-based format using what are called GRIBS (Gridded Binary files).  I won’t talk in detail about GRIBs here.  Suffice it to say that they are the outputs of weather models from NOAA and other agencies that provide weather predictions over space and time.  This is just one tool in the arsenal, though.  The national weather service provides both analysis and forecasts that apply some human interpretation to the model outputs.  The two that I have been looking at lately are these:

Ocean Prediction Center Pacific Analysis https://ocean.weather.gov/Pac_tab.php

This is a one-stop shop for analysis and forecast maps.  I look at each of these, focusing on the surface, wind and wave, and wave period and direction forecasts.   These give a sense of what is going to happen over the next couple of days.

National Weather Service Eureka Marine Forecasts https://www.weather.gov/eka/marine

This page has links to the marine text forecasts all the way down the Pacific Coast.  These include a synopsis about general conditions in the region and forecasts for winds and sea state over the next 5 days, essentially a verbal interpretation of the various forecast maps.

The other thing I do is use the predict wind offshore application to download the data along our route.  It shows a simulation of the boat moving down the coast over time, allowing me to see what conditions we might encounter along the way.

One tool that I really like is the Probabilistic Wind Speed Guidance Page from the Ocean Prediction center https://ocean.weather.gov/prob_guidance.php?model=gefs&basin=pac&cycle=00&plot=15&loop=0#top

This allows you to look at a graphical representation of the probability that the wind speed will exceed a value that you set.  White or blue/green represent low probability (good), while reds represent high probabilities (not so good).  It has a loop that goes out over two weeks, and also allows you to look at data for sea state. 

Our goal is to learn from our weather router on the first segment of the trip down to San Francisco and then use our own knowledge and skill to make our way down the California coast.  We see this as being a series of shorter hops, and hopefully more benign conditions, at least after we get around Point Conception.

Do you have any favorite weather planning tools or services? Let us know in the comments section.