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GJW Direct 2020

Getting ready to go

by Rob Murray 10 Feb 13:11 UTC
Wind wave collage © Rob Murray

What do you do to get ready for a season? What resources do you rely on? How can you assess the weather and potential passages months in advance? The following is a list of some of the steps we take and resources we rely on aboard Avant to get ready for a major passage that's a few months down the line, or to get ready for a season of sailing.

First, we have a look at Jimmy Cornell's World Cruising Routes, a staple reference guide for cruisers. While a great resource, this book is a, "comprehensive guide to over 1,000 routes covering all the oceans of the world from the tropical South Seas to the high-latitudes of the Arctic and Antarctic" - all in some 600-odd pages.

While it provides breadth, it is somewhat lacking in depth. It suffers to some degree from the source of data, which is a mix of pilot charts and books overlaid heavily with the personal experience of many seasoned cruisers. Since some areas are not frequented by cruisers for various reasons, they are often omitted (for example, the 1987 edition omitted Colombia, since it was so dangerous it seemed no one cruised there).

Also, since Cornell's other endeavours (such as founding the Atlantic Rally for Cruisers [ARC]) have been long distance and circumnavigation focused, it often misses out on more coastal routes. Nonetheless, it is always our first stop for a broad overview.

Cornell does focus on the passage part of the planning and has virtually no information on local conditions to expect when you have arrived.

Regarding our plan to leave Panama, Cornell says, "Eastbound Passages from Panama can be extremely difficult at all times of the year, because of the prevailing direction of the winds and current" and that "better and more comfortable passages have been made in late spring or early summer". Good to know.

Before Cornell wrote his guides, sailors relied on Ocean Passages for the World, publication NP136 from the British Admiralty. I think the third edition of 1973 was the last to feature separate routing advice for sailing ships and power vessels (newer editions omit advice for sailing ships). It builds on the 1895, 1923 and 1960 editions and is the last Admiralty guide written for professional world sailors (the iron men in wooden ships). PDF versions can be found online and make interesting and instructive reading. While the sailing directions are directed for full rigged tall ships, they suit modern sailors because, although we may be able to sail upwind, none of us much like it. While I enjoy referring to it, I should note that its precision and brevity make Cornell look positively loquacious.

Next, we go shopping at the NGA store (National Geospatial-Intelligence Agency) is a support agency of the United States Department of Defense with the primary mission of collecting, analyzing, and distributing geospatial intelligence (GEOINT)). If the US Navy gave you command of a destroyer and said 'go there', the NGA would provide the travel guidebooks. The NGA annual budget is classified, but was estimated to be at least $4.9 billion in 2013. It is nice to be able to add that kind of horsepower to your cruising budget.

We get the Sailing Directions (Enroute) for our area (these include: "detailed coastal and port approach information, supplementing the largest scale chart of the area). Each publication is subdivided into geographic regions, called sectors, which contain information about the coastal weather, currents, ice, dangers, features and ports, as well as graphic keys to standard [MIMA/DMA] nautical charts available for the area."

They have some photos, and some sketch charts. While mainly designed for much larger vessels, they are very handy. After the introductory chapter, the detailed description of the region begins. A map/chart precedes each chapter and outlines the nautical charts used in the area to be discussed. In these chapters, as much as possible, the coastal description is in geographic sequence and gazettes the coastline, ports, anchorages, navigation aids and hazards. These are fairly current: it is unusual to find one that hasn't been updated in the last six months or so. For example, the 2017 Publication 148 was corrected (updated) through 26 September 2020 when I downloaded it in December 2020. Similar ADMIRALTY Sailing Directions are available from the UK Hydrographic Office, but they are priced at Hardback Paper Publication: £63.50, Electronic version (AENP): £38.70 per volume, so we don't use those.

Both publications have some information on local conditions along the coast and note currents and weather systems with much more detail than other readily available sources.

For the western Caribbean, where Avant is now, the Sailing Directions (Enroute) tell us:

"The prevailing winds are the NE trades, which frequently assume a N or E direction, also a gusty character close inshore. These winds flow strongly from December to March"


"During the dry season [December to March], the winds are stronger"


"During the dry season, the wind may freshen to a velocity of 15 knots in the vicinity of the Panama Canal, but frequently exceeds 20 knots for a period of 24 hours or more. During the wet season in the same locality, the average wind velocity is about 8 knots, but greater velocities are experienced during passing local rain squalls."

Hmmm. We are not fans of sailing to weather in strong or gusty winds; spring sounds much better.

We also get the Sailing Directions (Planning Guides) (these include, "relevant physical, political, industrial, navigational and regulatory information about the countries adjacent to a particular ocean basin in a single volume"). The information on each country is contained in a page or two. These are not hugely useful, but they do list national holidays and Search and Rescue (SAR) contact information for each country. You generally do not want to arrive on a holiday with the attendant overtime port fees, and while you don't want to have to call SAR, if you do need to, it's nice to have the number.

While you are in the NGA shop, you may as well get some other e-books that may be handy - the latest American Practical Navigator (Bowditch), the latest International Code of Signals (revised 2020 - you do have the new edition aboard, don't you?), etc.

We want to review the Pilot Charts which:

"depict averages in prevailing winds and currents, air and sea temperatures, wave heights, ice limits, visibility, barometric pressure, and weather conditions at different times of the year. The information used to compile these averages was obtained from oceanographic and meteorologic observations over many decades during the late 18th and 19th centuries. The Atlas of Pilot Charts set is comprised of five volumes, each covering a specific geographic region. Each volume is an atlas of twelve pilot charts, each depicting the observed conditions for a particular month of any given year. The charts are intended to aid the navigator in selecting the fastest and safest routes with regards to the expected weather and ocean conditions."

There are three main ways to get these, by:

    1. Buying paper copies at a chart dealer or online. (This is expensive and inconvenient, and a set is heavy to carry around for the use they get. They are rarely updated, however, so they will be current for many years). They are about $45.00 US per volume, plus shipping.

    2. Downloading the free PDF versions at the NGA. These are big PDF files, and some computers have difficulty managing them well. They are faithful copies of the paper charts and contain all the data.

    3. Downloading the free versions converted to *.BSB files for use within OpenCPN. The Chart Groups feature in OpenCPN is ideally suited for viewing and organizing Pilot Charts, but its often difficult to see the chart and the explanatory text or notes at the same time.

The downside of pilot charts is that they have been developed over many years and use data reaching back at least 100 years. Since a lot of the data is from pre-satellite times, they are primarily based on data derived from shipboard observations: since ships try to avoid areas of inclement weather, the observations tend to under-report gales and high waves, and the data quality for rarely travelled routes is poorer. The upside is that they combine a huge amount of data (tens of thousands of data points, if not millions combined in a very comprehensible format: wind, waves, currents, storm tracks, and more on a single page).

Here's a view of the Pilot Chart for the western Caribbean in January:

It shows there is almost no chance of calms, winds are typically Beaufort Force 5 (17-21 knots) from the east or northeast for the month, and that the area has a 10-40% chance of developing waves greater than eight feet. Not a great long range forecast.

Other, more 'modern' sources of climate data include:

  • Jimmy and Ivan Cornell's Cornell's Ocean Atlas, which is like a pilot chart, but rather than being based on 100s of years of observations, is based on satellite derived data sources. The first edition, published in 2012, was based on satellite observations undertaken in the previous 20 years (1991-2011). The second edition is fully revised and updated by incorporating data gathered during an additional five years (2011-2016), so make sure you get the latest edition. This volume dovetails well into Cornell's other works and is a reasonably cost effective way to get the data in hard copy. The current edition goes for about $80.00 USD

  • The Climatology "plug-in" for OpenCPN and the OpenCPN manual. This provides monthly data for wind, currents, sea level pressure, sea temperature, air temperature, cloud cover, precipitation, relative humidity, lightning (good source for this data, but not too granular), sea depth (not too useful), and cyclone tracks, all derived from the last ~30 years of satellite data. The climatology module is pretty cool because it allows the selection of a date (all other sources above are divided by month). In effect, if you look at a traditional pilot chart you are only looking at the average data for the month, but with the climatology module if you select the 30th or the 1st of the month it will weight the data for the month ahead or behind with the current month to approximate what the conditions might be like, making it more 'granular' than the pilot charts. Because the data is digital, it can be used with the passage planning capabilities of OpenCPN, either for sketching out a potential voyage months in advance, or for extending a passage plan past the available weather forecasts. This also means that you can see what the precise data is: there is a difference between 17 and 21 knots the pilot charts showed above, and if the windspeed is in the higher or lower end of the range it's nice to know.
This image from the Climatology screen in OpenCPN shows approximately the same area as the Pilot Chart and shows roughly the same data:

Where the red arrow is (just North of Santa Marta Colombia) is the region with the strongest average winds, about 23 knots. Because the data is digital, we can move our cursor around to see the average winds are almost exactly 20 knots throughout the region, which makes a bit of a difference from the 17-21 in the pilot charts. Remember, if the average wind is 20 knots, about half the time it is stronger than that and about half the time it is less.

We also like to root around a bit in satellite data sets. You can review years of data for many satellites with disparate data sets at the NOAA portal. I don't know what the combined budget is for this satellite array, but it's a nice data set to have access to for free.

For example, if we want to know what the waves were like in the western Caribbean, January 2020 mid-month we go to this data set and can extract wave height data:

Hmmm... up to about 20-22'. That puts the fun meter pretty deep in the red, we should probably look at another month for that passage.

We can also go to this data set and extract the satellite wind data for the same date:

Positively sporty, that is. I'm not liking January for voyaging in the Western Caribbean.

We also try to find cruising guides. Cruising guides for different areas in the world vary tremendously in quality, and many are out of date. For some areas, they're just not available. We have also found errors in waypoints and just plain bad advice in some, so do check the data and be careful. As Ronald Reagan said, "trust, but verify". Sometimes you can find cruisers going 'the other way' that you can trade guidebooks and check guidebook reviews with.

I spend the time to find or make satellite charts for the cruising area to use in conjunction with OpenCPN, and download satellite views to the OvitalMap application on our tablets and in SASPlanet on our PC for reference. We get at least large-scale paper charts to carry aboard (which we have never used but carry 'just in case'). Last time I checked, the best deal was at Frugal Navigator, at about $16.00 per chart for DMA charts. For some more travelled areas, chart books are available and make a cost-effective alternative.

We also look for rallies and races in our area of interest as their websites often have good local intel (fleet briefing documents, weather synopses, lists of marine facilities, etc.). We join rallies if their interests coincide with ours, but generally avoid those that have a 'fleet' approach with all vessels sailing in 'convoy' with set departure dates, since we like to pick our own weather windows. So, sailing down the coast we looked at the website for the Baja Haha and didn't join up, but we did join the Panama Posse since it seemed useful.

In the Pacific, the Single Handed Transpac, the Pac Cup, and the Vic-Maui are good sources; in the Atlantic, the ARC (westbound) and ARC Europe (eastbound) have some useful bits. These rallies and races give you a means to meet cruisers in the area and get up-to-the-minute local knowledge from people in the area, and often offer discounts at marinas and similar places of interest.

We round out our research by looking for cruising blogs on the internet, seeking out Facebook groups for specific cruising areas, and looking at the Center for Disease Control website for health information, and UK and USA consular sites for information on safety. While some of the safety advice seems histrionic, it can be useful to have a relative gauge of what to expect in each area. The Canadian consular sites are usually not as good or up to date simply because we have fewer diplomats abroad.

To prepare for time ashore we may look at general travel guides such as the Barefoot guides or the Lonely Planet guides (printed or online), trip advisor, reviews in google maps, etc. We also download offline accessible street maps to our phones and tablets in Google Maps or another app (like for navigation in our land-based adventures.

Generally, gathering all this research takes an afternoon or perhaps a day (except for making the satellite charts, which can take a lot longer), then reviewing and sorting our ideas on when and where we want to move can be done at our leisure.

This article has been provided by the courtesy of Ocean Cruising Club.

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