Riding out the blow at Black Point

And FINALLY getting to Georgetown.
A constellation of anchor lights at Monument Beach.

The Exumas, and Bahamas in general, is a windy place. While this is awesome for living a fairly insect-free existence, weather is always a concern for moving the boat or finding a good anchorage. Monday, March 8, found us picking up anchor near Staniel Cay and moving further south to wait out a week-long blow (what cruisers call windy conditions typically brought on by cold fronts). We figured the anchorage at Black Point Settlement on Great Guana Cay would be a better place to sit it out. The sail was short, and the wind was blowing pretty good, so we just scooched on down with the Genoa only. The evening brought very gusty winds, but the bay was well protected from the east wind and the anchor held like a champ. We did make it into town a couple of times, but taking the dinghy in the windy chop meant a wet ride every time. I had planned to get a lot of linens and rugs washed during our visit (Black Point has a pretty sweet laundromat), but I abandoned that errand figuring my clean laundry would just get sprayed with salt water on the ride back.

By the end of the week, Ed and I were getting antsy for the weather to quell so we could move on. Sitting in a windy anchorage with little else to do other than boat chores and one person to talk to gets old in a hurry. Before you get too deep into reading, I’m offering a fair warning that this blog post will be more on the technical side.

Saturday, March 13, started looking like a promising day to keep travelling south. We were leaning toward making a stop at Rudder Cut Cay and then waiting for more of a westerly wind to jump over to the east side of the Exuma chain which you have to do to get to Great Exuma Cay, Georgetown’s location. As Saturday approached, and both Ed and I were desperate to interact with other people, we decided to rip off the band-aid and take on yet another upwind sail with not-so-flat water. At least I’ve finally gotten enough of a handle on my forecasting and navigation skills to know exactly what we were getting into this time! I think it actually made the sail better just knowing it wasn’t going to be great. It got me thinking a little bit about the technology available now, that wasn’t available even ten years ago, that makes it possible for a pretty inexperienced sailor to take on the critical task of getting a sailboat from point A to B…safely AND comfortably.

Thoughts on modern technology

First, I must share that I’ve really started rethinking my relationship with technology. I started out my adult life as an aviator, and with that came a transferable skill of basic concepts in navigation, weather theory, and using forecasting products. GPS and cell phones were also pretty new technology when I soloed my first airplane at the age of 17 and they really weren’t all that ubiquitous quite yet. When driving to somewhere new, the first step was breaking out the Thomas Guide (do they even make those anymore?), and if you screwed up along the way, you stopped at a gas station to ask directions. Well, aviation wasn’t all that appreciably different. We all carried paper charts and various other publications that had information about airports, radio navigation facilities, and radio frequencies. The key difference between driving and flying, however, was, and still is, is that one cannot pull off to the side of the road if lost or encountering bad weather in an airplane. For this reason, and other reasons, pilots are given much more of a formal education in navigation and weather. When I started flying there were basically three different tools for navigation, and about the same for acquiring weather products. GPS and mobile computing (i.e. cell phone data) were functionally not in this toolbox. Getting weather data involved a dial-up internet connection or calling a flight service station, and, therefore, weather reports and forecasts were all textual (not graphic) and heavily coded to keep file sizes small.

Navigation was (and still is) very much a math game, and cross-country flying (term used for anything other than flying around your local airport) was probably not the activity for you if you weren’t very good at making a graphic mental picture out of a bunch of numbers. It took me a while with a lot of study, but I finally learned how to do it, and do it well. I had learned a skill that few women ever developed, which is unfortunately is still true in many ways. It made me feel like a queen among common men. I had put in a lot of work into becoming a safe and proficient aviator, and I had learned to intuit a picture of the world around me with little more than a chart, a clock, a compass, basic aircraft instrumentation, and some math skills.

As time went on, GPS technology improved drastically, and the introduction of the smart phone changed the aviation landscape faster than you could say landscape. Every airplane now had a moving map display, radio navigation is going the way of the dinosaur, and anyone who has gotten their pilot license in 2010 or later would probably tell you they had to learn “dead reckoning” just enough to pass their checkride (pilot license test)…maybe. The Garmin GPS became the primary navigation tool followed up by sophisticated iPad apps for navigating and everything else aviation. I enjoyed and made good use of these tools. I also snickered at all the pilots who didn’t have “real” navigation skills. I called them “the children of the pink line” in honor of Garmin’s magenta-colored course to follow on their moving map display. I truly believed a pilot who was not proficient at analogue (for lack of a better term) methods of navigation was not as safe as me.

I’ve since changed my tune. We now live in a world where the necessity to actually navigate by dead reckoning alone is so statistically remote as to not really be a primary skill with which one must be proficient nowadays. Learning what it is and how it works is still a worthwhile exercise, but it is no longer a practical way to navigate in the modern world. It’s much like teaching your kids to drive a manual transmission: great if said kid has some specific purpose that requires that skill, but otherwise there just aren’t that many cars left (in the U.S.) that use that technology. I used to cringe a little bit that modern technology made it “too easy” for people to become pilots. I had to work hard to learn navigation skills to keep me safe, why should modern technology present navigation wrapped neatly in box with a pretty bow on top? Old, salty sailors, no doubt, view a sailor like me the same way. I suppose it’s the natural evolution of aging…KiDs ThEsE dAyS hAvE nO iDeA hOw EaSy ThEy HaVe It!

Yep…this is correct. And it’s a good thing in a lot of ways. In the case of sailing and cruising I think one of the most important consequences of better technology is that it makes it accessible to more people. Generally speaking, technology allows (but doesn’t guarantee) more people to experience many things in life that without the technology would not be possible. It can foster understanding and communication across different cultures. And yes, I realize the opposite is also true. Looking optimistically though, people who are way smarter than me found a way to share the magic of sailing by making it possible to learn without the huge time investment of learning how to do a number of tasks that a bunch of zeros and ones can take care of.

With that said, I don’t find it terribly necessary to learn celestial navigation, how to use a sextant, how to use an SSB radio, or those “older” navigation tools…boat doesn’t even have the equipment for it. I can still lean on the earlier more rudimentary methods of navigation in a pinch, but no one in their right mind would embark on a crossing without a modern chart plotter, back ups on a couple of tablets and phones, a satellite communication device, a subscription to a sailing weather forecasting app, emergency beacon, etc. Think about it: if you were to board a commercial flight and the pilot said he was going to get you to your destination using only paper charts, a compass, and a watch, you’d look at him or her sideways and think, “what the hell is wrong with using GPS?!” and probably get right back off that plane. The fact is, we have so much redundancy of being able to rely on modern technology that if we find ourselves needing to navigate by paper, compass, and watch alone, we have bigger problems than navigation. I still get paper charts, I still prefer them for the planning stage of things, but it is necessary in the 21st century to use a chart plotter and have GPS sources to get access to the data needed to carry out the mission.

This brings me to my next point. Navigation essentially has two main components when planning: plotting the route and determining the weather. Both of these obviously work hand in hand, and it is a bit artificial to separate them as stand-alone elements, but the weather forecasting tools available to the “everyman” has made a significant technological leap in the last decade…more so than the actual navigation tools in my opinion. This topic could go on for ages if I discuss both in their entirety, so I will focus on the products I’ve learned to rely on for getting the weather information I need to make safe sailing decisions. Perhaps weather theory and route planning I’ll leave for another time.

Learning the ins and outs of modern-day forecasting

Weather forecasting, on the grand scheme of things and as we know it, is new…less than 100 years old. Heck, the ability to even measure and record the weather in any kind of meaningful way is only a few hundred years old at best. The best we humans could do for millennia, when it came to planning around weather, was understand the seasonal nature of it. Farming required us to know when to plant, and that’s really the best we could do in trying to forecast the weather.

Sailing ships have been with us in some capacity since around 5,000 BCE. Because of limitations in navigation (the ability to determine one’s longitude), it wasn’t until the late 1400’s that sailboats were able to navigate when very far from land. These early ocean crossers no doubt ran into all kinds of awful weather and rough seas. Many were lost. Keeping boats out of bad weather was essential for trade. Through experience, mariners developed a seasonal sense of where and when one was likely to encounter adverse weather such as hurricanes. Mariners also relied on various rules of thumb, such as red sky at night sailors’ delight…. As navigation technology improved so did the ability to measure the weather. The anemometer, thermometer, and barometer were all invented fairly contemporaneously. At least sailors had a few tools to observe the weather and land on some short-range conclusions of what was coming next. It would not have been enough to avoid it though.

The invention of the telegraph was really the first essential leap in weather forecasting–the ability to communicate weather data instantly over great distances. This worked great for land, but it wasn’t until the invention of radio telegraphy about 50 years later that sailboats and steamboats could get this data at sea.

The 19th century ushered in an era of weather data collection and transmission, and the advent of the 20th century saw the beginnings of trying to make sense of, or model, the weather. Upper atmosphere observing became possible in the 1920s with the invention of weather balloons, or radiosondes. Attempts at numerical data forecasting began around the same time. Mathematicians were able to develop the equations needed to produce a forecast model, but the complexity of the atmosphere required very large numbers of calculations to be made. Without computers, it was impossible for humans to process the data fast enough to make a forecast.

The invention of the computer, and then its explosive growth in computing power finally made modern numerical forecasting possible. The first forecasts became available in the 1950s but were only accurate out to roughly 24 hours. The 1970s and early 1980s saw the creation of the first global forecast models, and improvements in computing power and data processing have made them more accurate and have allowed for longer range forecasts.

Getting the data and forecasts on demand and in graphical format is a very recent development that has come with the invention of the smart phone.

One of the more popular sailing weather apps is called Predict Wind which purchases (or gets for free) a variety of weather forecast models and then displays the data graphically in a very user-friendly format. Currently, Predict Wind has four global models available (minus their proprietary models which are based on data from the list below), along with a few regional models.

The global models:

  1. ECMWF or “the European model”: European Centre for Medium-Range Forecasts
  2. GFS: Global Forecast System
  3. Spire
  4. UKMO: United Kingdom Meteorological Office

All four have very sophisticated methods data collection and processing, but they do differ, and some perform more accurately for certain things than others. Learning what those are has been my latest learning task. I have noticed that many folks regard the ECMWF as “better,” and most folks tend to operate with the idea that as long as the models agree with each other (forecasting the same thing) that’s good enough to rely on. I am of the opinion that operating that simply is a good way to miss a good weather window or fall into a trap of disregarding one data set at the preference of another.

My first task has been understanding, in general terms (this woman is no mathematician), how these models are made. I have found, so far, there are a few broad questions to get answers to first. 1. What data are being input? 2. What assumptions does the model make? 3. What resolution and update frequency does the model offer? These seem to be where the larger differences lie between the models.

With the first question, the ECMWF, GFS, and UKMO appear to all have great similarity on the data that are input. Spire, which is relatively new, appears to input some different data than the other three. Spire uses a technology called radio occultation to gather data for its model. As I understand it, the other three models gather this data as well, but on a much smaller scale. Radio occultation, in simple terms, is like a satellite version of radar or sonar. The satellite network shoots a radio signal through the atmosphere at different angles, and a great deal of information can be gathered based on how the signal bounces back. Essentially, the satellites are using refraction at a lower frequency…a sort of radio rainbow. Spire does also source data from other places, but its heavy reliance on forecasting with space-based weather data give this model an edge over the others when it comes to off-shore (I’m talking really in the middle of the ocean) wind direction and speed. This model is not one I rely on very heavily while coastal cruising, but knowing its strength, I will likely heed this model more heavily when on ocean crossings.

Question two is still going to require more research on my part. First, I don’t yet know how Spire and UKMO make their assumptions. For this question, I will just compare the GFS and ECMWF. One of the biggest differences between ECMWF and GFS (so far as I understand it) is that GFS models use a hydrostatic model, and ECMWF is a nonhydrostatic model. As I am not a meteorologist I am not able to really give a good primer on what that all exactly means, but the important part of the difference is that a hydrostatic model does not account for how terrain affects weather, but a nonhydrostatic (dynamic) model will. The computing power required to create a global forecast with a nonhydrostatic model far exceeds the computing power required for a hydrostatic model. That said, the nonhydrostatic assumption tends to be more accurate in coastal areas and also predicting how convective activity will affect weather. As most cruisers tend to stick to more tropical areas and coastal cruising, this is likely why most will tell you that the ECMWF is “better.” It is…for the kind of sailing they are typically engaged in.

Question three is also a question that I need to educate myself on more, but it is fairly easy to tell that resolution refers to the size of a grid square, and update frequency…well…how often does the model send an update and at what intervals does it show change? Both the Spire and UKMO show a 25km resolution at best. On an ocean crossing, this is a pretty decent resolution to work with; in coastal areas it’s a bit broad and doesn’t always capture the nuances in weather that terrain can produce. ECMWF produces an 8km resolution, and GFS 22km. UKMO and GFS have a six-hour update frequency, and ECMWF has a 12-hour update frequency. Although the ECMWF has a tighter resolution, there is something to be said about getting quicker updates. If for some reason there was erroneous data input, or there is rapid change, a quicker update frequency can correct itself faster. The GFS, while it tends to be less accurate than its European counterpart, can also “fix itself” faster than the ECMWF. This makes the GFS and UKMO useful to see how things might be changing in time that the ECMWF does not do as well.

The take-away I’ve landed on so far with weather forecasting models is that having multiple models to review is quite helpful to see where the differences are and also how disparate they are. When the models agree, there is more certainty in the forecast, but that isn’t always enough. Learning WHY the models sometimes disagree is just as important. It’s also important to understand which models have which kind of reliability and also HOW to compare them and use them together.

I am still on a learning curve of marine weather and navigation, and in some ways a learning curve of what kind of modern tools I need to focus on learning to become a good navigator and sailor. The tools and information I might have had to learn 20 years ago are different than those I have to learn now. My old, salty sailor friends: you had a bigger time investment than I might have now, but I am doing my due diligence to get the job done right.

One thought on “Riding out the blow at Black Point

  1. Wow. Superb writing. Looks like a perfectly edited chapter from a good book. I am jealous of your writing skills! I am a voracious reader and almost always see lots of minor edits needed in the material I read. I didn’t find a single thing that needed improvement in your post. And it flows. Keep learning and teaching!

    Like

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