Picking Weather Windows

When trip planning, picking weather windows is one of the toughest chores for boaters and also one of the most important. Make the right choice and you have an enjoyable trip. Make the wrong one? At best, it’s uncomfortable But it’s also possible that things break on the boat, people get injured, people refuse to ever go boating again, or – the absolute worst – you lose the boat. 

Here’s my take on choosing a weather window. 

Know Your Crew 

First off is to know your crew and their tolerance for boisterous conditions. Always make the go/no go decision based on the least tolerant member of the crew. 

First-timers, small children, and people who are just plain scared or uncertain about being on the ocean call for the most benign conditions. You really want to give them a good experience. 

Beyond that, there are no hard and fast categories. Think of factors such as a person’s propensity for injury, surefootedness, strength, general adventurous spirit (or not, such as a lack of self confidence), strength, and overall knowledge and ability to help should something go wrong. 

Propensity for seasickness is also important to consider and whether it can be mitigated by taking meds in advance of the trip (I start taking meds 36 hours before departing). Are any drugs (for seasickness or otherwise) likely to make them drowsy and thus less helpful in an emergency? 

Looking at Weather Forecasts 

After thinking about who will be on board, I can form a rough idea of what will be too much for them (and me!). I next turn to the weather forecast. It’s important to note that forecasts tend to be based on one of several models. The various sources that you look at are basically just different ways of presenting what the model says. For example, Windy and Predict Wind create easy-to-understand graphics. Others use mostly text.  

However, many DO show the results of various models and this is what is important to look at: the various models. In other words, looking at Windy and Predict Wind doesn’t give you two opinions if you are looking at the same underlying model on both of them. It’s better to look at two (or more) models on one app to see if they agree or not. 

In Windy, click on the various model names to switch from one to another. 

A particular forecaster – such as Chris Parker for the US East Coast and the Caribbean – may throw their own analysis into the mix, but they are starting with the same models. And that forecaster may have a good opinion as to which model tends to be the most accurate in the existing conditions. 

Below, I talk about the various things that I’m looking at, but I’m also looking for a few more general things to give me confidence in the forecast: 

• Consistency between models. Is it just a timing difference or are they radically different? 
• Overall trends 
• How long any window is and what is coming after? If it came early, how nasty would it be? 

Wind Direction and Strength 

I generally look first at wind direction and strength. You pretty much never want wind on the nose over 10 knots – or over 5 knots if trying to give a particularly smooth ride. Some places may have other “no go” winds, such as crossing the Gulf Stream with any north in it if the winds are over 5 knots. 

As for strength, you probably know what you’re comfortable with on your boat, but most powerboats don’t want anything over 10 knots from any direction and sailboats generally don’t want more than 15 or 20 knots from any direction. 

Be sure to look at the gusts and not just the sustained waves! 

Waves 

Waves are a big part of a comfortable passage. Look at the wave height in FEET and the period in SECONDS. 

• You never want the wave height in feet to be approximately equal to the period in seconds. That’s called “square waves” and is just nasty. Things will break on the boat and people will be injured.  
• When the period in seconds is getting to be about double the wave height in feet, things are starting to smooth out. You’ll feel the waves but they won’t be dangerous. The passage will be okay for most people but if you have anyone with mobility or balance issues, you may want to opt for an even longer period. 
• If the period is three, four or more times the wave height, the ride will be quite smooth. 

For example, when we returned from the Bahamas in 2016, the wave height in the middle of the Gulf Stream was 20 feet with swell from the remnants of a tropical storm that was then hitting New England. However, the period was over 90 seconds, making it a very smooth ride. We’d go up, up, up – take a quick look around for any other boats – then down, down, down. Up, up, up, look around, down, down, down.  

Be sure to look at the waves in the different models and also check if there are different wave and swell patterns and periods. Often, there will be waves from two directions and swell from a third. Check them all! 

Squalls 

A series of squalls can turn an otherwise nice day into an awful one. Now, in some places and seasons there is almost never a perfectly squall-free forecast. Southern Florida in the summer is one place like that. In such cases, you just pick the least squally day.  

I look at the absolute number of squalls as well as the coverage. I really don’t like big lines of squalls as they tend to really pack a punch. 

Further, I look not just at “rain blobs” but also at the possibility of lightning. Just rain isn’t too bad but lightning is not at all fun – and thunderstorms often pack a greater wind punch than a gentle rainfall. 

Timing 

If the weather has been averse, I look for I look for at least one day before my planned departure for the seas to settle down (two days if it’s been really nasty). Then a good day (or however long I’ll need) for my trip. And then another good day as insurance in case the weather progresses faster than expected (the new bad weather will move in during that extra day and not during my trip) or in case my trip is slower than expected. 

So for a one-day trip from Florida to the Bahamas, I’m looking for a three-day window: one to settle the seas, one to cross, and one more for good measure. 

Admittedly, the longer the passage, the less confidence there is in the forecast for the few days. And you probably won’t even get a forecast further out than a week. In those cases, you have to be confident in your seamanship to handle whatever conditions may come your way. The trick is to slowly build your skills; don’t take off on a week-long passage the first time you see blue water. 

Poking Your Nose Out 

Finally, if you “poke your nose out” – that is, start to head out – and find that conditions aren’t to your liking, there is nothing wrong with turning around, heading back in, and waiting for a better forecast. Don’t risk injury or damage to the boat. And this is doubly true if you have newbies or anyone who is a little nervous or reluctant aboard. Make sure they have a good experience! 

Picking Weather Windows – An Art

So many times I’ve seen very experienced boaters (some even circumnavigators) turn around to wait for better conditions, only to see newbies charge on. Willingness to turn back is a sign of good decision-making.

Picking weather windows is an art. It’s informed by good choices. But it’s a decision that you continue to evaluate during a passage. And you must be flexible enough to pivot when something changes.

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