The Most Important Forecast: A Boater’s Guide to Marine Weather
The sky can be a beautiful, clear blue, but 20 miles offshore, a storm that you can’t even see yet might be brewing. As a captain, the weather forecast is your bible. It’s the one piece of information that dictates whether you go, where you go, and when you come home. A regular land-based forecast telling you the temperature and chance of rain is not enough. You need a marine-specific forecast that tells you about the things that truly matter on the water: wind and waves. Misinterpreting this forecast is one of the most dangerous mistakes a boater can make.
Wind Speed and Direction: The #1 Factor
Wind is the engine that creates waves and dangerous conditions. A marine forecast will give you wind speed in knots (1 knot = 1.15 mph) and the direction it’s coming from. “West wind 10 to 15 knots” means the wind is blowing *from* the west at about 12-17 mph.
- Know Your Limits: Every boat is different, but for most small boats under 25 feet, 10-15 knots is the point where you need to start paying close attention. Anything over 20 knots is generally considered unsafe for small craft.
- Direction Matters: An “onshore” wind (blowing from the sea to the land) can create big waves in the surf zone. An “offshore” wind (blowing from the land to the sea) can feel deceptively calm near the beach, but it can make your return trip a brutal, wave-bashing nightmare.
Understanding Wave Height and Period
This is where many beginners get confused. A forecast might say “Seas 2 to 4 feet.” But there’s another crucial number: the wave period.
- Wave Height: This is the average height from the trough to the crest of the highest one-third of waves.
- Wave Period: This is the time (in seconds) between wave crests. This tells you how “steep” the waves are.
Here’s the key: 4-foot waves with a long period (8-10 seconds) are rolling swells that are usually comfortable. 4-foot waves with a short period (4-5 seconds) are a steep, nasty “chop” that will beat you and your boat to death. I would much rather be in 5-foot seas with a 9-second period than 3-foot seas with a 4-second period.
Decoding Weather Alerts: What is a “Small Craft Advisory”?
When you hear these terms on the forecast, take them seriously. They are issued by the National Weather Service for a reason.
- Small Craft Advisory: Issued for sustained winds of 20-33 knots and/or seas of 7 feet or more. For the average angler, this means stay in port.
- Gale Warning: This is a major step up, for sustained winds of 34-47 knots. These are dangerous conditions for all but the largest vessels.
- Storm Warning: A serious warning for sustained winds of 48-63 knots. Only fools and the desperate are on the water.
The Best Sources for Marine Weather
Your phone’s default weather app is not good enough. Get your information from dedicated marine sources.
- NOAA Weather Radio: This is the gold standard. A VHF radio with a weather function is a critical piece of safety gear.
- NOAA’s National Data Buoy Center: Their website provides real-time data from buoys offshore, so you can see what the conditions actually are, not just what they’re forecast to be.
- Reputable Apps: Apps like Windy, FishWeather, and PredictWind are excellent tools that provide detailed graphical forecasts for wind and waves.
Captain’s Rule: When in Doubt, Don’t Go Out
This is the simplest and most important rule. A fish is never worth your life. If the forecast looks iffy, if the sky looks dark, if your gut tells you it’s a bad idea—stay at the dock. The fish will be there tomorrow.
Mastering the forecast is the first step in being a responsible captain, a core part of our Guide to Choosing a Fishing Boat.
-Captain Sal
