Our Blog
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Diurnal vs Semi-Diurnal Tides: Regional Patterns
The tide station at San Francisco shows two high tides and two low tides every day, with roughly equal heights. Travel south to the Gulf of Mexico near Pensacola, and you’ll find only one high and one low tide per day. Head to Seattle, and you’ll encounter two daily tides—but with wildly different heights between
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Tide Predictions in Rivers and Estuaries: Navigation Guide
Tide predictions get complicated when you move inland from the coast. That morning high tide at the river mouth might not reach thirty miles upstream until afternoon. The twelve-foot range at the harbor entrance could drop to just four feet where you’re anchored. Understanding how tides behave in rivers and estuaries transforms navigation safety and
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Understanding Tidal Datums: MLLW, MLW, and Chart Depths
You’re planning a passage through a narrow channel. Your chart shows 8 feet of depth at the entrance. The tide table predicts 2.5 feet at your crossing time. Simple math says you have 10.5 feet—plenty for your 5-foot draft, right? Not necessarily. Those two numbers use different reference points. Understanding tidal datums transforms how you
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Bridge Clearance Planning with Tide Data
The tide gauge at the Charleston Bridge showed 4.2 feet above MLLW. The chart listed the bridge clearance as 65 feet at MHW. With our mast height of 62 feet, did we have clearance? The answer required understanding not just the numbers, but what they actually meant. Bridge clearance planning is one of the most
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Tide Favorites: Monitor Multiple Tide Stations Simultaneously
Introduction You’re planning a weekend cruise from your home marina through a narrow channel, across an open bay, and into a protected anchorage. Each leg has different tidal considerations. The channel requires adequate depth. The bay entrance demands slack current timing. The anchorage needs sufficient water at low tide. Checking three separate tide stations for
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Slack Water Timing: Finding the Perfect Transit Window
I’ve transited Deception Pass more than 200 times, and every single trip begins with the same calculation: when will slack water occur? Miss that 15-minute window by even 10 minutes, and you’re fighting 7-knot currents that can push a small vessel sideways into the bridge pilings. Get the timing right, and the passage is routine.
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Tide Stations: Understanding NOAA’s Monitoring Network
The captain squinted at his tide table, puzzled. His GPS showed him anchored near Charleston, but the closest tide station listed was 12 miles away at Fort Sumter. Would those predictions work for his location? How far could he trust station data? And why were there so many stations in some areas but none in
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Spring Tides vs Neap Tides: Complete Planning Guide
Introduction: Why This Matters I learned about spring and neap tides the hard way. Planning a departure from a shallow harbor on what I thought was “just another high tide,” I arrived at the dock to find we had three feet less water than expected. The tide was high, all right—but it was a neap
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Tide Prediction Algorithms: How We Calculate Future Tides
The tide table on your phone isn’t a guess—it’s the result of 150 years of mathematical refinement. Every time you check whether you’ll have enough water to cross a bar or clear a bridge, you’re looking at predictions calculated by algorithms that combine celestial mechanics, local geography, and centuries of observation data. Understanding how tide
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Swell Windows: Finding Calm Between Storm Systems
Introduction: Why Timing Matters More Than You Think I was planning a 220-mile coastal passage from San Francisco to Monterey Bay when I noticed something interesting in the seven-day wave forecast. A powerful storm was currently hammering the coast with 15-foot northwest swell at 17 seconds. Three days later, another significant system would arrive, bringing