Merrimack River Mouth — Wave Height Calculator

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Estimated Wave Height

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Wind & Wave Direction

Tide Level

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Tidal Range

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24hr Hi/Lo

Wind Speed

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Offshore Sea State

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River Level

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water level · Newburyport

River Flow

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streamflow · Lowell

Wave Period

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Air Pressure

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Air Temp

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HRRR model

Cloud Cover

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HRRR model

    ⚠ This is an AI-assisted estimate, not a certified navigation tool. Conditions at the Merrimack bar can be life-threatening. Never rely solely on this application. You assume all responsibility for crossing decisions.
  

⚠ Mariners Advisory Loading current conditions…

⚡ EASTERLY WIND + EBB TIDE — STANDING WAVE HAZARD —

Ocean waves driven by ENE–ESE winds (70°–110°) are meeting the outgoing ebb current head-on at the Merrimack bar, creating steep, near-standing waves. Wave crests can be significantly taller and more abrupt than indicated by offshore buoy data alone. Breaking waves are likely on the bar.

Wind Direction—

Wind Speed—

Tidal Ebb Current—

River Outflow—

Total Opposing Flow—

Standing Wave Boost—

Wave Height & Period · ±12 Hours Merrimack River Mouth · Estimated · NOW centered

Estimated Hs ±20–30% range <1ft Calm 1–2ft Choppy >2ft Rough+

Wind Forecast · ±12 Hours NOAA HRRR via Open-Meteo · NOW centered

Tide · ±12 Hours NOAA CO-OPS · NOW centered

River Current at Mouth · ±12 Hours Estimated from tidal ebb + river flow · NOW centered

Wave Anatomy height & period factors · live data

Coastal Marine Forecast · Ipswich Bay (ANZ251) — National Weather Service

Safety Disclaimer & Terms of Use

IMPORTANT SAFETY NOTICE — PLEASE READ BEFORE USE

Merrimack Wave Calculator is an informational tool that estimates wave height and bar crossing conditions at the mouth of the Merrimack River in Newburyport, Massachusetts. It is provided for general informational purposes only and must not be used as the sole basis for any navigation or crossing decision.

AI-Assisted Development
This application was developed with the extensive assistance of artificial intelligence. While the underlying physical model is based on established coastal engineering principles, AI systems — including those used in the development of this application — are known to produce errors, omissions, and confident-sounding but incorrect outputs, a phenomenon commonly referred to as "hallucination." The wave height model, its calibration constants, and its methodology have not been independently certified, peer reviewed, or validated against measured Merrimack bar conditions. Users should treat all outputs as estimates subject to significant uncertainty.

Assumption of Risk & Limitation of Liability
The Merrimack River bar is one of the most dangerous inlet crossings on the New England coast. People have died attempting to cross it in conditions that appeared manageable. No application, forecast, or instrument replaces direct visual observation of bar conditions, local knowledge, and the judgment of an experienced mariner. By using this application you acknowledge that you have read and understood this disclaimer, that crossing the Merrimack River bar involves inherent and serious risk, that this application may contain errors, and that you assume full and sole responsibility for all navigation and crossing decisions. The author and operator of this application, Caleb Barlow, and any associated parties accept no liability whatsoever for injury, death, vessel damage, or any other loss arising from decisions made in reliance on its output.

This application is provided "as is" without warranty of any kind, express or implied. Use at your own risk.

  © 2026 Caleb Barlow · All rights reserved · Merrimack Wave Calculator

  Proprietary wave height methodology · For informational use only