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It’s time for some more science on the night shift! You’ve probably seen some of our discussions on tides and coastal flooding in the past, but have you ever wondered how we forecast tide levels? Tide forecasts are influenced by a variety of factors.
First, we start with an astronomical tide forecast. This is the water level if we were only looking at the gravitational factors. Our colleagues at NOAA Tides and Currents provide astronomical tide predictions for coastlines all over the U.S. here: https://tidesandcurrents.noaa.gov/
This part of the tide is dependent on the relative position of the Earth, Sun, and Moon. When the three bodies are aligned (called syzygy), astronomical tides typically have the largest differences between the low and high tides. More info: https://tidesandcurrents.noaa.gov/restles1.html
The next step in tide level forecasts is meteorological factors. Most commonly, onshore winds (winds coming from the NE, E, or SE for most of our shore) usually increase the tide levels, while offshore winds (commonly W and NW in our area) will typically lower tide levels.
Southerly winds can also increase tide levels especially on the bays in our region, including the Chesapeake, Barnegat, and Little Assawoman Bays, as this wind direction can limit water evacuating from the bays. Other factors, like swells, can also have an impact on tide levels.
With the new moon on Sunday, our astronomical high tides are relatively high. Spotty minor flooding is possible with the high tide this morning and again on Sun. morning. However, offshore flow for much of the weekend should keep other high tides below minor flooding thresholds.
To see tidal water level forecasts, visit https://water.weather.gov/ahps2/forecasts.php?wfo=phi (note, this page also includes freshwater forecasts for inland rivers)
