Tidal Accuracy: The Surprising Reality Behind Your Daily Surf Forecast

As you're probably aware, surf forecasts are crucial for planning your day at the beach. But have you ever stopped to think about just how accurate those predictions really are? In this blog post, we'll delve into the factors affecting tidal accuracy, model simplifications, and assumptions that might be surprising you.

Scenario: A Perfect Storm

Let's say you're heading out to catch some waves on a sunny Saturday morning. You've checked your surf forecast app for 30 minutes, and it shows a high tide with a predicted wave height of 6 feet (1.8 meters) at 10 am. You grab your board and hit the beach, eager to ride the swells.

As you paddle out, you notice that the water is calm, with no waves breaking. Suddenly, a strong wind blows in from the north, blowing at 20 knots (37 km/h). The surf forecast app warns of a "high risk of rough seas" due to the changing tides and strong winds.

The Chaos Unfolds

Fast forward to when you're trying to get back to shore. The winds have picked up, and the waves are crashing against your board. The predicted wave height has changed significantly, now standing at 3 feet (0.9 meters) due to the changing tides. Your surf forecast app had warned of rough seas due to the "high tide" mentioned earlier.

But why did the actual conditions deviate so much from the forecast? And what about other factors that might have affected tidal accuracy?

Factors Affecting Tidal Accuracy

1. Wind and Currents: As we saw in our scenario, strong winds can alter tides quickly, making it difficult to predict wave heights accurately.
2. Atmospheric Pressure: Changes in atmospheric pressure can also impact tides, as seen in the example below.
3. Ocean Currents: Ocean currents play a significant role in shaping tidal patterns and can influence wave heights.
4. Coastal Geometry: The shape of the coastline can also affect tidal patterns, with some areas experiencing more pronounced tidal cycles than others.

Model Simplifications & Assumptions

Now that we've discussed the factors affecting tidal accuracy, let's take a closer look at how surf forecasting models are simplified and their assumptions:

1. Simple Harmonic Analysis (SHA): Many surf forecasting models use SHA to analyze tides and predict wave heights. However, this approach assumes a constant tidal rate, which is not accurate in reality.
2. Atmospheric Forecasting: Surf forecasting models often rely on atmospheric forecasts to understand wind patterns and currents. However, these forecasts can be subject to error, especially for complex weather systems like storms or hurricanes.
3. Ocean Model Simulations: Some surf forecasting models use ocean model simulations to predict tidal patterns. However, these simulations are often simplified and oversimplified, neglecting important factors like ocean currents and sediment transport.

The Reality Check

In reality, tidal accuracy is significantly lower than predicted by surf forecasts. According to a study published in the Journal of Coastal Research, the accuracy of coastal tides can be as low as 70% for some areas.

This means that you should always check the forecast multiple times before heading out to catch waves. It's also essential to consider other factors like wind direction and speed, ocean currents, and coastal geometry when planning your day at the beach.

Conclusion

Surf forecasting is a complex task that involves many variables and simplifications. While models can provide some useful predictions, they should always be taken with a grain of salt. By understanding the factors affecting tidal accuracy and model simplifications, you'll be better equipped to make informed decisions about your day at the beach.

Stay tuned for our next blog post, where we'll explore more topics related to coastal weather forecasting! I can help you with that. Here is the information in a table view:

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