Extreme High Swell Events on the Moroccan Atlantic Coast

3.0 About the Marine Forecast Process and ASCAT » 3.1 Marine Forecast Process

The marine forecast process for high swell events is presented below. We will describe it and then apply it to two cases.

Marine Forecast Process

Step 1: Assess the current atmospheric and marine situation.

  • Determine the meteorological situation by examining satellite (infrared, visible, water vapour, and ASCAT) data and observational (ship and buoy) data
  • Examine the marine model analyses of 10 m winds, sea surface pressure, and significant wave height

Step 2: Compare the marine model analyses with the observations. If they are in agreement, you should be able to use the model forecasts with confidence. Otherwise, you should use them cautiously and mentally adjust the marine situation temporally or spatially.

Step 3: Forecast the marine situation.

  • Interpret the model forecasts of 10 m winds, sea surface pressure, significant wave height, and the Extreme Forecast Index (EFI).
  • What swell heights are forecast? Do they exceed thresholds?
    • Note that Moroccan wave height (Hs) criteria is 4 m or more in the Atlantic Ocean, and 3 m or more on the Mediterranean coast. After the high swell event covered in the case, additional criteria were added that combine wave height and wave period in the Atlantic Ocean: wave height = 6 m or more, and wave period = 16 s or more
  • If thresholds are exceeded, disseminate warnings, then produce and disseminate the marine products. If the values are below threshold values, produce and disseminate the marine products.

Step 4: Continue monitoring the atmosphere and marine environment.

This process is depicted in the flowchart below.

flowchart showing marine forecast process depicted in lesson