Meteorology and Oceanography
What the exam tests
Meteorology and Oceanography tests synoptic interpretation, local wind and fog, sea state, icing, ocean currents and weather routeing. The exam expects a practical decision, such as when to reduce speed, alter course or secure deck cargo.
Core rules and concepts
- Buys Ballot in the Northern Hemisphere: with your back to the wind, low pressure is to your left. In the Southern Hemisphere it is to your right.
- Geostrophic wind blows parallel to the isobars; surface friction turns it about 10–30° toward low pressure, more over land than sea.
- Warm fronts give prolonged precipitation and poor visibility; cold fronts give squalls, rapid visibility loss and a wind veer.
- Fog forms when air cools to dew point. Radiation fog is common over land at night; advection fog forms over cold water.
- Sea state depends on wind speed, fetch and duration; swell persists after the wind drops.
- Icing risk rises with air temperature near 0°C, sea temperature below about 5°C and strong wind.
- Weather routeing uses pressure, wave and current models; in a tropical revolving storm avoid the dangerous semicircle.
Worked example
Wind is reported from NE at 25 kn in the Northern Hemisphere. Face the wind, so your back is to NE; left is NW. The low centre lies roughly NW of the vessel. If pressure is falling 3 hPa in 3 h and the wind is backing, expect the low to approach and the weather to worsen. Reduce speed and secure deck cargo before the pressure gradient tightens.
Traps
Confusing true and apparent wind; using a single pressure reading; assuming swell disappears when wind drops; ignoring squall lines; and applying Northern Hemisphere Buys Ballot in the Southern Hemisphere.
Key points: Buys Ballot; geostrophic and friction; front weather; fog types; icing and swell; pressure tendency.