Instructions on using Atlantic Ocean forecasts
Keep the following points in mind:
- Forecast maps for the Atlantic Ocean are automatic weather forecasts, made using a computer model.
- View the shipping forecast in addition to the automatic, map-based forecast.
Bear in mind that short-term forecasts are more likely to be accurate than long-term forecasts.
Forecast map for the Atlantic Ocean
- The black isobars signify the air pressure, in millibars, at the ocean surface (1 mb = 1 hPa).
- The red, purple and blue isotherms show the temperature at 2 m above the ocean surface. A blue line denotes sub-freezing conditions; a purple line denotes 0°C and; a red line denotes temperatures above freezing.
Wind speed is displayed in metres per second (m/s).
The angle of the wind barb is indicative of the wind direction.
Wind-speed is symbolised by diagonal lines at the end of the barb; a long line represents 5 m/s, a short line 2.5 m/s and a triangle represents 25 m/s.
Temperature levels are shown over the Atlantic Ocean in degrees Celsius (°C) at an altitude of about 1,500 m above the ocean surface. This altitude equates to an air pressure of 850 hPa.
The temperature at 1,500m altitude provides insight into the advection of warm or cold air.
The temperature scale on the image changes according to the temperature range of the forecast.
The map displays a forecast for the cumulative level of precipitation over a 6-hour period.
The colour scale denotes precipitation rates. The intensity ranges from 0.5 mm to 30 mm every six hours. Light and heavy precipitation is represented by light-green and purple shading, respectively.
Atmospheric pressure at the ocean surface is also shown in millibars (1 mb = 1 hPa).
The sliding bar below the map is used to change the validity time of the forecast
It is possible to change the validity time in many ways:
- It is possible to click anywhere on the bar.
- It is possible to click on the days above the bar to view the noon forecast for a specific day.
- It is possible to click on the time below the bar.
- It is possible to click on the arrows on either side of the bar to view the previous or the next validity time.