Tide Tables and Water Level Forecast at Se havnivå

The most authoritative information regarding tides and water level for the Norwegian coast are available at Se havnivå. These data are regularly developed and updated by the Norwegian Mapping Authority. Tides and water level data are also available through an API, which makes it possible to extract data and integrate them with your own systems.

The need for the traditionally pdf-publication “Tide Tables for the Norwegian coast with Svalbard” has therefore become limited, and the Norwegian Mapping Authority has decided to stop producing this publication.

Which data should you use?

Data

The Norwegian Mapping Authority has 24 permanent tide gauges that registers the water level continuously. These data are available at Se havnivå. The water level measurements are used to calculate the tide tables. Tide tables, or predicted tides, are also called astronomical tides because they result from gravitational effects from the sun and the moon.

The coast is divided into zones that have roughly the same tidal conditions, based on water level measurements from the permanent stations and many shorter measurement series from other locations. The tide in each zone is related to the nearest permanent tide gauge, using a time lag and a conversion factor for the height. The closer to a permanent tide gauge the zone is, the more accurate the data are.

Changes in air pressure and wind can change the water level

In addition to tides, the water level is affected by meteorological effects, especially variations in air pressure and wind. The meteorological contribution can cause water levels to deviate more than a meter higher or lower than what the tide table says.

Low air pressure leads to higher water levels, and high air pressure leads to lower water levels. Generally, if the air pressure drops by one hectopascal (hPa) or one millibar (mb), the water level rises by one centimetre. A powerful low pressure system of 960 hPa will cause the water to rise approximately 50 centimetres.

Wind also plays a crucial role in how high the water level gets. The wind can push water towards the shore and into the fjords, creating an excess of water concentrated along the coast. For the Norwegian coast, it is mostly winds from the south and west that cause this effect.

Water level forecast

With the help of models, the Norwegian Meteorological Institute predicts the effect the weather has on the water level five days ahead of time. These forecasts are added to the Norwegian Mapping Authority’s predicted tides, and we can provide a water level forecast five days in advance.

Areas with small differences between low- and high tide

In the south of Norway, the tide tables may differ substantially from the observed water level. The difference in height  between low- and high tide is small in these areas, and so the weather effect may dominate the water level. We recommend that you use the water level forecast in these areas.

Which data should you use to your purpose?