New reference system for sea level warnings

As of June 3, 2019 sea level information in SMHI’s forecasts and warnings will be expressed in RH 2000  instead of relative mean sea level (RW). RH 2000 is the Swedish national reference system for heights and depths, and corresponds to the Baltic Sea Chart Datum 2000 which is used for depth information on updated nautical charts. This transition has led to changed warning levels.

The new warning levels are conversions of previous levels into to the new reference system. This means that they are not significantly different from the previous levels. Thus, sea levels that trigger warnings are the same as they were before. However, due to geographical variances in mean sea level long the Swedish coast, the levels are now more differentiated than before.

New classifications for low sea levels

In conjunction with the transition to a new reference system, SMHI has changed the classification for low sea levels along the Swedish coast. What was previously class 2-warnings will now be class 1-warnings. This is because the impacts of low sea levels along the coast better correspond to SMHI’s definition of class 1-warnings. Exceptions have been made for the Sound, the Belts and the South-Western Baltic, where heavily trafficked and partly shallow fairways justify the use of two classifications (i.e. class 1 and class 2).