Weather & tidal info

This chapter provides all the weather and tidal information required for entering or departing from the port of Rotterdam. Besides clear overviews of currents and tides, this chapter describes relevant weather and tide conditions. 

Online updates:
Hydro-meteo information, online observations of water levels, wave heights, water velocity and wind at various locations within the Rotterdam port region. The gauges are linked to the AMETHYST-database of the Port of Rotterdam Authority and can be consulted in graphs that cover the last 24 hours.

General
For general information regarding traffic, weather, tides, current, sea conditions, fog, ice, etc. the appropriate Traffic Center sector can be contacted via VHF channel 11.

Wind
All measured at Hook of Holland:

• Prevailing winds: W – SW, force 4 or 5.
• Relative frequency of wind forces greater than force 7 Beaufort: 1.1%. 

Tide

General
In a period of 24 hours there are 2 high waters and 2 low waters, with different amplitudes (i.e. one high water is higher than the other, one low water is lower than the other). 
A special phenomenon manifests itself at Hook of Holland, which has a double low tide with the second low water lower than the first. 

At sea

• Strong and sustained winds from the north-west raise water levels along the Dutch coast.
• Strong and sustained winds from the south-east have the opposite effect. 

On the river
The timing and actual tidal levels in the waterway depend greatly on the wind and state of the river. 

When the river outflow is low (in the summer and winter), HW and LW levels are about 0.1 to 0.2 meters lower than predicted.
When the river outflow is high (in the spring and autumn), HW and LW levels may be more than 0.1 meter higher than predicted.

During spring tides with strong W to NW winds, the river level may increase by 1 meter or more.
Mean tide is 1.70 meters, and spring tide 1.80 meters.

Current
At sea, Maas Entrance, in front of breakwater
Vessels passing the port entrance should beware of the current running across the entrance.
This current attains its maximum rate at HW Hook of Holland. 

After the tide turns, the flood current sets in quickly, whereas the ebb current sets in more gradually. The flood current flows to the north-east. The ebb current flows to the south-east. 
The ebb current continues to run outward along the inner side of Noorderdam after the flood has started off Zuiderdam.
The general flow is north-easterly, and therefore the flood current is stronger than the ebb current.
Mean current rates are 2.5 knots during flood and 2.0 knots during ebb. Weather conditions and river discharge can influence the average current rate.

The wind influences only the rate of the currents, and not their direction.
Strong SW winds cause a strong NE current, and a weak SW current.
Strong NW winds cause a strong SW current, and a weak NE current.
Current rates up to 4 knots may occur in stormy periods.

Off the Maas Entrance (52°00’N, 004°02”E), during the ebb current, the meeting of the discoloured river water and the cleaner North Sea water is plainly visible. This meeting is usually indicated by a line of ripples extending WNW, NW or N from the Noorderdam mole head, but never S of a line running seaward of the Noorderdam axis.

The distance to which the line of ripples extends, and its direction, depends on the relative rate and direction of the ebb and outer currents, and the force and direction of the wind. For example, with a strong E wind and ebb current, it may extend 7 or 8 miles seaward in the direction of Noorderdam, whereas at other times it may only extend for a very short distance.

On the river
When the discharge of the river Rhine is high because of melt water from the Swiss mountains (in the spring) or during heavy rainfall, the river is running at full spate. In that situation, the outgoing current at Hook of Holland and Maassluis (51°55’N, 004°15’E) can exceed 3 knots. If, in addition, the prevailing winds are from the E and S, then there may be little or no ingoing current at Hook of Holland. 

Further up river the rate and duration of the ingoing stream are reduced.
During spring tides and with strong W to NW winds, the duration of the ingoing current is increased.
The current is stronger near the axis of the river than at the side of the river.

Cross section of Nieuwe Waterweg and Oude Maas. 
Attention should be paid to the area where the river Oude Maas runs into the Nieuwe Waterweg / Nieuwe Maas junction (51°53.5’N, 004°19.5’E).
From half an hour before to 4 hours after high water at Hook of Holland there is a strong set to the south. At other times there is a strong set to the north. 

Failure to pay sufficient attention to this effect could cause you to end up on the wrong side of the river.

Overview of currents in relation to High Water Hook of Holland (HW HoH)