South coastal water hights are forecast MEDIUM on 23/24 ( max high ), then dropping over the next Week, due to the Moon phase. Bulldozers have been busy at several vulnerable points today, building up the defences, I suspect in anticipation of a storm surge.
Tidal predictions are computed for average barometric pressure. The average barometric
pressure for the United Kingdom varies between 1016mb along the south coast of the U.K. to
1011mb in the north of Scotland. A difference from the average of 1mb can cause a difference in
height of about 0.01 metre. Low pressure will tend to raise sea level and high pressure will tend
to depress it. The water level does not, however, adjust itself immediately to a change of
pressure, it responds to the average change in pressure over a considerable area.
Changes in level due to barometric pressure seldom exceed 0.3 metres but, when mean sea level
is raised or lowered by strong winds or by storm surges, this effect can be important
Can anyone confirm if the flood barriers in Portsmouth have been raised in the old town ?.