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Safety at Sea
Weather is a major element in safety at sea. An accurate
forecast can inform seafarers and help them to plan their route
or even decide whether they will set out or not.
 The weather at Mizen Head is a classic alternation of low and
high-pressure systems (depressions and anticyclones). The
prevailing wind is from the northwest. Mizen Head, the most
southwesterly point of Ireland, is projecting out into the
Atlantic Ocean where the currents bring the warm waters of the
tropics past in the Gulf Stream. The tides around Ireland and
the Atlantic Ocean meet in a turbulent swirl. It is only
possible to land onto the Fastnet Rock directly from a boat
approximately twelve times in the year. Mid-Atlantic storms send
huge waves to crash on the cliffs at Mizen.
Until recently the only way to predict the weather accurately
was to rely on people collecting up to the minute data about the
weather in their area. They passed it on to a central office
where it was collated and analysed.
Lightkeepers had an important role in the collection of weather
data. As a part of their daily routine they collected
information about the weather for the Irish Lights. At regular
intervals during the day they collected measurements and
recorded them in ledgers. This information was not passed on
daily. The information they collected was air temperature,
barometric pressure, sea state, visibility, wind force and
direction, Beaufort Weather Notation (Present weather).
The three lightkeepers on a station had 4-hour watches. 6am – 10
am., 10 am. – 2pm., 2pm. – 6pm., 6pm. – 10pm., 10pm. – 2am.,
2am. – 6am. It went in rotation all week with a double watch on
Sunday to move them into a different routine for the next week.
As he went off watch a Lightkeeper would record the weather
readings in the Irish Lights ledger.
At some stations including the Fastnet and Mizen, readings were
taken by the Lightkeepers for the Meteorological Office, which
contacted the station by telephone every day and the information
was given in a coded form for speed and precision. Weather
readings were quite complicated procedures.
There were nine readings to report.
Table I (1) N Amount of Sky Covered
Table II (2) DD Wind Direction
Table III (3) ff Wind Speed
Table IV (4) VV Visibility
Table V (5) ww Present Weather
Table VI (6) W Past Weather (in the last 6 hours)
Table VII (7) State of Sea
TT Air Temperature
PPP Atmospheric pressure
Each of these tables had a different code. It was much easier
for a Lightkeeper to say to the weather office ‘N8’ than to say
‘the sky is completely overcast’.
The code at the top of the Table gives the order in which
readings were given at Mizen Head
MMDDHHHH (MIZEN HEAD) Nddff (Tables I, II, III) VVwwW (Tables
IV, V, VI) PPPTT (Atmospheric pressure, Air Temperature) Sea
State (Table VII) MINVIS/…
So see if you can interpret this weather reading using the
tables.
Coded weather reading:
N = 5
DD = 27
ff = 6
97
81
8
TT 10ºC
PPP 92
5
The coded weather data means:
The sky is five eighths covered with cloud
The wind is from the west
The wind is a strong breeze blowing at 22 – 27 knots
The visibility is 6 miles
There are moderate to heavy rain showers
In the last six hours it was raining
TT The air temperature is ten degrees Celsius
PPP The atmospheric pressure is 992 millibars (low)
The Sea State is rough with the height of the waves 2.5 – 4
metres in height.
The Lightkeepers had to take these readings at set times every
day – 6am., 11 am., 2pm., 4pm., 6pm. and 10pm.
Present Weather Data
Collection
With the development of satellites, weather data collection has
been automated. A computer can collect data constantly and
quickly. Mizen Head Signal Station has been automated since 1993
and when the Lightkeepers left the collection of weather
information ceased. There has been no weather data collection
here since. Now an Automatic Weather Station has been installed
at Mizen Head and Met Éireann can access the readings by modem.
The MILOS 520 System Automatic Weather Station is on a mast on
the way down to the Signal Station.
On the mast there is:
An anemometer to read wind speed.
A wind vane to read direction
A digital barometer
A humidity and temperature probe
A rain gauge
A ground temperature sensor
In the Fastnet Hall the present weather is displayed on a
monitor. It shows measurements of various elements of the
weather in the last 24 hours.
Present Weather Monitor
Air Temperature – how warm or cold it is
Humidity - how much moisture is in the air
Dewpoint Temperature - the temperature to which the air must be
cooled for condensation to occur (for fog to form)
Pressure – to show low or high pressure
Precipitation – rain, sleet, and snow
Soil Temperature
Wind Direction
Wind Speed
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