On 14/15 December 1986, the explosive deepening of a very active
depression between Greenland and Iceland resulted in the central
pressure falling below 920 millibars (mb). This is believed to be
the lowest pressure recorded in the North Atlantic and, perhaps,
the lowest in the world outside tropical storms and possibly the
centres of violent tornadoes. The average atmospheric pressure is
around 1013 mb, but the central pressure weather systems typically
range from 950 to 1040 mb around the UK.
Two become one
Two active depressions which formed in the general area of Newfoundland
followed converging paths and combined to produce the major feature
generating the record reading. Before the two circulations were
absorbed into each other, their central pressures were 956 mb
and 960 mb - both already deep. Afterwards, the single depression
deepened explosively and started to move in a north-easterly,
then northerly direction, towards south-east Greenland.
A ship at some distance from the centre of the storm recorded
a pressure of 938.8 mb. Later, when the storm started to move
a little more towards the north-west, another ship reported 926.2
mb. The same ship reported 920.2 mb at midnight on the 15th -
it was still at some way from the centre.
Lowest pressure reached
At this time the Met Office analysis of the North Atlantic indicated
that the central pressure was about 916 mb, and other national
weather services suggested it could be as low as 912 mb. The centre
of this storm did not approach the UK, so it was only ships at
sea and automatic buoys that were 'lucky' enough to report winds
of between 60 and 75 knots in the circulation around it. Weather
fronts associated with the storm crossed the UK during the 15th
but the conditions they brought were nothing out of the ordinary
for December.
Lowest pressure equalled
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A depression to the west of Ireland passed over one of
the Met Office's Ocean Weather Stations on 10 January 1993.
The ship recorded a pressure of 939 mb in average wind speeds
of 70 knots which produced waves 11 m high. This depression
later deepened to equal the record set in 1986.
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| Record
low pressure 10 Jan 1993 |
How Met Office numerical model handled the
record depression
When compared with actual analyses of the storm, the operational
model used by the Met Office in 1986 produced extremely good forecasts.
It predicted a surface pressure of 916 mb. However, the Head of Forecasting
Services at the time said that the analysed central pressure may not
have been low enough!
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SOME OTHER LOW PRESSURE READINGS
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Pressure (mb)
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Details
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1979
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870.0
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Typhoon 'Tip' (16° 44' N. 137°
46' E). World record
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1958
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877.0
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Typhoon 'Ida' (19° N, 135°
E)
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1927
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886.0
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Ship Sapoeroea (east of Luzon)
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1870
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921.1
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Ship Neier (49° N, 26° W)
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1929
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925.5
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Ship H.M.S Tarifa (51° N, 24°
W)
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1884
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925.6
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Ochtertyre (lowest pressure on record
for the UK)
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1886
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927.2
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Belfast
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1962
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931.1
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Ocean Weather Station 'Lima' (56°
N, 19° W)
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1983
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936.0
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South-east Greenland
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