Von: joel carlinsky
Datum: 02/17/05 03:15:06
Great weather events: the 'Burns' Day' storm of 1990
The depression which brought severe weather to north-west Europe during
25 and 26 January began on the 23rd as an innocuous-looking wave on a cold
front in the North Atlantic about 400 miles south-east of Nova Scotia.
By midday on the 24th the central pressure of the low had dropped to 992
mb, and conditions were favourable for it to deepen explosively.
The storm arrives
As the low approached Ireland during the early hours of a the 25th the
most rapid strengthening phase of the storm was taking place with the central
pressure now down to 968 mb and the whole system showing a 'hook' shape
in satellite imagery - this shape normally indicating the development of
a severe storm. The storm centre tracked across Northern Ireland on the
morning of the 25th (with falls in pressure in the order of 16 mb in three
hours) and by midday was centred over Ayrshire. The lowest central pressure
of 949 mb was estimated at around 1600 to the east of Edinburgh as the
storm continued its rapid movement towards Denmark.
The strongest winds occurred on the western and south-western flanks of
the storm with average speeds of 40-50 knots over large areas of England
and Wales. In exposed areas on the south coast of England and west Wales,
the mean speeds reached 60-65 knots. But it was the gusts that did most
of the damage. The highest gust was 93 knots (104 m.p.h., recorded at Aberporth)
but several gusts of 90 knots occurred over large areas of southern England.
Met Office warnings
The Met Office gave excellent warning of this storm. Forecasters are expert
at handling an ensemble of solutions from different forecast centres and
on this occasion the signal for marked strengthening of the depression
was clear.
Emphatic guidance of severe gales was issued in a routine TV broadcast
four days before the storm arrived, but with uncertainties about the track.
As the event drew closer, more precise forecasts were issued on 24 January
based on the forecast from the 'fine-mesh' model then in use. A press release
was issued about the possibility of structural damage, and the Ministry
of Defence was notified that military assistance to the civilian population
might be required owing to the severity of the winds.
This storm produced winds of comparable strength to the storm of 1987 but
they covered a much wider area. Despite timely warnings from the Met Office,
the casualties were higher than in 1987 because of the daytime arrival
of the storm (compared with overnight in 1987) and the greater area affected.
Storm damage
In its wake the storm left a trail of death and destruction both on land
and at sea. It was reported that 97 people died in northern Europe, with
half this number being in the UK. Road, rail and ferry services were disrupted
and great damage was inflicted on the countryside - an estimated three
million trees were blown down in the UK alone. Power lines were also brought
down in this country and parts of mainland Europe.
Parts of Hereford and Worcester were flooded when the River Severn rose
by 3.5 m, while in West Germany a coastal village was evacuated when threatened
by floods from a breached dyke. The port area of Hamburg was also flooded.
.