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Old January 22nd 05, 03:54 PM posted to uk.sci.weather
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Default Sfc. Pressure Development - February 2005

Disclaimer: The forecaster is not responsible for damages or losses
incurred by the forecast-user. The forecast-user is responsible for his
own actions at all times.
---------------------------------------------------------------
Dates on which cooler periods in February are expected: 1st to 3rd -
5th to 7th - 9th to 12th - 18th - 23rd - 25th to 26th

1st - 5th (mainly a LP spell)
On 1st, a complex low pressure area stretches from the near-Atlantic
E and ENE'wards, past the top of Northern Ireland, and up to E
Scotland. There are a few LP centres enclosed in the depression, but
the main centre appears to be to the W and NW of Northern Ireland. A
ridge of HP stretches E'wards just south of the Channel and influences
the southern tip of SW England and also the near continent and part of
the southern North Sea. As the winds to the W of Ireland at the 500mb
level are strong from the west, the surface pressure systems are
pushed quickly eastwards so that on the 2nd, the high pressure over the
Channel is now over France and the main low pressure centre is placed
just to the N and NW of Scotland. Another LP centre, probably a
secondary depression, is crossing Northern Ireland on its way
eastwards. This latter depression draws in cooler air down the west
side of Scotland into northern areas. During the afternoon of 2nd, a
short pulse of HP is expected to bring an improvement to S and SE
parts of England, before a depression starts to influence NW areas of
Britain later. On 3rd The cool air, associated with the low pressure
leaving E Scotland, moves off into the northern North Sea. A new
depression just to the west of Ireland has a short trough to the SW of
Ireland. Mild winds enter Britain from the SW as high pressure touches
the south coast of England. On 4th a mild south-westerly airstream
crosses the country. A medium sized LP lies to the north-west and
west of Scotland. There may be a small disturbance over Wales and the
Midlands. High pressure lies to the west, south-west and south of
the country, with a further HP centre over France. On 5th a complex
area of LP runs from Scandinavia westwards to LP near NW Scotland. A
small disturbance lies near S England and cool northerly winds flow
down the W side of Britain. The warm air which was over Britain
yesterday is slowly drifting into the continent. During the day,
pressure begins to rise over England from the SW.

6th to 10th (some HP slots)
On 6th, high pressure moves into the south of England and spreads
north-eastwards up to south-east Scotland. Low pressure lies to the NW
of the country so that west or south-west winds cover the British
Isles. An upper cold-air trough is positioned to the west of
Ireland. On 7th, low pressure forms a belt to the north of
Scotland and high pressure lies over and to the south and south-east
of England. A new feature is a small depression approaching SW Ireland
which is moving eastwards. On 8th, low pressure to the north-west of
Scotland has a trough southwards to a small depression in the south of
England. This breaks down the fine weather which transfers to the
continent On 9th, low pressure to the north of the country and a small
depression near SW England move slowly east A small area of high
pressure moves into western districts. On 10th, as the high pressure
to the south of the country moves eastwards into the continent, a
depression with its secondary to the west of Ireland drifts into
western districts.

11th to 15th (one or two HP slots)
On 11th, low pressure lies to the NW of the country and has a trough to
SW Norway. The Azores high stretches along the Channel and affects
the south and south-east of England. On 12th, Strong winds in the
upper-air draw a depression with its secondary into W and SW Ireland.
The Azores high runs from the Channel into the near continent
covering the extreme SE of England. On 13th, The depression now lies
to the north of the country and its secondary is crossing the south of
the country. The strong upper winds have moved towards the North Sea.
On 14th, a belt of low pressure stretches from Northern Ireland towards
SW Norway. Mild south-westerly winds cover the country. Over the near
Atlantic, pressure begins to rise. On 15th, a small anticyclone covers
the country. South-westerly winds spread into Ireland and W Scotland.
There doesn't seem to be much change happening.

16th-20th (HP spell then LP slots)
On 16th, high pressure still covers England and SE Scotland. Low
pressure to the W of Ireland draws in SW and S winds which cover
Ireland and W Scotland. On 17th, high pressure remains on station and
low pressure to the W and NW of Britain has a secondary depression near
SW Ireland which is moving eastwards. On 18th, the secondary
depression of yesterday is near Wales and is part of a trough which
stretches SE'wards from the main depression to the NW of Britain. The
anticyclone which was over SE Britain yesterday, has moved into the near
continent. On 19th, the main feature is the low pressure to the NW of
Britain. High pressure in the south has stretched eastwards, along
the Channel into the near continent. Some small disturbances track E
and NE in the south-westerly airstream across England. On 20th, a
complex area of low pressure stretches W to E across the northernmost
tip of Scotland. The Azores high, which stretches eastwards through
the Channel forms a small HP centre to the SW of England and this drifts
eastwards along the Channel.

21st to 25th (LP spell, then HP slot, then LP spell)
On 21st, the small anticyclone in the west Channel yesterday has moved
eastwards and just covers part of south-east England. A depression
lies to the W of Scotland and has a trough southwards covering
Ireland. Out in the Atlantic, HP begins to build up and move towards
Ireland. On 22nd, low pressure moves towards the NE of Scotland drawing
cooler NW winds into the country. Small disturbances flow with the
winds from NW to SE Britain. High presssure approaches Ireland. On
23rd, high pressure has moved into England and SE Scotland. Low
pressure to the W and NW of the country moves NE'wards On 24th, the
depression to the NW of the country deepens and strong SW winds cover
the country. A belt of high pressure runs from SW to NE just to the
south of the Channel. On 25th the deep depression lies to the north of
Scotland with cooler NW winds coming in behind it. A small disturbance
is possible in the strong W or SW winds to the SE of England.

26th to 28th (HP slot then LP slot)
On 26th, the depression near Scotland yesterday has moved further
eastwards and cooler NW winds flow into the country. High pressure
to the SW of the country is moving quite quickly eastwards across the
southern half of the country. Some small disturbances over the NE of
England are moving off into the North Sea. On 27th, high pressure is
moving into the continent, but still covers S and SE England. Low
pressure out in the Atlantic is moving towards W and NW Scotland. On
28th, a complex area of low pressure stretches from the NW of the
country eastwards across Scotland to E Scotland. High pressure from
the Azores reaches as far as S Ireland and SW England as it moves
eastwards along the Channel.

Well, that's the February forecast. I can't see any worthwhile period
of cold, dry weather because the anticyclones don't last any length of
time. I think the coldness of February will come from night frosts
when the HP slots appear. Another source of coldness is when the
north-west winds bring us the cold showery weather on the couple of
occasions. Otherwise I see a lot of mild SW winds often lifting the
temperatures away from the snow levels which a lot of people still
expect. So February is more or less dominated by low pressure lying to
the N and NW of the country with HP to the SW, S, SE and E of Britain.
Any incursion of HP is only short lived and transitory.

Cheers, Keith





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