September 2008: Synoptic Overview
- From: "Philip Eden" <philipATweatherHYPHENukDOTcom>
- Date: Wed, 1 Oct 2008 18:01:20 +0100
A month of two contrasting periods: mostly cyclonic until the
13th (strongly so during the first week), and mostly anti-
cyclonic during the second half. So the monthly figures
tell only part of the story. Nevertheless, there were some
interesting statistics. Some places in E&W had already
passed their normal September rainfall by the 6th; there was
a complete absence of very warm days (23.7°C the highest
anywhere) and many places even in southern England failed
to reach 21°C; yet another dull month (actually, exceptionally
dull for the first half but much better during the second half);
and northern Scotland again ended up with a rather warm
and dry month.
Mean pressure charts are already available at:
Charts: http://www.climate-uk.com/monpre/0809.htm
The Monthly Review will be uploaded later today to:
http://www.climate-uk.com/monthly/0809.htm
Graphs: http://www.climate-uk.com/graphs/0809.htm and
http://www.climate-uk.com/graphs/200809.htm
Not The Long Range Forecast should be available by Oct 4 on:
http://www.climate-uk.com/page4.html
The sea-level pressure chart shows the Icelandic low deeper
than usual at 999 mbar centred in the Denmark Strait, and the
Azores high just north of its normal position at 1021 mbar.
There is also a large area of relatively high pressure over
central, eastern, and especially northern Europe with its main
centre 1020 mbar just east of St Petersburg. The mean flow
over the British Isles is SSW-ly in the east, and W-ly in the
west.
At the 500 mbar level the main trough is rather tilted and
extends from Iceland across the UK to France.
The sea-level pressure anomaly field shows well below
normal pressure over Greenland and Iceland, and well above
normal pressure over Scandinavia and the Baltic. Anomalies
are relatively small over the Atlantic and Europ south of
latitude 57degN.
The main anomaly centres were:
- 8mbar over SE Greenland
+ 9mbar over northern Sweden
+ 4mbar in mid-Atlantic at 51N 30W.
Over the British Isles pressure anomaly ranges from +4mbar
over Shetland to -0.5mbar along the south coast of England.
The anomalous flow is weakly E to SE-ly over Great Britain
and weakly NE to N-ly over Ireland.
CET (after Manley) 13.43°C (-0.3 degC wrt 1971-2000)
CET (after Hadley) prob 13.5°C
E&W Rain (provisional): 102.0mm (141% of 1971-2000 mean)
E&W Sunshine (prov): 125.3 hr ( 87% of 1971-2000 mean)
It was the coolest and cloudiest September since 2001 and
the wettest since 2000, averaged over E&W.
CScotT: 12.7°C (+0.4degC)
ScotRain: 69mm ( 83%)
ScotSun: 93hr ( 91%)
NIT: 13.0°C (+0.1 degC)
NI Rain: 81mm (105%)
NI Sun: 111hr ( 103%)
Rainfall totals ranged from 268mm at Capel Curig
(Snowdonia) to 35mm at both Kinloss (Moray) and
Sheoburyness (Essex).
Percentages ranged from 272 at Carter Bar (Roxburghshire)
to 42 at Loch Glascarnoch (Wester Ross)
Sunshine totals ranged from 197.0h at Guernsey airport [CS
recorder] to 45.8h at Eskdalemuir (Dumfriesshire) [KZ sensor].
Next dullest were Kinlochewe (Wester Ross) with 51.6h, and
Bishopton (Renfrewshire) with 57.5h.
The two month total of 88h for Aug/Sep at Eskdalemuir
must be unprecedented for two months in the summer
half-year anywhere in the UK. (Usual caveats about
change of sensor apply).
(c) Philip Eden
.
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