Geoscience Reference
In-Depth Information
Table 10.1
General weather characteristics and airmasses associated with Lamb's 'Airflow Types' over the British Isles.
Type
Weather conditions
Westerly
Unsettled weather with variable wind directions as depressions cross the country. Mild and stormy in
winter, generally cool and cloudy in summer (mP, mPw, mT).
Northwesterly
Cool, changeable conditions. Strong winds and showers affect windward coasts especially, but the
southern part of Britain may have dry, bright weather (mP, mA).
Northerly
Cold weather at all seasons, often associated with polar lows. Snow and sleet showers in winter,
especially in the north and east (mA).
Easterly
Cold in the winter half-year, sometimes very severe weather in the south and east with snow or sleet.
Warm in summer with dry weather in the west. Occasionally thundery (cA, cP).
Southerly
Warm and thundery in summer. In winter it may be associated with a low in the Atlantic, giving mild
damp weather especially in the southwest, or with a high over central Europe, in which case it is cold and
dry (mT, or cT, summer; mT or cP, winter).
Cyclonic
Rainy, unsettled conditions, often accompanied by gales and thunderstorms. This type may refer either
to the rapid passage of depressions across the country or to the persistence of a deep depression
(mP, mPw, mT).
Anticyclonic
Warm and dry in summer, occasional thunderstorms (mT, cT). Cold and frosty in winter with fog,
especially in autumn (cP).
A
B
C
Figure 10.5
Average climatic conditions associated with Lamb's circulation types for January, April, July and September, 1861 to
1979. (A) Mean daily temperature (°C) in central England for the straight (S) airflow types; at the right side are the quintiles of mean
monthly temperature (i.e. Q1/Q2 = 20 per cent, Q4/Q5 = 80 per cent). (B) Mean daily rainfall (in millimetres) over England and
Wales for the straight (S) and cyclonic (C) subdivisions of each type and terciles of the mean values (i.e. T1/T2 = 33 per cent, T2/T3
= 67 per cent). (C) Mean frequency (per cent) for each circulation type, including anticyclonic (A) and cyclonic (C).
Source
: After Storey (1982), reprinted from
Weather
, by permission of the Royal Meteorological Society. Crown copyright ©.
