Newsletter

Occluded fronts

Cold fronts generally move faster than warm fronts so eventually the cold front will catch up with the warm front (or occlusion). An occluded front may be described as "warm" or "cold" depending on the change of temperature as it passes, but both types generally produce cloud getting lower, then rain breaking up into showers.

Anticyclones ("Highs")

Anticyclones, or areas of high pressure, are much less active than depressions.

Their isobars are usually more widely spaced than those of a depression, so winds are generally light and the weather is generally fine, though in winter the sky may be overcast.

Once an anticyclone becomes established its movement is likely to be slow and irregular, and it may remain stationary for days or weeks on end.

The atmospheric stability associated with a high is likely to promote coastal fog in spring and autumn. In summer, trapped dust particles may form haze.

Weather around depressions

The fronts associated with a typical depression divide the area around it into distinct sectors, each with distinctive weather patterns.

The warm front

Wind	increases and backs (e.g. SW to S) as the front approaches, then veers (e.g. from SW to W) as the front passes
Cloud	cloud cover increases and cloud base lowers as the front approaches
Weather	rain, becoming heavier and continuous
Visibility	reducing as the front approaches
Pressure	falling as the front approaches

The warm sector

(between the fronts, generally S or SE of the depression's centre)

Wind	steady
Cloud	low cloud, almost 100% cover
Weather	steady drizzle or light rain
Visibility	moderate or poor, possibly foggy
Pressure	steady

The cold front

Wind	may increase and possibly back (e.g.from W to SW) as the front approaches then veers (e.g. from W to NW) as the front passes
Cloud	dense cloud, possibly towering to great heights at the front itself, quickly breaking up into to smaller puffy clouds once the front has passed
Weather	heavy rain, followed by showers once the front has passed
Visibility	poor in rain, then good or very good
Pressure	rises as the front passes

The cold sector

Wind	may veer a little and freshen or become gusty immediately behind the cold front (depending on the depth and movement of the depression)
Cloud	apart from any frontal cloud nearby generally clear skies with scattered showers or white 'fair weather cumulus'
Weather	fair
Visibility	generally good
Pressure	depends on the depth and movement of the depression, but generally rises quickly as the cold front passes, then more slowly