Depressions & Anticyclones Flashcards
What two air masses usually are involved in the formation of a depression in the UK?
Tropical Maritime and Polar Maritime
Where do depressions that usually affect the UK originate from?
Atlantic Ocean
Explain step 1 of the formation of a depression in the UK
The polar and tropical maritime air masses collide
Explain step 2 of the formation of a depression in the UK
The polar maritime air mass is faster than the tropical maritime so as they collide and wrap around each other the colder one wraps faster and so begins the early formation of the fronts
Explain step 3 of the formation of a depression in the UK
As the polar maritime air mass continues to wrap the Tropcial maritime the fronts of a warm and colder air mass begin to form
Describe how winds perform around a depression
They spin anti-clockwise to catch up with the cold front and cut the warm front
What is the occluded front and describe the weather
The place where the cold front has undercut the warm front and so there is no longer anything to undercut so the weather conditions are relatively stable
What is an anticyclone?
A high pressure air mass in which air descends
What allows for an anticyclone to exist over the UK?
Development of high pressure systems at the meeting of the Hadley and Ferrell cell at around 30 degrees latitude can move to the higher latitudes due to the tri-cellular model and if the Rossby waves cause the PF jet stream to bend in a way that allows an anticyclone to take its place then the UK experiences an anticyclones. The UK usually gets these high pressure systems from North Africa (Tropical Continental)
Why are there few clouds in an anticyclone?
Because air descends and therefore there is no conventional uplift
Describe weather at the undercutting phase of a depression
Heavy rain, cumulonimbus clouds, strong winds, decreased temperature and humidity
Describe the weather of an anticyclone in Winter in 4 ways
1) Cold daytime and nighttime temperatures due to no cloud blanket
2) Weak winds
3) Clear skies
4) Fogs and smog due to temperature inversions
How long can anticyclones last?
Weeks
Describe the weather associated with an anticyclone in summer in 5 ways
1) Hot temperatures in day and night as sun passes through easily
2) Weak winds
3) Clear Skies
4) Fogs, smogs, mists and dews
5) Thunderstorms due to humidity
Which direction do weak winds in anticyclone spin?
Clockwise
