Pressure Systems Flashcards
Describe the typical pressure pattern in an active pressure system
Generally the pressure at the surface and the tropopause will be opposite
What does a surface low lead to?
Convection at the surface and rising air which must diverge in an upper high
What does a surface high lead to?
Divergence at the surface and consequently subsidence and an upper low
Where is the typical level of mean non-divergence?
14,000ft or 600hPa
What is the level of mean non-divergence otherwise referred to as?
The barostatic level
Are the pressure systems highs or lows at the barostatic level?
Neither, they are between the two
What is the name for a high pressure system?
Anti-cyclone
What are the general properties of anticyclones?
Large, slow to form or dissipate and stationary or slow moving
What are depressions associated with?
Strong winds, precipitation, surface convergency and convection
What are the general properties of depressions?
Small, 300NM, active, form rapidly, move at fair speeds and fill rapidly when they die
How are orographic depressions formed?
When low level airflow swirls around land features
What is another name for a thermal low ?
Warm low
Over land in winter a col produces deteriorating visibility. What might this be due to?
Radiation fog
What are the properties of a col?
Located between 2 highs and 2 lows. Virtually no low level wind. Anti-cyclone type weather. Light winds, clear skies and an inversion at low level.
What are cols noted for in summer?
Air mass thunderstorms. Isolated, thermally generated CBs that pop up all over the area.
