Air Masses and Fronts Flashcards
What is an air mass?
A large volume of air that has uniform:
- Horizontal temperature
- Relative Humidity
- Environmental Lapse Rate
What is a front?
A narrow boundary of transition between air masses of different temperatures
What are source regions?
When air masses remain in a particular area for a lengthy period and the regional surface conditions are relatively uniform, the air mass will acquire the characteristics of that area.
What classifications of air masses are used in Australia?
- Pm (Polar Maritime)
- Tc (Tropical Continental)
- Tm (Tropical Maritime)
What is an airstream?
A moving air mass
What occurs if an air mass moves towards the equator?
Destabilizes and increases the ELR
What occurs if an air mass moves towards the pole?
Stabilizes and decreases the ELR.
What front moves faster, cold or warm?
Cold fronts move faster.
Are warms fronts more common in Australia or NZ?
NZ
What is the approach of a warm front characterized by?
- Direction and speed of approach are generally towards the east at less than 20 kts
- Clouds develop well ahead of the front, thicking and cloud base lowering as the front approaches
- Wind from north to northeast
- Barometric pressure falling
- Rain at about 150 NM ahead of the surface position.
What is the passage of a warm front characterized by?
- Wind backs to west to northwest
- Rain easing and eventually stopping
- Cloud clearing to the SE
- Temperature rising
- Relative humidity decreasing
- Barometric pressure steadying
What weather conditions are produced by a cold front?
- Potential thunderstorms and violent winds.
- Icing could be a problem, especially in winter and visibility may be reduced due to precipitation.
What is the approach of a cold front characterized by?
- The formation of cirrus cloud, forming to the SW
- General speed of advance of 15 - 50 kts
- Wind from the NW, backing and strengthening
- Temperature increasing
- Barometric pressure failing
- Cumulus and possible cumulonimbus with increasing rain
What is the passage of a cold front characterized by?
- Wind backs to south to southwesterly
- Temperature falling
- Humidity rising
- Pressure starts to rise
- Possible thunderstorms and squall
- Low cloud.
What is an occluded front?
When two fronts collide with one another, and cloud is forced up at the boundary between then.