Progress Test 9 Flashcards
(35 cards)
What direction does wind flow in the Northern Hemisphere, and why does this occur?
Anti-Clockwise (Cyclones), this occurs because of unstable air rising due to the air being less dense (water vapour content being present).
What is a front?
A front is a boundary between two types of air masses, where those air masses meet, weather occurs due to the forced lifting of the air.
Describe a warm front.
A warm front is an area of warm air pushing into colder air (not a straight line)
Describe a cold front.
A cold front is an area of cold air pushing into warmer air (not a straight line). Cold fronts move faster than warm fronts.
Describe an occluded front.
Where cold and warm fronts join together, cold front catch up warm fronts.
What are the two types of occlusion?
Cold Occlusion and Warm Occlusion.
Sectors is where one front follows another and is the area between the fronts. Describe a warm sector?
A warm sector is the area of warmer air behind a warm front, usually between the warm and cold fronts in a depression.
A cold sector is an area of cold air immediately behind a cold front, usually between the cold and warm fronts in a depression. What is the cool sector?
-A cool sector is the area immediately ahead of a warm front.
-Caused by the mixing of warm and cold air
-From the cold front ahead of the warm front.
What are the characteristics of the three types of sectors?
Warm Sector : Warmer temperatures,
Southerly winds
Cold Sector : Colder temperatures, Northerly winds
Cool Sector : Cool Temperatures, Easterly Winds
What is a stationary front?
Where warm air and cold air reside next to each other (not a straight line)
The formation of a front is when air masses sit beside each other when stationary a catalyst is required to initiate air movement. What typically is responsible for this formation?
A polar low depression is responsible.
When the depression starts (low air pressure) in creates a kink in the stationary front, what follows from this?
-The air begins to rise in the depression
-Airflow begins to take on a circular motion due to the Coriolis force
-A well defined front begins to form
True or False? In Warm fronts the warm air rises up colder air, the air rises and cools leading to the relative humidity to increase.
True. condensation then occurs leading to clouds to form of varying types.
The slope of a warm front is around 1:150nm, how much distance can this spread over?
500nm. Warm fronts a therefore quite prolonged in there passage over a point on the surface.
The characteristics of a warm font is a High Cirrus cloud that would be the first sign of an approaching warm front (500nm ahead). Where would this cloud formation occur and will pressure increase or decrease prior to the front passing?
The High Cirrus clouds will form at the top of the troposphere, prior to the front passing air pressure will generally decrease. Cloud will continue to thicken and lower as the front approaches.
During a warm front at 15, 000ft what will occur with the clouds?
The clouds will produce rain or snow but evaporates before reaching the surface, only around 100nm to 200nm ahead of the front where light rain will fall and my reach the surface.
What occurs 90nm ahead of a Warm Front.
rain falls from Stratus clouds and reaches the surface, this can be prolonged and rain is moderate.
What kind of weather occurs at a warm front?
Prolonged low cloud and precipitation, visibility is also poor.
What happens after the passing of a warm front?
-The surface wind veers
-Pressure steadies and slowly decreases again
-Temperature and dew point increase
-precipitation gradually decreases
-some low cloud, drizzle and poor visibility may lag behind the front.
At a cold front the air forges into warm air, what occurs ahead of the front (200nm)?
Some cumulus clouds may be present.
What occurs at the cold front?
The warm air is forced to rise, it cools and the relative humidity increases. Condensation occurs in the form of heaped clouds.
True or False? The slope of the cold front lasts longer and spreads over more miles than a warm front.
False. A cold front slope’s normally 1:50nm and only spreads across a few miles.
Cold fronts have sharp showers and heavy rain over a short period of time, at what distance does weather normally occur?
50km.
During cold fronts CB’s may be present and prior to air pressure will gradually decrease, what will happen at the front?
sharp showers sometimes proceeded by rain from stratus type clouds in the warm sector, the visibility can be changeable in the precipitation and can be generally hazy proceeding the front.
