Weather Flashcards
4 basic types of cumuliform clouds
Cumulus (CU)
Towering cumulus (TCU)
Cumulonimbus (CB)
Altocumulus castellanus (ACC)
CU
Cumulus
Develop vertically
Bulging upper part
Appear detached from other clouds
White at the tp and relatively dark bases
TCU
Towering cumulus
Rapidly growing cumulus
Height exceeds the width
CB
Cumulonimbus
Contain thunderstorm activity
Upper portion is smooth/ fibrous & always flattened
ACC
Altocumulus castellanus
White/ gray/ both
Composed of rounded masses & rolls, may/ may not be merged
Pressure gradient
Rate of change of pressure with horizontal distance measure in km
Calculated by 4 hPa in ‘x’ km (distance between isobars is always 4 hPa)
Buys Ballot’s Law
In N. hemisphere: wind at your back = area of low pressure lies to your left
Veering
Wind makes a clockwise change in direction
Backing
Wind makes a counter-clockwise change in direction
Arrows on surface maps indicate the direction wind is ____
Blowing from
Full barb on arrow represent ___ knots
10
5 lifting agents
Convection
Orographic lift
Frontal lift
Mechanical turbulence
Convergence
Convection
Air is heated from below by contact with Earth’s surface
Orographic lift
Air is force up sloping terrain by the wind
Frontal lift
Air is forced to rise by a wedge of colder/ denser air
Mechanical turbulence
Friction between the air and ground cause the air to be stirred up into series of swirling motion known as eddies
Convergence
Air converges at the centre of low-pressure systems and is force to rise, resulting in cloud & precipitation
Air mass
Large section of troposphere with relatively uniform properties of temperature and moisture
Takes on its original properties from the surface over which it has formed
2 types of air masses
Maritime air masses (form over water/ humid)
Continental air masses (form over land/ dry)
Artic air masses
Form in the Arctic/ high latitudes
Polar air masses
Form in the temperate zones (permafrost line to 30 degrees N)
Tropical air masses
Form in the tropics/ low latitudes (between 30 degrees N & the equator)
4 air masses commonly found in N. America
Continental Arctic (cA) (winter only)
Maritime Arctic (mA)
Maritime Polar (mP)
Maritime Tropical (mT)
Front
Transition zone between 2 air masses
Cold front
Transition zone between advancing cold air and warm air
Symbol: arrowhead (triangle)
Warm front
Transition zone between warm air and retreating cold air
Symbol: half circle
Stationary front
Transition zone between two air masses that are not moving
Symbol: alternating arrowheads and half circles
Polar front theory
Earth is covered by polar (cold) air in polar regions and tropical (warm) air in equatorial regions, separated by the polar front
(2 air mass 1 front model)
Severity of the weather created by the front depends on…
Slope of the frontal surface
Speed of frontal movement
Temperature of the lifted air mass
Moisture content of the lifted air mass
Stability of the lifted air mass
High pressure is generally associated with ___ weather, while low pressure is associated with ____ weather.
Nice
Cloudy/ rainy/ snowy
Before a cold front arrives, the wind ahead of the front is typically out of the ___. Once the front passes, the wind will shift to the ____.
SSW
WNW
Before a warm front arrives, the wind ahead of the front is typically from the ___. Once the front passes, the wind will shift to the ____.
E
SSW
Passage of warm front will result in ____ in temperature.
increase
Arrival of a cold front will result in ____ temperature.
sudden decrease
Dew point temperature generally ___ with a warm frontal passage and ___ with a cold frontal passage.
increase, decrease
Visibility is ___ well in advance of warm fronts.
reduced
Ahead of cold fronts, visibility is ___. Close to the front, visibility may be ___.
good, reduced
Pressure will ___ as warm front approaches a location.
fall
Pressure will ___ once the cold front has passed a location.
rise
Frontal turbulence is strongest when the lifted warm air is ___ and ___.
moist, unstable
Most severe cases of frontal turbulence are generally associated with fast-moving ___ fronts.
cold
3 factors that determine the type of cloud and precipitation at a warm front
Moisture content of the overrunning warm air
Stability of the overrunning warm air
Degree of overrunning (pressure gradient in the warm air & angle of warm air motion relative to the frontal surface)
3 factors that determine the type of cloud and precipitation at a cold front
Moisture content of the lifted warm air
Stability of the lifted warm air
Degree of lift (slow of the frontal surface & speed of the front)
