Review Questions for Final Exam
1) What is the difference between a Colorado Cyclone and an East Coast Cyclone?
Colorado Cyclones are closer to the cold air coming from the northwest than East
Coast Cyclones. The lifting mechanisms (cold fronts) are stronger than they are on
the East Coast. Colorado Cyclones also have a second lifting mechanism on top of the
cold front, the Rockies Mountains. These mountains add to the lifting of the warm
air. However, the East Coast cyclones are much more intense than the Colorado
cyclones due to the fact that there is warmer air coming from the Gulf of Mexico for
the east coast and not as much warm air more up north. There is more contribution
from latent heat release from the condensation and more heat from the warm ocean.
Also, there are stronger thermal contrasts along the coastal boundaries, hot land vs.
cooler water, and there is more than one jet streak available for the cyclone’s
2) What is a cold wave?
A cold wave is a wave of cold air, that is 2 standard deviations (or more) colder
than the mean cold temperature experienced in a certain area.
3) Why are cold waves more common in Canada and the United States than in
Cold waves are more common in Canada and US than in Western Europe because
the cold air coming from the arctic (Arctic air mass) and Western Europe mostly
experiences air coming from the ocean (Polar air mass). The air is colder coming
from the arctic because the heat capacity of land is much less than water therefore
the air stays cold. As opposed to the ocean that has a higher heat capacity therefore
the temperature is regulating.
4) What are the ingredients for Lake Effect Snow?
Instability: To have lake effect snow you need the atmosphere to be absolutely
unstable. To get this you need the environmental lapse rate to be higher than the
dry adiabatic lapse rate (10degrees/km) and the moist adiabatic lapse rate
(5degrees/km). The lake temperature needs to be around 1-4 degrees and the cold
air mass around -15 to -20 degrees, which makes the lapse rate at around 15
degrees/km (need at least 13degrees/km). That way the air parcel will always be
warmer than the environment therefore always buoyant and rising.
Fetch: Fetch is the direction and amount of time the air stays on the lake. The longer
the air stays on the lake the more moisture can be evaporated into the air the
stronger the lake effect snow. There are long and short axis to the lakes. If the air
travels the long axis it will spend more time over the lake as opposed to the short
axis. Wind shear: If there is less change in the direction of the wind it’ll create stronger
wind bands, with more change the bands will weaken and so will the intensity of the
storm. Winds blowing from too many different angles/directions will blow the cloud
Upstream Moisture: Impacts the precipitation potential, it preconditions the air
mass. With a higher relative humidity there is more moisture in the air, which will
give you more precipitation. If the relative humidity is low then it is difficult to get
condensation, clouds and precipitation.
Upstream Lakes: The effect of other lakes upstream will impact the snowfall of
downwind lakes. It may increase the amount of precipitation formed at the end of
Topography: Rougher terrain contributes to the convergence/lifting of the air. It
forces the air to rise, which adds to more clouds and precipitation
Snow/ice cover on the lake: If the lake is covered with ice there is no water that can
be evaporated into the air therefore lake effect snow cannot occur. The more ice that
covers the lake the less lake effect snow that you will occur.
5) In what season is Lake Effect snow most common?
Lake effect snow is most common in early to mid winter. This is when the lake
waters are relatively warm and the air is cold enough to create a large temperature
difference between the lake and the air above.
6) How does the intensity of Lake Effect Snow compare to Cyclones in review
7) What is the typical progression of winter precipitation as a warm front
approaches you and why? Be sure to keep in mind the impact of phase changes of
water on the temperature of the atmosphere.
The precipitation goes from snow to ice pellets to freezing rain to rain. Before the
warm front passes the temperatures are below zero throughout the atmosphere
thus snow forms. As a warm front approaches the temperatures at the higher levels
is cold, middle level a few degrees above zero, surface level is below zero. This leads
to ice pellets because the snow melts at the middle level but refreezes as it goes
down. The refreezing of the ice pellets leads to latent heat release and that warms
the (middle) temperatures further leading to freezing rain. Rain that is super cooled
and is frozen upon contact with a surface, which also gives latent heat release and
eventually leads to temperatures that are too warm for freezing (rain).
9) What are the ingredients necessary in order to get a thunderstorm? You need a source of moisture, conditionally unstable atmosphere, a mechanism
to trigger the updraft and for super cell thunderstorms you need vertical wind
10) What are typical thunderstorm hazards? Be sure to be able to explain how each
of the hazards of a thunderstorm is formed.
The downburst or microburst of the storm is a hazard for planes landing or taking
off in a thunderstorm. The downburst is made by the cool dry air entering the back
side of the storm, evaporation due to the updraft causes the air to be negatively
buoyant and flow down rapidly.
Flash floods can also be created due to a thunderstorm. The heaviest rain happens in
the downburst. If it rains heavily in a valley or on a hill leading to a valley it can
accumulate quickly and create a flash flood.
Hail is formed with the updraft is strong enough and can carry the raindrops up into
extremely cold regions of the atmosphere. It occurs when an updraft lifts an ice
particle or nucleus that super cooled water can attach to and form ice around once it
reaches extreme cold air temperatures. The stronger the updraft the larger the
Lightening is another hazard formed by thunderstorms. The snow and ice crystals in
the thunder cloud transfer there negative charge to the heavier rain drops and hail
stone which move to the