Weather Flashcards
What are the primary means of obtaining a weather briefing?
1800-WX-Brief
Flight Service Station
Name some sources of obtaining weather information
1800-WX-Brief
Aviationweather.com
Foreflight
National Weather service
What are the standard temperature and pressure values for sea level?
15°C
29.92
1013.2 hectopascal
How does air flow in the northern hemisphere for a high-pressure
system?
Downwards, Clockwise and out
Stable air
How does air flow in the northern hemisphere for a low-pressure system?
Counter clockwise, in, and upward
Unstable air
What kind of weather can you expect to come from a high-pressure system?
A high-pressure system typically brings clear skies, calm winds, and fair weather due to the descending air mass which inhibits cloud formation and results in dry conditions; essentially, settled weather with little to no precipitation
dry cool air declines and warms up
anti-cyclone
What kind of weather can you expect
to come from a low-pressure system?
A low-pressure system typically brings cloudy, unsettled weather with a high chance of precipitation, including rain, snow, or storms, often accompanied by wind as air moves towards the low pressure area, causing the moist warm air to rise to condense and form clouds; essentially, expect potentially stormy conditions with varying levels of precipitation depending on the system’s strength and moisture content.
low moist warm air rises and cools down
cyclone
Describe the four types of fronts
Cold Front
Warm Front
Occluded Front
Stationary Front
what would the weather look like in a cold front
A cold front typically brings a narrow band of precipitation, often including thunderstorms, heavy rain, and sometimes hail or snow squalls, as the colder air mass pushes up the warmer air, causing moisture to condense and fall as precipitation; after the front passes, the weather usually clears with cooler temperatures and drier conditions.
what would the weather look like in a warm front?
A warm front typically brings a gradual increase in temperature, increased humidity, and steady, light to moderate precipitation, often appearing as widespread cloud cover with rain or drizzle, as the warm air mass rises over a cooler air mass, causing moisture to condense into clouds and precipitation; you might see high cirrus clouds approaching before the front arrives, followed by thicker altostratus clouds and eventually rain.
what would the weather look like in a cold front?
Cold fronts are the opposite of warm fronts, with colder air advancing close to the surface.
This forces the air up and away as the front moves.
Cold fronts generally move at 25-30 miles per hour, but cold fronts have been recorded at up to 60 miles per hour in extreme cases. This quick movement of warmer air upwards causes the creation of clouds as moisture condenses.
Depending on the stability of the warmer air mass, the cloud type may change.
Typically, these clouds are either towering cumulus or cirriform. However, cumulonimbus clouds may develop.
Cumulonimbus clouds can result in lightning, thunder, hail, and even tornadoes in severe cases.
what would the weather look like in a warm front?
Warm fronts occur when a warm air mass advances and replaces a colder body of air, covering the colder air from the top and forcing the cold air out below.
This type of front moves slowly, typically at about 10-25 miles per hour.
Generally, as this air is forced upwards by the frontal change, stratiform and cirriform clouds and fog can be expected.
In the summer months, this lifting action can trigger cumulonimbus clouds.
Precipitation is light to moderate, accompanied by poor visibility.
During the passage of a warm front, stratiform clouds are visible, and drizzle may fall.
The visibility is generally poor but improves with variable winds. The visibility eventually improves after the passage of a warm front, but hazy conditions may exist for a short period after passage.
There is generally a slight rise in barometric pressure, followed by a decrease in barometric pressure.
what would the weather look like in a Stationary Front?
Stationary fronts occur when the forces of two air masses are relatively equal, causing the front not to move.
A stationary front can sit over an area for a prolonged amount of time.
Weather conditions associated with a stationary front vary widely, but they’re generally a mix of cold and warm front conditions.
what would the weather look like in a Occluded Front?
Occluded fronts occur when a faster-moving cold front catches up to a slower-moving warm front.
As the occluded front approaches, we can expect warm front weather immediately followed by cold front weather.
Occluded fronts have two variants: a cold front occlusion and a warm front occlusion.
The type depends on the temperature of the air mass ahead of both warm and cold fronts, compared to the cold front that is catching up to the warm front.
Let’s look at both variants in further detail.
What is dew point?
the temperature at which air must be cooled to become saturated with water vapor and produce condensation
What can you
expect if the temperature and dew point are close together?
When the temperature and dew point are close together (within 5°), you can expect high humidity because the air is near saturation with moisture, which means there is a high likelihood of fog, clouds, or precipitation forming, especially if the temperatures continue to cool further.
Stable air brings what type of clouds, visibility and precipitation?
Stable air brings layered clouds, such as stratus clouds, and can cause steady precipitation. Stable air can also cause low visibility due to particles like dust, haze, and smoke.
Unstable air brings what type of clouds, visibility and precipitation?
Unstable air is associated with cumulus clouds, showery precipitation, and good visibility.
What are isobars and what does it mean when they are close together?
Isobars are lines on a weather map that connect areas of equal atmospheric pressure, and when they are close together, it indicates a steep pressure gradient, meaning strong winds are likely to occur in that region; essentially, the closer the isobars, the stronger the wind speed.
What is the difference between a trough and a ridge?
A “trough” refers to an elongated area of relatively low atmospheric pressure, while a “ridge” is an elongated area of relatively high atmospheric pressure
What do you need for a
thunderstorm to form?
Moisture
Water vapor is necessary to create clouds and precipitation. Moisture usually comes from oceans.
Instability
The air must be unstable, meaning it’s warmer than the air around it and rises on its own. This can happen when warm, moist air is near the ground and cold, dry air is above.
Lift
A lifting mechanism is needed to provide the “nudge” that starts the air moving. This can be caused by hills or mountains, or when warm/cold or wet/dry air bump together.
Name the thunderstorm Stages
Developing Stage:
This is when the cumulus cloud begins to form and rise due to updrafts of warm air.
Mature Stage:
The storm reaches its full intensity with strong updrafts and downdrafts, producing heavy rain, lightning, thunder, and potentially hail.
Dissipating Stage:
The storm weakens as the downdrafts become dominant, cutting off the updraft and causing the cloud to dissipate.
Name the types of thunderstorms
Single-cell
Small, weak storms that usually last less than an hour. They are often caused by heating on a summer afternoon.
Multi-cell
Made up of many convection cells that move together. These storms can produce a lot of rain and are more likely to cause flooding.
Squall line
A line of multi-cell storms that forms along a cold or warm front. Squall lines can be up to 600 miles long and are often preceded by strong gusts of wind.
Supercell
Large, organized storms that can produce severe weather, including:
High winds
Large hail
Strong tornadoes
Heavy rain
Downbursts that can produce outflow winds of over 100 mph
Explain the different types of fog?
S - Steam Fog
Formation: Occurs when cold air moves over warmer water. The water vapor rises, cools, and condenses.
Example: Seen over lakes or oceans in colder months.
Appearance: Wispy or patchy fog above the water, sometimes called sea smoke.
U - Upslope Fog
Formation: Created when moist air is forced up a slope (e.g., mountains or hills). As the air rises, it cools adiabatically and condenses.
Example: Found along the windward side of mountains.
Appearance: Dense fog covering elevated terrains.
G - Ground Fog
Formation: A type of radiation fog forming near the ground, usually less than 20 feet deep.
Example: Common in valleys during calm, clear nights.
Appearance: Thin, localized fog close to the surface.
A - Advection Fog
Formation: Develops when warm, moist air moves over a cooler surface, causing the air to cool to its dew point.
Example: Seen near coastal areas when warm ocean air drifts over colder land.
Appearance: Thick, widespread fog.
R - Radiation Fog
Formation: Forms on calm, clear nights when the ground cools rapidly, cooling the air above it to the dew point.
Example: Common in the early morning in low-lying areas.
Appearance: Shallow and dissipates with the sun’s heat.
P - Precipitation Fog
Formation: Occurs when rain falls through cooler air, and the rain evaporates into the air, saturating it to the dew point.
Example: Found ahead of warm fronts during rain.
Appearance: Dense fog accompanying rainy conditions.
I - Ice Fog
Formation: Develops in extremely cold temperatures (below -25°F), where water vapor sublimates directly into ice crystals.
Example: Common in Arctic or Antarctic regions.
Appearance: Sparkling ice crystals in very cold environments.
Define wind shear?
Wind shear is a change in wind speed and/or direction over a short distance. It can occur either horizontally or vertically and is most often associated with strong temperature inversions or density gradients. Wind shear can occur at high or low altitude.
