Weather Flashcards
What causes Weather?
- The Sun’s uneven heating of Earth
Who issues all weather regarding aviation?
- National Weather Service
What is a Meteorological Aerodome Report (METAR)?
- They report the current weather within 5NM of an airport
- They are updated every hour and are good for an hour
What is a Terminal Area Forecast (TAF)?
- They forecast the weather within 5NM of an airport
- They are updated every 6hrs and are good for 24-30hrs
What is an Airmen’s Meteorological Information (AIRMET)?
- They advise of weather that maybe hazardous to single engine, other light aircraft, and VFR pilots. However, operators of large aircraft may also be concerned with these reports
- They are updated every 6hrs and are good for 6hrs
What are the types of AIRMETs?
- T: Turbulence
- Z: Icing
- S: Mountain Obscurations
What is a Significant Meteorological Information (SIGMET)?
- They are a severe weather advisory that concern the safety of all aircraft
- They are unscheduled and most of them are valid for 4hrs
What are the types of SIGMETs?
- Icing
- Turbulence
- Duststorms/Sandstorms
- Volcanic Ash
- Hurricane - valid for 6hrs
- Convective - valid for 2hrs
What could be considered a Convective Sigmet?
- Thunderstorms
- Hail
- Tornadoes
What is a Center Weather Advisory (CWA)?
- They are an unscheduled weather advisory for conditions approaching or meeting WA, WS, or WST criteria
- They are valid for 2hrs and conditions are expected to begin within 2hrs of issuance
What are Notice To Air Mission (NOTAM)?
- They are a notice containing information essential to flight operations but not known far enough in advance to be publicized
What are Pilot Weather Reports (PIREPs)?
- They are reports of current weather encountered by pilots
- They can be submitted to a FSS, NWS website, or to ATC (say “with pilot report”)
What is a High Pressure system?
- An area where the atmospheric pressure is higher than its surroundings
What are the characteristics of a High Pressure system?
- They move down and outward in a clockwise direction
- They generally bring fair weather
What is a Low Pressure System?
- An area where the atmospheric pressure is lower than its surroundings
What are the characteristics of a Low Pressure system?
- They move up and inward in a counter-clockwise direction
- They usually bring bad weather
What is a Trough?
- It is an extended area of low pressure
How can you indentify a Trough on a Prog Chart?
- They are represented by an orange line
What are Isobars?
- They are light gray lines on a prog chart that connect areas with the same pressure (measured in millibars)
What happens when you fly across Isobars?
- You may encounter changes in wind speed and direction
What is an Air Mass?
- A large body of air with generally uniform temperature and humidity
- They are created by source regions
What is a Front?
- The boundary between air masses
- They bring a change in weather
What happens when you fly across a Front?
- You will notice a change in temperature, pressure, wind, and other factors
What is a Sea Breeze?
- It is not a front but it also generates weather
What is a Cold Front?
- When a cold air mass wedges underneath a warm air mass, forcing the warm air to rise. The cold air advances, replacing the warm air at the surface. Rain and even thunderstorms can form as the moisture in the warm air mass rises, cools, and condenses
What are the characteristics of a Cold Front?
- They typically travel between 10-30kts
- They usually bring light to heavy rain and thunderstorms, depending on the steepness of the front’s slope
- As the front passes, cool and fair weather is expected
What are Squall Lines?
- It is a line of thunderstorms, often forming along or ahead of a cold front
What is a Warm Front?
- It is when a warm air mass advances and rises above a colder air mass. As the warm rises, the temperature drops and condensation occurs, forming clouds
What are the characteristics of a Warm Front?
- They typically travel between 10-15kts
- They usually bring widespread precipitation, bad visibilty, low ceilings and turbulence
- As the front passes, warmer and milder weather is expected
What is an Occluded Front?
- The most common type is when a warm air mass gets caught between two cold air masses. The warm air mass rises as the cool air masses push and meet in the middle
What are the characteristics of an Occluded Front?
- They typically bring strong winds and heavy precipitation
- As the front passes, the sky is usually clearer
What is a Stationary Front?
- This is when two air masses are pushing against each other, but neither is powerful enough to move the other
What are the characteristics of a Stationary Front?
- They typically last for a few days
- They bring a mix of weather from warm and cold fronts
What is a Microburst?
- It is a strong downward and outward gushing wind system
What is Wind Shear?
- It is a sudden change in wind direction and/or wind velocity
- They can cause a sudden loss of airspeed
What are the types of Fog?
- Radiation
- Advection
- Steam
- Upslope
What is Radiation Fog?
- It forms when the ground cools the surrounding air
- It is most prevalent during the fall and winter
What is Advection Fog?
- It forms as warmer, moist air moves over a cold ground
What is Steam Fog?
- It forms when a cold and dry air mass moves over a warm body of water
What is Upslope Fog?
- This occurs when sloping terrain lifts air, cooling it to its dew point
What is Dew Point?
- It is the temperature which an air molecule must be cooled to in order for it to become saturated
What does it mean when Dew Point and Temperature are close together?
- There will be visible moisture in the air
How does Icing occur?
- When your flying through visible moisture and the temperature where the moisture strikes the aircraft is 0° C or colder
What are the types of Icing?
- Clear Ice
- Rime Ice
- Mixed Ice
What is Clear Ice?
- When water flows over the aircraft surface gradually freezing as a smooth sheet of solid ice
- This is the most dangerous type of ice becasue it is heavy, hard to see, and changes the shape of the wing
What is Rime Ice?
- This forms when water instantly freezes as it hits the aircraft’s surface
What is Mixed Ice?
- It is a combination of clear and rime ice
What is Freezing Rain?
- It is when warm rain falls through a freezing layer causing them to become super cooled
- This causes rapid and severe ice accumulation
What are Freezing Levels?
- It represents the altitude in which the temperature is at 0° C
How can you find the Freezing Levels?
- Take a look at the Winds Aloft
- Temperature drops about 2° C for every 1,000ft of altitude gained
What is Stable Air?
- Air that resists vertical movement
What are the characteristics of Stable Air?
- Stratiform Clouds
- Smooth Air
- Low Visibility
- Continous Precipitation
What is Unstable Air?
- Air that is prone to vertical movement
What are the characteristics of Unstable Air?
- Cumuliform Clouds
- Turbulent Air
- Good Visibilty
- Showery Precipitation
What are Cumulus clouds?
- They are clouds that have flat bases and are often described as puffy, fluffy, or piled up
- They have some vertical developmet but not bad to fly in
What are Stratus clouds?
- Clouds with horizontal layering with a uniform base
- They are not good flying weather
What are Lenticular Clouds?
- They are visual signs of mountain waves
How do you calculate the base of a cloud?
- Temperature - Dew Point
- Divide by 4.4
- Add Field Elevation (your answer will be in thousand of feet)
What is a Thunderstorm?
- It is a rain-bearing cloud that also produces lightning
What ingredients are required to create a Thunderstrom?
- Moisture
- Unstable Air
- A Lifting Action
What are the stages of a Thunderstrom?
- Devolping Stage
- Mature Stage
- Disspating Stage
Describe the Devolping Stage
- It consists of a cumulus cloud that is being pushed upward by a rising column of air (updraft). The cumulus cloud soon looks like a tower (called towering cumulus) as the updraft continues to develop. There is little to no rain during this stage but occasional lightning
Describe the Mature Stage
- Precipitation begins to fall out of the storm, creating a downdraft. The mature stage is the most likely time for hail, heavy rain, frequent lightning, strong winds, and tornadoes
Describe the Dissipating Stage
- Eventually the updraft is overcome by the downdraft beginning the dissipating stage. Rainfall decreases in intensity, but lightning remains a danger
What is a Temperature Inversion?
- It is a layer in the atmosphere in which air temperature increases with altitude
- It usually indicates a warm air mass over a cold air mass
What are the characteristics of a Temperature Inversion?
- They are stable while flying in it but become very unstable below and above it
- It creates an elevated level of low visibilty becasue it traps dust and pollutents
What is Surface Friction?
- The surface of the Earth exerts a frictional drag on the air blowing just above it. This friction can act to change the wind’s direction and slow it down keeping it from blowing as fast as the wind aloft
- The difference in terrain conditions directly affects how much friction is exerted
What are considered Ceilings?
- Broken or Overcast
Saturation vs Condensation
- Saturation: When the air contains the maximum amount of water vapor it can hold at a given temperature and pressure. If more water vapor is added beyond this point, it will result in condensation
- Condensation: The process by which a gas or vapor changes into a liquid
