Weather Information Flashcards
METAR
Meteorological Terminal Aviation Routine Report
- Observation - Current Forecast - Updated every hour
- SPECI: special report to update current METAR for rapidly changing weather conditions
- Location, time, wind direction (magnetic), wind speed (knots), visibility (statute miles), cloud cover, cloud height, temp, dew point, altimeter, remarks
TAF
Terminal Aerodrome Forecast
- Forecast - Valid 24 hrs - Updated 4 times/day
- Location, time issued, valid time, wind direction, wind speed, visibility, cloud cover, cloud height, potential severe weather
FA (Area Forecast)
- Size of several states ( about 3,000 sq miles)
- Broken up into different regions -updated 3x a day
- 24 hr period ( 18 hr forecast, 6 hr categorical outlook)
- Cloud height, cloud cover, visibility, expected precipitation type and intensity
PIREP
Pilot Weather Report
- UA: Routine PIREP
- UUA: Urgent PIREP
- Confirm conditions, ceiling, visibility, precipitation, icing, turbulence
ATIS
Automated Terminal Information Service
- Updated after receipt of weather observation
- Wind direction, speed, temp, dew point, pressure, cloud type, ceiling, type of precipitation, remarks (runways in use, runway/taxi way closures, ect.)
ASOS
Automated Surface Observation Service
- Continually updates
- Wind direction, speed, temp, dew point, pressure, cloud type, type of precipitation
AWOS
Automated Weather Observation Service
- Continually updated
- Wind direction, speed, temp, dew point, pressure, cloud type, ceiling
Surface Analysis Chart
- METAR Reports shown over continental US
- Updated every 3 hours
- Shows Fronts
- High/Low Pressure systems
Weather Depiction Chart
- METAR Reports shown over continental US
- Consists of fronts, high/low pressure, cloud cover, visibility (doesn’t show pressure millibars like Surface Analysis Chart)
- IFR/VFR/MVFR areas
- updated ever 3 hours
Weather Ceiling/Visibility Categories
VFR- ceiling >3000, visibility >5 sm
MVFR- ceiling 1000-3000, visibility 3-5 sm
IFR- ceiling 500-1000, visibility 1-3 sm
LIFR - ceiling <500, visibility <1 sm
Significant Weather Prognostic (SIGWX)
- Used to review flight conditions for flight planning/briefing
- Low level is Surface to FL240
- Mid level is FL100 to FL450
- High level FL250 to FL630
- 12 hr periods for areas of VFR, MVF, IFR, turbulence, freezing levels
- Updated every 6 hours
AIRMET
-Forecast for hazardous weather for light aircraft (under 41,000 lbs)
-Issued every 6 hours
Sierra: IFR and mountain obscuration
Tango: moderate turbulence, strong surface winds (over 30kts), low level wind shear
Zulu: icing and freezing levels
SIGMET
- Non-convective hazardous forecasts for all aircraft
- Issued as required valid for 4 hours
- severe icing not associated with T-Storms
- severe turbulence or CAT not associated with T-Storms
- sandstorms/dust storms that lower vis. <3sm
- volcanic ash
- November through Yankee
Convective SIGMET
- Issued as required - Valid for 2 hours
- Moderate to severe thunderstorms covering 40% of the area
- Thunderstorm lines at least 60 miles long
- Embedded thunderstorms -Tornadoes
- Hail over 3/4’’ -Surface winds greater than 50 kts
G AIRMET
Graphical AIRMET
Radar Summary
- Observed areas of precipitation, intensity, heights of tops of echoes, types of precipitation, sever weather watches
- Updated hourly
Winds and Temperatures Aloft
- Forecast based on upper air observations from a weather balloon
- Determine winds for flight planning
- Location, altitude, wind direction (true north)/(temp c)
- Updated 2 times a day -chart updated 4 times a day
- 9900 Light and variable less than 5 kts -0000KT calm
- no winds given 1500 AGL
- no temps given if stations is within 2500 AGL
Flight Service Station (FSS)
-primary source for preflight weather information
1-800-WXBRIEF
HIWAS
Hazardous Inflight Weather Advisory Service
-AIRMETs, SIGMETs, Convective SIGMETs, Urgent PIREPS
Weather Briefings
- Standard: most complete briefing
- Abbreviated: shortened version of standard, used to update previous briefing
- Outlook: forecast information 6 or more hours away
Composition of the Atmosphere
78% Nitrogen
21% Oxygen
1% Trace gases (argon, CO2, etc)
0-5% water vapor, this amount of water vapor is responsible for major changes in weather
Layers of the Atmosphere (Lowest to Highest)
-Troposphere (Tropopause-boundary layer that traps moisture and associated weather in the troposphere) -Stratosphere -Mesosphere -Thermosphere
Atmosphere Circulation
- Atmosphere is always in motion trying to find its equilibrium
- Major factor in atmospheric circulation is the uneven heating of Earth’s surface
Standard Atmospheric Properties
Sea Level Pressure and Temperature
-29.92”Hg (1,013.25millibars) and 15°C
Pressure change with altitude
1” Hg per 1000 ft
Characteristics associated with Low Pressure System
Air circulation is inward, upward, and counterclockwise.
-Area or rising air, which is conductive to cloudiness, precipitation, and bad weather
Characteristics associated with High Pressure System
Air circulation is outward, downward, and clockwise
-Area of descending air which tends to favor dissipating clouds and good weather
Unstable Air
Warm moist air
Stable Air
Cool dry air that resists vertical movement
Standard Lapse Rate
2°C per 1,000’
Isobar
Lines drawn on a weather chart to depict lines of equal pressure
Ridge
- Elongated area of high pressure
- High pressure ridge is depicted as yellow zig zag lines on a surface analysis chart
Trough
- Elongated Area of low pressure
- Low pressure trough is depicted as an orange dashed line on a surface analysis chart
Temperature Inversion
- When the temperature of the air rises with altitude
- smooth stable air, but usually poorer visibility if realative humidity is high
Relative Humidity
Actual amount of moisture in the air compared to the total amount of moisture the air could hold at the temp.
Dew Point
Temperature at which the air becomes saturated and the air condenses into fog, dew, frost, clouds, rain, or snow.
Sublimation
Solid to Gas. The water absorbs heat from surroundings
Deposition
Gas to Solid. (Snowflakes). Water releases heat to surroundings
Evaporation
Liquid to Gas. The water absorbs heat from surroundings.
Condensation
Gas to Liquid. The water releases heat to surroundings.
Radiation Fog
Occurs on cool calm nights when surface cools and brings cooling temperatures to dew point
Advection Fog
- When warm moist air moves over a cooler surface.
- Usually in coastal areas
- Requires wind
- Golden Gate Bridge in SF good example
Upslope Fog
- When moist stable air is forced up sloping land features like a mountain
- Requires wind
Steam Fog
Dry, cool air moving over warm body of water
Ice Fog
Occurs in cold weather when temp is much below freezing and water forms directly into ice crystals
Cloud classification
Clouds are classified based on Height:
- Low: Surface-6,500 AGL
- Middle: 6,500-20,000 AGL
- High: 20,000 and above (usually stable air)
- Vertical development: Cumulus clouds (unstable)
Air Mass
Large bodies of air that take on the characteristics of the surrounding area
-Unstable Air mass: an air mass passing over a warmer surface causing convective currents of rising unstable air
Sources of Lifting
- frontal
- convective
- low pressure
- orographic
Front
Boundary layer between two types ofair masses
Warm Front
- Occurs when a warm air mass advances and replaces a body of colder air
- Gernerally stable air with poor visibility
- Slower moving front 10-25mph
Cold Front
- Occurs when a mass of cold, dense stable air advances and replaces a body of warmer air
- Cold dense air lifts the warm air up (stability of the front is dependent on the stability of the forced up warmer air mass)
- Bad Weather usually associated
- Faster moving 25-30mph or higher
Occluded Front
Occurs when a fast moving cold front catches up with a slow moving warm front
Cold Front Occlusion
When a fast moving cold front is colder than the air ahead of the slow moving warm front
Warm Front Occlusion
When the air ahead of the warm front is cooler than the overtaking air of the cold front behind (embedded thunderstorms if cold air being forced upward is unstable)
Thunderstorm Needs
- Lifting action
- Moisture
- Unstable air
3 Stages of a Thunderstorm
1) Cumulus (updrafts, towering cumulus formation)
2) Mature - Greatest Intensity (downdrafts, shear, precipitation)
3) Dissipating (downdrafts, anvil shape)
Squall Line
- Narrow band of active thunderstorms
- Single most intense weather hazard to aircraft
Microburst
Small scale intense downdrafts, 6,000fpm that can last up to 15min
Wind Shear
Sudden or drastic change in wind speed/direction
Mountain Wave Turbulence
Wind speed at least 20 knots and perpendicular to the range
Types of Icing
Rime
Clear
Mixed
Rime Icing
- Milky in color
- Typically forms in stratiform clouds
- Builds upwards, doesn’t really flow across the wing
Clear Icing
- Clear/transparent, hard to detect
- Supercooled water typically in cumulous clouds
- Flows over the back of the wing and keeps building up
Frost
- Forms under the same conditions that are favorable for dew
- Dewpoint is less than 0 degrees Celsius (frost point)
- Surface temperature is less than dewpoint
Types of Icing
- Induction
- Airframe
- Instrument
