Weather Flashcards
What is a trough?
Elongated area of low atmospheric pressure.
Can result in cloudiness and precipitation when in contact with high pressure system.
State the general characteristics of a low pressure and high pressure systems in the Northern Hemisphere.
Low Pressure - inward, upward, and counterclockwise
High Pressure - outward, downward, and clockwise
What is a ridge?
Elongated area of high atmospheric pressure.
Can result in clear skies and good weather.
What are the standard temperature and pressure values of sea level?
Atmospheric Pressure: 29.92
Temperature: 15C
What are isobars?
Lines on a weather chart which connects areas of equal or constant barometric pressure
If the isobars are relatively close together on a surface weather chart?
Steep pressure gradient and results in gusty winds.
What causes the winds aloft to float parallel to the isobars?
Coriolis force
Why do surface winds generally flow across the isobars at an angle?
Surface friction
At what rate does atmospheric pressure decrease with an increase of altitude?
1 inch per 1000ft
What does dew point mean?
Temperature a sample of must be to attain the state of saturation.
Could result in fog and lower visibility.
When temperature and dew point are within 5 degrees of each other what type of weather could occur?
Fog, low visibility, dew, carburetor ice
What factor primarily determines type and vertical extent of clouds?
Stability of the atmosphere
How do you determine the stability of the atmosphere?
“Rough” air is unstable
“Smooth”air is stable
During preflight planning what meteorological information should you be aware of with respect to icing?
Location of fronts Dew point Cloud layers Freezing levels - temperature Air pressure
What conditions are necessary for structural icing to occur?
Visible moisture
Freezing temperatures
Name the main types of icing an aircraft may encounter in-flight.
Structural
Induction system - carburetor and air filter
Instrument - static port and pitot tube
Name the three types of structural icing?
Clear ice - smooth sheet of ice
Rime ice - rough ice with milky white texture
Mixed ice - mixed with snow or ice particles
What action is recommended if you inadvertently encounter icing conditions?
Leave the area
Ascend above clouds
Descending below clouds
Changing course
Is frost considered hazardous to flight? Why?
Yes, the roughness of its surface spoils smooth air flow resulting in a loss of lift
What factors must be present for a thunderstorm to form?
Water vapor
Unstable air
A trigger - upward lifting such as a front
What are the three stages of a thunderstorm?
Cumulus
Mature
Dissipating
What is temperature inversion?
An increase of temperature with height instead of a decrease in temperature.
Air is stable with little to no turbulence
State two basic ways that fog may form.
Cooling the air to dew point
Adding moisture to air near surface.
Name several types of fog.
Radiation Advection Upslope Precipitation induced Ice
What causes radiation fog to form?
Ground cools adjacent air to the dew point on calm, clear nights
What is advection fog, and where is it most likely to form?
Results in transportation of warm humid air over a cold surface. Occurs around large bodies of water. Lakes, oceans, etc.
What is upslope fog?
Forms as a result of moist, stable air being cooled adiabatically as it moves up sloping terrain. Mountains, hills, etc.
What is wind shear and which areas is it likely to occur?
The rate of change of wind velocity, speed and direction. Very dangerous and abrupt.
Low level temperature inversion
Frontal zones or thunderstorms
Clear air turbulence as high levels (jet streams)
Why is wind shear an operational concern to pilots?
Unexpected changes in wind can be dangerous to operations at low levels on approach to and departing from airports.
What types of weather information will you examine to determine if wind shear conditions might affect your flight?
Terminal forecasts - LLWS or possibilities of thunderstorms and other severe weather. METARs SIGMETs LLWAS PIREPS
What is the primary means of obtaining a weather briefing?
A briefer at the AFSS/FSS. Tailored for your specific flight, available 24/7 using 1-800-WX BRIEF
What are some examples of other sources of weather information?
At least two.
Telephone Information Briefing Service
Private industry resources
Direct User Access Terminal System (DUATS) - medical needed
Transcribed Weather Broadcast (TWEB) - call TEL-TWEB
Where can you find a listing of AFSS/FSS and weather information numbers?
Airport/Facility Directory under “FAA and NWS Telephone Numbers”
What types of weather briefings are available from an AFSS/FSS briefer?
Standard
Abbreviated - update or need only a few items
Outlook - departure is six or more hours; planning only
Inflight - update of preflight
What pertinent information should a weather briefing include?
Adverse conditions VFR flight not recommended Synopsis Current conditions Enroute forecast Destination forecast Winds aloft Notices to Airmen (NOTAMs) ATC delay
What is EFAS?
En route Flight Advisory Service - “Flight Watch”
What is HIWAS?
Hazardous In-Flight Weather Advisory Service is a continuous broadcast of in-flight weather advisories. Depicted in sectionals with an “H” in the upper right corner of identification box.
What is a “flight information service”?
Method of receiving aviation weather and other operational data in the cockpit that augments traditional pilot voice communication with FSS or ATC facilities. Do not use as replacement of traditional voice communications.
What is a METAR and what are he two types?
Hourly surface observation of conditions observed at an airport.
Routine - transmitted every hour
SPECI - selected special weather report; given at anytime to update the METAR
Describe the basic elements of a METAR.
Type of report ICAO station identifier Date and time of report Wind Visibility Runway visible range Weather phenomena Sky condition Temperature/dew point Altimeter Remarks
Describe several types of weather observing programs available.
Manual observations
AWOS - Automated Weather Observing System
ASOS/AWSS - Automated Surface Observing System/Automated Weather Sensing System
What are PIREPs, and where are they usually found?
Pilot reports, routine (UA) or urgent (UUA).
Usually transmitted as an individual report but can be put into a surface aviation weather report or collective.
What are Radar Weather Reports (SD)?
Contains information about precipitation observed by weather radar.
What are Terminal Aerodrome Forecasts (TAFs)?
Concise statement of the expected meteorological conditions significant to aviation for a specified time period.
Define “aviation area forecast”.
(FA) forecast of specified weather phenomena covering a flight information region or other area.
What information is provided by an FA?
Covers a specific area between the surface and 45,000 feet MSL.
Synopsis
Clouds & weather
12-18 hour categorical outlook
What are Inflight Aviation Weather Advisories (WST, WS, WA)?
Forecasts to advise en route aircraft of development of potentially hazardous weather in 3 types: SIGMET, convective SIGMET, and AIRMET.
What is a Convective SIGMET (WST)?
Implies severe or greater turbulence, severe icing and low-level wind shear. Hazardous to ALL categories of aircraft. Forecast is valid for 2 hours. Issued hourly special bulletins as required and updated hourly.
What is a SIGMET (WS)?
Advises of non-convective weather that is potentially hazardous to all aircraft.
What is an AIRMET (WA)?
Advisories of significant weather phenomena that describe conditions at intensities lower than those which requires a SIGMET
What are the different types of AIRMETs?
Sierra - IFR conditions and/or extensive mountain obstructions.
Tango - moderate turbulence, surface winds of 30 knots or greater, or non-convective low-level wind shear.
Zulu - moderate icing and provides freezing level heights
Describe the winds and temperature aloft forecasts?
Computer prepared forecasts of wind direction, wind speed, and temperature at specified times, altitudes, and locations. Four times a day. Not issued for altitudes within 1500 feet of location’s elevation.
What valuable information can be determined from winds aloft forecasts (FB)?
Most favorable altitude
Areas of possible icing - +2C to -20C
Temperature inversions
Turbulence
What are Center Weather Advisories (CWA)?
Aviation warning for use to anticipate and avoid adverse weather conditions. Not a flight planning product. Valid for 2 hours.
Give some examples of current weather charts available at the FSS or NWSO used in flight planning? At least 3.
Surface analysis chart Weather depiction chart Radar summary Short-range surface prognostic chart Significant weather prognostic chart Convective outlook chart Constant pressure analysis chart
What is a surface analysis chart?
Computer prepared chart that covers the contiguous 48 states. Transmitted every 3 hours. Useful for locating pressure systems, fronts, winds, temperatures and dew point. For use in conjunction with other information
What information does a weather depiction chart provide?
Computer generated from METAR reports. Gives a broad overview of observed flying category conditions. Starts 01Z every day, updates every 3 hours.
Covers total sky coverage, cloud height/ceiling, weather, and obstructions to visibility.
Define the following terms: LIFR IFR MVFR VFR
Low IFR - ceiling lees than 500ft and visibility less than 1 mile
Instrument Flight Rules - ceiling 500 to 999ft and visibility less than 3 miles
Marginal VFR - ceiling 1000-3000ft and visibility 3-5 miles
Visual Flight Rules - ceiling greater than 3000ft and visibility greater than 5 miles
What are radar summary charts?
Computer generated graphical display of a collection of automated radar weather reports.
Aids in preflight planning in identifying areas of precipitation and severe weather.
What are short-range surface prognostic charts?
Portray forecasts of selected weather conditions at specified valid times. Low-level prog charts and High-level prog charts.
What is a convective outlook chart?
Depicts areas forecast to have the potential for severe and non-severe convections and specific severe weather threats during the following three days.
What are constant pressure analysis charts?
Upper air weather map where all information depicted is at the specified pressure of the chart.
How can a pilot receive updated weather information inflight?
EFAS through a FSS
Define ceiling.
The lowest level of broken or greater cloud coverage.
Give some examples of charts and reports useful in determining the potential for and location of thunderstorms along your route.
METAR
TAF
area forecast
Prog charts
