Weather Flashcards
Define: Trough
An area of low pressure.
Area of rising air. Rising air is conducive to cloudiness and precipitation. (bad weather with low pressure)
Define: Ridge
An area of high pressure.
Area of descending air. This favors dissipation of clouds. (good weather with high pressure)
Define: Isobars
Connects areas of equal pressure
What does it mean when isobars are close together?
There is a steep pressure gradient and higher wind speeds exist.
What causes the winds aloft to flow parallel to the isobars?
The Coriolis Force
Why do surface winds generally flow across the isobars at an angle?
Surface friction
Define: Dew Point
The temperature at which the air must be cooled to become saturated
Dew point and temperature close together means what?
Clouds, fog, dew
How do you determine stability of the atmosphere?
Unstable: temperature decreases uniformy and rapidly 3 degrees celcius every 1000ft
Stable: temperature remains unchanged or decreases slightly with altitude
During pre-flight, what type of meteorological information should you be aware of with respect to icing?
Location of fronts
Cloud layers
Freezing levels
Air temperature and pressure
Define: Freezing Level
Lowest altitude in the atmosphere at which the air temperature is 0 degrees celcius.
Where can you get icing information?
PIREPs
AIRMETs
SIGMETs
Area Forecasts
What conditions are necessary for structural icing?
Visible moisture
Below freezing temperatures at the point moisture strikes the aircraft
What are the main types of icing an aircraft may encounter?
Structural icing
Induction system icing
Instrument icing
What are the 3 types of structural icing?
Clear ice
Rime ice
Mixed ice
What action should you take if you encounter icing conditions?
Leave the area of visible moisture
What factors must be present for a thunderstorm?
Sufficient water vapor
Unstable lapse rate
Lifting force
What are the 2 ways fog can form?
Cooling air to the dewpoint
Adding moisture to the air near the ground
5 types of fog
Radiation fog Advection fog Upslope fog Precipitation induced fog Ice fog
Define: Wind Shear
Big change in wind velocity and direction Can occur: -low level temperature inversion -frontal zone / thunderstorm -clear air turbulence
What types of weather reports will you use to determine if wind shear might exist?
Terminal forecasts METARs SIGMETs LLWAS (low level wind shear alert system) PIREPs
What is the primary means of obtaining a weather report?
FSS
1-800-WX-BRIEF
What types of weather briefings are available from FSS?
Standard briefing
Abbreviated briefing
Outlook briefing
In-flight briefing
Define: EFAS
En Route Flight Advisory Service
- weather advisories in flight
- PIREPs
- 122.0 “flight watch”
Define: HIWAS
Hazardous In flight Weather Advisory Service
Define: PIREPs
Pilot weather reports.
UA - Standard Pilot Report
UUA - Urgent Pilot Report
Define: Radar Weather Report (SD)
Contains information on precipitation observed by weather radar
Define: Aviation Area Forecast (FA)
Used to determine en-route weather and to interpolate weather conditions at airports with not TAFs
What is the use of In-flight aviation weather advisories (WST, WS, WA)?
Warn of potentially hazardous weather
- SIGMET
- Convective SIGMET
- AIRMET
Define: Convective SIGMET
Severe thunderstorm -50 knot surface winds -3/4" hail -tornadoes Embedded thunderstorms Line of thunderstorms
Define: SIGMET
Severe icing not associated with thunderstorms
Severe turbulence or clear air turbulence
Volcanic ash
Dust or sand storms
Define: AIRMET Sierra
IFR conditions or mountain obstructions
Define: AIRMET Tango
Moderate turbulence
30 knot surface winds
Wind shear
Define: AIRMET Zulu
Moderate icing
Freezing level heights
Why use Winds and Temperatures aloft?
Determine most favorable altitude
Possible icing
Temperature inversions
Turbulence
Examples of weather charts available for flight planning?
Surface analysis charts Weather depiction chart Radar summary chart Short range surface prog chart Significant weather prog chart Convective outlook chart Constant pressure analysis chart
Define: Surface Analysis Chart
Pressure systems and fronts
Winds, temperatures, dew point temperatures
- transmitted every 3 hours
Define: Low IFR
Ceiling less than 500 ft
Visibility less than 1 mile
Define: IFR
Ceiling 1000-500 ft
Visibility 1-3 miles
Define: Marginal VFR (MVFR)
Ceiling 1000-3000 ft
Visibility 3-5 miles
Define: VFR
Ceiling greater than 3000 ft
Visibility 5+ miles
Define: Radar Summary Chart
Shows areas of precipitation
-general areas of movement of precipitation and storms
Define: Short Range Surface Prognostic Chart
“progs”
surface up to 24,000 ft
forecast weather conditions (12, 24, 36, 48 hr progs)
Define: Low Level Significant Weather Prog Chart
Forecast significant weather from surface to FL240
- 2 lower panels depict 12 & 24 hour surface progs
- 2 upper panels depict 12 & 24 hour sig weather progs
Define: Mid-Level Significant Weather Chart
Forecast and overview of significant en-route weather from 10,000 to FL450
-4 times daily
Define: Convective Outlook Chart
Depicts area forecasts to have the potential for severe and non-severe weather threats (every 3 days)
