Weather Information Flashcards
What weather is associated with a cold front?
Gusty Winds Hail Dropping Temps Thunder Lightening (Tornados)
What happens when warm air gets lifted ahead of a front?
Cumulous or cumulonimbus clouds & thunderstorms
What is a SIGMET and what conditions are included?
Indicates Significant weather such as: Severe icing (w or w/o thunderstorms) Severe turbulence (w or w/o thunderstorms) Dust/Sand storms Volcanic ash Valid 4 hours (6 for hurricanes)
What is an AIRMET and what conditions are included??
An AIRMET is a concise description of weather phenomena that are occurring or may occur (forecast) along an air route that may affect aircraft safety. Considered less severe than SIGMETS.
Sierra = IFR & Mtn obscuration
Tango = Turbulence, strong surface winds, low level wind shear
Zulu = Icing & Freezing
What is a Convective SIGMET?
Thunderstorm related - valid for 2 hours
What is the dew point?
Temp at which an airmass can hold no more moisture.
Moisture becomes visible when temp to dew point spread is within 2 degrees c (3.5 f)
What should you do if you have and inadvertent encounter with IMC?
Make a 180 - radio for assistance
Keep wings level and stay calm
Spatial disorientation is likely - trust the instruments not your own sensations
How far should you remain from thunderstorms?
20 miles
What is Density Altitude?
Is Pressure Altitude corrected for nonstandard temp.
As density of air increases (lower density alt), aircraft performance increases and vice versa.
What is Pressure Altitude?
Height above standard datum plane which is a theoretical level where the weight of the atmosphere is 29.92 “Hg.
What is a Temperature Inversion?
Typically air cools as it rises and expands. Inversion happens when the temperature rises with altitude. Typically creates shallow layers of smooth, stable air near the ground. Air at top acts like a lid trapping weather and pollutants trapped below. If high humidity it can contribute to the formation of clouds, fog, haze or smoke.
How does Humidity effect Density?
Water vapor is lighter than air.
Higher humidity = air becomes less dense and density altitude increases
TAFs cover what area?
Specific to an airport - 5 sm RADIUS around it.
What are the 3 stages of a thunderstorm?
Cumulus stage, mature stage & dissipating stage.
What are the 3 conditions necessary to create a thunderstorm?
Unstable air, high moisture content and a source of lift.
What values are used for Winds Aloft Forecasts? Magnetic or True direction? Knots or MPH?
True & Knots
Is stable air more likely to have better or worse visibility?
Worse.
During which stage are thunderstorms most intense?
Mature stage
What are the general characteristics of air flow around high & low pressure systems in the Northern Hemisphere?
Low pressure - inward, upward and counterclockwise
High pressure - outward, downward and clockwise
Are you better off flying towards a high or low pressure system?
High - area of descending air which tends to favor dissipation of cloudiness and good weather.
Describe a Cold Front
Occurs when a mass of cold, dense, and stable air advances and replaces a warmer body of air.
As it passes, expected weather can include towering cumulus or cumulonimbus, heavy rain accompanied by lightning, thunder and/or hail; tornadoes possible; during passage, poor visibility, winds variable and gusting; temperature/dew point and barometric pressure drop rapidly.
*associated weather varies with moisture available, degree of stability, slope & speed of front as well as upper wind flow
Describe an Occluded Front
A frontal occlusion occurs when a fast-moving cold front catches up with a slow-moving warm front.
Describe a Warm Front
The boundary area formed when a warm air mass contacts and flows over a colder air mass. As the front passes, expected weather can include stratiform clouds, drizzle, low ceilings and poor visibility; variable winds; rise in temperature.
*associated weather varies with moisture available, degree of stability, slope & speed of front as well as upper wind flow
Describe a Stationary Front
When the forces of two air masses are relatively equal, the boundary or front that separates them remains stationary and influences the local weather for days.
