Weather Theory Flashcards
what causes weather?
a heat exchnage. The sun heats the earth unevenly
how does the FAA classify clouds?
low, middle, and high
status clouds
low level gloomy overcast (flat, layered, smooth)
cumulus cloud
low level puffy clouds (all updrafts)
define low level clouds
clouds 6500 and below
-nimbus
rain cloud suffix (cumulonimbus, nimbostratus = rainclouds)
-alto
middle cloud suffix
cirrus clouds
wispy high level clouds composed of ice crystals and dust
cirrocumulus
high level clouds that look a little thinner than altocumulus
define high level clouds
clouds above 23000 ft (cirra)
define mid level clouds
clouds between 6500 feet and 23000 feet (alto)
cirrostratus
high level clouds that appear as a halo around the sun
stratocumulus
combination of puffy clouds and flat layered clouds (stratus and cumulus)
min safe distance from clouds with vertical development
FAA recommends 20 miles. always stay away from clouds with vertical development (towering cumulonimbus clouds)
stable Air
Stratiform clouds, smooth air, fair to poor visibility, continuous precipitation
unstable Air
Cumuliform clouds, turbulent air, good visibility, showery precipitation
what is an airmass?
a large body of air of similar temperature, humidity and pressure
define the two types of air masses
high (Blue H) and low (Red L) pressure systems
low pressure air mass
moves counterclockwise and creates poor weather (think hurricane)
high pressure air mass
moves clockwise and creates good weather
4 types of fronts
warm fronts (red semi-circle) cold fronts (blue triangles) stationary front (blue and red triangles/semicircles) occluded front (purple triangles/semicircles)
3 ingredients that make up a thunderstorm
moisture, temperature inversion, uplifting action
what conditions are almost always associated with a thunderstorm?
when a cold front overtakes a warm front
poor weather is usually associated with
cold fronts
stationary fronts
occur when neither the warm or cold front is powerful enough to take each other over. usually results in rain for a long period of time (depicted by blue and red triangles/semicircles)
occluded front
severe weather that occurs when a cold front overtakes a warm front and another cold front comes in behind. usually results in tornados
low pressure airmasses and cold fronts
poor weather
4 types of fog
radiation fog
radiation fog
75% of the fog you experience. caused by heat radiating from the surface at night when cooler air comes in (brings the dewpoint closer to the temp) usually occurs in spring and fall
advection fog
requires wind usually happens along the coastlines. occurs when warm moist air moves over a colder surface (water and land generally have diff temps making this occur at coastlines and in hardpack snow)
up slope fog
requires wind. warm moist air flows up a slope and gets cooled then turns to fog and rolls back down
precipitation induced fog
rain hits hot surface and evaporates creating fog
two types of fog that require wind
advection and up-slope
airmet tango
turbulence
4 categories of turbulence
light
moderate
severe
extreme
light turbulence
slight or light changes to altitude or airspeed
moderate turbulence
larger variations in speed as well as altitude and attitude may occur but the acft remains in control
severe turbulence
large abrupt changes in attitude and altitude with large variations in airspeed. brief periods where effective aircraft control is impossible.
extreme turbulence
capable of causing structural damage and resulting in prolonged, possibly terminal loss of control
turbulence vs chop
turbulence = erratic chop = consistent
causes of turbulence
shearing wind, uneven dissipation of heat, terrain
clear air turbulence
only occurs in the jetstream. does not occur in low level PPL flight. very severe turbulence
microbursts
very strong concentrated downdraft. occurs beneath developing (towering) cumulus clouds. procedure make 5 degree bank to the left or right and ride it out. should be out in ten seconds
3 types of ice
clear
ryme
mixed
clear ice
caused by supercooled droplets that freeze on the wing. rapidly adds weight to the acft
ryme ice
frosty, brittle like type ice. disrupts aerodynamic flow over the wing
mixed ice
ryme and clear ice. worst possible because it disrupts airflow and adds weight
how do you avoid icing conditions?
dont fly into clouds
how do you escape icing conditions?
change altitude and find warmer air either above or below you
CFIT
controlled flight into terrain (flying a plane into a mountain)
what causes CFIT?
weather that keeps lowering the ceiling and pilots that lower their altitude and think it will get better (it usually gets worse as you close in on a mountain)
how do i avoid CFIT?
make a go/no-go decision early. make a 180 turn early and divert.
rotor clouds
downdraft on one side updraft on the other. avoid at all costs. they happen on the lee (downwind) side of the mountain. ALWAYS check the wind direction when flying near the mountains. never fly on the lee side of a mountain.
lenticular clouds
look like stacked contact lenses stacked on top of each other. ALWAYS indicate that rotor clouds (or invisible rotor waves) are on the lee side. a standing lenticular cloud is the worst cloud to fly through.
adiabatic cooling
expansion cooling. air being forced up will cool at a rte of 3C per 1000 ft
standard lapse rte
every 1000 ft gain loses 1 mmHg
standard temp/press
15C/29.92mmHg
troposphere
lowest layer of the atmosphere. where all weather occurs. at the equator it extends to 60k and the poles it varies from 20-25k
mesosphere
above the stratosphere, temp decreases as altitude increases
stratosphere
starts above the troposphere. temperature is stratified. lower altitudes it is cooler, higher it is warmer.
thermosphere
atmospheric temps increase with altitude. gases separate by molecular weight and the air is so thin (near vacuum) temps as high as 1700 degrees wont even read 0 on a normal thermometer
dewpoint
the temp at which moisture in the air is visible
