WEATHER Flashcards
4 types of weather briefings
standard- initial brief and haven’t received any preliminary information
abbreviated- supplemental information, update a previous briefing or only need one or two items.
outlook- departure time of six or more hours
inflight briefing- update a preflight briefing
what should a weather briefing include (SACREDWIND)
Synopsis
adverse conditions
current conditions
en route forecast
destination forecast
winds aloft
notams
atc delays
how can you recieve updated weather information
FSS on 122.2
ATIS
ASOS/AWOS
Air traffic control center
Sigmet
Airmet
Pireps
CWA center weather advisories
ATC
AWOS
automated weather observation system
various sensors a processor, a computer-generated voice, broadcast local minute-by-minute weather data.
What Can PIREPs inform
confirm heights of clouds, locations of wind shear and turbulence, inflight icing.
UA- routine
UUA- urgent
can report to ATC or FSS
Convective sigmet
severe or greater turbulence, severe icing and low-level wind shear. greater or equal to 50 knots. valid up to 2 hours
Sigmet
weather hazardous to all aircraft
valid for 4 hours
unless associated with tropical cyclones and volcanic ash are good for 6 hours. icing, severe turbulence, clear air turbulence, dust storms and sandstorms.
G-Airmet
graphical advisory of weather may be hazardous to other aircraft, less severe.
IFR conditions
mountain obscurations , icing, turbulence low level wind shear
3x a day and for 12 hours.
Airmet
significant textual weather that may be hazardous to other aircraft/other than convective activity. good for 6 hours.IFR conditions,mountain obscurations,icing,llws,turbulence and strong surface winds.
different types of Airmets
Sierra (dessert)- IFR conditions and mountain obscurations
Tango(turbulence) - moderate turbulence, winds greater 30 kts , nonconvective LLWS
Zulu ( subzero) - moderate icing and provides freezing level of heights.
what can be determined in winds aloft information
best altitude
areas of possible icing
temp inversions
turbulence
Convective outlook (AC)
outlook of potential severe weather- tornadoes, winds greater than 50, hail etc. following 8 days
LIFR
low instrument flight rules- ceiling less than 500 and viz less than 1 mile
IFR
ceiling 500 to 1000
viz 1 to 3 miles
MVFR
ceiling 1,000 to 3,000
3 to 5 miles viz
VFR
ceilings greater than 3000 feet
viz greater than 5 miles
what is considered a ceiling ?
height above the surface of lowest layer of cloud- broken, overcast, obscuration.
where does majority of our weather occur
troposphere- extends up to 36,00 feet
how can you determine the stability of the atmosphere
unstable- temp decreases uniformly and rapidly. air near the surface is warm and moist
stable- temp remains the same or decreases slightly with altitude.
what causes wind
difference in air density caused by changes in temp which change pressure. creates motion in atmosphere .
3 forces that effect wind
pressure gradient(PGF)
Coriolis effect
friction
define pressure gradient
in pressure difference area PGF makes the wind blow to equalize the pressure . higher height /pressure to lower height/pressure.
coriolis effect
northen hemisphere- deflects winds to the right . directionally proportional to wind speed.
local winds examples
sea breeze
land breeze
lake breeze
mountain breeze
windhsear definition
sudden and drastic change in wind direction and velocity. usually vertical, can affect in any altitude.
where can you find wind shear information
metar
sigmets
terminal forecast
pireps
low level windshear
lens shaped cloud over mountains
mountain wave
formed from a disturbance of stable airflow over a mountain. forms mechanical turbulence and causes severe turbulence.
what does temp do to moisutre in air
every 20f increase it doubles the amount of moisture the air can hold
relative humidity
ratio that water vapor in air compared to the amount of water vapor the air could hold at a particular temp and pressure.
dew point
the temperature of air must be cooled at constant press and constant water vapor for condensation to form.
different precipitation types
drizzle, rain, freezing rain, snow, hail
3 ingredients need to form precipitation
water vapor
sufficient lifting force to condense wator vapor into clouds
growth process that allows clouds droplets to grow large and heavy enough to fall
low pressure system
high pressure system
low- inward, upward and counterclockwise warm air up from surface “vaccum” (unstable)
high- cold air in atmospher sinks outward downward and clockwise
in northern(stable air)
low pressure to high pressure difference when flying
low pressure is categorized by rising air which brings cloudiness, precipitation, and bad weather. high press- descending air and brings dissipation of cloudiness and good weather.
occluded front
fast moving cold catches to slower moving warm front.
cold front occlusions- fast moving cold front is colder than air ahead(Warm front) replaces air and forces warm front aloft.(nimborstratus)
warm- air ahead of the warm front is colder that the air of cold front.(embedded TS-towering cumulus)
stationary front
two air masses are relatively equal,theboundary or front that seperates them remains stationary , influences weather for days. mix of both warm and cold weather
cold front meaning and characteristics
mass of cold ,dense and stable air replaces body of warmer air and be as fast as 60mph.
characteristics- cumolonimbus, heavy rain,lighting , thunderstorms.poor viz.
warm front
warm replaces cold, slower up t0 25mph. warm front slides over the top of cooler air and gradually pushes it out.
characterisitics- startiform clouds,drizzle,low ceilings and poor visibility.rise in temperature.
what is a trough
elongated area of low atmospheric pressure. must go upward, its an area of rising air and conducive to cloudiness and precip. low pressure and bad weather
what is a ridge
elongated area of high press descending air and dissipated cloudiness so its associated with good weather.
how do clouds form
condensation of water vapor rising in currents of air by evaporation of the lowest layer of fog.
cirriform clouds
high level above 20k feet, thin white in apperance.
nimbo clouds
nimbus means rain, 7k to 15k and bring steady precip.as it thickens the cloud base tends to be closer to the ground.
cummuliform
shows the vertical motion or thermal uplift of air taking place in atmosphere. height depends on humidity ,more humid the lower the cloud base. tops can reach 60k
3 primary causes for turbulence
convective currents
obstructions
wind shear
trubulence levels
light- slight erraticear air trubulence changes
moderate-changes in altitude and attitude occur but can remain in positive control
severe- causes large and abrupt changes and large variations of airspeed. momentarily out of control
extreme- large changes impossible to control and can cause structural damage .
clear turbulence
sudden severe turbulence in cloudless regions. above 15k. core of jet stream and surrounding air. no visual cues and are reported by Pireps.
what does a thunderstorm need to form
sufficient water vapor, unstable lapse rate, initial lifting force
stages of thunderstorms
cumulus- strong updrafts,lifting action begins.
mature- most dangerous , precip begins to fall and downdrafts develop.warm rising air and cool precipation induced descending air create violent turbulence.
dissipating- downdrafts spread out and replace the updrafts which are needed to sustain the storm.
3 types of thunderstorms
sing cell- one cell easy to navigate except at night.navigate
multicell- cluster of celss in different stages of life cycles.as cells mature they are carried downward and new cell forms upwind to take its place.several hours.
supercell-single, qausi-steady rotating updrafts. speeds can reach up to 9kfpm.many hours long.
microburst
small scale of downdrafts that reach the surface and spread out in all directions. horizontal/vertical wind shears. short life span. without surface precip
what are the main types of icing aircrafts can encounter
structural, induction system, instrument icing
clear icing
glaze ice, glossy, clear and translucent ice. slow freezing of large supercooled droplets.found in warmer temps
rime ice
rough,milky, opaque formed by insant freezinf of smalll water droplets. colder temps
mixed icing
clear ice and rime ice due to small scale variations in liquid water,temp and droplet size.
freezing level
lowest altitude in a given location that temps reches 0 celsius.can be found on pireps, sigmets, airmets
how does fog form
temp and dewpoint are identical cooling of the air beyond its dewpoint or by the addition of moisture elevating the dewpoint
radiation fog
clear skies , no winds, heat absorbed by the surface and radiated to space, as temps cools and moist warm air near the ground small dew-temp spread ( high humidity)mostly at night or daybreak.
advection fog
moist air moves horizontally over colder ground or water,coastal areas. can occur with winds or cloudy skies at anytime of the day/night.
upslope fog
wind pushed moist stable air being cooled adiabatically up sloping terrain. air becomes saturated and condensation occurs. Covers a large area.
frontal fog/precip induced fog
warm moist air is lifted over a front. precip may form.if cold air is near dew point , evaporation from precirp may saturate the cold air and form fog.
steam fog
very cold air moves across relatively warm water, moisture may evaporate. as the rising water vapor meets the cold air it cools until 100% humidity immediately re-condenses. Wisp of smoke of water.
freezing fog
temps falls to 0 degrees Celsius.or below tiny, supercooled liquid water droplets in fog can freeze instantly.
what is frost
ice crystal deposits formed by sublimation when temp and dewpoint are below freezing. cam form on clear night when moisture is present and airplane skins falls below freezing
TAF
terminal aerodrome forecast
24 hours
issued 4x daily
prognostic chart
low level prog chart forecast chart.
issued 4x daily
12 hour
24 hour forecast for a given region
from surface to 400milibar pressure - 24k feet
flight planning under 24k feet
surface analysis chart
depicts weather conditions as it was a few hours Earlier
issued every 3 hours
high/low press systems
frontal movements
weather depiction chart
computer generated chart based on metars and gives wide overview of weather
begins at 0100zulu and updated every 3 hours
only valid at time of issue
center weather advisory (CWA)
issued by control centers both sigmet and airmet conditions described in detail for specific air route traffic control center areas.
air mass vs front
air mass- large body of air that has similar temp and moisture can take up the characteristics of the surface below
front - the transition zone of two different air masses of different density
what causes turbulence
convective currents
obstruction wind flow
windshear
ingredients needed for thunderstorm
sufficient water vapor
unstable lapse rate
uplifting action
