Weather Information Flashcards
What are approved sources to obtain weather?
AC-00-45h 2-2
(Contracted by the FAA (federal aviation administration) and NWS (national weather service)
1. Federal Government (Aviationweather.gov)
2. Commercial weather information providers (ForeFlight)
METAR is?
PHAK 13
Aviation Routine Weather Report
Updates every hour
What is a TAF?
PHAK 13
Terminal Aerodrome Forecast
Usually shows 4 time slots of 0000, 0600, 1200, 1800 Zulu time
Valid from 24 hrs- 30 hrs.
What is AIRMET?
PHAK 13
Airmens Meteorological Information
Issued every 6 hours
Potentially hazardous to light aircraft
AIRMET codes
PHAK 13-11
S- IFR and MT obscuration.
T- Turbulence, strong surface winds, and low level wind shear
Z- Icing and freezing levels
What is a SIGMET
PHAK 13-12/AIM 7-1-6
Significant Meteorological
Non convective weather potentially hazardous to all aircraft
Not associated with thunderstorms
Valid for 4 hours or 6 hours for hurricanes
SIGMET Codes
AIM 7-1-6 UWS is urgent weather SIGMET N-W Excluding S,T, and Z No 2 different phenomena across the country can have the same alphabetic designator. CAT is clear air turbulence
SIGMET Phenomenas
SSSDV
AIM 7-1-6
- Severe Icing
- Severe Turbulence or CAT (clear air turbulence)
- Sandstorm surface visibility below 3 miles
- Dust storm surface visibility below 3 miles
- Volcanic ash
Convective SIGMET are valid for? Reason for issuance is?
6 thunderstorm reasons
AIM 7-1-6
2 hours
Severe thunderstorms due to:
1. Surface winds greater than or equal to 50 knots
2. Hail at surface greater than or equal to 3/4 in. in diameter
3. Tornadoes
4. Embedded thunderstorms
5. Line of thunderstorms
6. Thunderstorms producing precipitation affecting 40% or more of 3,000 sq.mi.
(Atmospheric Composition)
What is our atmosphere made of?
PHAK 12-2/AC 00-06b
78% nitrogen
21% oxygen
1% of Argon/Carbon Dioxide and other trace gases
What is the vertical structure of the atmosphere? Or what are the various atmospheres?
Earth surface to space
- Troposphere- vast majority of weather happens.
- Tropopause - up to 48,000 feet in height, but varies with season.
- Stratosphere - temperature gets warmer due to absorption of ultralight radiation
- Stratopause - gets up to negative 3 degrees Celsius.
- Mesosphere - gets colder
- Mesopause - down to negative 100 degrees Celsius.
- Thermosphere - temp increases with height
- Thermopause
- Exosphere - atoms an molecules escape to space, satellite orbit earth.
How does weather systems form?
Hydrologic cycle
Water to vapor rises
- Evaporation - liquid to vapor
- Transpiration - liquid from plants to vapor
- Sublimation - solid to vapor (snow, ice to vapor)
- Condensation - vapor condenses to a cloud
- Transportation - wind pushes it
- Precipitation - rain, snow, ice, mist… that falls to the earths surface
What are Air Masses?
00-06b 10-1
Is a large body of air with generally uniform temperature and humidity.
Source Region- is where an air mass originated from.
How many air masses are there and what are they?
00-06b 10-1 There are 5 types. 3 continental- which means dry air masses that developed over land. cA - Continental Arctic cP - Continental Polar cT - Continental Tropical 2 Maritime- which means moist air that developed over water. mP - Maritime Polar mT - Maritime Tropical
What are the type of fronts?
Cold front - cold air replaces warm air.
Speed - 20-35 mph… steeper frontal slope… cold fronts typically have violent wx.
Warm front - warm air replaces cold air.
10-25 mph… low ceilings, poor visibility, and rain.
Stationary front - when cold and warm pushes against each other.
Occluded front - cold front catches warm front and are moving in same direction.
What is atmospheric stability?
Is the property of ambient air that either enhances or suppresses vertical motion of air parcels and determines which type of clouds and precipitation a pilot will encounter.
What are the different kinds of atmospheric stability, or air parcels?
Stable parcel - if the lifted parcel is colder than surrounding air it will be denser than the surrounding air and sink back to its original state.
Neutral parcel - if lifted parcel is same temperature as air it will be the same density and remain at the same level.
Unstable parcel - if lifted parcel is warmer therefore less dense than surrounding air, it will rise on its own until it reaches same temperature as its environment.
What are the wind forces, or what makes the wind move?
00-6B ch. 7
1. Pressure Gradient Force (PGF)
Wind falls from high pressure to lower pressure… like a stream going down hill.
2. Coriolis Force
The earth spinning effects the wind. Note: north of equator pushes wind to the right. South of equator pushes wind to the left.
3. Friction
Whenever the wind hits the surface, it slows the wind down.
High pressure versus lower pressure
High pressure specifics
PHAK 12-7
High pressure
Clockwise circulation (anticyclonic circulation)
Dry descending air - good weather is typically associated.
High pressure versus low pressure
Low pressure specifics
PHAK 12-7
Low pressure
Wind is inward and counterclockwise (cyclonic circulation)
Rising air - usually brings cloudiness and precipitation
Normally associated with bad weather.
Tailwind Hazard
Takeoff- longer take off roll… upon lift off tailwind creates a smaller initial climb gradient possibly making it insufficient to clear obstacle.
Wind shear is?
The sudden drastic change in speed and or direction over a very small area.
What is a mountain wave?
Mt. Wave occurs downwind on the other side of the mt. Which disrupts the flow of wind downward and upward again creating a wave like turbulence or oscillation.
This can often push a pilot into the mountain.
Microbursts indications and attributes
PHAK 12-11
Indication: intense rain shaft at the surface but Virga at the cloud base and a ring of blowing dust is often the visual clue.
Note: virga is the evaporation of precipitation before it reaches the earths surface.
Attributes: 1-2 miles in diameter. Depth of 1000 ft. Lifespan is 5-15 min. Downdrafts up to 6000 ft. Per. Min. (FPM). Headwind loss of 30-90 knots.
Cloud types
Low clouds: sfc-6500ft. 1. Stratus 2. Stratocumulus 3. Nimbostratus Middle clouds: 6500-20,000ft. 1. Altostatus 2. Altocumulus High clouds: above 20,000 ft. 1. Cirrostratus 2. Cirrocumulus 3. Cirrus Vertical development clouds: 1. Towering cumulus 2. Cumulonimbus
Thunderstorms requirements and stages
Requirements. Stages.
- Unstable Air. 1. Cumulus stage
- Sufficient moisture. 2. Mature stage
- Lifting action. 3. Dissipating stage
How does fog form?
Fog forms when temps turn and dew point of the air becomes identical or nearly so.
Fog types?
Think RAUFIS
00-6B 16-1 Radiation fog Advection fog Upslope fog Frontal fog Ice fog Steam fog (Each fog will have its own flash card)
Radiation fog
(R)AUFIS
Often occurs on clear nights when the ground cools rapidly due to terrestrial radiation.
Advection Fog
R(A)UFIS
Often occurs on coastal areas where warm moist sea breeze blows the air over cooler land masses. 15 knots or more can form low stratus clouds.
Upslope fog
RA(U)FIS
Occurs when moist stable air is forced upsloping land features.
Frontal Fog
RAU(F)IS
Occurs when warm moist air is lifted over a front, creating clouds and precipitation, but when the cold air toward the ground is near its dew point evaporation or sublimation occurs creating fog.
Basic explanation: warm air on top of cold air, it rains and reaches dewpoint creating fog.
Ice fog
RAUF(I)S
Occurs in cold weather when temperature is much below freezing and water vapor forms directly into ice crystals… usually in arctic regions -25 degrees in Fahrenheit.
Steam fog
RAUFI(S)
Forms when cold dry air moves over warm water.
Different types of structural icing.
00-6B 18-1
Rime ice: rough, milky… happens when water droplets hit the plane rapidly freezing trapping air inside.
Clear ice: glossy, clear… slow freezing of water
Mixture ice: both of above explanations occur.
Dangers of frost
Frost disrupts the air flow over the wing and can drastically reduce the production of lift.
If frost or ice no thicker or rougher than sandpaper can reduce lift by 30% and increase drag by 40%… if more accumulation occurs both increase and drag increases 80%.
Obstructions to visibility include?
Fog Mist Haze Smoke Precipitation Blowing snow Dust storm Sandstorm Volcanic ash (Definitions are in 00-6B ch. 16)
