Task C - Weather Information (Chap 12&13 PHAK) Flashcards
What is an FSS? What does it do?
Flight Service Station (FSS) (PHAK 13-4/13-9
* Primary source for preflight weather information.
* Call 1800-WX-BRIEF (FSS)
* Provides also provides inflight weather briefing services
* www.aviationweather.gov
* www.1800wxbrief.com
What is the difference between an Outlook, Standard, and Abbreviated Weather Outlook?
-Outlook briefing- 6 hours or more away, forecast.
-Standard briefing- provides the most complete information and more complete weather picture. Get it before departure. No more than 5 hours in advance.
-Abbreviated briefing- a shortened version of the standard briefing. Updates on the previous briefing
What is a TAF? What is the radius and valid period?
- TAF- terminal aerodrome forecast. Established for the 5 statute mile radius around larger airports. It is valid between 24-30 hour period. Updated 4 times a day, every 6 hours.
How long is an AIRMET valid for?
6 Hours
What is an AIRMET?
Hazardous weather, moderate in intensity that affects all aircraft.
What are the three different identifiers with an AIRMET? And describe what each one is.
-TANGO- turbulence, surface winds greater than 30 knots, low-level wind shear
-SIERRA- IFR conditions, mountain obscuration
-ZULU- Icing, freezing levels
What is a SIGMET?
Hazardous weather, severe to extreme in intensity that affects all aircraft
How long is a SIGMET valid for?
Valid for 4 hours unless it relates to a hurricane, it’s valid for 6 hours.
What is a Convective SIGMET?
- Severe thunders with surface winds greater than 50 knots
- Hail at the surface greater or equal to 3/4 inch in diameter
- Tornados
- Squall lines
- Thunderstorms with heavy or greater precipitation that affect 40% or more of a 3,000 square mile or greater region.
How long is a Convective SIGMET valid for?
2 Hours
What is a METAR?
An observation of current surface weather reported in a standard
international format. They are issued on a regularly scheduled basis unless significant weather changes have occurred. Then a special (SPECI) meter can be issued anytime between routine meter reports.
What is a PIREP?
Pilot weather reports. Provide valuable information regarding the
conditions as they exist in the air which cannot be gathered from any other source. Can confirm the weather, or tell about unforecasted weather
What is the weather delay on the MFD?
15 to 20 minutes
What are the percentages of gas that make up the atmosphere?
78% Nitrogen
21% Oxygen
1% Trace Gases
How much water vapor is in the air?
0-5%
What are the levels of the atmosphere?
Troposphere
Stratosphere
Mesosphere
Thermosphere
What is the standard lapse rate?
2 Degrees Celsius every 1000ft
How far does the Troposphere extend up to?
Around 20,000 ft.
How much does the pressure decrease per 1000ft altitude gain?
1 inch
What two layers have the most influence on weather?
Troposphere and Stratosphere
How far does the Stratosphere extend up to?
160,000ft
What is the definition of stability?
The air’s ability to resist vertical motion
What causes instability in the atmosphere?
Vertical air movements
What can instability in air lead to?
Significant turbulence, clouds with vertical development, and severe weather
What causes weather changes?
Currents and winds of atmospheric circulation
How does air flow?
High-pressure to low pressure
What are some examples of uneven heating at GMU?
385, the golf course, the patch of grass prior to 19, Lauren’s Road
What are some examples of obstruction of wind?
Large buildings, hangars, mountains, canyons can break up the flow of the wind and create wind gusts that changes rapidly in direction and speed
What is low-level wind shear?
Sudden drastic change in wind speed and directions
What is low-level wind shear commonly associated with?
Passage of fronts, temperature inversions, and strong upper-level winds
What are the details of a microburst?
-Most severe low level wind shear
- Strong downdrafts up to 6,000 ft per minute.
- 1 to 2 miles and 1,000 ft in depth.
- Lifespan 5 to 15 minutes
- Headwind loss of 30 to 90 knots
- Strong turbulence
- Hazardous wind direction changes
- Performance increases & decreases.
-clues are a visible ring of blowing dust and Virga
How do Dew Point and temperature correlate to one another?
- The dew point given in degrees is the temperature at which the air can hold no more moisture
- The air is completely saturated and moisture begins to condense out of the air in the form of fog, dew, frost, clouds, rain and snow.
What is the definition of a temperature inversion?
When the temperature of the air rises with altitude
What is the analogy used when talking about a temperature inversion?
The top of the inversion acts as a lid, keeping weather and pollution trapped below.
What is an air mass?
Large bodies of air that take on the characteristics of surrounding air
What is a “Front”?
As air masses move in eventually come in contact with another air mass with different characteristics. The boundary layer between two different air masses is known as a front.
How do warm fronts move?
Slowly, usually 15 to 25 mph.
How does a warm front overtake a cold front?
The front slides over top of the cool air mass, and gradually pushes it down out of the air.
What weather is associated with a warm front?
- Light to moderate precipitation
- Poor visibility, improves with variable winds but hazy conditions may continue
- Rise in pressure then a gradual decrease
- Stratiform clouds are visible
How do cold fronts move?
Fast, usually 25 to 30mph, but can reach up to 60mph.
How does a cold front overtake a warm front?
Like a snowplow
What weather is associated with a cold front?
- Clouds with towering cumulus clouds (vertical development)
- Cumulonimbus clouds may develop
- Heavy rain showers with lightning, thunder, and hail.
- Poor visibility
- Possibly tornados
- Winds variable and gusty.
- Temperature and dew point drop.
- Drop in pressure and then gradual increase
What is a stationary front?
forms when a cold front or a warm front stops moving. When air masses are pushing against each other neither is powerful enough to move the other.
What is an occluded front?
when a fast-moving cold front catches with a slow-moving warm front. And a cold front is ahead of the warm front as well. The two cold fronts come together and push the warm front in the middle up.
How is cloud type determined?
By its height, shape, characteristics
What are clouds with vertical development?
Cumulous clouds that build into towering cumulus clouds or cumulonimbus clouds.
What are clouds with horizontal development?
Stratus type clouds
What are towering cumulus clouds a sign of?
Indications of unstable air and the air around and inside is turbulent. They often develop into cumulonimbus clouds or thunderstorms
What are the side effects of cumulonimbus clouds?
Large amounts of moisture and unstable air and produce hazardous weather such as lightning, hail, tornados, gusty winds, and wind shear.
What are the three stages of a thunderstorm?
Cumulus, mature and dissipating
Define the cumulus stage of a thunderstorm
The lifting action of the air begins, and sufficient moisture and instability are present. The clouds continue to increase with height. Updrafts only.
Define the mature stage of a thunderstorm
Within approx. 15 minutes the mature stage is reached. Which is the most violent time of the storm. Drops of moisture begin to start, and the rain/snow/hail is too heavy for the clouds to hold. Updrafts & downdrafts during this stage.
Define the dissipating stage of a thunderstorm
Downdrafts only. The cell begins to die.
How far do you want to fly away from a thunderstorm?
At least 20 miles
What must there be for a thunderstorm to form?
water vapor, unstable lapse rate, & lifting action
What is a squall line?
A narrow band of active thunderstorms
What is Structural Icing?
Sticks to the outside of the airplane. It occurs when supercooled water droplets strike the airframe and freeze.
What are the three types of structural icing?
Clear, Rime, and Mixed
What is Clear Ice?
Most dangerous, heavy & hard to see, covers a larger area. Freezes slowly
What is Rime Ice?
Rough, milky ice. Most frequently reported ice. It grows when droplets rapidly freeze upon striking an aircraft.
What is Mixed Ice?
Combination of rime & clear. Similar hazards as clear, causes handling & performance problems.
What are the three types of Icing?
Structural, Instrument and Induction Icing
What is an example of Instrument Icing?
Pitot Icing
What is an example of Induction Icing?
Carburetor Icing
When does fog form?
When the temperature and dew point are identical or close
What are the four types of fog?
Radiation Fog, Advection Fog, Upslope Fog, Steam Fog
What is Radiation Fog?
Forms over land on calm, cool, clear nights. When radiation cooling reduces air temperature to or below its dew point.
What is Advection Fog?
Forms when moist air moves over a colder surface. Winds are necessary. Usually in coastal areas.
What is Upslope Fog?
Forms when moist stable air to or below its dew point, as it moves up terrain. Needs winds, speeds 5 to 15 knots are most favorable
What is Steam Fog?
Forms when cold air is over warm water.
How can frost affect our plane?
Frost disrupts the flow of the air over the wing and can drastically reduce lift. It also creates drag and can affect the ability of the aircraft to takeoff.
