Weather Flashcards
Troposphere
Nearly all weather occurs here
Pressure gradient force
The initiating force for all winds
Visible moisture is also
Cloud, super cooled water, freezing rain, liquid water below freezing
Cold fronts
Winds
Direction
Shifts
20kts
Moves from NW to SE
Shifts from SW to NW clockwise
Warm Fronts
Winds
Direction
Shifts
15kts
Moves from SW to NE
SHifts from SE to SW
Stationary fronts
Neither air mass is replacing the other. They are indicated on surface charts by an alternating warm and cold front symbols, retaining their original red and blue colors, but pointing in opposite directions.
PIREP Turbulence reporting term
Occasional: Less than 1/3 of the time
Intermittent: 1/3 to 2/3 of the time
Continuous: More than 2/3 of the time
Lifting actions
Frontal
Orographic
Convergence
Thermal
Occluded front
Where do the winds shift from?
When a faster moving cold front overtakes a slower moving warm front. Winds shift from SE to NW
Where layer does the ceiling start
Broken layer
Definition of fog
Visible layer of condensed moisture
Base at or within 50 feet of surface
Greater than 20 feet thick
Reduces visibility to less than 5/8 of a mile
Roll and wall clouds
Roll clouds occur in severe and fast moving thunderstorms. Indicate the presence of low level wind shear and extreme turbulence
Gust fronts
Forms on the surface at the leading edge of an advancing thunderstorm. 5-20 miles from the thunderstorm
Difference between funnel cloud and tornado
Funnel cloud is not touching the surface and tornado is.
Manual METAR observations…
Are required to be started no earlier than 15 minutes prior to the reporting time which is a window between 55 and 59 minutes past the hour.
Air traffic facilities are required to solicit PIREPs whenever the following conditions are reported or forecasted:
Ceilings are at or below 5000ft, vis at or below 5 miles, thunderstorms and related phenomena, icing of a light degree or greater, turbulence of moderate degree or greater, and wind shear.
Discontinuities between air masses
- Temperature
- Dew points: Larger contrasts produces more severe weather
- Wind: Usually clockwise 90 degrees
- Pressure: Falls ahead of front, rises after
Factors influencing frontal weather
Moisture Contrast Stability Slope Speed
Intensity differences between Turbulence and Icing
Turbulence: Light, moderate, severe, extreme
Icing: Trace, light, moderate, severe
Thunderstorm avoidance (In order)
- Circumnavigate
- Over the top - 1000ft for every 10kts
- Underneath - 1/3 distance from the ground to cloud base
- Penetrate - Lower 1/3 of the storm
Vertical air movement happens:
Both up and down
Types of turbulence
Windshear: Jet stream, gusty winds, temperature inverstion
Thermal
Frontal
Mechanical
At what temperature does Rime, mixed, clear, and engine ice occur
Rime: -20 to -10 degrees celsius
Mixed: -15 to -8 degrees celsius
Clear: -10 to 0 degrees celsius
Engine: 0 to 10 degrees celsius
Clear air Turbulence can…
Occur in any 4 classifications of turbulence
Standard lapse rate
2 degrees celsius per 1000ft
Standard day
15 degrees celsius
Why is there a temperature inversion in the stratospher
Ozone and to close to the sun
What is the tropopause
Transition between troposphere and stratosphere, isothermal layer is located here
What type of weather is associated with the stratospher
smooth, clear air
What percentages of elements found in pure, dry air?
78% nitrogen, 21% oxygen, 1% mix of 10 other gases
How much water vapor is in the atmosphere?
0-5% by volume
What is the coriolis force and what does it do?
It is created by earth’s rotation, diverts air to the right and circulates air in our atmostphere
High pressure rotates and is what color… Low pressure
High: Clockwise descending and out
Low: Counterclockwise, converging and ascending
Less than 2000 ft what affects the winds?
Coriolis force and surface friction
Jet stream dimensions and speeds
- 100-150kts avg
- 250kts center
- 50kts outer
- 1000 - 3000 miles long
- 3000-7000ft tall
- 100-400 miles wide
What breezes happen during the day and at night?
Sea, valley day
Land and mountain, night
Saturation
When temperature and dew point are equal
Fog will begin..
when the temperature dew point spread reaches 4 degrees farenheight, or the relative humidity will be 90%.
Three characteristics of precipitation
SHowers, continuous (steady), and intermittent
Three common types of precipitation
Drizzle, rain, frozen
Middle clouds
Alto
6500ft-20000ft AGL
Low clouds
Less than 6500 ft AGL
Worried about terrain
High clouds
Cirro - Icing
Above 20000ft AGL
Nimbostratus
Violent, downward
Cumulonimbus
Heavy, upwards
Squall lines occur how far in front of what kind of front
50-300 miles, cold front
Orographic types
Steady, neutral, unstable
Thermal lifting action caused by
Cold air moving over warm surface
Two characteristics that are the same across a uniform horizontal plane and what is this called?
Temperature and moisture, an Airmass
How are fronts named?
The overtaking air mass temperature
What are occluded fronts and where can their weather be found?
When a faster moving cold front overtakes a slower moving warm front, the type is dependent on which front stays in contact with the ground. 100nm south and 300NM north of the frontal intersection
Cloud formations associated with Mountain wave turbulence
Rotor Cloud
Forms downwind from and parallel to the mountain range
Cylindrical shape
Downward flow has been known to reach the ground
Cap Cloud
Cover the top of the mountain
Remain stationary
Lenticular Cloud
Forms on leeward side of the mountain from standing waves
Mountain wave turbulence found where and at what speed
Extreme turb found on leeward side of mtn up to 50kts or greater at the peak.
- Severe turbulance 150 miles downsind, moderate turbulence as far as 300 miles downwind.
Where should you fly to avoid mountain wave turbulence
Circumnavigate if possible or at a level at least 50% higher than the height of the highest mountain range along your flight path. Approach at a 45 degree angle so that a quick turn can be made away from the ridge if a severe downdraft is encountered.
Types of icing
Clear (most dangerous), rime, mixed, and frost
Types of engine icing
Induction (increased risk of FOD into engine ahead of compressor) and compressor(ice forming on compressor inlet screens)
When will icing occur?
Visible moisture and freezing temps(0- -20degrees celsius)
Visibility defined as
- Ability to see and identify prominent unlighted objects by day and prominent unlighted objects by night.
Flight visibility defined as
The average forward horizontal distance, measured in SMs from the cockpit where the pilot can see unlit and lit objects whether it be day or night.
Prevailing visiblility
Greatest horizontal visibliity, equaled or exceeded throughout at least 50% of the horizon circle, which need not be continuous.
Slant range visibility Define
Distance on final approach with the runway environment in sight
Runway visual range
Horizontal distance, expressed in hundreds of FEET OR METERS, a pilot will see by looking down the runway fromt he approach end
Fog
Is a visible aggreagate of minute water droplets that is based or within:
- 50 feet of the surface
- greater than 20 feet in depth
- reduces vis to less than 5/8 of a SM
Radiation fog
Occurs due to nocturnal cooling, usually on clear nights, when the earth releases relatively large amounts of radiation into the atmospher, cooling the surface. It can dissipate with winds greater than 10 knots or solar heating.
Advection fog
occurs when warm, moist air moves over a cold surface and the air is cooled to the dew point. It can only be dissipated by winds.
Thunderstorm hazards
H: Hail I: Icing M: Microbursts E: Extr Turb. L: Lightning T: Tornados
Everything in a TAF/METAR is in zulu time except
weather watches
Microbursts
- Downward vel: 2000-6000ft/min
- Velocities: 20-200kts
- Diameter: 1/4-2 1/2 miles
- Span: 5-10 mins
METARs last
1 hr
TAFs last
24 hrs
NEXRAD finds
H: Hail
T: Tornados
M: Microbursts
L: Low level wind shear
TAF for Military is in what unit of measurement
Meters, everything else is in SM
On Prognostic charts if above 36?
Subtract 50, add 100
Weather warning is for what and what are the req. for a thunderstorm to be reported
Tornado, funnel cloud, or
TS: 50kts or greater
Hail greater than 3/4in
10000 SM area
What size hailstones can cause significant damage?
1/2 to 3/4 inch
SIGMETS
- Abbreviation:
- Duration:
- S/U
- Abbreviation: WS
- Duration: 4 hrs
- S/U: U
Convective SIGMET
- Abbreviation:
- Duration:
- S/U
- Abbreviation:WST
- Duration: 2hrs
- S/U: U
AIRMET - Abbreviation: - Duration: - S/U Sierra: Tango: Zulu:
- Abbreviation: WA
- Duration: 6hrs
- S/U: S
Sierra: IFR conditions
Tango: Mod turb
Zulu: Icing
Prognostic chart: 1733
170 degrees true and 33 kts
Prognostic chart: 740957
240 degrees true at 109 kts -57 degrees celsius
How should pilots flight plan given tailwinds and headwinds
Greater tailwinds, and lighter headwinds