Weather Flashcards
Tropopause
- thin layer above the troposphere
- abrupt change in temperature lapse rate
Stratosphere
- small change in temperature with increasing altitude
The Jet Stream
- “river” of high speed winds (50 knots +)
- winter = south and increased velocity
- summer = north and slower velocity
Standard temperature
15* C at sea level
Average lapse rate
2*C per 1000’
Troposphere
- Surface to 37,000’ (20,000-65,000)
- higher over the equator
- higher in the summer
- Decrease in temperature with increasing alt
Wind rules northern hemisphere
- air circles clockwise around high pressure systems
- air circles counterclockwise around low pressure systems
- closer the isobars together, stronger the wind
- due to surface friction, to about 2000’ winds move outwards from the center of high pressure to low pressure
- coriolis effect deflects wind to the right
Relative humidity
- how much water vapor thats present in the air vs. how much it can actually hold
- 100% is considered “saturated
- warm air can hold more water vapor than cold air
Dew point
The temperature air must cool too to become saturated (100%) by the water already present in the air
Wet snow
- temperature is above freezing at your altitude
Atmospheric stability
The resistance of the atmosphere to vertical motion.
Characteristics of unstable air
Cumuliform clouds, showery precipitation, rough air (turbulence), and good visibility
Characteristics of stable air
Stratiform clouds and fog, continuous precipitation, smooth air, and fair to poor visibility in haze and smoke
Dry adiabatic lapse rate
3*C per 1,000’
Family’s of clouds
- high clouds
- middle clouds
- low clouds
- clouds with extensive vertical development
Radiation Fog
(ground fog) is formed when the ground cools the air to its dew point.
- typically in warm, moist air over low, flatland areas on clear, calm nights.
Advertise Fog
- (sea fog)
- formed when warm, moist air moves over colder ground or water
Upslope Fog
- formed when moist stable air is cooled to its dew point as it moves up sloping terrain
- dry adiabatic rate (3*C per 1000’)
Thunderstorm
- sufficient water vapor
- unstable lapse rate
- initial upward boost (lifting)
Cumulus stage
thunderstorm
Continuous updrafts, creating low pressure areas
Mature stage
thunderstorm
- Up and downdrafts inside the cloud
- start of rain at the base
- most intense stage of the storm
Dissipating stage
thunderstorms
Mostly consists of downdrafts
Microbursts
Small scale intense downdrafts which spread outward as they near the ground.
- downdrafts can be as great as 6,000 fpm
- usually Las less than 15 minutes
Wind Sgear
A change in wind direction and/or speed in a very short distance
- can occur at any level of the atmosphere
- detected by the pilot as a sudden change in airspeed
Low-level wind shear
- All sides of a thunderstorm and directly under the cell
- Also found near frontal activity
Warm front wind schear
- most critical before the front passes
- may exist below 5,000’ for about 6 hours before the surface passage of the front
- more extreme than cold front wind schear
Cold front wind schear
Usually found behind the front, if the front is moving greater than 30 knots
- schear zone 5,000’ agl 3 hours after the front passes
