Weather and Minimums Flashcards
VFR minimums for surface based class E airspace
1,000’ ceilings and 3 statute miles visibility
Steam fog
Also known as sea smoke fog, forms when cold, dry air moves over warm water.
It’s most common over bodies of water during the coldest times of year.
Low level turbulence and icing are commonly associated with steam fog.
Upslope fog
Occurs when moist, stable air is forced up slipping land features like a mountain range. Wind is required to form.
Advection fog
Common in coastal areas where sea breeze can blow the air over cooler land masses. Wind required to form, up to 15 knots.
Radiation fog
When there is little to no wind present on a clear night. Usually forms in low-lying areas like mountain valleys.
The lifespan of a microburst is about 5-15 mins during which time it can produce downdrafts of up to ________ fpm and headwind losses of ________ knots.
6,000 fpm; 30-90 knots
Low level wind shear is commonly associated with?
Passing frontal systems, thunderstorms, temperature inversions, and strong upper level winds (greater than 25 knots)
Convective currents cause the bumpy, turbulent air sometimes experienced when flying at lower altitudes during warmer weather. Typically, these conditions can be avoided by?
Flying at higher altitudes, even able a cumulus cloud layer.
Updrafts are likely to occur where?
Over pavement or barren places
Downdrafts are likely to occur over where?
Water or expansive areas of vegetation like a group of trees.
Convective currents can occur anywhere there is?
An uneven hearing of the earths surface
The reactions of the average person become impaired at an altitude of about?
10,000 feet
On average, with every 1,000 feet of increase in altitude, the atmospheric pressure decreases by?
1” Hg (1 inch of mercury)
Visible moisture will form when
Temperature and dew point are equal
Generally, the wind 2,000’ AGL ___________ degrees to the right of surface winds , and the speed is greater.
20 to 40 degrees
Clouds type is determined by?
It’s height, shape, and characteristics
Low clouds
- Form near the earths surface and up to about 6,500 AGL
- Can include supercooled water droplets that include hazardous aircraft icing
- Typical los clouds are stratus, stratocumulus, and nimbostratus
Middle clouds
- Range in heights from around 6,500 AGL and extend up to 20,000 AGL
- Include altostratus and altocumulus clouds
- Altostratus clouds can produce turbulence and may contain moderate icing. Altostratus, form when altostratus is breaking about can produce the same.
High clouds
- Form above 20,000 AGL and usually form in stable air only.
- Made up of ice crystals and pose no real threat of turbulence or aircraft icing.
- Typical high level clouds are cirrus, cirrostratus, and cirrocumulus.
Cumulonimbus clouds
- Dangerous
- Appears individually or in groups
- indicate areas of instability
Warm fronts
- Move slowly, typically 10-25 mph
* Light to moderate precipitation is probable with nimbostratus cloud formation.
Cold fronts
- Move at a rate of 25-30 MPH, but extreme ones can move faster
- Create cumulonimbus clouds along the line of the front
Thunderstorms stages
- Cumulus stage; lifting action of the air begins.
- Mature stage; most violent time period. Drops of moisture become too heavy for the cloud to support and begin falling in the form of rain or hail.
- Diss a pairing stage; vertical motion near the top of the cloud slows, and the top of the cloud takes an anvil-like shape. Downdrafts spread out and replace the updrafts needed to sustain the storm.
Ingredients of a thunderstorm
Air must have sufficient water vapor, an unstable lapse rate, and an initial lifting action.
Lapse rate
Rate of vertical temperature change. The steeper the lapse rate, the more unstable the atmosphere becomes.
Class G airspace minimums
1 mile and clear of clouds
Controlled airspace VFR (Class E, C, B, D)
3 miles visibility, 500ft below clouds, 1,000ft above clouds, and 2,000ft vertical separation
