WEATHER FLASH CARDS
Everything else being equal, why is a wind blowing across isobars slower at the surface than aloft?
Answer: Friction between the wind and the terrain surface slows the wind.
What is the definition of wind shear?
Answer: Any rapid change in wind direction or velocity which causes airspeed changes greater than 15 knots or vertical speed changes greater than 500 feet per minute.
Describe radiation fog…
Answer: Usually occurs; High humidity during the early evening. Cool cloudless nights with light winds. Favorable topography.
In what condition will snowflakes form?
Answer: Snowflakes are formed by sublimation in below freezing temperatures Sublimation is the transition of a substance directly from the solid to the gas phase, without passing through the intermediate liquid phase.
What are the 3 belts of prevailing winds in the northern hemisphere?
Answer: Polar easterlies (north of 60 latitude), prevailing westerlies (between 30 and 60 latitude) and trade winds (between the equator and 30 latitude).
What is terrestrial radiation?
Answer: The Earth radiates energy, this outgoing energy is terrestrial radiation. THATS LIKE SOMETHING FROM OUTER SPACE.
Standard atmosphere at sea level is 15° and 29.92” Hg, by definition however, how would you describe what standard atmosphere is?
Answer: the result is specified sea pressure level temperature and specific rates of change of temperature and pressure with height.
CAT is best predicted where horizontal wind shear exceeds what values?
Answer: Expect and avoid areas of CAT where horizontal wind shear exceeds 40 knots per 150 NM.
What are the parameters that define wind shear?
Answer: Wind shear is defined as “any rapid change in wind direction or velocity”. Severe wind shear is defined as a rapid change in wind direction or velocity causing air speed changes greater than 15 knots or vertical speed changes greater than 500 feet per minute.
What type of icing will cause formation more quickly?
Answer: Clear ice. A condition favorable for rapid accumulation of clear ice is freezing rain below a frontal surface.
What kind of winds are associated with a warm front?
Answer: warm fronts move slowly. Generally the winds in a warm front are from 10-25 mph as opposed to cold. Fronts which move much more quickly and experience wind gusts from 25-35 mph.
What is diurnal variation?
Answer: It is the change in temperature from day to night brought about by rotation of the Earth.
What percentage of the sun” energy is absorbed by Earth?
Answer: About 45%, the other 55% is reflected by the Earth and its atmosphere.
Adiabatic changes to air imply….
Answer: No heat is removed from or added to air as it expands or contracts. HE IS ADIABATIC DON’T GIVE HIM ANY HEAT.
What type of weather report would you find CAT on?
Answer: Clear Air Turbulence Forecast – CAT (3 and 6 hrs. US Forecast).
What is the jet stream and where is it found?
Answer: The jet stream is a narrow band of strong wind (by arbitrary definition, it has wind speeds of 50knts or greater) meandering through the atmosphere at a level near the tropopause. The jet stream is always found at a vertical break in the tropopause where the tropical and polar tropopauses meet.
Mountain waves can produce stationary cloud group of rotor clouds and standing lenticular clouds. Pf the two, which are usually found at lower altitudes?
Answer: Rotor clouds are likely to be the lowest. ROTOR CLOUDS, SPINNING THERE WHEELS ON THE GROUND.
How is the standard atmosphere determined?
Answer: average conditions throughout the atmosphere for all latitudes, seasons and altitudes.
Describe how the general circulation of air in the northern hemisphere from the equator to the poles is formed…
Answer: Warm air forced aloft at the equator moves north toward the poles and turns to the right (Coriolis Effect), becoming a westerly wind at about 30 lat. Cool polar air descends and makes its way towards the equator, it too shifts to the right and by the 60 lat forms the polar easterlies. Air piles up at the 30 and 60 lat in both hemispheres. This creates a high press belt that ids the basis for mid-lat band of storms and weather.
Are METAR winds reported in relation to magnetic or true north?
Answer: True north. Remember, if it’s written, it’s true (expect for the paint on the runway).
What does 1013.2mb equate to in inches of mercury?
Answer: Standard atmospheric pressure at sea level is 1013.2 millibars, which is the equivalent of 29.92 inches of mercury.
You experience wind shear on final, what is the best course of action?
Answer: While aircraft procedures may vary, the pilot on experiencing severe wind shear should maintain or increase pitch attitude, increase power to the maximum available and accept lower than normal airspeed indications. If this does not arrest the descent, the pilot should continue to pitch up until the descent does stop or until the “stick shaker” is encountered.
Winds aloft are 270/20, they shift to 210/15, have you experienced frontal passage?
Answer: Yes, even though shifts are usually to the right after passage. The question I got had to do with ground weather and frontal passage, low ceilings and heavy rain proceeding a cold front.
In the northern hemisphere, high pressure air circulates…
Answer: Outward, downward and clockwise.
Name the 5 temperature variations which create forces that drive the atmosphere its endless motions…
Answer: Dirunal, Seasonal, Latitude, Topography and Altitude.
