Weather

Question 1

What is Windshear?

Answer 1

Windshear is a sudden change in either wind speed or direction, or both, over a relatively short distance

Question 2

Classifications of clouds

Answer 2

Cirrus - high clouds
Nimbus - clouds giving off precipitation
Alto - medium height (7,000 - 25,000)

Question 3

Lows vs Highs (Depressions vs Anticyclones)

Answer 3

Lows:

• air circulates counter-clockwise around area of low pressure in the N. Hemisphere (opposite in S. Hemisphere)
• move quickly
• large cloud cover
• precipitation

Highs:

• air circulates clockwise around areas of high pressure in the N. Hemisphere (opposite in S. Hemisphere)
• moves slowly
• little cloud cover
• no precipitation
• generally good weather

Question 4

Ridge vs Trough

Answer 4

Ridge = elongated area of low pressure

Trough = elongated area of high pressure

Question 5

Types of Fog

Answer 5

• Radiation Fog
• Advection Fog
• Steam Fog
• Frontal Fog
• Upslope/Hill Fog

Question 6

Types of Frontal systems

Answer 6

• Fronts are boundary’s between two or more air masses
• all front are different
• an approach of front of any type means a change in weather is imminent
• classified by the air mass that is overtaking
• cold front (typically move faster than warm fronts; 25 - 30+ mph)
• warm front (typically slow moving at 10 - 25 mph)
• stationary front
• occluded front (typically travel at the speed of the cold front)

Question 7

Conditions necessary for a Thunderstorm

Answer 7

• unstable air
• relatively high moisture content
• lifting action

Question 8

Thunderstorm Life Cycle

Answer 8

• Growth stage (cumulus stage): updrafts 3000fpm
• mature stage: downdrafts 2500fpm plus downdrafts 6000fpm
• dissipating stage: downdrafts only

Question 9

Types of Icing

Answer 9

• Rime Ice
• Clear Ice
• Mixed Ice
• Freezing Rain
• Snow

Question 10

What is required for ice formation on an aircraft surface?

Answer 10

• moisture must be present

- aircraft surface must be below 0°C

Question 11

Effects of icing

Answer 11

• changes aerodynamics of an airfoil
• adds weight
• reduces lift (up to 30%)
• increases drag (up to 40%)
• loss of performance
• Radio interference

Question 12

Types of Turbulence

Answer 12

• Low-Level (below 15,000 MSL)
  
  • mechanical turbulence (created by buildings and rough terrain)
  • Convective/Thermal turbulence (created by surface heating)
  • Frontal turbulence (occur ahead of fast moving cold fronts)
  • wake turbulence (caused by wingtip vortices)
• Clear Air Turbulence (usually above 15,000’ MSL, but can take place at any altitude)
  
  • caused by air masses moving over each other at different speeds
• Mountain Wave Turbulence (stable air crossing mountain barrier)
• Wake Turbulence

Question 13

Contaminated runway

Answer 13

Contaminated Runway:
More than 25% of the runway surface is contaminated with:

> 3mm. surface water, slush or loose snow

Snow that is compressed into a solid mass

Ice or wet snow

Question 14

What defines Severe Windshear

Answer 14

Airspeed changes greater than 15 knts and vertical speed changes greater than 500 fpm

Question 15

Common sources if windshear

Answer 15

Thunderstorms, temperature inversions, jet stream winds

Question 16

Define a microburst

Answer 16

Small downburst about 1 mile diameter with outbursts of damaging winds extending 2.5 miles or less

• downdrafts as strong as 6,000 fpm and horizontal winds near the ground as strong as 45 knts

Question 17

Cold front vs warm front

Answer 17

Cold Front: faster moving than a warm front with increasing pressure. Colder air overtaking and replacing warmer air. Fast moving cold front has showers and thunderstorms. Slow moving cold front has embedded CBs and TSs

Warm Front: tend to move at half the speed of a cold front with a decrease in pressure. Warmer air replacing colder air. Stratiform clouds and widespread precipitation

Question 18

Stable vs unstable air

Answer 18

Stable: stratiform clouds and fog, continuous precipitation, fair to poor visibility

Unstable: cumuliform clouds, showery precipitation, good visibility

Question 19

Low-level WINDSHEAR

Answer 19

Identified by wind shear events within 1000’ of the ground

Question 20

Jet stream

Answer 20

• A narrow band of high speed wind that meanders west to East around the globe at altitudes near the tropopause
• speeds from 50 to over 150 knts
• lower and weaker in the summer
• higher and stronger in the winter

Question 21

Causes of CAT

Answer 21

CAT = clear air turbulence

• jet stream…especially flying perpendicular; and in areas where the jet stream curves around surface lows
• mountain waves … caused by stable air being moved up the side of a mountain (frequently found east of the Rockies

Question 22

CAVOK meaning

Answer 22

At least 10km of visibility and no clouds below 5000’

Question 23

Weather associated with a Low pressure system

Answer 23

• air flows counter clockwise and toward Low center (northern hemisphere)
• rising air
• cloud formation
• continuous precipitation with possibilities of Thunderstorms
• milt temps
• moderate to strong winds
• low vis under precipitation…good vis outside of precipitation

Question 24

Weather associated with High pressure system

Answer 24

• air flows clockwise and outward from High center (Northern Hemisphere)
• descending air
• generally good weather
• low winds
• no clouds or precipitation
• hazy conditions in the summer
• warm temp in the summer and cold temps in the winter

Question 25

Forecast area of a TAF

Answer 25

5NM radius of the airport VC = vicinity = 5-10 NM from airport

Question 26

When are Mid and High Level Prog Charts issued

Answer 26

4 times daily: 0200Z 0800Z 1400Z 2000Z

Question 27

Weather Radar Tilt Guidlines

Answer 27

- 4º up for take off - aim for 0º at FL250 - +/- 1º per 5,000’ above or below FL250