Weather Ch. 5

Question 1

DESCRIBE the hazards associated with thunderstorms

Answer 1

• Hail:
  
  • circulate in updrafts and downdrafts
  • hailstones larger than 1/2 to 3/4 an inch can cause sig damage to aircaft in a few seconds
  • Hail has been encountered
    
    • as high as 45,000 ft in clear air
    • carried 10-20 miles downwind
• Ice
• Microburst
• ​Extreme Turbulence
  
  • can cause changes in altitude
  • structural damage
  • extra srress on the airframe
  • effects depend on severity of turbulence and aircarft speed
  • most sever hazard assoicated with TS
  • Gust Front
    
    • ​Forms on surface at the leading edge of an advancing TS
    • can travel 2-20 mi from TS
  • Roll and Wall Clouds
    
    • ​occur in severe and fast moving thunderstorms
    • indicate the pressence of low level wind shear and extreme turbulence
• Lightning
  
  • results from seperation of pos and neg charge, from water and ice passing in up and down drafts
  • static charge builds up on aircraft while in the clouds
  • can strike A/C flying in the clear
  • structural damage possible
  • fuel ignition possible
  • pilots can experience flash blindness
  • static buildup sometimes released through St Elmos Fire
• Tornado
  
  • voilent destructive whirling wind acomplished by a funnel shape cloud
  • tornado if touches the ground
  • funnel cloud if it doesn’t reach surface
  • water spout if it touches water

Question 2

DESCRIBE the signs and hazards associated with microbursts

Answer 2

• Signs:
  
  • virga
  • localized blowing dust
  • shaft of rain which diverges closer to the ground
  • severe TS
  • heavy rain
  • low or no visibility
  • gusty winds
  • frequent lightning
  • tornado activity
• Hazards
  
  • 2000 to 6000 feet/minute downdrafts
  • wind veloctiy from 20 to 200 kts
  • area 1/4 to 2.5 miles
  • lasts 5-10 minutes
  • emenates from any convective
  • strong winds are destructive to gorund objects
  • many aircraft mishaps have been attributed to microbursts
• Can be found outside of TS

Question 3

EXPLAIN how radar can aid a pilot when flying in the vicinity of thunderstorms

Answer 3

• Ground-based Doppler radar now has the capability to accurately detect hazards
  
  • weather observations or recordings mention low-level wind shear, or call for gusty winds, heavy rain, or severe thunderstorms be vigilant
• Detection and warnings are more accurate with the modern NEXRAD Doppler radar systems
  
  • most accurate means of tracking TS
  • scale signifys wind intesnity or speed
  • tv shows doppler compostie
• Direct relationships exists between
  
  • strength of radar echoes
  • presence of icing
  • intensity of turbulence
  • height of tops of CBs indicate TS severity
• A thunderstorm with radar echo tops indicated above 35,000 feet often contains extreme turbulence and hail.
• Not used for TS penetration
• used to avoid and cirumnavigate scattered TS

Question 4

DESCRIBE the recommended techniques for avoiding thunderstorm hazards

Answer 4

• cirgumnavigate isolated TS
• Over the Top
  
  • avoid most hazards
  • altitiude margin for turbulence and hail (1000 ft for every 10 knots of wind speed)
• Underneath
  
  • not in the worst of hazards
  • Alt margin: 1/3 distance from ground to cloud base
  • penetrate lower 1/3 of storm
• TS COMMON SENSE
  
  • Don’t take off or land if one is approaching
  • Don’t fly into cloud mass containing TS without airborne radar
  • avoid flying under a TS