JX104 T-Storms Flashcards
List the 3 requirements for t-storm development
Moisture, Unstable Air, Lifting Action
What is the point called when lifted air continuous to rise freely (ie the cumulus cloud grow rapidly, forming into cumulonimbus clouds)
Level of free convection
Describe the effects of turbulence
Can cause changes in altitude, can cause structural damage, extra stress on the airframe, and the effect depends on severity of turbulence and speed of aircraft
What is a gust front?
Forms on the surface at the leading edge of an advancing t-storm
Describe Roll and Wall Clouds
They are typically fast moving cold fronts that occur in severe fast moving t-storm; they indicate the presence of low level wind shear and extreme turbulence
What are the characteristics of hail?
They circulate in updrafts and downdrafts; hailstones larger than 1/2 to 3/4 of an inch can cause significant damage to aircraft in a few seconds; has been encountered as high as 45,000 feet in clear air, and carried 10 to 20 miles downwind
Describe lightning hazards
Static charge builds up in the aircraft while in the clouds; can strike a/c flying in the clear; structural damage is possible; catastrophic fuel ignition possible; pilots can experience flash blindness; static buildup sometimes released through St. Elmo’s fire (purple/blue lights)
Name the tornado cloud types
Tornado touches ground; funnel cloud (not touching surface); waterspout (touches water surface)
Define a Microburst
An intense, highly localized downward atmospheric flow with velocities of 2,000 to over 6,000 fpm; outflow produces wind shear of 20 to 200 knots
Describe characteristics of microbursts
Small area (1/4 to 2.5 miles wide; short duration (lasts only 5-10 minutes); emanates from cumuliform cloud, not necessarily a t-storm
Describe dry microbursts
Form when there are large temperature (dew point) spreads at the surface; rain evaporates as it descends (virga), which cools the air; colder air accelerates as it descends
T/O during microburst
Edge of vortex ring produces wind blowing upward from ground; increase in HW causes IAS to jump upward rapidly; in center of downdraft, a/c descends, but soon enters other side of outflow; HW shifts to TW, IAS drops rapidly, causing stall
LDG during microburst
Natural reaction to reduce power and re-est descent; removes power and wastes valuable time to get a/c away from ground before entering outflow; *MAX SPEED AND CLEAN
What are visual cues of microbursts?
Virga, localized blowing dust, shaft of rain which diverges closer to ground, severe t-storms
Define virga
Precip that evaporates before reaching the ground
What are some ways to detect microbursts?
Doppler radar, low level shear alert systems, PIREPS, and Departure and Arrival Weather Reports
Techniques for avoiding t-storm hazards
cirCUMnavigate, NEXRAD, airborne radar
What is airborne radar used for?
Used to cirCUMnavigate and avoid scattered t-storms; not used for t-storm penetration (lol)
T-storm Hazard Avoidance steps
CIRCUMNAVIGATE; Overtop (avoids most hazards; altitude margin for turbulence and hail, at yeast 1,000 feet higher for every 10 knots of wind speed at cloud top level), Underneath (not in the worst of hazards; altitude margin 1/3 distance from ground to cloud base…4,000-6,000AGL
T-storm penetration procedures
Penetrate perpendicular to minimize storm; Penetrate storm below the freezing level (altitude wise, warmer air) or above the -15 C level (to avoid icing); Minimum altitude should be 4,000-6,000AGL above the highest terrain; Establish recommended turbulent air penetration airspeed; Expect deviations in altitude and attitude; disengage autopilot; Avoid abrupt control movements; Turn up cockpit lighting to prevent temporary blindness; Turn on pitot heat
What do roll and wall clouds indicate?
The presence of low level wind shear and extreme turbulence
A _____ front forms on the surface at the leading edge of an adv t-storm
Gust
What methods can be used to detect a microburst?
Visual cues, wind shear alert systems, PIREPS, Departure/Arrival weather reports
Why should you fly over the top, at least 1,000 feet per knots of wind speed at cloud top level, to avoid a t-storm?
Because it allows an altitude margin for turbulence and hail
Why should you penetrate the lower 1/3 of a t-storm?
Because most storms are most severe in the top 2/3 of a cell
What combination of atmospheric conditions is necessary for the formation of a t-storm
Moisture, Unstable Air, Lifting Action
What effects can turbulence have on an a/c?
Changes in altitude, structural damage, extra stress on the airframe, effect depends on severity of turbulence and speed of a/c
What hazards are associated with lightning?
Static charge builds up in the a/c, can strike a/c flying in the clear, structural damage, catastrophic fuel ignition, pilots can experience flash blindness
Why should you penetrate a t-storm in a perpendicular manner?
To minimize time in the storm
What hazards to flight are associated with t-storms?
Hail, turbulence, and lightning
