101-6 Stability

Question 1

Stable Air

Answer 1

Resists vertical displacement

Ex. Cloud base that flattens out

Question 2

What type of air does not resist vertical displacement

Answer 2

Unstable air

Ex. Cloud base continually being pushed up (cumulus)

Question 3

Neutral stability

Answer 3

Borders both

Ex. Stratocumulus

Question 4

Unsaturated air cools at ….

Answer 4

3 degrees C / 1000’

*** same mass of air moves upward (not lapse rate)

Question 5

Saturated Air cools at a …..

Answer 5

slower rate than unsaturated air once temp of lifted air cools to dew point (forms cloud base)
(Less than 3 C/1000’)

Question 6

Ambient Lapse Rate

Answer 6

If ALR < or = 2 degrees C / 1000 = Stable Air
If ALR > 2 degrees C / 1000 = unstable air

Question 7

Embedded Cumulonimbus

Answer 7

Hidden convective clouds w/in stratiform or cirriform layers.

Hazardous without operative radar

Question 8

Lifted Index

Answer 8

(LI): a measure of atmospheric stability

-lift a parcel of air near surface to ~18000 (500 mb) and subtracting the temp of the parcel to temp of environment

*Negative index - parcel will rise = unstable (less dense)
*positive index = parcel will sink = stable (more dense)

Question 9

Severe TSTM potential (LI index)

Answer 9

0 to -2 = weak potential
-3 to -5 = moderate
< or + to -6 = strong

+8 values = stable
0 = neutral

Question 10

Severe thunderstorm characteristics

Answer 10

Surface wind speeds at least 50kts and/or
Hail diameter @ surface of 3/4 inches

Question 11

Unstable Characteristics

Answer 11

Cumuliform Clouds
Showers
Turbulent
Good Visibility

Question 12

Stable Characteristics

Answer 12

Stratiform clouds or fog
Continuous precip
Smooth air
Fair to poor vis.