See upper level system.
Inflow Bands (or Feeder Bands) -
Bands of low clouds,
arranged parallel to the low-level winds and moving into or toward a
thunderstorm. They may indicate the strength of the inflow of moist
air into the storm, and, hence, its potential severity. Spotters
should be especially wary of inflow bands that are curved in a
manner suggesting Inflow Jets - Local jets of air near the ground
flowing inward toward the base of a tornado.
Inflow Notch -
A radar signature characterized by an
indentation in the reflectivity pattern on the inflow side of the
storm. The indentation often is V-shaped, but this term should not
be confused with V-notch. Supercell thunderstorms often exhibit
inflow notches, usually in the right quadrant of a classic supercell,
but sometimes in the eastern part of an HP storm or in the rear part
of a storm (rear inflow notch).
Inflow Stinger - A beaver tail cloud with a stinger-like shape.
- Incoming solar radiation. Solar heating; sunshine.
Instability - The tendency for air parcels to accelerate when
they are displaced from their original position; especially, the
tendency to accelerate upward after being lifted. Instability is a
prerequisite for severe weather - the greater the instability, the
greater the potential for severe thunderstorms.
- Generally, a departure from the usual increase or
decrease in an atmospheric property with altitude. Specifically it
almost always refers to a temperature inversion, i.e., an increase
in temperature with height, or to the layer within which such an
increase occurs. An inversion is present in the lower part of a cap.
Isentropic Lift -
Lifting of air that is travelling along an
upward-sloping isentropic surface.
Isentropic lift often is referred to
erroneously as overrunning, but more accurately describes the
physical process by which the lifting occurs. Situations involving
isentropic lift often are characterized by widespread stratiform clouds and precipitation, but may include
elevated convection in the form of embedded thunderstorms.
Isentropic Surface - A two-dimensional surface containing
points of equal potential temperature.
A line connecting points of equal pressure.
Isodrosotherm - A line connecting points of equal dew point
A line connecting points of equal precipitation
- General term for a line connecting points of equal
value of some quantity. Isobars, isotherms, etc. all are examples of
A line connecting points of equal wind speed.
Isotherm - A line connecting points of equal temperature.