Other UKAWC Stability Indices:
| Lifted Index (LI) | K-Index | CIN | Showalter Index | SWEAT | Total Totals |
|
|
The SI is based on the properties of
the 850 and 500 mb levels. The SI is calculated by lifting a parcel
dry adiabatically from 850 mb to its LCL, then moist adiabatically
to 500 mb, and comparing the parcel versus environmental 500 mb
temperatures similar to the LI. The SI may be better than the
LI in showing instability aloft given a shallow low-level cool
airmass north of a frontal boundary. However, the SI is an unrepresentative
index and inferior to the LI in showing instability if the low-level
moisture does not extend up to the 850 mb level.
SI
= T(500 mb envir) - T(500 mb parcel) in degrees C.
| SI over 0: | Stable, but weak convection possible for SI = 1-2 if strong lifting is present. |
| SI = 0 to -3: | Moderately unstable. |
| SI = -4 to -6: | Very unstable. |
| SI below -6: | Extremely unstable. |
Generally,
SI values will not be quite as unstable as LI values (except for
the case of shallow low-level cool air discussed above).
Other UKAWC Stability Indices:
| Lifted Index (LI) | K-Index | CIN | Showalter Index | SWEAT | Total Totals |
|
|
|