Other UKAWC Stability Indices:
| Lifted Index (LI) | K-Index | CIN | Showalter Index | SWEAT | Total Totals |
|
|
The Total Totals Index consists of two
components, the Vertical Totals (VT) and the Cross Totals (CT).
The VT represents static stability or the lapse rate between 850
and 500 mb. The CT includes the 850 mb dewpoint. As a result,
TT accounts for both static stability and 850 mb moisture, but
would be unrepresentative in situations where the low-level moisture
resides below the 850 mb level. In addition, convection may be
inhibited despite a high TT value if a significant capping inversion
is present.
TT
= VT + CT
VT = T(850 mb) - T(500 mb)
CT = Td(850 mb) - T(500 mb)
in degrees C, where T represents
temperature at the indicated level and Td represents dewpoint
temperature.
VT = 40 is close to dry adiabatic for the 850-500 mb layer. However,
VT generally will be much less, with values around 26 or more
representing sufficient static instability (without regard to
moisture) for thunderstorm occurrence. CT > 18 often is necessary
for convection, but it is the combined Total Totals Index that
is most important.
TT
= T(850 mb) + Td(850 mb) - 2[T(500 mb)] in
degrees C.
TT = 45 to
50: Thunderstorms
possible.
TT = 50 to
55: Thunderstorms
more likely, possibly severe.
TT = 55 to
60: Severe thunderstorms
most likely.
Other UKAWC Stability Indices:
| Lifted Index (LI) | K-Index | CIN | Showalter Index | SWEAT | Total Totals |
|
|
|