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Whilst CAPE may be the preferred variable for many, note that using CAPE alone does not always bring the best results.

K-index (K)

The formula is:

K-Index (K) = (T₈₅₀ - T₅₀₀) + Td₈₅₀ - (T₇₀₀ - Td₇₀₀)

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Charts of K-Index derived from ensemble control forecast values are available on ecCharts. If users have access to ensemble K-Index values (these are not currently available on ecCharts) they should refer to those alongside the ensemble control values.

Total Totals Index (TT)

The formula is:

TT = (T₈₅₀ – T₅₀₀) + (Td₈₅₀ – T₅₀₀)  =   T₈₅₀ + Td₈₅₀ – 2(T₅₀₀)

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Charts of Total Totals Index derived from ensemble control forecast values are available on ecCharts.  If users have access to ensemble Total Totals Index values (these are not currently available on ecCharts) they should refer to those alongside the ensemble control values.

Examples

Fig9.6.2-1: Composite diagram showing ecChart presentation of the vertical profile product, and of CIN, CAPE, K-index, and Total totals index from ensemble control/HRES, all valid for T+60hr valid 12UTC 28 July 2018, forecast base time 00UTC 26 July 2018.

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