Calculator Inputs
Enter 850 mb temperature, 850 mb dew point, and 500 mb temperature. Choose your unit system, result precision, and graph sweep settings.
Formula Used
Total Totals combines a lapse-rate term and a moisture term. The lapse-rate part is Vertical Totals, while the moisture-sensitive part is Cross Totals.
Where:
- T850 = environmental temperature at 850 mb
- Td850 = dew point at 850 mb
- T500 = environmental temperature at 500 mb
How to Use This Calculator
- Enter the 850 mb temperature from a sounding or model output.
- Enter the 850 mb dew point in the same unit system.
- Enter the 500 mb temperature.
- Select Celsius, Fahrenheit, or Kelvin.
- Choose display precision and graph sweep settings.
- Press the calculate button.
- Review VT, CT, TT, interpretation, and the sensitivity chart.
- Export the result summary as CSV or PDF when needed.
Example Data Table
| Case | T850 (°C) | Td850 (°C) | T500 (°C) | VT | CT | TT | General Reading |
|---|---|---|---|---|---|---|---|
| Stable Example | 8 | 2 | -8 | 16 | 10 | 26 | Limited thunderstorm potential |
| Active Example | 18 | 14 | -10 | 28 | 24 | 52 | Heavy convection / few severe |
| Very Unstable Example | 22 | 18 | -12 | 34 | 30 | 64 | Very strong convective support |
Frequently Asked Questions
1) What does the Total Totals Index measure?
It is a meteorological stability indicator using 850 mb temperature, 850 mb dew point, and 500 mb temperature. It estimates whether the atmosphere may support thunderstorm development.
2) What inputs do I need?
You need temperature at 850 mb, dew point at 850 mb, and temperature at 500 mb. These usually come from upper-air soundings or forecast model data.
3) Can I enter Fahrenheit or Kelvin?
Yes. The calculator accepts Celsius, Fahrenheit, and Kelvin. It converts everything internally to Celsius before calculating VT, CT, and TT.
4) What are VT and CT?
VT is Vertical Totals, equal to T850 minus T500. CT is Cross Totals, equal to Td850 minus T500. Their sum produces Total Totals.
5) Does a high TT guarantee severe weather?
No. TT is only one indicator. Lift, wind shear, moisture depth, capping, and storm forcing all matter. Use TT with broader forecast analysis.
6) Why is dew point included at 850 mb?
The 850 mb dew point represents lower-tropospheric moisture. More moisture often supports stronger convection, so it is included through the CT component.
7) Why does colder 500 mb air increase TT?
A colder mid-level temperature steepens the lapse rate and raises both VT and CT. That usually increases instability and pushes TT upward.
8) Can I export results from this page?
Yes. After calculation, use the CSV or PDF buttons to save a quick summary of your entered values, derived terms, and interpretation.