Enter the 500 millibar environmental temperature and the 500 millibar parcel temperature into the Calculator. The calculator will evaluate the Showalter Index. 

Showalter Index Formula

SI = T500 - Tp500

Variables:

  • SI is the Showalter Index ()
  • T500 is the 500 millibar environmental temperature
  • Tp500 is the 500 millibar parcel temperature

To calculate Showalter Index, subtract the 500 millibar parcel temperature from the environmental temperature at the same pressure.

How to Calculate Showalter Index?

The following steps outline how to calculate the Showalter Index.

  1. First, determine the 500 millibar environmental temperature. 
  2. Next, determine the 500 millibar parcel temperature. 
  3. Next, gather the formula from above = SI = T500 – Tp500.
  4. Finally, calculate the Showalter Index.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

500 millibar environmental temperature = 4

500 millibar parcel temperature = 5