| Untitled Document


 






source:http://www.wetterzentrale.de

Color scale:<40 yellow, >40 orange.

<44 Convection not likely
44-50 Likely thunderstorms
51-52 Isolated severe storms
53-56 Widely scattered severe
>56 Scattered severe storms
The Total Totals index (TT) is yet another severe weather index. It is computed using the temperature and dewpoint at 850 hPa and the temperature at 500 hPa. The higher the 850 hPa dewpoint and temperature and the lower the 500 hPa temperature, the greater the instability and the resulting TT value.
TT is a widely-used severe weather index that is very easy to compute. However, it is limited in that it uses data from only two mandatory levels (850 and 500 hPa) and thus does not account for intervening inversions or moist or dry layers that may occur below or between these levels. In addition, it does not work for areas in the western Great Plains or the Rocky Mountains, where 850 hPa is near the surface or below ground. Last, like several other severe weather indexes, it does not take into account wind shear, which is a critical factor in many severe convective environments.
 

The TT is a combination of the Vertical Totals (VT) and Cross Totals (CT). The VT is the temperature difference between 850 and 500 mb while the CT is 850 mb dewpoint minus the 500 mb temperature.TT = (T850 - T500) + (Td850 - T500)

Total totals Index calculator

Enter the 850 hPa temperature (°C)
Enter the 850 hPa dewpoint (°C)
Enter the 500 hPa temperature (°C)
The Total totals Index is

 

The TT is a combination of the Vertical Totals* (VT) and Cross Totals** (CT). The VT is the temperature difference between 850 and 500 mb while the CT is 850 mb dewpoint minus the 500 mb temperature.
TT = (T850 - T500) + (Td850 - T500)

 




 

  source:http://www.theweatherprediction.com  http://www.meted.ucar.edu http://www.skystef.be