To explain briefly: a TCPU is a bloc 110 km long, by 110 km wide and 16 km high.  
All atmospheric and sea surface parameters are closely examened:  
        -sea surface temperature  
        -sea surface courants  
        -hygrometry of the lower, mid and upper tropospher, as well as pressure, wind speeds and direction, and temperature.  

   > If all necessary atmospheric and oceanic conditions are favorable (click here to see what are favorable conditions for cyclogenesis) but that there is no organised tropical system with a low pressure and cyclonic spin at sea level then the value of the TCPU is arbitary set at 50%.  
   > If there is a large area of disturb weather with a sea level cyclonic spin and at least a 1010 mb low pressure center and conditions are favorable then chances will be at 75, 87.5 or 100%, all depending on how well the system is organised, the dynamics (wind convergence and convection ...) and if anything will not interfear with the good conditions of the TCPU (example: an approaching upper tropospheric trough).
 
The computer calculates the probability or chances for a cyclone to form base upon all the given data from the sea to the upper troposphere and even the lower stratosphere.
 

TCPU at 100%	TCPU at 12.5%
Sea surface temperature is about 29°C (sufficently higher then the required value). A tropical system with a well define cyclonic spin around a 1008 mb low (L). The air is relatively moist, humidity saturation (100%) at certain points.   Because of 0 vertical shear and rapid fall of temperature with height, converging air at sea level can rise rapidly and higher within thunderstorm clouds (cumulonimbus) and increase the potential and dynamic energy of the system.   To prevent "suffocation" , once reach the upper troposphere, the rising air is then diffused horizantly by an existing anticyclonic system (A).	Sea surface temperature is about 28°C (a little higher then the required value). A tropical system with a poor define cyclonic spin around a 1010 mb low (L). The air is not that moist, humidity level only reaching 70% at certain points.   Dryer and stable air have a sinking tendancy, subsidence. This prevent coulds to form or to develop and high pressure zones (H) are oftentimes the results of this subsidence.   Even if temperature falls rapidly with height, because of strong vertical shear (in this case caused by an upper tropospheric low (L), converging air at sea level will rise but will be blown off in a certain direction. Cumulonimbus will be shorter and twon appart, this will decrease the potential and dynamic energy of the system.