Both the central dense overcast and embedded eye pattern use the size of the CDO . The CDO pattern intensities start at T2.5 , equivalent to minimal tropical storm intensity ( 40 mph , 65 km / h ) . The shape of the central dense overcast is also considered . The eye pattern utilizes the coldness of the cloud tops within the surrounding mass of thunderstorms and contrasts it with the temperature within the eye itself . The larger the temperature difference is , the stronger the tropical cyclone . Once a pattern is identified , the storm features ( such as length and curvature of banding features ) are further analyzed to arrive at a particular T @-@ number . The CCC pattern indicates little development is occurring , despite the cold cloud tops associated with the quickly evolving feature .