Below are some points that shows the difference between convectional rainfall and orographic rainfall :Convectional rainfall occurs when the moist air (over the heated ground) becomes warmer than the surrounding whereas the orographic rainfall takes place when moist wind is forced to rise over a mountain or upward heading slope. The conventional rainfall generally occurs in the tropical region (where temperature and evaporation is high) whereas orographic rainfall occurs in the upwind side of the mountain region. In conventional rainfall, we can experience heavy rainfall with thunder and lightning. but, in orographic rainfall, leeside of the mountain gets less rainfall due to the lack of moisture in the clouds.