2. 
 Tornadoes

3. 
 Embedded thunderstorms

4. 
 Line of thunderstorms

5.  
Thunderstorms with very heavy precipitation and severe turbulence affecting 40% or more of an area of at least 3,000 square miles.

conventional current (electrical current). An imaginary flow of electricity said to go from the positive terminal of an electrical source to its negative terminal. The actual movement within an electrical circuit is that of electrons and is called electron current.
The arrowhead in a semiconductor diode symbol points in the direction of conventional current, while electron current moves in the opposite direction.

conventional landing gear (airplane landing gear). The type of airplane landing gear with the main wheels ahead of the center of gravity and a small wheel supporting the tail when the airplane is on the
ground.
A conventional landing gear requires a great deal of pilot skill to keep the airplane from ground looping (accidentally turning around) when it is moving at a fast speed on the ground.
The other type of landing gear, which is now the most commonly used, is the tricycle landing gear. The two main wheels are behind the center of gravity, and the auxiliary wheel supports the aircraft nose.

converge. To draw closer together and eventually to meet. Converging lines are lines which, if continued, will meet and cross one another.
convergence (meteorology). The condition that exists when the distribution of winds within a given area is such that there is a net horizontal inflow of air into the area. In convergence at lower levels, the removal of the resulting excess air is accomplished by upward movement.
Clouds and precipitation are likely to occur in areas of low-level convergent winds.
convergent-divergent duct. A duct that has a decreasing cross section in the direction of flow (convergent) until a minimum area is reached.