Why do some thunderstorms have straight line winds that blow in one direction througout the storm?

Question

while other thunderstorms have straight line winds that blow from a point of contact and spread out in all directions?

Answer 1

The straight line winds that pretty much stay in the same direction are typically the result of strong mid level winds that blow into the storm, then descend with the rain down to the surface before continuing onward.  Thus the direction changes little.  

In the other instance, what happens is that basically the core of the storm is initially held aloft due to the rising air into the storm.  Eventually the updraft weakens and the central part of the storm collapses and falls straight down.  Upon hitting the surface, it spreads out in all directions.  This event is known as a downburst or microburst and can be very strong somtimes.