STORM2K

is it true raindrops are shaped like hamburger buns?

Depends on the size of the drop. See here:

http://www.ems.psu.edu/~fraser/Bad/BadRain.html

The fact that large raindrops are wider in the horizontal than in the vertical is exploited by a new generation of radars known as polarimetric radars. These radars send out two combined beams, one of which is vertically polarized, the other which is horizontally polarized. The radar then "listens" for the return power of both beams. If the beams are hitting large raindrops, the power returned from the horizontally polarized beam will be greater than the power returned from the vertically polarized beam, because the raindrops are wider in the horizontal. By comparing the relative power of the horizontal and vertical beams in this manner, as well as several other related quantities, the radar can distinguish what type of precipitation particles it is seeing in a given area of a storm, and even distinguish precipitation from non-meteorological targets such as birds and insects. The plans are in motion to upgrade all the existing WSR-88D radars in the U.S. eventually to have dual-polarimetric capability.