(Similar question from Sharon - "What is the difference between a cyclone, typhoon, and tsunami?")

MIKE MOSS SAYS:       Rhonda and Sharon,   Regarding the part of your questions asking about cyclones, typhoons and hurricanes, the only difference in those storms is "location, location, location." When you read about Hurricane Fran, Typhoon Tip, or Cyclone Nargis (which recently struck Myanmar), these are all regional names that refer to the same type of storm. The term hurricane is used for the Atlantic and eastern north Pacific basins, typhoon is used for the western Pacific basins, and cyclone (sometimes lengthened to "severe tropical cyclone") is used for the Indian Ocean.

There is some room for confusion here, because the word "cyclone" is also a more general meteorological term for any closed low pressure circulation that has a sense of rotation that matches that of the earth at the nearest pole. In the northern hemisphere, the earth rotates counterclockwise around the north pole (as seen from above), so a northern hemisphere low pressure area of any size or type which has a counterclockwise ciculation can be called "cyclonic," or be said to rotate cyclonically. Likewise, low pressure in the southern hemisphere with a clockwise circulation of air is also cyclonic, since the clockwise rotation of air around the center matches the clockwise rotation of the earth about the south pole.

In that sense, all organized large scale low pressure systems (whether tropical or not, so this includes your typical low pressure frontal system or a nor'easter, etc, which we usually just call "lows") are cyclones, as are most (but not all) tornadoes and some small whirlwinds and dust devils. I hope the aside from the main answer in the first paragraph isn't more than you wanted to hear!

Sharon, a Tsunami is not a weather phenomena per se. Instead, that term describes a high energy ocean wave, which is usually initiated by an undersea earthquake, volcanic explosion or landslide. Displacement of huge amounts of water by these disturbances leads to a wave or series of waves that travel at high speed until reaching a coastline somewhere, at which time they slow down and the wave height increases. If the tsunami carries enough energy, the wave can reach heights that result in devastating impacts along coasts and a few miles inland, as we saw in December 2004 in places like Indonesia, Thailand, India and Sri Lanka.