how are tornadoes formed?
92110
Tornadoes are formed by the clashing of drasticlaly different masses of air known as fronts.  A high pressure front meets with a low pressure front and the difference in their temperatures and pressures creates a strong wind that can form into the funnel clouds known as tornadoes.  This is not to say that all colliding fronts will yield tornadoes, but there are certain elements that can increase the likeliness of a tornado forming.  The swath of the mid-west United States from N. Texas / Oklahoma through Kansas / Nebraska and into Iowa / Missouri is known as "Tornado Alley" because there are more tornados per year in this area than anywhere else in the world.
1085318
There are a couple reasons.  First off, Texas is the second-largest state in the US, next to Alaska.  So, there is more area in the state for tornadoes to occur.\n\nSecondly, Texas is right in the heart of Tornado Alley.  This is a place in the continental US where the airflow is just right for supercell thunderstorms (tornado-causing storms) to form, with warm, moist air rolling off of the Gulf of Mexico, dry air coming from the Mojave Desert, and cool air flowing off of the Rockies.  The combination of these air masses provide a lot of atmospheric instability, prompting thunderstorms.\n\nDue to the winds around Texas/Oklahoma, the storms are more likely to be supercells, and more likely to form tornadoes.\n\nTexas might have the most number of tornadoes in a given year, but Oklahoma actually has the most tornadoes per unit area in the US because of the wind patterns being even better for tornado formation there.
556432
Hurricanes are what scientists call "strong Tropical Cyclones". They are formed when large areas of the ocean become heated, and the air pressure over that area drops. This causes thunderstorms and strong surface winds. Cyclones develop over tropical or sub-tropical waters (for example, in the Atlantic off the coast of Africa, or in the Pacific). As they travel long distances gathering energy from the ocean, they are likely to be classified as strong Tropical Cyclones. When the winds of a tropical storm reach 74 mph, then the storm is classified as a hurricane.\n\nMore information on how hurricanes happen can be found on this good site : http://kids.earth.nasa.gov/archive/hurricane/creation.html
13372
According to answers.com\nhttp://www.answers.com/tornados%20\n\n"Tornadoes develop from severe thunderstorms, usually spawned from squall lines and supercell thunderstorms, though they sometimes happen as a result of a hurricane. They are believed to be produced when cool air overrides a layer of warm air, forcing the warm air to rise rapidly, though tornadoes over water (waterspouts) frequently are observed forming in the absence of convection or apparent strong surface temperature differences. Tornadoes, lightning, and sometimes hail are associated with thunderstorms. Many tornadoes appear at the tail end of mesocyclones. On weather radar screens, a characteristic "hook echo" marks the area where tornadoes are likely to exist."\n\nThe reference will give good idea for how do tornados form
305968
over the ocean it is hard to find out how many waterspouts (the correct term of tornadoes over water) form.  Tornadoes in the US turn out to be about 300, hurricanes/ tropical storms worldwide is about 100,  thunderstorms happen each day all over the world so it is hard to keep count.  Even us meteorologist have a hard time trying to predict hot spots for hurricane formation, it was a shock that Hurricane ivan came 8o lat, from the equator, becuase they need what is called the corriolis force to exist, near the equator the force is =0 so even we have a hard time keeping count, as well as predicting them.
814547
did you mean how do clouds form?\n\nIf so, they form from water evaporating on the surface of the earth. As the vapour rises, it reaches cooler, higher areas of the atmosphere and the vapour begins to condense, around microscopic particles in the air. Once this process has started, other molecules will start to join in, until the vapour condenses and clumps together. When enough forms, it is no longer lighter than air, and rain will occur.
466630
try this site http://www.howstuffworks.com/tornado.htm
972997
Hail forms when water frezes as it falls and then wind blows it back up high befor it hits the ground.  It colects another layer of water that frezes, and if the wind is strong enough, it will fly back up, and the cycle repeats untill the wind is not strong enough to cary the hevy ball of frozen water back up.\nSnow forms when water droplets in clouds freeze and crisylise.
356933
India is a very common place where tornadoes occur.\n\nOther ones include China, most middle-eastern countries (Iraq, Afghanistan, Pakistan), and northern Africa (Algeria, Egypt, Chad)\n\nIn general most places around 10-20 degrees above the equator.
427523
Theoretically they could if it snaows while the ground is warm and conditions right.\n\nTornadoes can happen anywhere as long as the ground is warm and the air is cold, they are not restricted to parts of the world, they are merely more likely to form there.\n\nHowever if it were to snow then the ground would quickly become cold and a tornado would cease from forming, thereby it would last only a fe seconds, if at all.\n\nI have never heard of one and would be interested if there were one.\n\nEDIT: since a tronado can form just before it rains, then i would not be suprised if one can form just before it snows.
105363
For a tornatdo to form, there must be cold air, warm air, horizontally spiraling air (casued by the coriolis effect), flat land, no water present. There must be an oncoming wind, and cold and warm aiar that is colliding from the northern and souther latitudes. When the masses of air meet, the warm or moist air will rise, since its density is lower than cold or dry air, ando this will create an upward motion. Now, the oncoming wind will come along (it will be spiraling already), and when it makes contact with the area in which the air masses met, the spiraling wind will basically be violently set upright and so a tornado will form. In the northern hemisphere, the winds will go in a counterclockwise direction and in an inward spiral. (This will be partailly due to the Coriolis effect& if you're in the southern hemisphere, the winds will go in a clockise direction). This is the basic science of tornadoes, as i have just learned this year in my Earth Science course.
35947
What causes tornadoes?\n\nThunderstorms develop in warm, moist air in advance of eastward-moving cold fronts. These thunderstorms often produce large hail, strong winds, and tornadoes. Tornadoes in the winter and early spring are often associated with strong, frontal systems that form in the Central States and move east. Occasionally, large outbreaks of tornadoes occur with this type of weather pattern. Several states may be affected by numerous severe thunderstorms and tornadoes.\n \nDuring the spring in the Central Plains, thunderstorms frequently develop along a "dryline," which separates very warm, moist air to the east from hot, dry air to the west. Tornado-producing thunderstorms may form as the dryline moves east during the afternoon hours. \nAlong the front range of the Rocky Mountains, in the Texas panhandle, and in the southern High Plains, thunderstorms frequently form as air near the ground flows "upslope" toward higher terrain. If other favorable conditions exist, these thunderstorms can produce tornadoes.\n\nTornadoes occasionally accompany tropical storms and hurricanes that move over land. Tornadoes are most common to the right and ahead of the path of the storm center as it comes onshore.
332776
Dust devils are smaller and weaker than tornadoes, and arise from significantly different atmospheric conditions. They are caused by convection on hot, calm summer days. Air near the surface (ground) becomes much warmer than the air above, creating an updraft. Dust devils may rotate clockwise or counterclockwise, and their movement is slow and sporadic as they travel from one patch of warm air to another.
969063
one myth could be that tornadoes occur when a small asteroid hits the atmosphere with enough rotational velocity to twist the air\n\nor that they happen when god sneezes\n\nor that there is always at least one tornado on earth at any given time
173251
A cumulonimbus cloud forms in rising air (updraft).  The air cools as it rises, and at a certain point the water vapor in the air condenses into water droplets, forming a cloud.  Around a large Cb there is often downdraft - the air gets warmer as it subsides, and any water droplets (=clouds) will evaporate.
851662
Water Tornadoes as you call them are usually referred to a Water Spouts, they are born the same way as a regular tornado, the only thing that makes them water spouts is that they occur when a tornado is over a body of water.  Instead of picking up houses, dirt, and debris, they pick up the only thing around.... WATER!\n\nTo recreate one you would have to have a clear column of plexiglass tube about 12 inches in diam, some plywood, to build a base from,  and a VERY strong fan to create the updraft.  You need to space the bottom of the plexiglass up about 2 inches from a block of wood and place some "fins" in that space and angle them so they help to start the rotation of the air as it enters the column.  \n\nMount the fan on the top of the column so that it pulls the air trough the cylinder.  and place a plan of water in the middle of base.  if your creative you can cut a hole in the base so that the pan of water drops in.  This will take a lot of wind, so you might be better just using steam or smoke.
563821
Increase.  I have seen a tornado up close, like right over head.  It brought in two different winds and they ran around in a circle.  The faster they blew, the stronger the storm.  A hurricane is like a great big whirlwind.  A large amount of the damage attributed to a hurricane is often done by the tornadoes it creates by the unstable air on its edges.  Best advice...Stay out of their way.