This is called wind shear.
No. It is not uncommon for conditions to become unusually calm before a tornado strikes.
In very simple terms, tornadoes form when thunderstorms start to spin when they run into winds blowing in different directions. The spinning air in the storm can then get squeezed tighter, causing it to spin faster and reach down to the ground to become a tornado.
A tornado watch is issued when general weather conditions in a region are favorable for the formation of tornadoes. Tornado watches are numbered in the order that they are issued. So tornado watch 4 is the 4th tornado watch issued in the country that year.
If a thunderstorm is capable of producing a tornado in the immediate future or if a tornado has been detected then a tornado warning is issued. If general conditions are favorable for tornadoes but there is not necessarily an immediate threat, then a tornado watch is issued.
No. Tornadoes do not form in blizzards. Sometimes the same system can produce tornadoes and blizzard conditions, but they will be in different parts of a large storm complex.
This is called wind shear.
This condition is called wind shear.
Tornado development begins when wind shear, wind blowing in different directions at different altitudes, starts air rolling horizontally. This horizontally rolling air can then get turned vertical by a thunderstorm. The updraft of the storm then starts rotating as a result, becoming a mesocyclone. Under the right conditions a downdraft can wrap around the mesocyclone, tightening and intensifying it to form a tornado.
That itself does not cause tornadoes, but a similar phenomenon is a factor in tornado formation. When wind at different altitudes blows in different speeds and directions, the air in between and start to roll horizontally. This is called wind shear. Again, wind shear alone cannot produce a tornado, but it is an important factor in how tornadoes form.
In order for a tornado to form there usually need to be two initial conditions: instability that can create thunderstorms (usually along a boundary between warm and cold air) and wind blowing at different speeds and directions at different altitudes. This difference in speed and directions produces rolling air currents called wind shear. This wind shear can get taken into the updraft of a thunderstorm and turned vertical. This turns the storm into a supercell, a thunderstorm with a strong, rotating updraft called a mesocyclone. Under the right conditions a downdraft can descend from the storm can wrap around the mesocyclone, tightening and intensifying it into a tornado.
No person or group of peal affects tornadoes. Tornadoes are affected by factors such as temperature, humidity, and wind speed and direction at different altitudes.
A tornado forms from thunderstorms. The thunderstorm starts turning because the wind at different heights is going in different directions and at different speeds. Sometimes this turning in the storm gets focused into a smaller area and starts spinning faster, becoming a tornado.
A whirlpool is a small "underwater" tornado. It is created by two currents or tides coming from different directions and colliding.
In Tornado Alley, a number of different conditions frequently come together that are very ideal for the formation of tornadoes. Thee include warm, moist air from the Gulf of Mexico, cool air from Canada, dry air from the Rockies, and winds blowing at different speeds and directions at different levels. Tmperature contrasts and instability are high, and low pressure systems tend to intensify in this region. In most other regions, such specfic conditions do not come together as often.
When conditions are favorable for tornadoes a tornado watch is issued. However the criteria for a hurricane watch are different. A hurricane watch is issued of an existing storm is threatening an area and hurricane conditions are possible within 48 hours.
Tornado development (called tornadogenesis) begins when differences in wind speed and/or direction at different altitudes, called vertical wind shear, creates horizontal vortices of air. These vortices can then be turned vertical by a thunderstorm updraft, which takes on this rotation to become a mesocyclone. Under the right conditions a downdraft can descend from th back of the storm and wrap around the mesocyclone, tightening and intensifying it. This smaller, stronger circulation is the tornado.
If the two air masses are moving together in different directions, you could get a tornado.