Why are tornadoes uncommon in the northeast?

Answer 1

Tornadoes require very strong, rotating thunderstorms called supercells to form. A number of factors usually have to converge for these storms to produce tornadoes.

1. A collision of air masses of very different temperature and/or humidity usually with at least one of the air masses being very warm. The northeast does not see this sort of collisions as often as Tornado Alley and is generally not as warm.
2. A "cap" or layer of stable air in the upper atmosphere. This holds back thunderstorm development, but sometimes allows instability to build up under it so that if thunderstorms do break through it they will be very powerful. This cap is often weaker over the northeast so storm development is not so explosive.
3. Wind shear is a condition where wind changes speed and/or direction with altitude. This can do two things for a thunderstorm. First it can tilt the storm, separating the updraft, allowing the storm to become more powerful and last longer. Second, wind shear is what actually gives a thunderstorm the rotating that makes it a supercell. It is this same rotation that can develop into a tornado. Wind shear is weaker of the the northeast.

Answer 2

Tornadoes are less common in the northeast because the region is closer to the cooler Atlantic Ocean, which tends to stabilize the atmosphere. Additionally, the northeast has more varied terrain, such as mountains and forests, which can disrupt the atmospheric conditions needed for tornado formation. Overall, the atmospheric ingredients required to produce tornadoes are less frequently present in the northeast compared to other regions like the Great Plains.