How do the rocky mountains contribute to the development of tornadoes over the central US?

3 comments

1. 

   UALog on March 1, 2010 at 2:12 pm

   When air moves through the Rockies, the air must rise in elevation. This will cool the air mass and also condense out the moisture through the process of orographic precipitation. This would exit the rockies as a cold, dense, and relatively dry air mass. The leading edge of cold air becomes a strong cold front as It enters the central plains and meets up with the warm moist air that flows in from the Gulf of Mexico. The meeting of these two completely different types of air masses will trigger the development of very strong to severe convective storms that would support large hail and damaging wind gusts.

   What makes this situation more likely to be tornadic is the wind shear. The cold dry air are moved out of the Rockies by the strong westerlies aloft. When this strong west to northwest winds aloft moves over the low level southeast winds associated with the advection of warm moist gulf air, you will have the classic conditions for tornadic activities. This condition is know as strong low level wind shear. This is a condition of having southeast winds at the surface, then as you go slightly higher in elevation, the winds will speed up and veer to the west to northwest. This type of wind conditions are needed to produce the strong low level spin that are seen with severe thunderstorms that usually form tornadoes.

2. 

   TJ on March 1, 2010 at 2:12 pm

   They can affect the jet stream which can allow cold dry air into areas that have warm moist air.

3. 

   тσяиα∂σ fαиαтι¢ on March 1, 2010 at 2:12 pm

   Tornadoes need three ingredients to form,

   1. Warm, moist air
   2. Warm, dry air
   3. Cool. dry air

   The warm, dry air isn’t vital to the formation of super-cell thunderstorms and tornadoes, but it sometimes accompanies these setups. The warm, dry air comes from Mexico. The warm, moist air comes from the Gulf of Mexico. The cool, dry air comes from the Rocky Mountains. When the cool, dry air and warm, moist air mix, it creates instability, which leads to wind shear. When this wind shear becomes vertical, it creates a rotating column of air known as the mesocyclone. The mesocyclones rotation causes the whole storm to start spinning. With the help of a RFD (rear flank downdraft), the rotation is focused into a small point near the bottom of the mesocyclone. This is now the tornado. A powerful updraft also accompanies these super-cell thunderstorms. When this powerful updraft races up into the storm, it leaves behind a low pressure area near the surface of Earth. The combination of the RFD and low pressure area draws the tornado downwards toward the ground.

   Hope this has answered your question!