What is a secondary low?
A Secondary Low begins to deepen within the occluded front in the area of a local vorticity maximum. The part of the front around the low has a Wave – like structure for a short time (compare Wave ). This Wave does not amplify, however, but turns into an Occlusion spiral.
What is an upper low in weather?
An upper level low is a region of positive vorticity. This positive vorticity can be caused by counterclockwise curvature around the upper level trough and counterclockwise shear associated with the speed shear of a jet streak. The circulation around an upper level low can build to the surface over time.
What is an upper level disturbance?
Upper Level Disturbance A disturbance in the upper atmospheric flow pattern which is usually associated with clouds and precipitation. This disturbance is characterized by distinct cyclonic flow, a pocket of cold air, and sometimes a jet streak.
What causes an upper level disturbance?
Simply put, an upper-level disturbance is an area of rotating air found around 18,000 feet above the ground that forms as a result of wind speed differences aloft. These wind speed differences form as a result of low and high pressure differences above the ground.
How does an upper level disturbance create thunderstorms?
Thunderstorms form when an air mass becomes so unstable that it overturns (convects) violently. “Unstable” means that the air in the lowest layers is unusually warm and humid, or that the upper layers are unusually cool, or oftentimes, both.
What air masses are associated with thunderstorms?
Air mass thunderstorms tend to occur within a maritime tropical air mass. The wind shear is weak and this is why the air mass storms are not severe, do not last long and do not move quickly. The main threats from an air mass thunderstorm are lightning and brief heavy rain.
Is the following sentence true or false like air masses most fronts are very large?
Much of the weather in eastern North America is influenced by continental tropical and maritime polar air masses. Like air masses, most fronts are very large. False. Air flow is almost parallel to the line of the front, and the position of the front does not move.
What causes air parcels to rise?
A rising parcel of air expands because the air pressure falls with elevation. A falling parcel of air contracts because the air pressure increases. • The contraction causes the air to warm.
What are three things that cause air to rise?
Science Chapter 8 Part 1
| A | B |
|---|---|
| three ingredients for clouds | water, rising air, dust |
| three things that cause air to rise upward, often forming clouds | solar heating, mountains, fronts |
| the three kinds of fog | steam, radiation, sea |
| three major wind systems | trade, prevailing westerlies, polar easterlies |