We often hear weather forecasters talking about ‘low pressure areas’ bringing cloudy weather and precipitation in a particular region. A low-pressure area, low, low area or low is a region on the topographic map where the air pressure is lower than that of surrounding locations. Blood pressure fluctuates naturally throughout the day and tends to increase around the time a person wakes up. Due to the subsiding warm air associated with the system's formation, clearing skies are associated with the wake low. I do know that it is supposed to be lower when waking than when going to bed, but the thing is that sometimes it will be a really low drop (not considered dangerous low) & I will have a hard time waking & when I get up I have a really hard time keeping my eyes open & I usually wind up with a really bad headache. These cells also narrow the blood vessels and increase blood pressure. Recirculation is a specific condition where the flow separates from the body of the obstacle. The large eddies are formed at a regular frequency and they produce pressure disturbances in the flow which we can sometimes hear as sound waves. What causes it? In the front, the flow smoothly passes over the cylinder, but in the wake the flow is usually highly unsteady and large eddies or vortices are shed downstream. Because of viscous losses, the stagnation pressure in the wake is lower than the stagnation pressure at the front of the cylinder. The pressure around the downstream side of the cylinder remains nearly constant at the value at the separation point, so is much lower to the stagnation pressure on the front side, leading to massive pressure drag. Learn about feeling pressure in your rectum. The Effects of Wakes on Separating Boundary Layers in Low Pressure Turbines Rory Douglas Stieger Peterhouse A dissertation submitted for the degree of doctor of Philosophy Cambridge University Engineering Department February 2002 . How is it treated? However, for many people, abnormally low blood pressure (hypotension) can cause dizziness and fainting. I have been having a problem with my blood pressure for awhile. Because the converging air is wet and full of excess energy, it expands and cools as it rises, creating the clouds and heavy rainfall that are prominent throughout the area. In this article we will find out what a low pressure is, why it forms and what effects it has on weather. Vortex Shedding : The boundary layer separates from the surface forms a free shear layer and is highly unstable. Low-pressure systems form under areas of wind divergence that occur in the upper levels of the atmosphere. A wake low, or wake depression, is a mesoscale low-pressure area which trails the mesoscale high following a squall line.