Mbar in the context of Barometric formula

Hurricane Marie is tied as the seventh-most intense Pacific hurricane on record, attaining a barometric pressure of 918 mbar (hPa; 27.11 inHg) in August 2014. The fourteenth named storm, ninth hurricane, and sixth major hurricane of the season, Marie began as a tropical wave that emerged off the west coast of Africa over the Atlantic Ocean on August 10. Some organization of shower and thunderstorm activity initially took place, but dry air soon impinged upon the system and imparted weakening. The wave tracked westward across the Atlantic and Caribbean for several days. On August 19, an area of low pressure consolidated within the wave west of Central America. With favorable atmospheric conditions, convective activity and banding features increased around the system and by August 22, the system acquired enough organization to be classified as Tropical Depression Thirteen-E while situated about 370 mi (595 km) south-southeast of Acapulco, Mexico. Development was initially fast-paced, as the depression acquired tropical storm-force winds within six hours of formation and hurricane-force by August 23. However, due to some vertical wind shear its intensification rate stalled, and for a time it remained a Category 1 hurricane on the Saffir–Simpson hurricane wind scale.

On August 24, Marie developed an eye and rapidly intensified to a Category 5 hurricane with winds of 160 mph (260 km/h). At its peak, the hurricane's gale-force winds spanned an area 575 mi (925 km) across. Marie subsequently underwent an eyewall replacement cycle on August 25 which prompted steady weakening. Over the next several days, Marie progressively degraded to below hurricane strength as it moved into an increasingly hostile environment with cooler waters and a more stable atmosphere. On August 29, after having lost all signs of organized deep convection, Marie degenerated into a remnant low. The large system gradually wound down over the following several days, with winds subsiding below gale-force on August 30. The remnant cyclone eventually lost a well defined center and dissipated on September 2 about 1,200 mi (1,950 km) northeast of Hawaii.

The Azores High also known as North Atlantic (Subtropical) High/Anticyclone or the Bermuda- High, is a large subtropical semi-permanent centre of high atmospheric pressure typically found south of the Azores in the Atlantic Ocean, at the Horse latitudes. It forms one pole of the North Atlantic oscillation, the other being the Icelandic Low. The system influences the weather and climatic patterns of vast areas of North Africa, Western Asia, Southern Europe, and to a lesser extent, eastern North America. The aridity of the Sahara Desert and the summer drought of the Mediterranean Basin is due to the large-scale subsidence and sinking motion of air in the system.

In its summer position, the high is centered near Bermuda, and often referred to as the Bermuda High. In the Northern Hemisphere summer, the Bermuda High often migrates in the area between Bermuda and the East Coast of the United States. When the Bermuda High moves closer to the United States, this creates a deep southwest flow of hot and humid tropical air toward the East Coast of the United States. In summer, the Azores-Bermuda High is strongest. The central pressure hovers around 1024 mbar (hPa) often between Bermuda and North Carolina. Seasonally, the Bermuda High exerts its influence on the eastern United States between late May and October.

Free molecular flow describes the fluid dynamics of gas where the mean free path of the molecules is larger than the size of the chamber or of the object under test. For tubes/objects of the size of several cm, this means pressures well below 10 mbar. This is also called the regime of high vacuum, or even ultra-high vacuum. This is opposed to viscous flow encountered at higher pressures. The presence of free molecular flow can be calculated, at least in estimation, with the Knudsen number (Kn). If Kn > 10, the system is in free molecular flow, also known as Knudsen flow. Knudsen flow has been defined as the transitional range between viscous flow and molecular flow, which is significant in the medium vacuum range where λ ≈ d.

Gas flow can be grouped in four regimes: For Kn≤0.001, flow is continuous, and the Navier–Stokes equations are applicable, from 0.001<Kn<0.1, slip flow occurs, from 0.1≤Kn<10, transitional flow occurs and for Kn≥10, free molecular flow occurs.