How to Convert Wind Speed to Pressure

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Atmospheric pressure and wind are related both qualitatively and quantitatively. Differences in pressure in the atmosphere are what create the phenomenon called wind in the first place. Additionally, earth scientists have developed a number of mathematical models to determine pressure as a function of wind speed, mostly using data gathered from storm systems.

No convenient predictive equation exists linking these two variables; instead, the relationship is an empirical one, with plots of pressure versus wind speed using a host of data points within the same system used to generate an equation using a mathematical method called linear regression. Using one of a number of related equations derived this way, if you have wind speed, you can calculate the pressure to within a reasonable margin of error.

Background

Differences in air pressure between different points around the globe are fundamentally attributable to temperature differences, which in turn create differences in the density of air. As you might expect, winds tend to blow from areas of higher pressure to areas of lower pressure, in the same basic way that squeezing a plastic soda bottle drives air out of the mouth of the bottle.

Standard atmospheric pressure is 14.7 pounds per square inch (lb/in2), which equates to 760 millimeters of mercury (mm of Hg), 101.325 kilo-Pascals (kPa) and 1013.25 millibars (mb). The unit typically used in measurements within storm systems is the millibar.

Pressure, wind speed and temperature are interdependent, as noted. But researchers have developed two useful equations that eliminate temperature and relate wind speed to pressure directly.

Pressure as a Function of Wind Under Hurricane Conditions

The equation of interest in this case is:

P = 1014.9 – 0.361451w – 0.00259w2

With P in mb and w in m/s. For example, a wind speed of 50 m/s (about 112 miles per hour) would be associated with a local atmospheric pressure of:

1014.9 – 0.361451(50) – 0.00259(2500)

= 990.4 mb

Among the lowest pressures ever recorded is 870 mb, in the middle of a Pacific typhoon.

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