this may or may not help i sorta got online because what your question is asking is weather lore almost like folk lore but this has to do with weather..
The principal wind characteristics are speed and direction. The direction of a wind is the direction from which it blows. A north wind comes out of the north and blows southward, while a west wind comes out of the west and blows eastward. Wind direction is best described by its azimuth, measured clockwise from north from 0° to 360°. A wind of azimuth 200° blows from the SSW; a wind of azimuth 45° blows directly from the NE.
An approximate means of expressing wind direction that is usually quite accurate enough is to use points of the compass in the wind rose, a 16-point example of which is shown at the right. SSW is south-southwest, azimuth 202-1/2°. More crudely, only 8 points could be used: N, NE, E, SE, S, SW, W, NW and back to N. Four points is a bit too crude. Wind direction is measured with a rotating vane; the direction can be telemetered using a rotary encoder, which is now the cheapest and easiest way. Repeating servomotors can also be used, but they cost more.
The wind rose antedated the compass. Around the Mediterranean Sea, certain seasonal, identifiable winds that blew in fixed directions could be recognized, and by means of these winds the orientation of the wind rose could be determined when there was no other clue. The cardinal winds were named Boreas (N), Eurus (E), Notus (S) and Favonius (W) in Latin. Winds were then interpolated between each of these to give 8 winds, and the idea was extended further with less success. The sun by day and the stars by night gave other indications, so the wind rose could usually be oriented to find the direction of sailing. When the magnetic needle arrived in the 13th century, it was used as just another way to orient the wind rose, and one that was often not trusted. The mariner's compass originated in the marriage of the wind rose floating in a bowl with the Chinese necromantic needle attached to it.
Wind speed is measured by an anemometer, of which there are many kinds. Most common was probably the 3-cup freely rotating anemometer that is calibrated in a wind tunnel. The force on a spring-loaded vane, or the pressure in a Pitot tube can also be used. Pressure sensors allow the design of a variety of anemometers whose data is easily telemetered. Whatever the design, an anemometer should be equally sensitive to winds from any direction. This is done by making the design naturally isotropic, like the 3-cup anemometer, or by turning the device into the wind with a wind vane. The standard height of the anemometer is 10 m. Wind speeds increase rapidly with altitude, and most anemometers are in the surface boundary layer. A more detailed discussion of the vertical wind profile will be found in Turbulence, as well as below in the section on surface effects.
Free balloons can be used for measuring upper winds by tracking them as they ascend. The rate of ascent is assumed known, and the position of the balloon is calculated from its altitude as measured by a theodolite. There are more modern ways of doing this that do not require such a skilled observer, and can be carried out by the idiots currently available. Unless the altitude of the balloon is determined by some independent source (radar, GPS), and not by timing on the basis of the free lift, the results cannot be expected to be accurate.
Wind speed is officially reported in knots, nautical miles per hour, apparently because of the connection with air navigation, even though traditional graphical navigational procedures that are facilitated by this unit are probably no longer used. A nautical mile corresponds to 1' of arc on a spherical earth, or 6080.20 ft. The equalities 1 m/s = 1.942 kt = 2.237 mph = 3.600 kmph will be found useful. The Beaufort scale, an excellent way to determine and express rough estimates of wind velocity that are often good enough for many purposes, is given in a later section.
Winds are also not steady, either in velocity or direction, and the description of these variations, sometimes quantitatively, may be desired. The mean wind velocity and its standard deviation are useful statistics with considerable meaning. The range of velocities is another statistic, or the interquartile range of velocities. Maximum velocities exceeded only a certain small percentage of the time may be useful, or the root-mean-square velocity, if the energy of the wind is of interest. Such statistics are obviously of interest in designing a wind farm, or other similar installation. The frequency response of the anemometer must also be taken into account; some give average values, while others are more responsive to fluctuations.
A wind is said to veer when its direction changes clockwise, and to back when the change is anticlockwise, in the northern hemisphere. In the southern hemisphere, the behavior is opposite. Veering can be described as "sunwise" motion in either hemisphere. If a low passes west to east north of you, the wind will be southwesterly, then westerly, then northwesterly, so the wind will veer. When a low passes south of you, again west to east, the wind will be southeasterly, easterly, and then northeasterly, again veering. If a low passes directly overhead, the southerly winds will fall, then northerly winds will replace them. Since the weather generally moves from west to east in temperate latitudes, and consists mainly of lows, a veering wind is the usual thing. It might be interesting to correlate the winds with the TV weather forecast.
The Geostrophic Wind
The atmosphere is, of course, a compressible fluid, of low density and low viscosity, that obeys the ideal gas law to a good approximation. Let's describe its state in the Eulerian fashion by giving the pressure p, temperature T and vector velocity v as a function of position and time. Then, p = p(t,x,y,z) and similarly for the other quantities. These quantities must satisfy certain equations. First, the conservation of mass demands that ∂ρ/∂t + div(ρv) = 0, which is the differential way of saying that the mass within any closed boundary changes only because of the flow of mass across the boundary. ρ is the density of the air in g/cc and v the velocity in cm/s. This is called the equation of continuity, which must be satisfied by any wind flow. The pressure, temperature and density of the air are connected by the equation of state, p = ρRT, where p is in dyne/cm2, T is in K, and R is the gas constant for air, R*/M, where R* is the universal gas constant, 8.3144 x 107 erg/mol-K and M = 28.97 g, so that R = 2.870 x 106 erg/g-K.
The third set of equations that must be satisfied are the equations of motion, dv/dt = -grad(p)/ρ - 2ω x v, where the two forces that always act on the air are included. The first is the pressure gradient force, which acts in the direction of the maximum change in pressure, while the second is the Coriolis force, a force which allows us to consider the earth as a nonrotating coordinate system, although it rotates with an angular velocity 7.292 x 10-5 radians per second about an axis through the geographical poles. The direction is given by the vector relation, which is in the horizontal plane, and the magnitude is 2ω sin &phi, where φ is the latitude, tending to turn the velocity to the right in the northern hemisphere, or to the left in the southern hemisphere. This force is a maximum at the poles, and is zero at the equator. There is also the gravitational force -ρg, but this is usually balanced by buoyancy; when it is not, it must also be included. If the path of the air is curved, it is also subject to the centrifugal force v2/r. The equation of motion is written for one gram of air, and all the forces given are forces per gram.
The derivative dv/dt is not the usual time derivative of a function, but is the acceleration following a particle of fluid in its motion. In terms of the Eulerian functions, d/dt = ∂/∂t + v·grad is the substantial derivative that takes into account change due to the motion of the particle. Any hydrodynamics text will explain this in detail. It is the second term that makes the equations of motion nonlinear, and introduces so much difficulty into hydrodynamics. In our application, the velocities or time variations are small enough that we can often neglect the second term, thereby linearizing our equations.
The atmosphere is free and unrestrained by boundaries, only by the attraction that holds it to the earth and causes the density to decrease rapidly with height. This means that a very small horizontal force, acting for relatively short times, could give rise to very high velocities, which are not observed. We must conclude that most of the movement of the atmosphere, the winds, is mere coasting under no force. The pressure varies by only a small amount in any horizontal plane, and the Coriolis force is so small that it is scarcely sensible, but these forces act so widely that they control the winds. A difference of pressure is the only agency that can cause a wind; the Coriolis force acts perpendicular to the velocity (like the magnetic force on a moving electron) and cannot affect the velocity. Nevertheless, when we analyze winds we seldom if ever explicitly consider the forces that gave them motion; these forces perhaps acted for short times and far away, but their winds coast on continually. That some forces must act is shown by the proverbial fickleness of the wind, that is constantly varying in strength and direction.
We must assume, then, that the pressure gradient forces that we know must act because of the lateral variation in atmospheric pressure are exactly balanced by the Coriolis force, so that we have a time-independent flow. In this case, -grad(p)/ρ = 2ω sin φv, which we can write (1/ρ)∂p/∂n = lv, where l = 2ω sin φ, and n represents distance normal to the isobars, while v is the velocity parallel to the isobars. The constant l depends only on the latitude. This equation gives the wind velocity v in terms of the pressure gradient and the density. The balance of forces is illustrated at the right. This wind is called the geostrophic, or "earth-turning" wind, and is of fundamental importance. We know the velocity and direction of the wind if we know only the pressure distribution, which is remarkable. The forces causing the wind do not play a part in our analysis.
In general, when a wind is blowing towards you, the low pressure is on the right hand. Buys Ballot's Law, that the low pressure is to your left when your back is to the wind, is simply the inverse of this. Note that the diagram above is consistent with these statements. These qualitative predictions of the equation are well borne out in practice, and wind speeds are usually predicted from the density of the isobars.
Pressure is usually measured in millibars, 1 mb = 103 dyne/cm2. Distance is conveniently measured in the length of a degree of latitude, which is 111 km or 69 mi. Then, a pressure gradient of 1 mb per degree of latitude is 8.993 x 10-5 dyne/cm2/cm. The isobars on a weather map are usually drawn with a 4 mb contour interval, so to get the pressure gradient we multiply the above figure by 4 divided by the distance between the isobars in degrees of latitude. Of course, we can easily adjust this if we use km or miles instead. The constant l = (2)(7.292 x 10-5)(sin 40°) = 9.374 x 10-5 s-1. The density of air in Denver under normal conditions is close to 10-3 g/cc, so I shall use this round figure. The density at STP is 1.293 x 10-3 g/cc. Therefore, the geostrophic wind at Denver under normal surface conditions is 959(∂p/∂n) cm/s, where the pressure gradient is in mb per ° of latitude. Since 1 m/s = 1.942 kt, this is also 18.6(∂p/∂n) kt.
The Gradient Wind
In explaining the geostrophic wind, we assumed that the isobars were straight lines. This is seldom the case in practice, so we must allow for curvature of the isobars, which introduces centrifugal forces, and thus a cyclostrophic component to the winds.
A cyclone or low is an area of closed isobars surrounding an area of lower pressure. The wind blows along the isobars in the direction in which the pressure gradient balances the Coriolis force. The pressure gradient force is inward, so the wind must blow anticlockwise around the cyclone. An anticyclone or high is the opposite case, and now the wind must blow clockwise so the forces can balance. Let's consider circular isobars making idealized cyclones and anticyclones. The balance of pressure gradient, Coriolis and centrifugal forces for a cyclone gives (1/ρ)∂p/∂r = lv + v2/r. This is a quadratic equation for v, of which the meaningful solution is v = -lr/2 + √[l2r2/4 + (r/ρ)(∂p/∂r)], where r is the radius, and where we use the radial gradient of pressure.
For an anticyclone, the force balance is (1/ρ)(∂p/∂r) + v2/r = lv. The solution for v is v = lr/2 - √[l2r2/4 - (r/ρ)(∂p/∂r)]. If the pressure gradient is too large for a given value of r, the quantity under the radical may become negative, which cannot be allowed. In fact, large pressure gradients are never seen at the centres of anticyclones. For a given radius and pressure gradient, wind velocities are higher for anticyclones than for cyclones.
When centrifugal forces due to curved isobars are taken into account, the winds are called gradient winds, a term that includes the geostrophic winds as well.
