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## Local and Small-Scale Winds 

## Gradient Winds 

Pressure gradients initiate the movement of air and as soon as the air acquires velocity, the Coriolis force deflects it to the right in the Northern Hemisphere. As the speed of the air along the isobars increases, the Coriolis force becomes equal and opposite to the pressure gradient force. After a period of time, the air moves directly parallel to the curved isobars if there is no frictional drag with the surface. The air no longer moves toward lower pressure because the pressure gradient force is completely neutralized by the Coriolis force and the centrifugal force. 

## Orographic Winds 

The term “orographic” has multiple meanings, when placed in the context of weather phenomena. In a general sense, according to the American Meteorological Society, wind flows that are caused, affected, or influenced by mountains may be said to be orographic winds flows. The term has come to mean any winds that are affected by terrain, not just mountains; this definition is probably the most frequently used, when discussing balloon flight. 

As a specific term, “orographic lifting” is defined as an ascending air flow caused by mountains. The mechanisms that produce the orographic lifting fall into two broad categories: 

1. The upward deflection of horizontal large-scale air flow by the terrain acting as an obstacle or barrier, or 

2. The daytime heating of mountain surfaces to produce an anabatic flow (see below) along the slopes and updrafts in the vicinity of mountain peaks. 

This definition, while strictly referring only to lifting by mountains, is sometimes extended to include the effects of hills or long sloping terrain. When sufficient moisture is present in the rising air, Orographic fog or clouds may form. 

## Anabatic Winds 

Anabatic winds are those that blow up a steep slope or mountain side. It is sometimes referred to as an upslope flow. These winds typically occur during the daytime in calm, 

