Wind is the movement of air across the Earth’s surface, driven by differences in atmospheric pressure. Air flows from areas of high pressure toward areas of low pressure. Meteorologists name wind direction based on the direction from which the air is blowing, not the direction it is traveling toward. This convention is used because the origin of the air mass determines the kind of weather the wind carries.
Understanding Wind Direction Terminology
The convention for naming wind direction is based on the 360-degree compass system, where North is 0 or 360 degrees, and the degrees increase clockwise. A wind is labeled according to its point of origin; for example, a North wind blows from the North and travels toward the South.
The four cardinal directions (N, E, S, W) correspond to 0, 90, 180, and 270 degrees. Intermediate directions are positioned halfway between these points. Northwest (NW) is located between North and West, corresponding to 315 degrees. A Northwest wind originates from the northwest and moves toward the southeast, carrying the characteristics of its originating air mass.
Typical Weather Associated with Northwest Winds
In the mid-latitudes of the Northern Hemisphere, a Northwest wind indicates a shift toward colder and drier conditions. This airflow is a common consequence of a large-scale weather system moving through the area. Northwest winds frequently follow the passage of a cold front, which is the boundary where a colder air mass displaces a warmer one.
Once the cold front has passed, the wind direction abruptly shifts from a southerly or southwesterly flow to a northwesterly flow. This shift is associated with a high-pressure system, which brings descending air. This descending air warms slightly, lowering its relative humidity and resulting in clear skies and a significant drop in temperature. The air mass has low moisture content and excellent visibility, signaling a colder and more stable weather pattern.
Local Impacts of Northwest Airflow
The specific effects of Northwest airflow depend heavily on the local geography and the time of year. A noticeable effect is the increase in wind chill, which is the perceived lowering of the air temperature caused by the wind removing heat from exposed skin. Even if the thermometer reads a moderate temperature, a strong Northwest wind can make the conditions feel significantly colder, as the moving air accelerates the rate of heat loss.
In areas near large, unfrozen bodies of water, a Northwest wind can trigger “lake effect” snow. This occurs when a cold, dry air mass moves across the relatively warmer lake water. The air picks up heat and moisture, destabilizing the lower atmosphere and creating narrow bands of clouds that deposit intense, localized snowfall on the downwind shores.
The sinking air associated with the high-pressure system often scours the atmosphere of pollutants. Northwest winds correlate with better air quality and clearer visibility as they replace stagnant, hazy air.