Tawas Bay Michigan USA
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NWS Fire Weather Planning Forecast

The forecast for fire weather conditions for northern Michigan is provided below. The forecast is suspended during the winter months when the fire danger has diminished. Definitions of some of the terms used in the forecast are provided here:

HAINES INDEX... A Lower Atmospheric Stability Index used to forecast the potential for large fire growth and/or erratic fire behavior. The Haines Index focuses on dry, unstable air, whereas most conventional atmospheric stability indices key on moist, unstable air.

MIXING HEIGHTS... The height to which a parcel of air, or a column of smoke, will rise, mix or disperse. A column of smoke will remain trapped below this height.

TRANSPORT WINDS... The mean wind speed and direction of all measured winds within the mixed layer.

VENT RATE... Describes the ability of the atmosphere to ventilate smoke. Depends on the stability and winds in the lower layers of the atmosphere, i.e., a combination of mixing heights and transport winds.

SURFACE WIND (20 ft)... Air movement measured at 20 feet above the average vegetative cover. Averaged over a 10 minute period. Unless otherwise noted, this is the wind referred to in the general weather forecast.