Common Weather Terms
Incident: Sawtooth Fire Wildfire
Released: 9/19/2012
Sawtooth Fire
Common Weather Terms Explained
RAWS- Remote Automatic Weather Stations (RAWS) stations monitor the weather and provide weather data. It is a network of weather stations run by the U.S. Forest Service and Bureau of Land Management and monitored by the National Interagency Fire Center, mainly to observe potential wildfire conditions.
Unlike the automated airport weather stations which are located at nearly every airport large and small, RAWS stations are often located in remote areas, particularly in national forests. Because of this, they usually are not connected to the electrical grid, but rather have their own solar panels, and a battery to store power for overnight reporting. Some instead run on an generator. In both cases, data important to operating the station itself, such as battery voltage or fuel level, is often included in the hourly reports.
Also because of the remote locations, most communicate with a modem via telephone, or via a VSAT connection to a GOES satellite. Some stations are also portable.
There are two RAWS stations on this incident that can even be reached by radio command. Channel 15 Units, 24 and 25. On-line residents can reach the RAWS sites by going to. http://mesowest.utah.edu Select active fires and the Sawtooth fire and and select either Surface Date to see general information or RAWS for individual stations displayed on the map. You will see a number of RAWS stations that you can access for weather data in this area and across the United States. Inversion - Atmospheric inversion. An increase in temperature with increasing height. Also, the layer through which this departure occurs (also called inversion layer.) The lowest altitude at which the departure is found is called the base of the inversion. A standard atmosphere usually has decreasing temperature with height, thus the term Inversion. Upslope /Downslope winds- Small scale convective winds that occur due to local heating and cooling of a natural incline of the ground. Diurnal Winds-The diurnal, or daily, heating and cooling of land near a lake or ocean of fairly constant temperature causes air to blow toward the relatively warmer land during the day (sea breeze) and toward the relatively warmer water at night (land breeze). These breezes are shallow and seldom penetrate far inland or attain high velocity. Similar diurnal changes occur on mountain slopes, the air in the valley becoming heated and expanding so that it moves up the slope in the daytime, the cold air settling into the valley at night. Friction with the earth's surface, eddies caused by surface irregularities, and inequalities of heating with consequent convection currents tend to reduce wind velocity near the earth's surface and cause winds to blow in gusts Dewpoint - Temperature to which air must cool in order for saturation to occur. The dew point is always lower than the air temperature, except when the air is saturated. Dew, Fog or frost may form when temperature drops to equal the dew point. Condensed water is called dew when it forms on a solid surface. Fire Weather Watch - A Fire Weather Watch is issued to advise of conditions which could result in extensive wildland fire occurrence or extreme fire behavior, which are expected to develop in the next 12 to 48 hours, but not more than 72 hours. In cases of dry lightning, a Fire Weather Watch may be issued for the next 12 hours. Red Flag Warning- Term used by fire weather forecasters to alert forecast users to an ongoing or imminent critical fire weather pattern. A Red Flag Warning also known as a Fire Weather Warning is a forecast warning issued by the United States National Weather Service to inform area firefighting and land management agencies that conditions are ideal for wildland fire ignition, and rapid propagation. After drought conditions, and when humidity is very low, and especially when high or erratic winds which may include lightning are a factor, the Red Flag Warning becomes a critical statement for firefighting agencies. These agencies often alter their staffing and equipment resources dramatically to accommodate the forecast risk. To the public, a Red Flag Warning means high fire danger with increased probability of a quickly spreading wildland fire in the area within 24 hours RH- Relative humidity is amount of the moisture in the air compared to what the air can "hold" at that temperature. When the air cannot hold all the moisture, it condenses as dew.
RH recovery - The general term used to describe the maximum overnight value of atmospheric relative humidity.
