Current Fire Weather Conditions

The fire weather map displays the current values of some of the most important weather variables to wildland fire behavior: relative humidity, winds, and temperature. Mesonet stations are represented by solid dots on the map. To the upper left of each dot is shown the air temperature (F) in red; to the lower left, relative humidity (%) is shown in green; and to the upper right, if wind gusts >= 20 mph exist at that location, they are depicted by Gnn, where nn is the wind gust speed in mph at the 10-m level. 10-m winds (averaged over 5 minutes) are depicted by a wind barb system. A half barb along the staff represents 5 mph; a full barb, 10 mph, and a flag, 50 mph. One adds them up to get the total average wind speed. Winds blow in a direction along the staff from the barbed end to the station dot. Calm winds are depicted by an open circle around the station dot. This map is updated every 5 minutes.

Relative Humidity and Winds

The Relative Humidity and Winds map displays the current relative humidity (%) at each Mesonet site with wind vectors. Relative Humidity is the measure of the water vapor content of the air at a given temperature.

This map is updated every 5 minutes.

1-hr Relative Humidity Change

The 1-hour Relative Humidity Change map plots the change in relative humidity (%) at each Mesonet station over the past hour, information useful for showing recent RH trends so important to wildland fire behavior. This map is updated every 5 minutes.

3-hr Relative Humidity Change

The 3-hour Relative Humidity Change map plots the change in relative humidity at each Mesonet station over the past 3 hours. This map is updated every 5 minutes.

Today's Maximum Relative Humidity

This map depicts the maximum relative humidity (%) occurring since midnight. This information is useful to see if fuel recovery for 1- and 10-hour dead fuels has had a chance to occur in the overnight hours before sunrise. This map is updated every 5 minutes.

Wind Speed and Direction

The Wind Speed and Direction map displays the average wind speeds (in miles per hour) at 10 m (33 feet) across Oklahoma. Arrows indicate the average direction the wind is blowing toward across the state.

Wind Gusts

The current wind gusts map displays the highest wind gust (in mph) recorded at each Mesonet station in the past five minutes. This map is updated every 5 minutes.

2-meter Winds

The Gradient-Filled Wind Map displays the average wind speeds (in miles per hour) across Oklahoma at 2 meters (6 feet) above the surface. Arrows indicate the average direction the wind is blowing toward across the state at 10 meters (33 feet) above the surface.

Air Temperature

The Air Temperature map plots the current air temperature (degrees F) at the standard height of 1.5 m (5 feet). When temperatures are below freezing, a line will delineate the areas of the state that are above and below freezing. This map is updated every 5 minutes.

Dewpoint

The Dewpoint Temperature map displays the current dewpoint temperature (degrees F) observed at each Mesonet site. Dewpoint is the temperature to which air must be cooled for saturation to occur (given a constant pressure and water vapor content).

This map is updated every 5 minutes.

Wind Chill / Heat Index

This Apparent Temperature map plots either:

1. Wind Chill (degrees F) if temperatures are below 50 F and winds are greater than 5 mph,
2. Heat Index (degrees F) if temperatures are above 80 F and relative humidity is above 40%, or
3. Current Temperature (degrees F) if neither wind chill or heat index is a factor.

This map is updated every 5 minutes.

Dispersion Conditions and Winds

There are six categories of “dispersion conditions” which are calculated by the Oklahoma Dispersion Model (ODM): Excellent (EX), Good (G), Moderately Good (MG), Moderately Poor (MP), Poor (P), and Very Poor (VP). The first three categories appear in various shades of green on the dispersion maps, while the last three range from beige to orange to red. A numbered system is also used to represent the six dispersion categories: 1=VP, 2=P, 3=MP, 4=MG, 5=G, and 6=EX. The ODM estimates ground-level dispersion, which is the ability of the atmosphere to dilute and disperse a compound such as smoke as it travels downwind. The calculated dispersion categories are valid for downwind distances of 1/4 mile to several miles. The categories can be interpreted as follows – for a given downwind distance (e.g., 1 mile), the smoke concentration near the plume centerline will be greatest under VP conditions and the lowest under EX conditions. Thus, as a general guideline for prescribed burning, Moderately Good (MG) or better (G, EX) conditions should be present during the burn to avoid smoking out potential sensitive areas downwind. In this case, in the forecast element table on the Fire Prescription Planner, one would set a “Lower Limit” for Dispersion Conditions of “Moderately Good.” Note that since the dispersion calculations are a function of the forecast weather conditions, inaccuracies in the NAM weather forecast will lead to inaccuracies in the dispersion forecast.

Inversion Conditions

The Inversion Conditions map displays:

• Current Air Temperature at 30 ft (9 m) in degrees F
• Current Air Temperature at 5 ft (1.5 m) in degrees F
• Winds (mph)-- The Wind Barb is an "arrow" that depicts the wind speed and direction. The "feathers" of the arrow indicate the wind speed while the dot end of the arrow indicate the direction the wind is blowing toward.
• Dew Point Temperature in degrees F
• Difference between the 30 ft and 5 ft Air Temperature in degrees F

Normally, air temperature decreases with height (no inversion). During inversion conditions, air temperature increases with height. This map is updated every 5 minutes.

1-hr Rainfall Accumulation

The 1-hour Rainfall map displays accumulated rainfall observed at each Mesonet site in the last hour. This map also displays the NWS River Forecast Center's rainfall estimates (in color) across Oklahoma based on radar.

During precipitation events involving ice, hail, or snow, the rain gauges used by the Oklahoma Mesonet may freeze over and record no rainfall. Once air temperatures raise enough to allow thawing, accumulated frozen precipitation in the gauge will melt and be recorded.

This map is updated every 5 minutes.

24-hr Rainfall Accumulation

The 24-hour Rainfall map displays accumulated rainfall observed at each Mesonet site in the last 24 hours. This map also displays the NWS River Forecast Center's rainfall estimates (in color) across Oklahoma based on radar.

During precipitation events involving ice, hail, or snow, the rain gauges used by the Oklahoma Mesonet may freeze over and record no rainfall. Once air temperatures raise enough to allow thawing, accumulated frozen precipitation in the gauge will melt and be recorded.

This map is updated every 5 minutes.

Burning Index

The Burning Index (BI) value (10*feet) as calculated by the Oklahoma Fire Danger Model. This is probably the most useful index of the National Fire Danger Rating System (on which the Oklahoma Fire Danger Model is based) since BI directly relates to the intensity of the fire (and thus is related to the difficulty of containment) and is scaled such that BI/10 is equal to the flame length (FL) in feet at the head of the fire. It is an index which integrates both the spread component (SC) and energy release component (ERC). The traditional U.S. Forest Service interpretation of burning index with respect to fire behavior and suppression is listed below:

BI < 40 (FL < 4 ft) Fires can generally be attacked at the head or flanks by persons using hand tools. Hand line should hold the fire.

BI = 40-80 (FL = 4-8 ft) Fires are too intense for direct attack on the head by persons using hand tools. Hand line cannot be relied on to hold fire. Equipment such as dozers, pumpers, and retardant aircraft can be effective.

BI = 80-110 (FL = 8-11 ft) Fires may present serious control problems – torching out, crowning, and spotting. Control efforts at the fire head will probably be ineffective.

BI > 110 (FL > 11 ft) Crowning, spotting, and major fire runs are probable. Control efforts at the head of the fire are ineffective.

Burning index is a function of the fuel model being used, the live and dead fuel moistures, and the weather conditions. Accordingly, inaccuracies in the NAM weather forecast will lead to inaccuracies in the BI forecast. Of course, if the fuel types and loads are substantially different than those in the fuel model being used, there will be inaccuracies as well. Finally, it is important to realize that these indices produced by the National Fire Danger Rating system are for the conditions modeled at 1-km resolution. In other words, the fuel model represents conditions over the entire 1-km square area, so indices such as BI are not meant to be used on a field-by-field basis. As an example, if the particular fuel in the area of concern (e.g., a particular field) differs from the assigned fuel model in that 1-km square, then the Oklahoma Fire Danger Model results for that square can be expected to be different than for the particular field in question (e.g., an open grassy area in a 1-km square that has been assigned a forest fuel model). Other limitations of the model can be found in the document entitled The Oklahoma Fire Danger Model.

Spread Component

The spread component (SC) is numerically equal to the theoretical forward speed of the headfire in feet/minute. It is the most variable of the fire danger indices, with variations being caused by changes in wind speed and in moisture content of the live and dead fuels. SC is another index produced by the Oklahoma Fire Danger Model. Wind speed, slope and fine fuel moisture are key inputs in the calculation of the spread component, thus accounting for a high variability from day-to-day. Spread component is a function of the fuel model being used, the live and dead fuel moistures, and the weather conditions. Accordingly, inaccuracies in the NAM weather forecast will lead to inaccuracies in the SC forecast. Of course, if the fuel types and loads are substantially different than those in the fuel model being used, there will be inaccuracies as well.

Energy Release Component

The energy release component (ERC) is a measure of the available energy (BTU/square foot) released per unit area in the flaming zone at the head of the fire. It is the least variable of the indices on a day-to-day basis, being a function solely of the fuels (and their moisture content, which is weather-dependent). ERC is another index produced by the Oklahoma Fire Danger Model. Conditions producing an ERC value of 24 represent a potential heat release twice that of conditions resulting in an ERC value of 12. Since ERC represents the potential “heat release” per unit area in the flaming zone, it can provide guidance to several important fire activities. It may also be considered a composite fuel moisture value as it reflects the contribution that all live and dead fuels have to potential fire intensity. Especially for fuel complexes containing the heavier 100- and 1000-hour fuels, the ERC is a cumulative or “build-up” type of index. As live fuels cure and dead fuels dry, the ERC values get higher, thus providing a good reflection of drought conditions. ERC is a function of the fuel model being used, the live and dead fuel moistures, and the weather conditions. Accordingly, inaccuracies in the NAM weather forecast will lead to inaccuracies in the ERC forecast. Of course, if the fuel types and loads are substantially different than those in the fuel model being used, there will be inaccuracies as well.

Ignition Component

The ignition component (IC) is equal to the probability (0-100%) of a firebrand producing a fire that will require suppression action. It says nothing about the intensity of the fire, which is indicated by the burning index (BI) value. IC is another fire danger index calculated by the Oklahoma Fire Danger Model. An IC of 100 means that every firebrand will cause a fire requiring suppression action if it contacts a receptive fuel. Likewise an IC of 0 would mean that no firebrand would cause a fire requiring suppression action under those conditions. Note the emphasis is on action. The key is whether a fire will result that requires a fire manager to make a decision. The ignition component is more than the probability of a fire starting; it has to have the potential to spread. Therefore spread component (SC) values are entered into the calculation of IC. If a fire will ignite and spread, some action or decision is needed. Ignition component is a function of the fuel model being used, the live and dead fuel moistures, and the weather conditions. Accordingly, inaccuracies in the NAM weather forecast will lead to inaccuracies in the IC forecast. Of course, if the fuel types and loads are substantially different than those in the fuel model being used, there will be inaccuracies as well.

1-hr Dead Fuel Moisture

The % moisture content on a dry-weight basis of 1-hour dead fuels as calculated by a calibrated version of the Nelson dead fuel moisture model. Calculated values can range from 1% to 85%. One-hour fuels are the fine dead fuels (< 0.25”) such as grasses which are often involved in the initiation and maintenance of wildland fires and whose moisture contents respond quickly (within minutes) to changing weather conditions. These dead fuels include herbaceous plants, roundwood, and also the uppermost layer of litter on the forest floor. For prescribed fire, the preferred range of 1-hour dead fuel moisture is from 7 to 20%. Below 7%, spot fires become a problem and above 20% there will be problems in starting and maintaining the fire due to too much moisture in the fine fuels. To understand the influence of 1-hour dead fuel moisture on prescribed burning and wildfire, consult OK-FIRE Basics for Prescribed Burning and OK-FIRE Basics for Fire Danger. Note that since the Nelson model calculations are a function of the forecast weather conditions, inaccuracies in the NAM weather forecast will lead to inaccuracies in the 1-hour dead fuel moisture forecast.

10-hr Dead Fuel Moisture

The % moisture content on a dry-weight basis of 10-hour dead fuels as calculated by a calibrated version of the Nelson dead fuel moisture model. Calculated values can range from 1% to 60%. Ten-hour fuels are the smaller diameter dead fuels in the 0.25" to 1" diameter range. They also respond quickly to changing weather conditions, but not as quickly as do 1-hour fuels. These fuels include roundwood and the layer of litter on forest floors extending, roughly, from 0.25" below the surface to 1" deep. For prescribed fire, the preferred range of 10-hour dead fuel moisture is from 7 to 20%. Below 7%, spot fires become a problem and above 20% there will be problems in maintaining the fire due to too much moisture in the 10-hour fuels. To understand the influence of 10-hour dead fuel moisture on prescribed burning and wildfire, consult OK-FIRE Basics for Prescribed Burning and OK-FIRE Basics for Fire Danger. Note that since the Nelson model calculations are a function of the forecast weather conditions, inaccuracies in the NAM weather forecast will lead to inaccuracies in the 10-hour dead fuel moisture forecast.

100-hr Dead Fuel Moisture

The % moisture content on a dry-weight basis of 100-hour dead fuels as calculated by a calibrated version of the Nelson dead fuel moisture model. Calculated values can range from 1% to 40%. 100-hour fuels include roundwood with diameters of 1-3” as well as organic materials beneath the surface at roughly 1-4” depths. 100-hour fuels respond more slowly than 10-hour fuels to changing weather conditions and are better indicators for extended dry or wet periods. Low 100-hr dead fuel moisture during the growing season is often associated with increased summer wildfire activity. This map is updated every hour.

1000-hr Dead Fuel Moisture

1000-hr Dead Fuel Moisture desc

Live Herbaceous Moisture

Live Herbaceous Moisture desc

Live Woody Moisture

Live Woody Moisture dsec

16-inch % Plant Available Soil Moisture

1- day Average 16-inch Plant Available Water Percentage Description

Keetch-Byram Drought Index (KBDI)

KBDI is a drought index calculated by the Oklahoma Fire Danger Model. Ranging from 0 to 800, the index is used to increase the amount of dead fuel available to the fire. KBDI, the Keetch-Byram Drought Index, was included in the 1988 revisions to the National Fire Danger Rating System (NFDRS) on which the Oklahoma Fire Danger Model is based. KBDI values at Mesonet sites are updated daily at 4 p.m. CST. Drought, as defined by KBDI, is a condition of dryness in the litter, duff, and upper soil layers that progresses from saturation to an absence of available moisture. The KBDI is based on an arbitrary 8 inches of water in the litter/duff/soil column. When the column is completely saturated, KBDI = 0. As water is removed from the column by evapotranspiration, the KBDI increases in value. When KBDI reaches 800 (its max), all the water has been removed. In the NFDRS and Oklahoma Fire Danger Model, as KBDI increases above a value of 100, increasing amounts of dead fuel are provided for burning. During combustion some of this fuel contributes directly to fireline intensity (BI), but most increases total heat release (ERC) and contributes to burn severity through smoldering combustion. In Oklahoma, the KBDI has shown itself to be more useful during the growing season than during the dormant season. Also, as it was developed mainly for forested landscapes, its usefulness for grassy landscapes is somewhat questionable. KBDI values in the 600-800 range represent the most severe drought conditions, and many states issue burn bans at these levels. In forested areas, prescribed fires should not be conducted at values over 700, as fires will be intense and deep burning.

Visual Greenness

Visual Greenness Desc

Relative Greenness

Relative Greenness desc

Oklahoma 3.9 micron Infrared Satellite

This is a map for 3.9 microns. Click here to see an animation of this map over the past four hours.

Oklahoma West 3.9 micron Infrared

This is an expanded view of western Oklahoma and the panhandle for the 3.9 micron map

Oklahoma Visible Satellite

This Oklahoma satellite image displays the visible channel of the GOES-East satellite (Channel 2). During the daytime this map is useful for seeing clouds as well as features such as smoke plumes from wildfires. This image is provided by the College of DuPage and is updated every 5 minutes. The time of the image is shown in UTC time (CST = UTC - 6 hours; CDT = UTC - 5 hours).

Oklahoma Water Vapor Satellite

This Oklahoma satellite image displays the mid-level water vapor channel of the GOES-East satellite (Channel 9), which is typically at a pressure level around 500 millibars (approximately 18,000 feet). This image is provided by the College of DuPage and is updated every 5 minutes. The time of the image is shown in UTC time (CST = UTC - 6 hours; CDT = UTC - 5 hours).