GFMC: Germany - Forest Fire Danger Index

The weather forecasts of the German Weather Service (Deutscher Wetterdienst - DWD) provides an agricultural service which includes the prediction of forest fire danger.

After entering the website please navigate to the upper right box where you see a small fire danger map – and click on “mehr”. The main map is the forest fire danger index of the current day. The small maps on the right side provide the forecast for the next 4 days (click on “vergrößern” for the enlarged map. On the left side detailed values of the States (Laender) are provided.

Overview of the M-68 Forest Fire Danger Index Forecast (according to international scaling)
During the forest fire season (March to October), the DWD provides forest fire danger prognoses for Germany, which are updated on a daily basis. (For the rest of the year the last chart of the previous season remains on the screen).

The operational calculation of the forest fire danger is based on the M-68 model. As it is international practice to describe the danger of forest fires using a scale ranging from 1 to 5, this has also been used on the M-68 model, which was originally planned with a scale of 0 to 4.

Scale ranging of the forest fire danger
International	Degree of danger	Original M-68
1	very little danger	0
2	little danger	1
3	moderate danger	2
4	high danger	3
5	very high danger	4

Calculating the Forest Fire Danger
The M-68 model has already been in operation in what are now the east German Laender, for three decades and has proved to be very reliable. It uses the noon values of air temperature, relative humidity, wind speed and 24-hour precipitation totals, as well as, during the spring months, the morning snow depth measurements. However, meteorological parameters are not the only decisive factors in evaluating the danger of fire. Vegetation also plays a considerable role, and thus indicator plants are used to estimate the phenological development of the forest ground vegetation and the crown area. When the fresh green growth of the ground vegetation and the foliation of the crowns has been completed, the spread of forest fires is diminished and the danger estimated as being lower. However, not all tree species are equally susceptible to ignition. Forest fire statistics show that different stand types are endangered by forest fires to a different extent. It has thus been shown to suffice and make sense when the forest landscapes are divided into three different classes, according to their ignition and burning ability. These are taken into account in the final evaluation of the forest fire risk.

The grassland fire index describes the fire danger for open, unshaded land with dried grass.

After entering the website please navigate to the lower right box where you see a small fire danger map – and click on “mehr”. The grassland fire index describes the fire danger for open, unshaded land with dried grass. The current test version (which is presently being further developed) is a fully automatic computer product which computes hourly time series of various meteorological parameters from approximately 200 stations in the measuring network of the DWD. Like the German M68 index for forests, the weather-related fire danger for grassland is classified into five levels:

Classified Levels
level of risk	description
1	very low risk
2	low risk
3	medium risk
4	high risk
5	very high risk

Only the 12 UTC value of the index is shown.

The grassland fire index takes into account risk-reducing deposits of water due to dew formation, interception of precipitation, or snow, as well as litter moisture and soil humidity (water absorption and evaporation) and the wind speed, which is relevant for the speed of a fire front. At times of high litter moisture and low wind speed or leaf wetness the risk level is low, whereas at times of low litter moisture and high wind speeds the risk level is high.

Attention: As compared with the M68 index, the fire risk displayed by the grassland fire index is often higher than in open land as radiation and wind have a stronger effect on evaporation and thus on the water content of the dead biomass. In rare cases, the index may be at three levels higher.