Originally designed as a short-life-span tool to explore the links between surface and crown fire behavior models, NEXUS was first released as an Excel spreadsheet in 1998. The modeling concepts developed for NEXUS have since been used in the Crown Mass program of Fuels Management Analyst Suite and the Fire and Fuels Extension to the Forest Vegetation Simulator. The 2003 revision to the National Wildfire Coordinating Group's S-490 course (Advanced Fire Behavior Calculations) used the spreadsheet version of NEXUS to teach crown fire hazard assessment.

NEXUS has grown up and moved out of the house. Systems for Environmental Management and Axiom IT Solutions, both of Missoula, Montana, collaborated to create NEXUS 2.0 as a stand-alone, public-domain program. Some of the spreadsheet functionality has not been retained, such as the Fire Shape Chart, but the added utility more than makes up for it. Other features may be added in future revisions.

Many of the original NEXUS features have been improved. Fuel and environment inputs can be saved as a "Scenario". Custom output units can be saved for later use. Specific scenario comparisons can be saved as a "Run". Display of all charts is fully customizable; charts can be captured as .JPG or PNG files. Data in the Output Table can be saved as a text file for use in graphics or analysis programs. The Crown Fire Hazard Assessment Chart can now be displayed in Flame Length and Fireline Intensity as well as the original Rate of Spread. The graphical interface allows the user to change units, the data being displayed, the range of inputs, etc., right from the output table or chart. The Fire Characteristics Chart displays surface and crown fire behavior over a range of 20-ft windspeeds, and indicates by color the type of crown fire expected.

A significant modeling addition to NEXUS is shrub-canopy fire modeling, in which the transition from one surface fuel model to another is modeled using a method similar to that used for conifer crown fires.

NEXUS 2.0 accomodates the new suite of dynamic fuel models now being released.

A beta version of NEXUS 2.0 is available at www.fire.org/nexus/nexus.html.

but a few new features have been added. The user interface is much improved, with increased ability to save input and output.

NEXUS