May 16, 2025

HYSPLIT run the WFO Portland used for this incident showing the concentration and path of the hydrogen gas. Credit: NOAA ARL

An incident in Milwaukie, OR last week highlighted the impact the Air Resources Laboratory HYSPLIT model has in emergency management. On May 10th, the fire department in Clackamas responded to an incident at a manufacturing facility, involving a chemical reaction that produced hydrogen gas.

Hydrogen gas is extremely flammable and is very harmful when inhaled. The Weather Forecasting Office (WFO) Portland used the HYSPLIT model to produce a spot forecast and a plume model within minutes of emergency managers requesting help. The information provided was used at the scene for critical decision making, including determining the need for evacuation and shelter-in-place alerts in the surrounding area. It also clearly showed that the original location of the emergency response staging area and command post needed to be shifted to get their staff out of harm’s way.

HYSPLIT is a complex model that takes into account many factors including weather and how chemicals react, disperse and travel once released into the atmosphere. This allows it to accurately forecast where a hazardous material will travel and who might be at risk. ARL works closely with the National Weather Service, providing a customized version of the model with continuous updates and improvements. The latest HYSPLIT model has recently been released and included several significant improvements.