May 7, 2026

The Environmental Modeling Center (EMC) and National Weather Service’s National Center for Environmental Protections (NCEP) approved ARL’s HYSPLIT version 9 (HYSPLIT v9) upgrade for operational use last year. It has now been successfully implemented at NCEP.

One of the most extensively used atmospheric transport and dispersion models in the atmospheric sciences community for over 30 years, HYSPLIT has been used for forecasting the direction and spread of nearly any substance in the air from radioactive material, wildfire smoke, volcanic ash and even insect swarms. Throughout the decades, ARL’s HYSPLIT modeling team continues to improve and add capabilities to the model. The HYSPLIT v9 upgrade adds a new interface and improved capabilities for forecasting the travel and dispersion of volcanic ash and radiological materials and has a stronger integration with global weather prediction models.

ARL and NCEP are one of the World Meteorological Organization’s Regional Specialized Meteorological Centers. As a designated center, they participate in monthly exercises practising the steps to take during early warning messaging and tracking fallout from a nuclear accident. This upgrade makes tracking radioactive material in the atmosphere more accurate, and gives emergency responders better information for making decisions regarding public safety.

HYSPLIT v9 went into operations at NCEP in late April thanks to ARL’s Sonny Zinn, Tiangfeng Chai, Alice Crawford, Barry Baker (now EMC) and Mark Cohen (retired); Binyu Wang, Raffaele Montuoro and Jeff McQueen (retired) of the EMC; and the whole HYSPLIT team. The  new interface was used successfully during the April Regional Specialized Meteorological Center exercise.

More information about the upgrade can be found here.

HYSPLIT animation showing radiological concentrations in a hypothetical situation originating from Germany on April 21, 2026, across the Mediterranean toward North Africa. Credit: NOAA ARL