NOUS41 KWBC 131530
PNSWSH

Service Change Notice 26-25
National Weather Service Headquarters Silver Spring MD
1130 AM EDT Fri Mar 13 2026

To:	 Subscribers:
	 -NOAA Weather Wire Service
	 -Emergency Managers Weather Information Network
	 -NOAAPort
	 Other NWS Partners and NWS Employees

From:	 David Michaud, Director
	 NCEP Central Operations
	 National Centers for Environmental Prediction

Subject: Upgrade to HYSPLIT 9.0 to implement a Transfer
Coefficient Matrix (TCM) methodology for faster simulation of
radiological and volcanic ash events. Effective April 16, 2026

On April 16, 2026, the HYbrid Single Particle Lagrangian
Integrated Trajectory(HYSPLIT) transport and dispersion model
version 8.0 will be upgraded to version 9.0.  In case of
Critical Weather Day or declaration of Enhanced Caution status,
this upgrade may be delayed to the next business day.  This
version includes the following upgrades and bug fixes:

- Update to the latest version of NOAA Air Resources Laboratory
(ARL) HYSPLIT model codes.
The highlights of HYSPLIT upgrades

 - increased the number of vertical levels to 99 (from 75).
 - enhanced compatibility with Google Earth (updates to xml
generation for kml xsd compliance )

- The implementation of a Transfer Coefficient Matrix (TCM)
methodology for faster simulation of radiological and volcanic
ash events.  The TCM allows rapid updates of emissions from
radiological and volcanic sources without the need to rerun
transport and dispersion simulations.  - Ten volcanoes are
included in the TCM for rapid ash prediction capabilities.

- HYSPLIT global prediction capability will be extended to 15
days.
- HYSPLIT global prediction capabilities have been extended to
higher altitudes. Altitude now extends to 0.01 mb for Global
Forecast System (GFS) 1 degree (from 100 mb) and to 2 mb for GFS
0.25 degree (from 13 mb).


This upgrade will increase the data volume for input, output,
post-process fields and products due to the proposed higher
vertical extent and longer forecast length.

Specifically, ARL-Packed format meteorological input files will
be extended as follows:

Global Forecast System (GFS) files at 1-degree resolution, all
cycles:
- The number of vertical levels will increase to 41 (up to 0.01
mb) from 21 (up to 100 mb)
- The forecast length will increase to 15 days
- Individual file size will increase to 1.68 GB per cycle

Global Forecast System (GFS) files, 0.25-degree resolution, all
cycles:
- The number of vertical levels will increase to 64 (up to 2 mb)
from 56 (up to 13 mb)
- The forecast length will increase to 15 days
- Individual file size will increase to 3.1 GB per cycle
- The timing of the GFS files will be 70 minutes later due to
the increased vertical levels and additional forecast length
- New files will be produced and named as follows:
- hysplit.t{CC}z.gfs0p25f{NNN}
where CC = 00, 06, 12, 18 Coordinated Universal Time (UTC) cycle
and NNN = 096, 120, 144, 168, 192, 216, 240, 264, 288, 312, 336
forecast hour

Current model data is available here:
https://nomads.ncep.noaa.gov/pub/data/nccf/com/hysplit/prod/

An event driven parallel feed of the HYSPLITv9.0 data will be
available March 17, 2026 on the NCEP sites at the following
URLs:
https://nomads.ncep.noaa.gov/pub/data/nccf/com/hysplit/para/


Send any comments on the science aspects of this upgrade to:

Fanglin Yang
Chief, NCEP/EMC Physics and Dynamics Division
Fanglin.Yang@noaa.gov

For questions on the dataflow aspects, please contact:

Margaret Curtis NCO Dataflow Team Lead
ncep.pmb.dataflow@noaa.gov


National Service Change Notices are online at:

https://www.weather.gov/notification