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NOUS41 KWBC 221600
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Public Information Statement 25-03
National Weather Service Headquarters Silver Spring MD
1100 AM EST Wed Jan 22 2025

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

From: Fanglin Yang
 Chief, Physics Group
 Modeling and Data Assimilation Branch
 NCEP/Environmental Modeling Center

Subject: Soliciting Comments through February 21, 2025, on the
Proposed Upgrade of the Hybrid Single-Particle Lagrangian
Integrated Trajectory model (HYSPLIT) to Version 9.0

The NWS is soliciting comments through February 21, 2025, on a
proposed upgrade of the operational HYSPLIT model to version
9.0.

HYSPLIT is a transport and dispersion model developed at NOAAs
Air Resources Laboratory (ARL) for real-time wind-blown dust
predictions over the contiguous U.S. (CONUS) and on-demand
dispersion predictions for: radioactive material, via World
Meteorological Organization (WMO) Regional Specialized
Meteorological Center (RSMC) and agreements with the
Comprehensive Test Ban Treaty Organization (CTBTO); volcanic
ash, via International Civil Aviation Organization (ICAO)
agreements; and hazardous material release.

The proposed model upgrade includes:

- The most recent revision of the HYSPLIT model code (v5.3.0).

- The implementation of a Transfer Coefficient Matrix (TCM)
methodology for faster simulation of radiological and volcanic
ash events.  The TCM allows rapid updates of source term
strength 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).

The proposed 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.
* 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, 288, 312, 336
forecast hour.

- Global Ensemble Forecast System (GEFS) files, 31 members, all
cycles:
* The forecast length will increase to 15 days.
* Total data volume per cycle will increase to 121 GB.
* New files will be produced:
** hysplit.t{CC}z.gefs.mrf.{MMM} (include forecast hours 87-240)
** hysplit.t{CC}z.gefs.lrf.{MMM} (include forecast hours 246-
360)
where CC = 00, 06, 12, 18 UTC cycle, and MMM = gec00 (control
member), gep01 through gep30 (ensemble member 1 through 30).

New products will be generated four times a day for volcanic ash
predictions with the new TCM capability:

- hysplit_tcm.${YYYYMMDD}_t{CC}z.volc${SITEID}.zip
where: YYYY = four-digit forecast year, MM = two-digit forecast
month, DD = two-digit forecast day; CC = 00, 06, 12, 18 UTC
cycle; and SITEID = six-digit volcano identifier number.

All new files will be available at the following URL:

https://ftpprd.ncep.noaa.gov/data/nccf/com/hysplit/v9.0/

GFS files will also be available from the NOAA Operational Model
Archive and Distribution Service (NOMADS)/FTPPRD web services.

Please submit comments, questions, or requests on science
aspects of the proposed upgrade to:

Fanglin Yang
Chief, Physics Group, Modeling and Data Assimilation Branch
NCEP/Environmental Modeling Center
College Park, MD
fanglin.yang@noaa.gov
301-683-3722

Mark Cohen
HYSPLIT Team Lead
NOAA/Air Resource Laboratory
College Park, MD
mark.cohen@noaa.gov
301-683-1397

For questions and comments on the dataflow aspect, please
contact:

Margaret Curtis
Dataflow Team Lead
NWS Central Operations
margaret.curtis@noaa.gov
207-200-5340

National Public Information Statements are online at:

https://www.weather.gov/notification