Forecast guidance of water levels from NOAA’s Global Surge and Tide Operational Forecast System 2-D (STOFS-2D-Global) are now available in S-104/HDF5 format on Amazon S3. The water level forecast guidance includes the combined effects of storm surge (sub-tidal) and tides (astronomical tide predictions). These files are part of a Test and Evaluation service for water level forecast guidance for marine navigation systems. The goal of this service is to provide manufacturers with samples of S-104 water level files to test and implement into their navigational systems.
This service is made possible through a public-private partnership enabled by the NOAA Open Data Dissemination Program.
The Amazon Resource Name (ARN) for the S3 Bucket is: arn:aws:s3:::noaa-s104-pds
The Amazon S3 Bucket URI is: s3://noaa-s104-pds
AWS S3 provides direct HTTP access to the files, so datasets can be downloaded using any HTTP client such as a web browser. To make discovering and accessing the data easier, a simple bucket explorer web application is also provided which allows you to navigate through the object key structure and download files using a web browser.
Access to the datasets is being provided on Amazon Web Services (AWS) via Simple Storage Service (S3). Files can be downloaded via the native AWS S3 API using tools such as the AWS CLI or AWS SDK libraries such as the Python boto3 package.
Common AWS CLI Access Examples (No AWS account required):
aws s3 ls --no-sign-request s3://noaa-s104-pds/
aws s3 sync --no-sign-request s3://noaa-s104-pds/ /path/to/local/directory/
Additionally, an AWS Simple Notification Service (SNS) Topic has also been created to provide automated notifications when new files are added to the S3 Bucket. Users who operate their own infrastructure on AWS can integrate directly with this SNS Topic to trigger automated workflows using AWS Lambda or other services.
The Amazon Resource Name (ARN) for the SNS Topic is: arn:aws:sns:us-east-1:123901341784:NewS104Object.
S-104 is a data encoding standard which is part of the International Hydrographic Organization's (IHO) S-100 Universal Hydrographic Data Model. Individual S-104 files are encoded in S-104 Standard. Because S-104 is built upon HDF5, files can be read and written using existing software such as the official HDF5 libraries/utilities and h5py.
S-104 data may be used for route monitoring and route planning, in combination with S-101 ENC and S-102 Bathymetric Surface data to provide navigation officers with dynamic water depth information for the purpose of route planning and route monitoring. This will allow efficient use of waterways with tidal or other dynamic variations of water levels, saving vessels transit time and fuel costs.
This collection provides S-104 files encoded in dataCodingFormat (DCF) 2 - Regularly-gridded arrays ("regular grids").
In most cases, the underlying data sources (modeling systems) generate predictions at irregular or unstructured gridpoints placed at varying spatial resolutions. In order to promote interoperability, these values have been interpolated to regular grids at a defined resolution, then encoded into S-104 DCF-2 (regular grid) format and subset into individual tiles. This tiling scheme is designed to keep file sizes small, increase interoperability with S-101 and S-102, and allow users to obtain data for only their area of interest, with each tile covering a small geographic area corresponding with the OCS Nautical Product Tiling Scheme, thus matching the coverage areas of other OCS products that will be disseminated in the future.
Datasets are comprised of a time series of water level height relative to chart datum (NOAA uses mean lower low water, MLLW, for many charts) and water level trend. The data represent an array of points contained in a grid. Time and datum information are contained in the metadata. The primary purpose of this data type is to enable displays of dynamic depth information on Electronic Chart Display and Information System (ECDIS) in combination with bathymetric and chart data, i.e. Water Level Adjustment; another purpose is to update water depths for under-keel clearance management. Water level trend is the change of water level at a given time; trend can be increasing, decreasing, or steady. When the change of the water level over a one hour period at a specific point is greater than or equal to a value set by the Producing Authority in metres (e.g. 0.2 metres/hour) it is considered “increasing”. When it is less than or equal to the value set by the Producing Authority, it is “decreasing”. When it is between the +/- value set by the Producing Authority, it is “steady”.
The National Oceanic and Atmospheric Administration (NOAA) operates a Global 2-D hydrodynamic modeling system, commonly referred to as the Global Surge and Tide Operational Forecast System 2-D (STOFS-2D-Global), which produces water level forecast guidance for astronomical tides alone, surge water level (sub-tidal), and the combined effects of surge and tides. STOFS-2D-Global is run four times per day and generates forecast guidance out to 180 hours (7.5 days). The S-104 files in this data collection are generated by extracting, post-processing, and interpolating the forecast guidance output from this modeling system to produce forecast guidance of water levels (combined surge + tides), which are then encoded in the S-104 HDF5 format.
S-104 Water Level datasets are provided from the following forecast modeling system:
S-104 datasets are organized in the S3 bucket using an object-key structure similar to a directory hierarchy. This key structure includes the version (edition) of the S-104 standard with which the files are compliant and the geographic coverage of the files.
Note: This key structure is subject to change in the future pending feedback from users. Please see the Contact section below to provide feedback.
Example Object Keys:
ed2.0.0/Southeast/Charleston/104US004SC1BO_20251217T12Z.h5
ed2.0.0 - Files compliant with edition 2.0.0 of the S-104 StandardSoutheast - RegionCharleston - Files were produced for Charleston Approaches 104US004SC1BO_20251217T12Z.h5
104US00 - This is an S-104 file produced by the U.S. NOAA/National Ocean Service/Office of Coast Survey4SC1BO - The file contains output for a geographic area corresponding with the Office of Coast Survey's (OCS) Nautical Product Tiling Scheme for Cell Identifier 4SC1BO20251217T12Z - The file contains forecast guidance derived from a model run initialized on December 17, 2025 at 12 UTC.h5 - The file extension denotes that this is an HDF5 encoded file.ed2.0.0/_CATALOG/CATALOG.xml
CATALOG.xml - S-104 Exchange Set Catalog file (XML Metadata)If you have any questions or would like to provide feedback about these datasets, please submit your inquiry using the NOAA Office of Coast Survey (OCS) Assist Tool