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This nowCOAST™ time-enabled map service provides maps of the latest nowcasts and forecast guidance of water currents and combined (tides + wind driven) water level from the NOS New York and New Jersey Harbor Operational Forecast System (NYOFS) at hourly increments out to 48 hours. The direction of the water currents are depicted by white streaklets. The maps of NYOFS forecast guidance are updated in the nowCOAST™ map service four times per day. The magnitude of the current is indicated by the length and width of the streaklet. The surface water currents velocity maps use white streaklets to indicate direction and are overlaid on different map backgrounds. Two color backgrounds are available: speed of currents and water level. For speed, a color scale from black to gray is used to depict speeds from 0 to 4 knots at 0.5 knot increments, except for 0.25 knot intervals from 0 to 0.5 knots. For water level, a color scale from pink to red is used to depict water levels from -14 ft to +12 ft at mainly 0.5 ft increments. The water levels are referenced to the OFS model sea level and not to MLLW, MSL, or NAVD88. For more detailed information about layer update frequency and timing, please reference the nowCOAST™ Dataset Update Schedule.
NYOFS is based on the Princeton Ocean Model (POM), a terrain following numerical ocean or hydrodynamic prediction model. The OFS grid domain covers Port of New York and New Jersey and the lower Hudson River in a nested-grid configuration. A high-resolution grid is embedded within and dynamically connected to a coarse grid to provide detailed current shears and eddies in the navigation channels of the Kill Van Kull. The spatial horizontal resolution of the coarse and fine grids are approximately 350-1000 m and 120-250 m, respectively. It has four forecast cycles per day (0500, 1100, 1700 and 2300 UTC) which generate forecast guidance out to 48 hours. The forecast cycle uses 3-hourly surface wind forecast guidance from NCEP North American Mesoscale (NAM) model (12 km resolution) for surface meteorological forcing. For forcing at the lateral ocean boundary, the OFS uses sub-tidal water level forecast guidance from the NWS Extratropical Storm Surge (ETSS) Model along with NOS tidal harmonics. Each forecast cycle is preceded with a 6-hr long nowcast cycle. The final nowcast serves as the initial conditions for each forecast cycle. The nowcoast cycle is driven by near-real-time water levels and surface wind velocities from the observing stations of the NOS Physical Oceanographic Real-Time System (PORTS). NYOFS was developed and evaluated by the NOAA/NOS Coast Survey Development Laboratory Coastal Marine Modeling Branch in collaboration with the NOS Center for Operational Oceanographic Products and Services (CO-OPS). NYOFS is run on Linux servers operated by CO-OPS. For more information, please see http://tidesandcurrents.noaa.gov/ofs/nyofs/nyofs.html.
The maps are generated using a visualization technique developed by the Data Visualization Research Lab at The University of New Hampshire's Center for Coastal and Ocean Mapping (http://www.ccom.unh.edu/vislab/). The method combines two techniques. First, equally spaced streamlines are computed in the flow field using Jobard and Lefer's (1977) algorithm. Second, a series of "streaklets" are rendered head to tail along each streamline to show the direction of flow. Each of these varies along its length in size, color and transparency using a method developed by Fowler and Ware (1989), and later refined by Mr. Pete Mitchell and Dr. Colin Ware (Mitchell, 2007).
This map service is time-enabled, meaning that each individual layer contains time-varying data and can be utilized by clients capable of making map requests that include a time component.
In addition to ArcGIS Server REST access, time-enabled OGC WMS 1.3.0 access is also provided by this service.
This particular service can be queried with or without the use of a time component. If the time parameter is specified in a request, the data or imagery most relevant to the provided time value, if any, will be returned. If the time parameter is not specified in a request, the latest data or imagery valid for the present system time will be returned to the client. If the time parameter is not specified and no data or imagery is available for the present time, no data will be returned.
This service is configured with time coverage support, meaning that the service will always return the most relevant available data, if any, to the specified time value. For example, if the service contains data valid today at 12:00 and 12:10 UTC, but a map request specifies a time value of today at 12:07 UTC, the data valid at 12:10 UTC will be returned to the user. This behavior allows more flexibility for users, especially when displaying multiple time-enabled layers together despite slight differences in temporal resolution or update frequency.
When interacting with this time-enabled service, only a single instantaneous time value should be specified in each request. If instead a time range is specified in a request (i.e. separate start time and end time values are given), the data returned may be different than what was intended.
Care must be taken to ensure the time value specified in each request falls within the current time coverage of the service. Because this service is frequently updated as new data becomes available, the user must periodically determine the service's time extent. However, due to software limitations, the time extent of the service and map layers as advertised by ArcGIS Server does not always provide the most up-to-date start and end times of available data. Instead, users have three options for determining the latest time extent of the service: