ArcGIS Online map viewer
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ArcGIS Online map viewer
This nowCOAST™ time-offsets map service provides maps depicting the NWS
surface wind velocity forecasts from the National Digital Forecast Database
(NDFD) at 6-hr increments out to 3 days (NDFD has forecasts out to 7 days which
are available via the nowCOAST™ time-enabled map service for NDFD
elements). The forecast is valid for the specified forecast projection hour.
The forecast is valid at 10 m (33 feet) above ground level. The wind velocity
is visualized using a curved wind barb with a small arrowhead indicating the
direction that the wind is blowing towards. The wind barbs are curved along
streamlines. The forecasts are updated in the nowCOAST™ map service four
times per day.
For more detailed information about layer update frequency and timing, please reference the
nowCOAST™ Dataset Update Schedule.
The wind velocity is defined as the sustained wind magnitude and direction. The
term sustained usually refers to a wind velocity determined by averaging
observed values over a two-minute period.
A curved wind barb with an arrow head is used to display the wind velocity
forecasts instead of the traditional wind barb. The curved wind barb was
developed and evaluated at the Data Visualization Laboratory of the NOAA-UNH
Joint Hydrographic Center/Center for Coastal and Ocean Mapping (Ware et al.,
2014). The curved wind barb combines the best features of the wind barb, that
it displays speed in a readable form, with the best features of the streamlines
which shows wind patterns. The arrow head helps to convey the flow direction.
The NDFD is a seamless composite or mosaic of gridded forecasts from individual
NWS Weather Forecast Offices (WFOs) from around the U.S. as well as the NCEP
Ocean Prediction Center and National Hurricane Center/TAFB. NDFD has a spatial
resolution of 2.5 km (1.6 miles). The time resolution of forecast projections
varies by variable (element) based on user needs, forecast skill, and
forecaster workload. Each WFO prepares gridded NDFD forecasts for their
specific geographic area of responsibility. When these locally generated
forecasts are merged into a national mosaic, occasionally areas of
discontinuity will be evident. Staff at NWS forecast offices attempt to resolve
discontinuities along the boundaries of the forecasts by coordinating with
forecasters at surrounding WFOs and using workstation forecast tools that
identify and resolve some of these differences. The NWS is making progress in
this area, and recognizes that this is a significant issue in which
improvements are still needed. The NDFD was developed by NWS Meteorological
This nowCOAST™ map service is not time-enabled, although it does contain
time-varying data. Instead of supporting the time dimension through use of a
time parameter in each map request, each individual map layer contains data
valid for a different "time offset", or forecast projection, from the dataset's
Due to software limitations, the full temporal resolution (i.e. maximum
forecast horizon and/or all forecast projections) of the data is not provided
by this service. Instead, a corresponding time-enabled service containing the
full temporal resolution is available for this dataset, and users are highly
encouraged to use that service instead, if possible.
This time-offsets map service is provided as a convenience for users who are
not yet capable of interacting directly with the time dimension, especially
users of legacy nowCOAST™ version 4 map services who wish to access the same
data using the new nowCOAST™ version 5 map services. However, this service may
be terminated with little advance notice at a later date.
In addition to ArcGIS Server REST access, time-enabled OGC WMS 1.3.0 access is
is also provided by this service.
In order to determine the latest time information about the data included in
this map service, users have two options:
Issue an Identify (ArcGIS REST) or GetFeatureInfo (WMS) request against
the proper layer corresponding with the target dataset. For raster
data, this would be the "Image Footprints with Time Attributes" layer
in the same group as the target "Image" layer being displayed. For
vector (point, line, or polygon) data, the target layer can be queried
directly. In either case, the attributes returned for the matching
raster(s) or vector feature(s) will include the following:
validtime: Valid timestamp.
starttime: Display start time.
endtime: Display end time.
reftime: Reference time (sometimes reffered to as
issuance time, cycle time, or initialization time).
projmins: Number of minutes from reference time to valid
desigreftime: Designated reference time; used as a
common reference time for all items when individual reference
times do not match.
desigprojmins: Number of minutes from designated
reference time to valid time.
Query the nowCOAST™ LayerInfo web service, which has been created to
provide additional information about each data layer in a service,
including a list of all available "time stops" (i.e. "valid times"),
individual timestamps, or the valid time of a layer's latest available
data (i.e. "Product Time"). For more information about the LayerInfo
web service, including examples of various types of requests, refer to
nowCOAST™ LayerInfo Help Documentation
- NWS, 2007: National Digital Forecast Database (NDFD) Experimental Gridded Data, Product Description Document, NWS, Silver Spring, MD (Available at http://products.weather.gov/PDD/NDFDGrids.pdf).
- NWS, 2013: Experimental Gridded Marine Offshore and High Seas Forecasts in the National Digital Forecast Database (NDFD) Product Description Document, NWS, Silver Spring, MD.
- NWS, 2013: National Digital Forecast Database Element Definition, NWS, Silver Spring, MD (Available at http://www.nws.noaa.gov/ndfd/definitions.htm).
- NWS, 2014: NDFD Spatial Reference System. NOAA/NWS Meteorological Development Laboratory. (Available at http://graphical.weather.gov/docs/ndfdSRS.htm)
- Ware, C., J.G.W. Kelley, and D. Pilar, 2014: Improving the Display of Wind Patterns and Ocean Currents. Bull. Amer. Meteor. Soc., 95, 1573-1581.
NOAA NWS NDFD Gridded Forecasts of Surface Wind Velocity Barb (knots) (Time Offsets)
All Layers and Tables
Dynamic All Layers
Surface (10m AGL) Wind Velocity (Barb, Knots) (+6 hrs) (0)
Surface (10m AGL) Wind Velocity (Barb, Knots) (+12 hrs) (4)
Surface (10m AGL) Wind Velocity (Barb, Knots) (+18 hrs) (8)
Surface (10m AGL) Wind Velocity (Barb, Knots) (+24 hrs) (12)
Surface (10m AGL) Wind Velocity (Barb, Knots) (+30 hrs) (16)
Surface (10m AGL) Wind Velocity (Barb, Knots) (+36 hrs) (20)
Surface (10m AGL) Wind Velocity (Barb, Knots) (+42 hrs) (24)
Surface (10m AGL) Wind Velocity (Barb, Knots) (+48 hrs) (28)
Surface (10m AGL) Wind Velocity (Barb, Knots) (+54 hrs) (32)
Surface (10m AGL) Wind Velocity (Barb, Knots) (+60 hrs) (36)
Surface (10m AGL) Wind Velocity (Barb, Knots) (+66 hrs) (40)
Surface (10m AGL) Wind Velocity (Barb, Knots) (+72 hrs) (44)
NOAA/NOS/OCS nowCOAST and NOAA/NWS
Single Fused Map Cache:
Supported Image Format Types:
Supports Dynamic Layers:
Keywords: surface weather,marine weather,wind direction,wind speed,wind velocity,wind barbs,streamlines,sustained,forecasts,gridded,mosaic,seamless,NDFD,NWS,NOAA,Meteorological Development Laboratory,Weather Forecast Office,NCEP,OPC,NHC,TAFB
Supported Query Formats:
JSON, AMF, geoJSON
Supports Datum Transformation: