Last Updated: January 2015
Map Information
This nowCOAST time-enabled map service provides map depicting the latest surface weather and marine weather observations at
observing sites using the international station model. The station model is method for representing information collected
at an observing station using symbols and numbers. The station model depicts current weather conditions, cloud cover,
wind speed, wind direction, visibility, air temperature, dew point temperature, sea surface water temperature, significant wave height,
air pressure adjusted to mean sea level, and the change in air pressure over the last 3 hours.
The circle in the model is centered over the latitude and
longitude coordinates of the station. The total cloud cover is expressed as a fraction of cloud covering the sky and is indicated by
the amount of circle filled in. (Cloud cover is not presently displayed due to a problem with the source data. Present weather information
is also not available for display at this time.) Wind speed and direction are represented by a wind barb whose line extends from the cover cloud
circle towards the direction from which the wind is blowing. The short lines or flags coming off the end of the long line are called barbs.
The barb indicates the wind speed in knots. Each normal barb represents 10 knots, while short barbs indicate 5 knots. A flag represents
50 knots. If there is no wind barb depicted, an outer circle around the cloud cover symbol indicates calm winds.
The map of observations are updated in the nowCOAST map service approximately every 10 minutes. However, since the
reporting frequency varies by network or station, the observation at a particular station may have not updated and may not
update until after the next hour. For more detailed information about the update schedule, please see:
http://new.nowcoast.noaa.gov/help/#section=updateschedule
Background Information
The maps of near-real-time surface weather and ocean observations are based on non-restricted data obtained from
the NWS Family of Services courtesy of NESDIS/OPSD and also the NWS Meteorological Assimilation Data Ingest System (MADIS).
The data includes observations from terrestrial and maritime observing from the U.S.A. and other countries. For
terrestrial networks, the platforms including but not limited to ASOS, AWOS, RAWS, non-automated stations, U.S. Climate
Reference Networks, many U.S. Geological Survey Stations via NWS HADS, several state DOT Road Weather Information Systems,
and U.S. Historical Climatology Network-Modernization. For over maritime areas, the platforms include NOS/CO-OPS National
Water Level Observation Network (NWLON), NOS/CO-OPS Physical Oceanographic Observing Network (PORTS), NWS/NDBC
Fixed Buoys, NDBC Coastal-Marine Automated Network (C-MAN), drifting buoys, ferries, Regional Ocean Observing System (ROOS)
coastal stations and buoys, and ships participating in the Voluntary Ship Observing (VOS) Program. Observations
from MADIS are updated approximately every 10 minutes in the map service and those from NESDIS are updated every hour.
However, not all stations report that frequently. Many stations only report once per hour sometime between 15 minutes
before the hour and 30 minutes past the hour. For these stations, new observations will not appear until 22 minutes
past top of the hour for land-based stations and 32 minutes past the top of the hour for maritime stations.
Time Information
This map 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.
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.
In addition to ArcGIS Server REST access, time-enabled OGC WMS 1.3.0 access is
also provided by this service.
Due to software limitations, the time extent of the service and map layers
displayed below does not provide the most up-to-date start and end times of
available data. Instead, users have three options for determining the latest
time information about the service:
Issue a returnUpdates=true request for an individual layer or for
the service itself, which will return the current start and end times of
available data, in epoch time format (milliseconds since 00:00 January 1,
1970). To see an example, click on the "Return Updates" link at the bottom of
this page under "Supported Operations". Refer to the
ArcGIS REST API Map Service Documentation
for more information.
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
time.
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
the nowCOAST help documentation at:
http://new.nowcoast.noaa.gov/help/#section=layerinfo
References
NWS, 2013: Sample Station Plot, NWS/NCEP/WPC, College Park, MD (Available at http://www.hpc.ncep.noaa.gov/html/stationplot.shtml).
NWS, 2013: Terminology and Weather Symbols, NWS/NCEP/OPC, College Park, MD (Available at http://www.opc.ncep.noaa.gov/product_description/keyterm.shtml).
NWS, 2013: How to read Surface weather maps, JetStream an Online School for Weather (Available at http://www.srh.noaa.gov/jetstream/synoptic/wxmaps.htm).
