ArcGIS Online map viewer
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ArcGIS Online map viewer
This nowCOAST™ time-enabled map service provides maps depicting the
geographic coverage of the latest NOAA/National Weather Service (NWS) Watches
for the following short-duration hazardous weather and hydrological events
which may affect inland and coastal areas: severe thunderstorms (surface winds
of 58 MPH [93 KM/H, 50 knots] or greater, or large hail of 1 inch (2.5 cm) or
greater in diameter), tornadoes, and flash floods. A watch indicates that the
risk of hazardous weather or hydrologic event has increased significantly, but
its occurrence, location, and/or timing is still uncertain. The geographic
areas covered by Severe Thunderstorm, Tornado, and Flash Flood Watches are
usually indicated by county or subdivided-county boundaries. The colors used to
identify the different watches are the same colors used by the NWS on their map
The NWS watches are updated in the nowCOAST™ map service approximately
every 10 minutes.
For more detailed information about layer update frequency and timing, please reference the
nowCOAST™ Dataset Update Schedule.
The NWS watches depict the geographic areas where the risk of hazardous weather
or hydrologic events has increased significantly, but their occurrence,
location, and/or timing is still uncertain. The watch is intended to give
enough lead time so people can set their plans into motion. NWS Severe
Thunderstorm and Tornado Watches are issued by the NWS/NCEP Storm Prediction
Center in Oklahoma. Flash Flood Watches are issued by the NWS regional Weather
Forecast Offices (WFOs). All watches are cancelled by WFOs when necessary.
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
Issue a returnUpdates=true request (ArcGIS REST protocol only)
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 the REST Service 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 referred 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, 2006: NWS Instructions 10-313, WFO Severe Weather Products
Specification, NWS, Silver Spring, MD.
NWS, 2007: NWS Instructions 10-922, Weather Forecast Office Hydrologic
Products Specification, NWS, Silver Spring, MD.
NWS, 2010: NWS Instructions 10-512, National Severe Weather Products
Specification, NWS, Silver Spring, MD.
NWS Instructions and other directives are available at http://www.nws.noaa.gov/directives/.
NOAA NWS Watches for Short-Duration Hazards for Inland, Coastal, and Maritime Areas (Time Enabled)
All Layers and Tables
Dynamic All Layers
NOAA/NOS/OCS nowCOAST and NOAA/NWS/CRH
Single Fused Map Cache:
[2018/10/05 08:31:00 UTC, 2018/10/06 18:00:00 UTC]
Supported Image Format Types:
Title: NOAA/NWS Watches for Short-Duration Hazards for Inland, Coastal, and Maritime Areas
Supports Dynamic Layers:
Author: John G.W. Kelley
Comments: This time-enabled map service provides maps depicting the geographic coverage of NOAA/National Weather Service's Severe Thunderstorm Watches, Tornado Watches, and Flash Flood Watches. These watches indicates the areas where the risk of severe thunderstorms, tornadoes, and/or flash floods has increased significantly, but their occurrence, location, and/or timing is still uncertain. The coverage areas of the watches are usually defined by county or sub-county boundaries. The NWS watches are updated in the nowCOAST map service every 5 minutes.
Subject: This map service provides maps of NWS watches for severe thunderstorms, tornadoes, and flash floods.
Keywords: weather watches,short-duration,hazardous weather,severe thunderstorms,tornadoes,damaging winds,large hail,flash floods
Supported Query Formats:
JSON, AMF, geoJSON
Supports Datum Transformation: