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This nowCOAST™ time-enabled map service provides maps depicting the geographic coverage of the latest NOAA/National Weather Service (NWS) Watches, Warnings, Advisories, and Statements for long-duration hazardous weather, marine weather, and hydrological, oceanographic, wildfire, air quality, and ecological conditions which may affect or are presently affecting inland, coastal, and maritime areas. A few examples include Gale Watch, Gale Warning, High Surf Advisory, High Wind Watch, Areal Flood Warning, Coastal Flood Watch, Winter Storm Warning, Wind Chill Advisory, Frost Advisory, Tropical Storm Watch, Red Flag Warning, Air Stagnation Warning, and Beach Hazards Statement. A complete list is given in the Background Information section below.
The coverage areas of these products are usually defined by county or sub-county boundaries, but for simplicity and performance reasons, adjacent WWAs of the same type, issuance, and expiration are depicted in this service as unified (merged/dissolved) polygons in the layers indicated with the suffix "(Dissolved Polygons)". However, a set of equivalent layers containing the original individual zone geometries are also included for querying purposes, and are indicated with the suffix "(Zone Polygons)". Corresponding zone polygon and dissolved polygon layers are matched together in group layers for each WWA category. The zone polygon layers are included in this service only to support query/identify operations (e.g., in order to retrieve the original zone geometry or other attributes such as a URL to the warning text bulletin) and thus will not be drawn when included in a normal map image request. Thus, the dissolved polygon layers should be used when requesting a map image (e.g. WMS GetMap or ArcGIS REST export operations), while the zone polygon layers should be used when performing a query (e.g. WMS GetFeatureInfo or ArcGIS REST query or identify operations).
The colors used to identify the different watches, advisories, warnings, and statements are the same colors used by the NWS on their map at http://www.weather.gov. The NWS products for long-duration hazardous conditions 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.
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. A warning depicts where a hazardous weather or hydrologic event is occurring, is imminent, or has a very high probability of occurring. A warning is used for conditions posing a threat to life or property. Advisories indicate where special weather conditions are occurring, imminent, or have a very high probability of occurring but are less serious than a warning. They are for events that may cause significant inconvenience, and if caution is not exercised, could lead to situations that may threaten life and/or property. Statements usually contain updated information on a warning and are used to let the public know when a warning is no longer in effect. NWS issues over 75 different types of watches, warnings, and advisories (WWAs). WWAs are issued by the NWS regional Weather Forecast Offices (WFOs) and also the NWS Ocean Prediction Center, National Hurricane Center, Central Pacific Hurricane Center, and Storm Prediction Center.
The NWS WWAs are organized on the nowCOAST™ map viewer and within this map service by hazardous condition/threat layer groups and then by the geographic area (i.e. coastal & inland, immediate coast or maritime) for which the WWA product is targeted. This was done to allow users to select WWAs for hazardous conditions that are important to their operations or activities.
Please note that the Tropical Storm and Hurricane Warnings are provided in both the High Wind Hazards: Maritime Areas and Coastal & Inland Areas layer groups and the Flooding Hazards: Coastal Areas layer group. These warnings are included in the Flooding Hazards/Coastal Areas layer group because the NWS uses those warnings to inform the public that tropical storm or hurricane winds may be accompanied by significant coastal flooding but below the thresholds required for the issuance of a storm surge warning. In addition, a tropical storm or hurricane warning may remain in effect when dangerously high water or a combination of dangerously high water and waves continue, even though the winds may be less than hurricane or tropical storm force. The NWS does not issue a Coastal Flood Warning or Advisory when a tropical storm or hurricane warning is in effect; however that does not mean that there is not a significant coastal flooding threat.
For descriptions of individual NWS watches, warnings, and advisories please see Section 2 of the NWS Reference Guide available at http://www.nws.noaa.gov/om/guide/Section2.pdf.
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:
NWS Instructions and other directives are available at http://www.nws.noaa.gov/directives/.