Zone Questions

[white3km]

I have a few questions about zones.

• Is there a unique id for zones? id? id + type? (ex. "id": "AKC013", "type": "county")
• How do you know a zone has been updated?
• Are expired zones returned by the API endpoint?
• Do alerts only apply to public and county zones?

[akrherz]

I have a side comment for this general question. UGC codes like AKC013 are not necessarily unique to a single geometry. The most troublesome one is Monroe County Florida, which has the following

UGC	WFO	Name
FLC087	KEY	Lower Keys in Monroe
FLC087	KEY	Middle Keys in Monroe
FLC087	KEY	Upper Keys in Monroe
FLC087	MFL	Mainland Monroe

There are a couple other edge cases, but this one is the most "fun"

[sullynole]

Only current zones are available in the API.

Any necessary zone updates typically happen in March or September each year and will be posted as Service Change Notices here: https://www.weather.gov/notification

This geolocation guide should help with understanding the relationship between zones and alerts: https://www.weather.gov/media/documentation/docs/NWS_Geolocation.pdf

[dwhitemv25]

Welcome!

Is there a unique id for zones? id? id + type? (ex. "id": "AKC013", "type": "county")

Yes and no. County zones use the Census Bureau numbering and the 'C' indicator (3rd letter), so there is a 1:1 map between zone name and county. As you found, though, counties aren't necessarily physically contiguous. You should be representing them as MultiPolygons so your GIS functions can handle that, and any holes in the county (i.e., bodies of water).

Forecast and fire weather zones use the 'Z' indicator and can be the same. (NB: What's fun is that the public forecast zone and the fire weather zone are the same in some states, but have different geometries in the shapefiles. Go figure.)

How do you know a zone has been updated?

Service Change Notices (SCNs) are posted by NWS in advance of zone changes. The link where those are published was provided. The next zone update is coming in a couple of weeks, on March 18, so mark your calendar.

Are expired zones returned by the API endpoint?

Any zones that are removed disappear on the effective date. You don't have to worry about getting any stale data. It is possible that old alerts might refer to deleted zones, so you'll have to watch for that.

Do alerts only apply to public and county zones?

There are also fire weather zones that get alerts too.

[JJKraw]

Tangent question: Does the geometry every change for a given zone? Or if that happens, does it get a new zone number?

I cache the geometry info long term so I don't have to fetch it on the fly. I've never noticed a problem with stale geometry data.

[white3km]

I'm hoping to do this as well... Adding to your question, if the geometry is updated and the zone number doesn't change will the effective date be updated?

[dwhitemv25]

Do the geometries change? Yes. Does it get a new zone number when that happens? That's up to the issuing WFO. Minor edits might not, but major overhauls typically do. Does the effective date change? Yes, once the effective date passes, queries to the zone metadata endpoint will return the new data with the new effective date.

The API is set up to perform historical and future queries though that doesn't seem to be working. I tried to preview some of the Alaska zones with an effective date after the change date but they just come up 404. I think there was a post about this last year...