Observation

Overview

NOAA NWS Observation is a collection of hourly weather data from US weather stations. Resolution is fixed on hourly and data is provided for the last week.

The values come from api.weather.gov, which keeps a rolling week per station and clips a window that reaches further back rather than refusing it — so a request for older data returns nothing rather than an error. The window a request asks for is passed to the endpoint, which otherwise answers with its whole week however little of it was wanted.

The station list comes from somewhere else: the MADIS METAR table, narrowed to the stations MADIS files under the United States. api.weather.gov publishes a listing of its own, but it runs to some fifty thousand stations across four hundred cursor-paged requests — mostly mesonet sites this provider does not read — which is not something to walk through to answer “which stations are there”.

[!WARNING] The station list is therefore a proxy rather than the truth, and it over-promises: of forty stations sampled at random, twenty-five returned observations and fifteen returned an empty list. Roughly a third of the listed stations are silent — decommissioned METAR sites, radar and office identifiers such as KPSR or KOHX that were never observation stations, and stations that simply have not reported this week.

A station that returns nothing is walked past by filter_by_rank without any setting and without using up a rank, so a request for the two nearest stations still returns two that carry data. What ts_skip_empty adds is the next step: passing over a station that did return data but too little of it, as ts_skip_threshold and ts_skip_criteria define. Naming a silent station outright with filter_by_station_id returns an empty frame either way.

MADIS files three genuinely American stations under a state code rather than a country code — Barking Sands on Kauai (PHBK) and the two US Virgin Islands airports (TIST, TISX) — so they are named one by one rather than caught by the country column, which cannot be read as a state code in general: PR in it is Peru and GU is Guatemala, and of its four VI rows two are American and two are British.

Six further rows sit outside the western hemisphere or below the equator and are United States territory all the same: three duplicate Amchitka entries (PAHT, KAHT, PAAH), Shemya (PASY), Pago Pago (NSTU) and Tinian (PGNT). They are listed, since deciding nationality by hemisphere is not something this provider should do — but only PASY and NSTU are stations api.weather.gov knows, and both are silent at present, so expect nothing from any of the six.