TSNO
Indicates that the automated station's thunderstorm detection sensor (lightning detector) is not operating. Without this sensor, the station cannot detect or report thunderstorms. This is important to note because the absence of TS in the observation does not mean no thunderstorms are present.
RMK TSNO
RMK AO2 TSNO
RMK TSNO $
TSNO stands for "Thunderstorm Sensor Not Available" in the remarks section of a METAR report. Indicates that the automated station's thunderstorm detection sensor (lightning detector) is not operating. Without this sensor, the station cannot detect or report thunderstorms. This is important to note because the absence of TS in the observation does not mean no thunderstorms are present.
TSNO appears in the remarks (RMK) section at the end of a METAR observation. The remarks section follows the main body of the METAR and provides additional details about the observation that don't fit into the standard coded format.
Here is an example: "RMK TSNO". This appears in the remarks section and indicates thunderstorm sensor not available information as part of the weather observation.