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Warning Lifecycle & Updates
full-bars edited this page May 3, 2026
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SPCBot provides more than just initial alerts; it tracks the entire lifecycle of NWS warnings in real time, from issuance to cancellation.
The bot's intelligence is rooted in VTEC (Valid Time Event Code) parsing. Every NWS product contains a VTEC string (e.g., /O.NEW.KOUN.TO.W.0042.../) that identifies:
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Action:
NEW(Issuance),CON(Continue),EXT(Extend),CAN(Cancel),EXP(Expire). -
Office: Issuing WFO (e.g.,
KOUN). -
Phenomenon & Significance:
TO.W(Tornado Warning),SV.W(Severe Thunderstorm Warning). - ETN: Event Tracking Number—a unique, stable identifier for that specific storm's lifecycle.
To ensure sub-10 second delivery, SPCBot uses a dual-path pipeline:
- Fast-Trigger (NWWS-OI/IEMBot): As soon as a raw text product is received, the bot parses the VTEC and posts a "NEW" issuance immediately.
- Polling Fallback (NWS API): The bot polls the NWS API every 30 seconds to catch any products missed by the push feeds and to rehydrate state after a restart.
Unlike basic bots, SPCBot updates its posts as the storm evolves:
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Continuing Updates (
CON): When a warning is continued, the bot posts a concise update note. -
County-Level Precision: The bot calculates which counties have been cancelled and which are continuing in each update (e.g.,
(cancels Clarke, continues Jones [MS])). - Severity Tags: Automatically detects and highlights PDS (Particularly Dangerous Situation), Tornado Emergencies, and Destructive Severe Thunderstorm tags.
When a warning expires or is cancelled:
- The bot posts a dedicated Cancellation Notice.
- The notice includes a relative timestamp (e.g.,
(cancelled 2 minutes ago)). - The original issuance post remains as a historical record, but the new notice signals the end of the threat to users.
Every warning post includes an IEM Autoplot 208 map showing the warning polygon, affected counties, and a storm-relative radar snapshot.