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HomeMy WebLinkAbout06222026 City Council Laydown - Tsunami Alert UpdateAlaska - Building a Weather-Ready Nation Tsunami Alert Update Seward City Council Meeting June 22, 2026 Aviva Braun Warning Coordination Meteorologist National Weather Service, Anchorage Detect the problem (rapid seismic analysis) and Alert (procedural) Adjust alerting strategy with better quality seismic parameters Confirm a tsunami exists at a DART station. Measure the tsunami and forecast Adjust alerting strategy with deep ocean tsunami observations Observe tsunami along the coast Confirm large-scale impactful tsunami event has ended. Tsunami Process 📣COMMUNICATE THROUGHOUT THE EVENT Observations Inform Tsunami Alerting Seismic observations NTWC-operated and worldwide partner networks detect local and global earthquakes Deep-ocean water level observations Coastal water-level observations NTWC-operated stations plus NOAA and worldwide-supported tide gauges networks measure a tsunami once it reaches the coast NOAA-operated DART underwater pressure sensors plus worldwide partner-supported networks detect deep-ocean water changes indicating a tsunami is present Tsunami water level story starts here How do we communicate over EAS and WEA? NWS Gateway (NOAA Weather Wire and CAP Encoding) 🌊⚠️ ⚠️NTWC Issues A Warning NAWAS / USCG NOAA WEATHER RADIO 3rd PARTY SOFTWARE EAS RADIO/TV BROADCAST STATIONS RADIO/TV BROADCAST STATIONS PUBLIC WEA IPAWS (FEMA) EMNET NIXLE, APPS, etc 5 Skip for: none 6 WEA Skip for: none 7 Overalerting Issue “Small” near-shore quakes may require a procedural tsunami warning. Breakpoint includes coastal zones into Cook Inlet. This publicly alerts unnecessary regions in the Kenai Peninsula Borough. NTWC tsunami “breakpoints” used to coordinate coastal broad alerting through NWS Public Weather Forecast Zones Breakpoints shown: 1- Chignik Bay 2- Kennedy Entrance 3- Hinchinbrook Entrance 1 2 3 Coastal public weather zone Coastal public weather zone Inland public weather zone Inland public weather zone Inland public weather zone Inland public weather zone Inland public weather zone Inland public weather zone Coastal public weather zone Coastal public weather zone Coastal public weather zone Coastal public weather zone 1 NTWC Breakpoint Segment FIPS boundary: abc FIPS boundary: stu FIPS boundary: jkl 2 Breakpoints and zones FIPS boundary: xyz Overalerting: Public WEA goes well beyond intended alert regions. Solution for Kenai Peninsula Borough Reduce unintentional overalerting due to breakpoint strategy and Census/FIPs boundaries Change for Future Small Sand Point Tsunami Alerts “Small” quakes near the coast require a procedural tsunami warning. Previous breakpoint includes coastal zones into Cook Inlet. In late Sep 2025, NTWC moved associated Cook Inlet zones to the Hinchinbrook Entrance Breakpoint Breakpoint locations Specific tsunami alerting strategy change Not a true “fix”. NTWC is shifting alerting issue to a less active earthquake region* *Note: we cannot predict earthquakes Cook Inlet public weather zones now included in Hinchinbrook entrance “Breakpoint” Benefit: *Reduce potential of overalerting using current tools and capabilities. A better systematic fix is being worked on. *Alerting capability continues for very large quakes and greater tsunami risk. Accepted risk: *Cook Inlet zones may still have overalerting issue when smaller quakes occur in the Northern Gulf or Prince William Sound How Did we Fix this with Current Tools? Challenges: NWS Weather Zones aren’t “Tsunami” zones Wireless Emergency Alert and EAS require other agency support Quick Solution: Shift assigned NWS Weather Zones from one breakpoint to another Better, long-term solution: Design, build, and implement a tsunami alerting dissemination system that uses a hazard alerting boundary made for tsunami, and delivers through the NWS and U.S. Federal alerting system Alaska - Building a Weather-Ready Nation What Does the Future Hold? Partial County Alerting - the ability to alert the intended portion of a Borough. This is based on NWS Forecast Offices’ forecast zones. Tsunami Warning Polygons - the ability to warn on a more precise area. This would effectively rid of breakpoints. Updated websites that show clearer messaging. NWS lost quite a bit of institutional knowledge from our agency in 2025, so this steps will take time to achieve. Call or Email 24/7/365! anchorage.weather@noaa.gov weather.gov/alaska US National Weather Service Anchorage or nwsntwc @NWSAnchorage or @nws_ntwc Anchorage: 907-266-5127, NTWC: 907-745-4212 Alaska Weather Information Line @ 1-855-937-4977 Aviva Braun Warning Coordination Meteorologist  Anchorage, Alaska aviva.braun@noaa.gov o: 907-266-5117 c: 907-230-1869 How do we communicate with partners? Tsunami Warning Centers State Warning Points NWS WFOs Interagency partners Local Community 18 Standard Procedure: Alerts will be downgraded/cancelled once waves have remained below threshold for 3+ hours. We do not say “all clear”. That authority remains with local emergency management. Cancellation Criteria Countdown to cancellation