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Home My WebLink About06222026 City Council Laydown - Tsunami Alert Update PDFTsunami Alert Update Seward City Council Meeting June 22, 2026 Aviva Braun Warning Coordination Meteorologist National Weather Service, Anchorage Alaska - Bui • ing a y ation Alert level WARNING ADVISORY ERN 'INFORMATION STATEMENT TSUNAMI ALERTS Action Get to high ground or inlan IMMEDIATELY! Follow evacuation signage Hazard DANGER! A TSUNAMI IS IMMINENT. Flooding & dangerous currents 3+ feet or 1+ meter Stay out of the water and away from the shore Prepare to take action. Monitor local TV, radio, social media, NOAA weather radio NO action needed ltJ • STRONG CURRENTS & DANGEROUS WAVES! In or near coastal waters 1-3feet or 0.3 -1 meter El A TSUNAMI IS POSSIBLE. Arrival time is several hours away. Prepare now. Alert level may change. NO tsunami impact expected. Prepare o Relax o THREAT —MESSAGE: Issued for International Partners; NOT for U.S. Coasts NATIONAL TSUNAMI WARNING CENTER Palmer, Alaska tsunami.gov 1. Detect the problem (rapid seismic analysis) and Alert (procedural) 2. Adjust alerting strategy with better quality seismic parameters 3. Confirm a tsunami exists at a DART station. 4. Measure the tsunami and forecast 5. Adjust alerting strategy with deep ocean tsunami observations 6. Observe tsunami along the coast 7. Confirm large-scale impactful tsunami event has ended. bCOMMUNICATETHROUGHOUTTHE EVENT NATIONAL TSUNAMI WARNING CENTER Palmer, Alaska tsunami.gov Observations Inform Tsunami Alerting an Tsunami water level story starts here Seismic observations NTWC-operated and worldwide partner networks detect local and global earthquakes DA RT Deep -ocean water level observations NOAA-operated DART underwater pressure sensors plus worldwide partner -supported networks detect deep -ocean water changes indicating a tsunami is present Coastal water -level observations NTWC-operated stations plus NOAA and worldwide -supported tide gauges networks measure a tsunami once it reaches the coast How do we communicate over EAS and WEA? NIXLE, APPS, etc 4-3tiF, 3rd PARTY SOFTWARE \ NWS Gateway (NOAA Weather Wire and CAP Encoding) NOAA WEATHER RADIO EAS RADIO/TV BROADCAST STATIONS • F �� A PUBLIC r"-7 RADIO/TV BROADCAST STATIONS I I I WEA Tsunami Warning Signs See a sudden rise or fall of the ocean Wireless Emergency Alerts and Text Messages OFFICIAL Tsunami Warnings (broadcast through) Radio Outdoor Sirens Telephone Notifications Tsunami Warning Signs Feel a strong or Long earthquake Hear a loud roar from the ocean See a sudden rise or fall of the ocean Wireless Emergency Alerts and Text Messages TV OFFICIAL Tsunami Warnings (broadcast through) Radio Outdoor Sirens Telephone Notifications NATIONAL TSUNAMI WARNING CENTER Palmer, Alaska tsunami.gov "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. +6hr • Samalya Passtc Unimak Pass® • Elrisrol..,Bay Point, aska M7.3 Ei At Knit DART4G Chirikof • • Hinchinbrook Entranfeg Cape Sucklingq ncEiscat NTWC tsunami "breakpoints" used to coordinate coastal broad alerting through NWS Public Weather Forecast Zones ' ! -'e% - Q7�• • c . e .F •`4 Jc` 4' r • �s -'1 • , CC (� Q.,C J o sQ wCo Q G• 4 O, • A 0 • • • • A Breakpoints shown: 1- Chignik Bay 2- Kennedy Entrance 3- Hinchinbrook Entrance 3 t,e, • CI L J r'• * f., O.., _ ,.ice.• Qs 1sas Vs • 'b 1 r C Co 4 NATIONAL TSUNAMI WARNING CENTER Palmer, Alaska tsunami.gov FIPS boundary: abc (( )) Inland public weather zone Inland public weather zone Coastal public weather zone Coastal public weather zone ((( Overalerting: Public WEA goes well beyond intended alert regions. FIPS boundary: jkl (()) Inland public weather zone FIPS boundary: stu ((wrth)) j)) Coastal public weather zone Coastal public weather zone FIPS boundary: xy NTWC Breakpoint Segment J Inland public weather zone Inland public weather zone Coastal public weather zone Solution for Kenai Peninsula Borough NATIONAL TSUNAMI WARNING CENTER Palmer, Alaska tsunami.gov Reduce unintentional overalerting due to breakpoint strategy and Census/FIPs boundaries Unimak ass* �r'ch Change for Future Small Sand Point Tsunami Alerts NATIONAL TSUNAMI WARNING CENTER Palmer, Alaska tsunami.gov AK826 "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 Unimak, 5,ass* AK702 a � AK729 K72 AA — Kennedy ' Entrande� Breakpoint locations Specific tsunami alerting strategy change NATIONAL TSUNAMI WARNING CENTER Palmer, Alaska tsunami.gov AK795 Not a true "fix". NTWC is shifting alerting issue to a less active earthquake region* *Note: we cannot predict earthquakes Benefit: *Reduce potential of overalerting using current tools and capabilities. A better systematic fix is being worked on. AK753 AK754 AK756 AK745 11/ A Kennedy , • Entrancep *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 AK762 K77 AK713 Cape SueVrig 75 miles SE et Cordova, Alaska M7.3 tl Cook Inlet public weather zones now included in Hinchinbrook entrance "Breakpoint" Unimak Pass NATIONAL TSUNAMI WARNING CENTER Palmer, Alaska tsunami.gov Challenges: • NWS Weather Zones aren't "Tsunami" zones • Wireless Emergency Alert and EAS require other agency support Attu a Samalga Pass ^ Amchitka Pass Kennedy Entrance Chignik Bay Quick Solution: Shift assigned NWS Weather Zones from one breakpoint to another Cape Suckling Cape Fairweather Salisbury Sound Cape Decision The BC/Alaska Border 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 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. Alaska - Building a We.ther-'eady Nation VIM Lw kkAli Call or Email 24/7/365! anchorage.weather@noaa.gov 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 weather.gov/alaska US National Weather Service Anchorage or nwsntwc @NWSAnchorage or @nws_ntwc How do we communicate with partners? • State Warning Points Local Community Tsunami Warning Centers Tsun�� on NWS WFOs ,EarhF Q,cP roi ** Interagency partners SWP'% NATIONAL TSUNAMI WARNING CENTER Palmer, Alaska tsunami.gov Countdown to cancellation 3:00:00 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. Alert level WARNING ADVISORY Maya TSUNAMI ALERTS Action or inland IMMEDIATELY! Follow evacuation signage Hazard DANGER! A TSUNAMI IS IMMINENT. Flooding & dangerous currents 3+ feet or 1+ mete Stay out of the water and away from the shore STRONG CURRENTS & DANGEROUS WAVES! In or near coastal waters 1-3feet or 0.3 -1 mete Prepare to take action. Monitor local TV, radio, social media, NOAA weather radio A TSUNAMI IS POSSIBLE. Arrival time is several hours away. Prepare now. Alert level may change. Prepare INFORMATION STATEMENT NO action needed NO tsunami impact expected. THREAT MESSAGE: Issued for International Partners; NOT for U.S. Coasts Relax