The Pacific Tsunami Warning Center (PTWC) is one of two tsunami warning centers that are operated by NOAA in the United States. Headquartered in ‘Ewa Beach, Hawaii, the PTWC is part of an international tsunami warning system (TWS) program and serves as the operational center for TWS of the Pacific issuing bulletins and warnings to participating members and other nations in the Pacific Ocean area of responsibility. It is also the regional (local) warning center for the State of Hawaii. The other tsunami warning center is the National Tsunami Warning Center (NTWC) in Palmer, Alaska, serving all coastal regions of Canada and the United States except Hawaii, the Caribbean Sea & Gulf Of Mexico.
The PTWC was established in 1949, following the 1946 Aleutian Island earthquake and a tsunami that resulted in 165 casualties in Hawaii and Alaska. After the 2004 Indian Ocean earthquake and tsunami, PTWC has extended its warning guidance to include the Indian Ocean, Caribbean and adjacent regions until regional capability is in place for these areas. These regional systems will form a global tsunami warning system once they are in operation.
The PTWC uses seismic data as its starting point, but then takes into account oceanographic data when calculating possible threats. Tide gauges in the area of the earthquake are checked to establish if a tsunami has formed. The center then forecasts the future of the tsunami, issuing warnings to at-risk areas all around the Pacific basin if needed. There are never false alarms—if the PTWC issues a tsunami warning for a particular area, the tsunami is already on its way and will hit. As it takes more time for tsunamis to travel trans-oceanic distances, the PTWC can afford to take the time to make sure of its forecasts.