The 22 May 1960 Chile tsunami (a) observed at Crescent City, California, and the 28 May 1964 Alaska tsunami (b) observed at Hilo, Hawaii. They illustrating how tsunami amplitude envelopes, together with the tides and other background sea level variations, might form the basis for short-term predictions of tsunami heights during tsunami events. When computed during a tsunami event from earlier waves of the same tsunami, and then compared with inundation thresholds, they would be useful to emergency managers who are responsible for guiding rescue and repair operations and for issuing the clear-all.