ZCZC PWMWRKPNS DEF TTAA00 KPWM DDHHMM MEZ007>009-012>014-018>022-023>028-NHZ001>010-013-014-241200 PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE GRAY ME 700 AM EST WED MAR 23 2011 The National Weather Service and the National Oceanic and Atmospheric Administration have declared the week of March 20th through 26th Tsunami Awareness Week in Maine and New Hampshire, as well as in the remainder of the coastal United States. ...THE GULF OF MAINE TSUNAMI THREAT... Tsunamis and tsunami-like waves can either enter the Gulf of Maine from the open waters of the Atlantic or originate in the Gulf of Maine. Those originating outside the Gulf of Maine would produce small but potentially dangerous and damaging impacts along the entire Northern New England coast. Those originating in the Gulf of Maine would also produce small but potentially dangerous and damaging impacts but only along a very localized portion of the coast. TSUNAMI WAVES ENTERING THE GULF OF MAINE... The Northern New England coast and the Gulf of Maine are somewhat protected from a major tsunami threat by the shallow waters of Georges Bank and the continental shelf . When tsunami waves generated outside the Gulf of Maine encounter the shallow waters of Georges Bank, a portion of the wave energy is reflected back out to sea. Much of the wave energy entering the Gulf of Maine would come through the Northeast Channel and the Great South Channel. Because of the deeper waters in these channels, the waves would move faster in the channels than in the shallower waters on either side. This would cause much of the tsunami wave energy to be refracted to the right and left of the channels. As a result, much of the tsunami wave energy entering the Gulf of Maine initially would move toward the Georges Bank and Nova Scotia. However, additional reflections and refractions of this wave energy would lead to very rapid and chaotic fluctuations of water levels in the Gulf of Maine that could last for more than 6 hours. These fluctuations could cause strong, dangerous, and damaging currents along the coast and could cause some minor inundation at the time of high tide. The two most significant tsunami sources outside the Gulf of Maine would be a major earthquake along the subduction zone of the Puerto Rican Trench (just to the north of Puerto Rico) or a large sediment slide on the continental slope of the East Coast. In the case of the Puerto Rican Trench, much of the tsunami wave energy would be directed north toward the Gulf of Maine. Travel time from the initial quake until the tsunami wave reached the coast would be about 5 to 6 hours, allowing plenty of time for a warning or advisory. Although dangerous and damaging, the impacts to northern New England of a tsunami generated along the Puerto Rican Trench would be relatively small compared to the potentially devastating impacts on Puerto Rico and Bermuda. The other source outside the Gulf of Maine would be a large sediment slide or slump on the continental slope. The exact impacts of slide or slump would depend on the orientation of the slide or slump with respect to the Northeast and Great South Channels and magnitude of the slide or slump. TSUNAMI WAVES GENERATED IN THE GULF OF MAINE... Similar to tsunamis initiated outside the Gulf of Maine, sediment slides or slumps in the Gulf of Maine could cause localized tsunami waves. In the Gulf of Maine, slides or slumps most likely would be near the coast or along the northern edge of one of the banks or ledges. In either case, the exact impacts of the tsunami waves would depend on the orientation and magnitude or the slide or slump and would affect only a localized area. These slides and slumps and the subsequent tsunami waves would occur without warning. Although technically not a tsunami, tsunami-like waves can develop in certain specific weather situations. These "meteo-tsunamis" develop when an atmospheric pressure wave moves at just the right speed across the Gulf of Maine, creating a resonance with a developing tsunami-like ocean wave below. This resonance would allow the ocean wave to grow with time as both waves move in unison. Since the forward speed of the tsunami-like wave is determined by the depth of the ocean, the atmospheric feature needs to move at the just the right speed as determined by the ocean depth. In the Gulf of Maine, very fast moving weather systems could meet this requirement. In addition, the movement of both the atmospheric and the tsunami-like waves would need to be toward the coast. While rare, meteo-tsunamis do occur in the Gulf of Maine. In fact, a meteo-tsunami is believed to have caused the unusual tidal fluctuations that were observed along the mid-coast in October 2008. JENSENIUS NATIONAL WEATHER SERVICE GRAY, MAINE NNNN