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The National Weather Service (NWS) is an agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the purposes of protection, safety, and general information. It is a part of the National Oceanic and Atmospheric Administration (NOAA) branch of the Department of Commerce, and is headquartered in Silver Spring, Maryland, within the Washington metropolitan area. The agency was known as the United States Weather Bureau from 1890 until it adopted its current name in 1970.
A small craft advisory is a type of wind warning issued by the National Weather Service in the United States. In Canada a similar warning is issued by Environment Canada. It is issued when winds have reached, or are expected to reach within 12 hours, a speed marginally less than gale force. A Small Craft Advisory may also be issued when sea or lake ice exists that could be hazardous to small boats.
A tsunami warning system (TWS) is used to detect tsunamis in advance and issue the warnings to prevent loss of life and damage to property. It is made up of two equally important components: a network of sensors to detect tsunamis and a communications infrastructure to issue timely alarms to permit evacuation of the coastal areas. There are two distinct types of tsunami warning systems: international and regional. When operating, seismic alerts are used to instigate the watches and warnings; then, data from observed sea level height are used to verify the existence of a tsunami. Other systems have been proposed to augment the warning procedures; for example, it has been suggested that the duration and frequency content of t-wave energy is indicative of an earthquake's tsunami potential.
The Pacific Tsunami Warning Center (PTWC), located on Ford Island, Hawaii, is one of two tsunami warning centers in the United States, covering Hawaii, Guam, American Samoa and the Northern Mariana Islands in the Pacific, as well as Puerto Rico, the U.S. Virgin Islands and the British Virgin Islands in the Caribbean Sea. Other parts of the United States are covered by the National Tsunami Warning Center.
This article describes severe weather terminology used by the National Weather Service (NWS) in the United States. The NWS, a government agency operating as an arm of the National Oceanic and Atmospheric Administration (NOAA) branch of the United States Department of Commerce (DoC), defines precise meanings for nearly all of its weather terms.
A Tropical Cyclone Formation Alert (TCFA) is a bulletin released by the U.S. Navy-operated Joint Typhoon Warning Center in Honolulu, Hawaii or the Fleet Weather Center in Norfolk, Virginia, warning of the possibility of a tropical cyclone forming from a tropical disturbance that has been monitored. Such alerts are generally always issued when it is fairly certain that a tropical cyclone will form and are not always released before cyclogenesis, particularly if the cyclone appears suddenly. The TCFA consists of several different checks that are performed by the on-duty meteorologist of the system and its surroundings. If the condition being checked is met, a certain number of points are given to the system.
This article describes severe weather terminology used by the Meteorological Service of Canada, a branch within Environment and Climate Change Canada. The article primarily describes various weather warnings, and their criteria. Related weather scales and general weather terms are also addressed in this article. Some terms are specific to certain regions.
Flood stage is the water level or stage at which the surface of a body of water has risen to a sufficient level to cause sufficient inundation of areas that are not normally covered by water, causing an inconvenience or a threat to life and property. When a body of water rises to this level, it is considered a flood event. Flood stage does not apply to areal flooding. As areal flooding occurs, by definition, over areas not normally covered by water, the presence of any water at all constitutes a flood. Usually, moderate and major stages are not defined for areal floodplains.
A significant weather advisory was a hazardous weather statement issued by certain Weather Forecast Offices (WFO) of the National Weather Service (NWS) in the United States to alert the public of thunderstorm activity that is below designated severe criteria for and/or is not expected to produce severe weather. The title assigned to the advisory — alternately titled "significant weather alert" or referenced by its originating product, "special weather statement" — varied by the issuing WFO.
A flood warning is closely linked to the task of flood forecasting. The distinction between the two is that the outcome of flood forecasting is a set of forecast time-profiles of channel flows or river levels at various locations, while "flood warning" is the task of making use of these forecasts to make decisions about whether warnings of floods should be issued to the general public or whether previous warnings should be rescinded or retracted.
Hurricane Felicia was a powerful Category 4 Pacific hurricane whose remnants caused significant rainfall and flooding on the Hawaiian Islands. Felicia was the third strongest tropical cyclone of the 2009 Pacific hurricane season, as well as the strongest storm to exist in the eastern Pacific at the time since Hurricane Daniel in 2006. Forming as a tropical depression on August 3, the storm supported strong thunderstorm activity and quickly organized. It became a tropical storm over the following day, and subsequently underwent rapid deepening to attain hurricane status. Later that afternoon, Felicia developed a well-defined eye as its winds sharply rose to major hurricane-force on the Saffir–Simpson scale. Further strengthening ensued, and Felicia peaked in intensity as a Category 4 hurricane with sustained winds of 145 mph (233 km/h) and a barometric pressure of 935 mbar. After reaching this strength, unfavorable conditions, such as wind shear, began to impact the storm while it took on a northwestward path. Henceforth, Felicia slowly weakened for several days; by August 8 it had been downgraded to a Category 1 hurricane, once again becoming a tropical storm the next day. It retraced westward towards Hawaii on August 10, all the while decreasing in organization. On August 11, Felicia weakened to tropical depression status, and soon degenerated into remnant low just prior to passing over the islands.
A teletsunami is a tsunami that originates from a distant source, defined as more than 1,000 km (620 mi) away or three hours' travel from the area of interest, sometimes travelling across an ocean. All teletsunamis have been generated by major earthquakes such as the 1755 Lisbon earthquake, 1960 Valdivia earthquake, 1964 Alaska earthquake, 2004 Indian Ocean earthquake, 2021 South Sandwich Islands earthquakes, and 2011 Tohoku earthquake.
The 2010 Chile earthquake and tsunami occurred off the coast of central Chile on Saturday, 27 February at 03:34 local time, having a magnitude of 8.8 on the moment magnitude scale, with intense shaking lasting for about three minutes. It was felt strongly in six Chilean regions that together make up about 80 percent of the country's population. According to the United States Geological Survey (USGS) the cities experiencing the strongest shaking—VIII (Severe) on the Mercalli intensity scale (MM)—were Concepción, Arauco, and Coronel. According to Chile's Seismological Service, Concepción experienced the strongest shaking at MM IX (Violent). The earthquake was felt in the capital Santiago at MM VII or MM VIII. Tremors were felt in many Argentine cities, including Buenos Aires, Córdoba, Mendoza, and La Rioja. Tremors were felt as far north as the city of Ica in southern Peru.
The National Tsunami Warning Center (NTWC) is one of two tsunami warning centers in the United States, covering all coastal regions of the United States and Canada, except Hawaii, Guam, the Northern Mariana Islands, Puerto Rico and the U.S. Virgin Islands. Until 2013, it was known as the West Coast and Alaska Tsunami Warning Center.
Hurricane Gil was the first of several tropical cyclones to affect Hawaii during the 1983 Pacific hurricane season. The seventh named storm and third hurricane of the annual season, Gil originated from a tropical depression that developed near Clipperton Island on July 23. Steadily intensifying, it attained tropical storm status six hours later and was upgraded to a hurricane on July 26. After attaining peak intensity on July 27, Gil encountered cooler sea surface temperatures and began to weaken. Moving west-northwest, the weakening system also accelerated and on July 31, was downgraded to a tropical depression. However, Gil began to re-intensify on August 1, becoming a tropical storm again later that day. Initially expected to veer north of Hawaii, it continued west-northwest and began to approach the Hawaiian group on August 3. While passing through the island group, Gil reached its secondary peak intensity. Subsequently, Gil began to weaken once again as it threatened the Northwestern Hawaiian Islands. After passing through the islands, Gil was downgraded to a tropical depression on August 5. Several hours later, the storm dissipated. The remnants of the storm moved into the West Pacific late on August 6 and were last noted the next morning while passing south of Midway Island.
The 2014 Aleutian Islands earthquake occurred on 23 June at 11:53 HDT (UTC-9) with a moment magnitude of 7.9 and a maximum Mercalli intensity of VIII (Severe). The shock occurred in the Aleutian Islands – part of the US state of Alaska – 19 miles (31 km) southeast of Little Sitkin Island.
Hurricane Darby was a strong tropical cyclone which affected Hawaii as a tropical storm. The fifth named storm of the busy 2016 Pacific hurricane season, Darby originated from a low pressure area that developed in the Eastern Pacific well southwest of Mexico during July 2016. It gained sufficient organization to be declared a tropical depression on July 11, and was upgraded to Tropical Storm Darby the next day. Further intensification ensued, and Darby became a hurricane on July 13. Over the next three days, Darby slowly strengthened to Category 3 status on the Saffir–Simpson scale, becoming a major hurricane. Cool waters and dry air caused Darby to weaken over the next three days, although Darby managed to restrengthen slightly on July 21 before weakening once again as the storm neared Hawaii. Just after midnight on July 24, Darby made landfall on the Big Island. Darby weakened into a remnant low two days later.
Hurricane Olivia was a Category 4 hurricane that impacted Hawaii as a weakening tropical storm in mid-September 2018, causing severe flooding and wind damage. Olivia was the first tropical cyclone to make landfall on Maui and Lanai in recorded history. It was the fifteenth named storm, ninth hurricane, and sixth major hurricane of the 2018 Pacific hurricane season.
An Ashfall advisory is a weather advisory issued by the National Weather Service of the United States. Ashfall advisories are issued when there is a likely future or present occurrence of ash rain caused by a large plume of suspended airborne ash, typically caused by large fires or volcanic activity. The National Weather service map color is Dark Grey.
An earthquake occurred off the coast of the Alaska Peninsula on July 28, 2021, at 10:15 p.m. local time. The large megathrust earthquake had a moment magnitude of 8.2 according to the United States Geological Survey (USGS). A tsunami warning was issued by the National Oceanic and Atmospheric Administration (NOAA) but later cancelled. The mainshock was followed by a number of aftershocks, including three that were of magnitude 5.9, 6.1 and 6.9 respectively.
References
- ↑ "Understanding Tsunami Alerts". National Weather Service . Retrieved January 12, 2022.
This article incorporates text from this source, which is in the public domain . - ↑ Source – Pacific Tsunami Warning Center
