Warnings and watches are two levels of alert issued by national weather forecasting Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location. Human beings have attempted to predict the weather informally for millennia, and formally since at least the nineteenth century. Weather forecasts are made by collecting quantitative data about the current bodies to coastal areas threatened by the imminent approach of a tropical cyclone A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones feed on heat released when moist air rises, resulting in condensation of water vapor contained in the moist air. They are fueled by a different heat mechanism than other cyclonic of tropical storm or hurricane intensity. They are notices to the local population and civil authorities to make appropriate preparation for the cyclone, including evacuation of vulnerable areas where necessary. It is important that interests throughout the area of an alert make preparations to protect life and property, and do not disregard it on the strength of the detailed forecast track. Tropical cyclones are not points, and forecasting their track remains an uncertain science.
Contents |
North Atlantic systems
The following terminology used by the US ^ b. English is the de facto language of American government and the sole language spoken at home by 80% of Americans age five and older. Spanish is the second most commonly spoken language National Hurricane Center is the model for countries around the North Atlantic The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about 106,400,000 square kilometres , it covers approximately twenty percent of the Earth's surface and about twenty-six percent of its water surface area. The first part of its name refers to the Atlas of Greek mythology, making the Atlantic the " and in the Caribbean The Caribbean is a region consisting of the Caribbean Sea, its islands , and the surrounding coasts. The region is located southeast of the Gulf of Mexico and North America, east of Central America, and to the north of South America basin (except Cuba The Republic of Cuba (pronounced /ˈkjuːbə/ ; Spanish: República de Cuba, pronounced [reˈpuβlika ðe ˈkuβa] ( listen)) is an island country in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos, see regional notes). This is also used for the Pacific coasts of Mexico In Pre-Columbian Mesoamerica many cultures matured into advanced civilizations such as the Olmec, the Toltec, the Teotihuacan, the Zapotec, the Maya and the Aztec before the first contact with Europeans. In 1521, Spain conquered and colonized the territory, which was administered as the viceroyalty of New Spain which would eventually become Mexico, Central America Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. Central America is considered to be part of the Mesoamerican biodiversity hotspot, excluding the southern portions of Panama, southern California California's geography ranges from the Pacific coast to the Sierra Nevada mountain range in the east, to Mojave desert areas in the southeast and the Redwood–Douglas fir forests of the northwest. The center of the state is dominated by the Central Valley, one of the most productive agricultural areas in the world. California is the most, and Hawaii The state encompasses nearly the entire volcanic Hawaiian Island chain, which comprises hundreds of islands spread over 1,500 miles . At the southeastern end of the archipelago, the eight "main islands" are (from the northwest to southeast) Niʻihau, Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Kahoʻolawe, Maui, and Hawaiʻi. The last is by.
Tropical storms
Before the 1987 Atlantic hurricane season, tropical storm alerts were described as Gale A gale is a very strong wind. There are conflicting definitions of how strong. The U.S. Government's National Weather Service defines a gale as 34 to 47 knots of sustained surface winds. Forecasters typically issue gale warnings when winds of this strength are expected Watches / Warnings, not distinguished from non-tropical storms.
Tropical Storm Watch
A tropical storm watch (TRA) is issued when tropical storm conditions, including winds Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space. Winds are commonly classified by their spatial from 39 to 73 mph (35 to 64 knots, 63 to 117 km/h) pose a possible threat to a specified coastal area within 36 hours. Maritime flags A flag is a piece of fabric, often flown from a pole or mast, generally used symbolically for signalling or identification. It is most commonly used to symbolize a country. The term flag is also used to refer to the graphic design employed by a flag, or to its depiction in another medium indicate this with a single square red flag.
Tropical Storm Warning
A tropical storm warning (TRW) is issued when tropical storm conditions (as above) are expected in a specified coastal area within 24 hours or less. Maritime flags indicate this with two square red flags.
Hurricanes
Hurricane Watch
A hurricane watch (HWA) is issued for a specified area for which a hurricane or a hurricane-related hazard is a possible threat within 36 hours. Maritime flags indicate this with a single square red flag with a black square in the middle.
The purpose of a hurricane watch is to inform families to obtain supplies, secure your home, and be prepared to evacuate.
Hurricane Warning
Hurricane warning flags (USA)A hurricane warning (HWW) is issued when a hurricane with sustained winds of 74 mph (65 knots, 118 km/h) or higher is expected in a specified coastal area in 24 hours or less. Maritime flags indicate this with two square red flags with a black square in the middle of each.
A hurricane warning can remain in effect when dangerously high water Storm surge is an offshore rise of water associated with a low pressure weather system, typically a tropical cyclone. Storm surge is caused primarily by high winds pushing on the ocean's surface. The wind causes the water to pile up higher than the ordinary sea level. Low pressure at the center of a weather system also has a small secondary effect, or a combination of dangerously high water and exceptionally high waves In fluid dynamics, wind waves or, more precisely, wind-generated waves are surface waves that occur on the free surface of oceans, seas, lakes, rivers, and canals or even on small puddles and ponds. They usually result from the wind blowing over a vast enough stretch of fluid surface. Some waves in the oceans can travel thousands of miles before continues, even though the winds may have subsided below hurricane intensity.
Where the intensity or track of a forecast cyclone are uncertain (such as a tropical storm bordering hurricane intensity or on the edge of a track), a Tropical Storm Warning and a Hurricane Watch are often in effect at the same time on parts of the coast. Maritime flags indicate this with two square red flags with a black square in the middle on only one of them.
Inland advisories
The following alerts are issued for inland areas that may see tropical storm or hurricane force wind and/or rain conditions, but are not located along the coast. These started appearing in the 2000s, originally with the word "Wind" inserted before the "Watch" or "Warning", which was dropped for 2005. All appear to be issued with an Emergency Alert System The Emergency Alert System is a national warning system in the United States put into place in 1997, superseding the Emergency Broadcast System (EBS) and the CONELRAD System and is jointly coordinated by the Federal Communications Commission (FCC), Federal Emergency Management Agency (FEMA), and the National Weather Service (NWS). The official EAS event codes HWA and HWW, used for high wind watches and warnings, though they may now be under the same codes and regular tropical cyclone advisories. Previously, standard High Wind Warnings and Watches were issued (which imply tropical storm force or stronger). When they are inland, watches and/or warnings are posted for tropical storm or hurricane force winds today (as known in 2008 by local NWS offices in the USA). Below are the older watches and warnings.
Inland Tropical Storm Watch
Issued for inland areas when sustained winds of 39 to 73 mph (62 to 117 km/h) associated with a tropical storm are anticipated beyond the coastal areas though the actual occurrence, timing and location are still uncertain.
Inland Tropical Storm Warning
Issued for inland counties when tropical storm conditions are anticipated beyond the coastal areas in the next six to twelve hours.
Inland Hurricane Watch
Issued for inland counties that sustained winds of 74 mph (118 km/h) or greater associated with a hurricane are anticipated beyond the coastal areas though the actual occurrence, timing and location are still uncertain.
Inland Hurricane Warning
Issued for inland counties that sustained hurricane force winds are anticipated beyond the coastal areas in the next six to twelve hours.
Other advisories
Other advisories are also commonly issued in association with tropical cyclones, but are not specific to them. Tropical cyclones often produce tornadoes A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. Tornadoes come in many shapes and sizes, but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled, prompting the issuing of severe thunderstorm A thunderstorm, also known as an electrical storm, a lightning storm, or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically-assigned cloud type associated with the thunderstorm is the cumulonimbus. Thunderstorms are usually and tornado watches A tornado watch is issued when weather conditions are favorable for the development of severe thunderstorms that are capable of producing tornadoes. A tornado watch therefore implies that it is also a severe thunderstorm watch. A tornado watch must not be confused with a tornado warning and warnings A tornado warning is an alert issued by government weather services to warn an area that a tornado may be imminent. It can be issued after either a tornado or funnel cloud has already been spotted, or if there are radar indications that a tornado may be possible. When this happens, the tornado sirens may start going off in that area, letting. A wind advisory A gale warning is an advisory or warning issued by the local competent authority in maritime countries about the existence of winds of gale force or above or the imminent occurrence of gales at sea. The purpose of gale warnings is to allow mariners to take precautionary actions to ensure their safety at sea would be issued for inland wind conditions (either at the extreme edges of the storm or far inland) that are strong (at least 25 mph/40 km/h) but sustained below tropical storm force. Heavy rains associated with tropical systems often result in flood watches and warnings. Gale warnings A gale warning is an advisory or warning issued by the local competent authority in maritime countries about the existence of winds of gale force or above or the imminent occurrence of gales at sea. The purpose of gale warnings is to allow mariners to take precautionary actions to ensure their safety at sea are typically issued for coastal areas surrounding the storm but where it is unlikely to travel. Still lighter winds at the extreme fringes carry a small craft advisory.
Regional notes
Before the 2004 Atlantic hurricane season The 2004 Atlantic hurricane season officially began on June 1, 2004, and lasted until November 30, 2004. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. However, the 2004 season exceeded these conventional limits slightly, as Tropical Storm Otto formed on the day before the last, these warnings were not issued in Canada The land occupied by Canada was inhabited for millennia by various groups of Aboriginal peoples. Beginning in the late 15th century, British and French expeditions explored, and later settled, along the Atlantic coast. France ceded nearly all of its colonies in North America in 1763 after the Seven Years' War. In 1867, with the union of three (who simply issued standard wind and rain warnings, which are now issued alongside the NHC-standard warnings). That policy was changed when it appeared that the population did not realize the dangers from four storms in 2003 The 2003 Atlantic hurricane season was an active Atlantic hurricane season with tropical activity before and after the official bounds of the season – the first such occurrence in 50 years. The season produced 21 tropical cyclones, of which 16 developed into named storms; seven cyclones attained hurricane status, of which three reached major that affected different land and offshore areas of Canada, the worst of which was Hurricane Juan in Nova Scotia Nova Scotia's economy is traditionally largely resource-based, but has diversified since the middle of the 20th century. Industries such as fishing, mining, forestry and agriculture remain very important and have been joined by tourism, technology, film, music and finance, even if regular warning bulletins where issued well in advance. The inland watches and warnings are not differentiated from the coastal watches and warnings in Canada; the hurricane and tropical storm watches and warnings can be issued for any forecast area.
In Cuba The Republic of Cuba (pronounced /ˈkjuːbə/ ; Spanish: República de Cuba, pronounced [reˈpuβlika ðe ˈkuβa] ( listen)) is an island country in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos, warnings are issued by province Administratively, Cuba is divided into fourteen provinces and one special municipality, not by coastal location or breakpoints. There are no differentials between coastal and inland warnings there as they are automatically issued for both types of areas.
West Pacific systems
Pearl River Delta
Main article: Hong Kong Tropical Cyclone Warning SignalsThe Pearl River Delta The Pearl River Delta or Zhusanjiao (simplified Chinese: 珠江三角洲; traditional Chinese: 珠江三角洲; pinyin: Zhūjiāng Sānjiǎozhōu) in southern People's Republic of China is the low-lying area alongside the Pearl River estuary where the Pearl River flows into the South China Sea. Since economic liberalisation was adopted by the uses a variety of warning systems to inform the public regarding the risks of tropical cyclones to the area. The Hong Kong Observatory Hong Kong Observatory , known as the Royal Observatory Hong Kong (Chinese: 皇家香港天文台) before 1997, is a department of the Hong Kong Government. The Observatory forecasts weather and issues warnings on weather-related hazards. It also monitors and makes assessments on radiation levels in Hong Kong and provides other meteorological and issues typhoon signals to indicate the existence and approximate location of a tropical cyclone from Hong Kong Hong Kong[note 3] is one of two special administrative regions (SAR) of the People's Republic of China; the other is Macau. Situated on China's south coast and enclosed by the Pearl River Delta and South China Sea, it is renowned for its expansive skyline and deep natural harbour. With a land mass of 1,104 km2 (426 sq mi) and a population of seven. The Direcção dos Serviços Meteorológicos e Geofisicos in Macau Macau , also known as Macao (pronounced /məˈkaʊ/) is one of the two special administrative regions of the People's Republic of China, the other being Hong Kong. Macau lies on the western side of the Pearl River Delta, bordering Guangdong province to the north and facing the South China Sea in the east and south uses a similar system.
China
A two-stage warning system was long-established in China for tropical cyclones of tropical storm intensity of above.[1]
- Warning: Winds may reach Beaufort Force 8 or rainstorm may occur in 48 hours.
- Urgent Warning: Winds may reach Beaufort Force 8 or rainstorm may occur in 24 hours.
Nowadays, the use of this system is restricted to coastal waters only. Thus, similar to the US system, warnings may be discontinued even the cyclone is maintaining tropical storm intensity inland. However, color-coded alerts (mentioned below) may be in effect.
Guangdong introduced a color-coded tropical cyclone warning system for land use in 2000.[2](no longer in use)
- White alert: A tropical cyclone may affect the area in 48 hours.
- Green alert: Winds may reach Beaufort Force The Beaufort scale is an empirical measure for describing wind speed based mainly on observed sea conditions. Its full name is the Beaufort wind force scale 6 in 24 hours or winds of Beaufort Force 6~7 are already blowing.
- Yellow alert: Winds may reach Beaufort Force 8 in 12 hours or winds of Beaufort Force 8~9 (gale force) are already blowing.
- Red alert: Winds may reach Beaufort Force 10 in 12 hours or winds of Beaufort Force 10~11 (storm force) are already blowing.
- Black alert: Winds may reach Beaufort Force 12 in 12 hours or winds of Beaufort Force 12 (hurricane force) are already blowing.
Similar systems were developed in Fujian and Shanghai.
Later, China Meteorological Administration standardized the system for national use.[3] This set is part of a larger warning system that covers other forms of severe weather conditions, such as extreme temperature, torrential rainfall, drought, etc.
- Blue alert: Winds may reach Beaufort Force The Beaufort scale is an empirical measure for describing wind speed based mainly on observed sea conditions. Its full name is the Beaufort wind force scale 6 in 24 hours or winds of Beaufort Force 6~7 are already blowing.
- Yellow alert: Winds may reach Beaufort Force 8 in 24 hours or winds of Beaufort Force 8~9 (gale force) are already blowing.
- Orange alert: Winds may reach Beaufort Force 10 in 12 hours or winds of Beaufort Force 10~11 (storm force) are already blowing.
- Red alert: Winds may reach Beaufort Force 12 in 6 hours or winds of Beaufort Force 12 (hurricane force) are already blowing.
Note that Guangdong maintained a white alert as in the old system.
Philippines
The Philippine Atmospheric, Geophysical and Astronomical Services Administration The Philippine Atmospheric, Geophysical and Astronomical Services Administration is a Philippine national institution dedicated to provide flood and typhoon warnings, public weather forecasts and advisories, meteorological, astronomical, climatological, and other specialized information and services primarily for the protection of life and (PAGASA) releases tropical cyclone warnings in the form of Public Storm Warning Signals (or just storm signals).[4] An area having a storm signal may be under:
- PSWS #1 - Tropical cyclone winds of 30-60 km/h are expected within the next 36 hours. (Note: If a tropical cyclone forms very close to the area, then a shorter lead time is seen on the warning bulletin.)
- PSWS #2 - Tropical cyclone winds of 60-100 km/h are expected within the next 24 hours.
- PSWS #3 - Tropical cyclone winds of 100-185 km/h are expected within the next 18 hours.
- PSWS #4 - Tropical cyclone winds of greater than 185 km/h are expected within 12 hours.
These storm signals are usually heightened when an area (in the Philippines only) is about to be hit by a tropical cyclone. Thus, as a tropical cyclone gains strength and/or gets nearer and nearer to an area having a storm signal, it may be heightened to another higher signal in that particular area. Whereas, as a tropical cyclone weakens and/or gets farther to an area, it may be downgraded to a lower signal or may be lifted (that is, an area will have no storm signal).
See also
- Severe weather terminology
- Tropical cyclone A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones feed on heat released when moist air rises, resulting in condensation of water vapor contained in the moist air. They are fueled by a different heat mechanism than other cyclonic
- storm warning A storm warning generally refers to an advisory issued by an official meteorological department to warn citizens of approaching dangerous weather. A storm watch, on the other hand, typically refers to an advisory issued to indicate that conditions are favorable for the development of dangerous weather patterns, although the dangerous weather
- gale warning A gale warning is an advisory or warning issued by the local competent authority in maritime countries about the existence of winds of gale force or above or the imminent occurrence of gales at sea. The purpose of gale warnings is to allow mariners to take precautionary actions to ensure their safety at sea
- small craft advisory
References
- ^ http://www.typhoon.gov.cn/zhishi4.php
- ^ 广东省热带气旋、暴雨预警信号发布规定
- ^ http://www.cma.gov.cn/cma_new/qxzt/typhoon/tfzs/t20060713_140077.phtml
- ^ The Modified Philippine Public Storm Warning Signals
External links
Categories: Tropical cyclone meteorology These articles cover the meteorology of tropical cyclones. There is a closely related category describing notable cyclones category:tropical cyclones | Weather warnings and advisories
|
901px x 1200px | 95.50kB
[source page]
was due to the small track forecast error and proved to be unnecessary For synoptic history and official watches and warnings please see the Tropical Cyclone Report on Hurricane Felix Mean track and intensity forecast errors for Hurricane Felix blue Black and red lines denote the NHC 10 year mean error and cliper shifor respectively
