Tropical cyclone forecasting is the science and art of forecasting where 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's center, and its effects, are expected to be at some point in the future. There are several elements to tropical cyclone forecasting: track forecasting, intensity forecasting, rainfall forecasting, storm surge, and tornado forecasting. While skill is increasing in regards to track forecasting, intensity forecasting skill remains nearly unchanged over the past several years.

Contents

History

The methods through which tropical cyclones are forecast have changed with the passage of time. The first known forecasts in the Western Hemisphere were made by Lt. Col. William Reed of the Corps of Royal Engineers at Barbados in 1847. Reed mostly utilized barometric pressure Atmospheric pressure is the force per unit area exerted against a surface by the weight of air above that surface in the Earth's atmosphere. In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. Low pressure areas have less atmospheric mass above measurements as the basis of his forecasts. Benito Vines introduced a forecast and warning system based on cloud cover changes in Havana Havana (Spanish: La Habana, pronounced [la aˈβana] , officially Ciudad de La Habana,) is the capital city, major port, and leading commercial centre of Cuba. The city is one of the 14 Cuban provinces. The city/province has 2.1 million inhabitants, the largest city in Cuba and the second largest in the Caribbean region. The city extends mostly during the 1870s. Before the early 1900’s, though, most forecasts were done by direct observations at weather stations, which were then relayed to forecast centers via telegraph Telegraphy is the long-distance transmission of written messages without physical transport of letters. It is a compound term formed from the Greek words tele = far and graphein (γραφειν) = write. Radiotelegraphy or wireless telegraphy transmits messages using radio. It wasn’t until the advent of radio Radio is the transmission of signals by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. Information is carried by systematically changing some property of the radiated waves, such as in the early twentieth century that observations from ships at sea were available to forecasters. The 1930’s saw the usage of radiosondes A radiosonde is a unit for use in weather balloons that measures various atmospheric parameters and transmits them to a fixed receiver. Radiosondes may operate at a radio frequency of 403 MHz or 1680 MHz and both types may be adjusted slightly higher or lower as required. A rawinsonde is a radiosonde that is designed to also measure wind speed and in tropical cyclone forecasting. The next decade saw the advent of aircraft-based reconnaissance by the military, starting with the first dedicated flight into a hurricane in 1943, and the establishment of the Hurricane Hunters Hurricane Hunters are manned aircraft that fly into tropical cyclones in the North Atlantic Ocean and Northeastern Pacific Ocean for the specific purpose of directly measuring weather data in and around those storms. In the Western Pacific Ocean and Indian Ocean, the titles of Typhoon Chasers or Typhoon Trackers (Navy) are used for these in 1944. In the 1950’s, coastal weather radars A weather radar, or weather surveillance radar , is a type of radar used to locate precipitation, calculate its motion, estimate its type (rain, snow, hail, etc.), and forecast its future position and intensity began to be used in the United States, and research reconnaissance flights by the precursor of the Hurricane Research Division The Atlantic Oceanographic and Meteorological Laboratory is a laboratory in National Oceanic and Atmospheric Administration's Office of Oceanic and Atmospheric Research (OAR) began in 1954.[1]

With the launch of the first weather satellite, TIROS-I, in 1960, introduced new forecasting techniques that remain important to tropical cyclone forecasting to the present. In the 1970’s, buoys were introduced to improve the resolution of surface measurements, which until that point, were not available at all over sea surfaces.[1]

Track

See also: Tropical cyclone track forecasting Tropical cyclone track forecasting involves predicting where a tropical cyclone is going to track over the next five days, every 6 to 12 hours. The history of tropical cyclone track forecasting has evolved from a single station approach to a comprehensive approach which uses a variety of meteorological tools and methods to make predictions. The See also: Tropical cyclone forecast model Track errors for the Atlantic Basin

The large-scale synoptic flow The synoptic scale in meteorology is a horizontal length scale of the order of 1000 kilometres (about 620 miles) or more. This corresponds to a horizontal scale typical of mid-latitude depressions. Most high and low pressure areas seen on weather maps such as surface weather analyses are synoptic-scale systems, driven by the location of Rossby determines 70 to 90 percent of a tropical cyclone's motion. The deep-layer mean flow is considered to be the best tool in determining track direction and speed. If storms are significantly sheared, use of a lower-level wind is a better predictor. Knowledge of the beta effect can be used to steer a tropical cyclone, since it leads to a more northwest heading for tropical cyclones in the Northern Hemisphere. It is also best to smooth out short term wobbles of the storm center in order to determine a more accurate trajectory.[2]

Because of the forces that affect tropical cyclone tracks, accurate track predictions depend on determining the position and strength of high- and low-pressure areas, and predicting how those areas will change during the life of a tropical system. Combining forecast models with increased understanding of the forces that act on tropical cyclones, and a wealth of data from Earth-orbiting satellites and other sensors, scientists have increased the accuracy of track forecasts over recent decades.[3] An accurate track forecast is important, because if the track forecast is incorrect, forecasts for intensity, rainfall, storm surge, and tornado threat will also be incorrect.

1-2-3 rule

Hurricanes Rita Hurricane Rita was the fourth-most intense Atlantic hurricane ever recorded and the most intense tropical cyclone ever observed in the Gulf of Mexico. Rita caused $11.3 billion in damage on the U.S. Gulf Coast in September 2005. Rita was the seventeenth named storm, tenth hurricane, fifth major hurricane, and third Category 5 hurricane of the and Philippe shown with 1-2-3 rule predictions.

The 1-2-3 rule (mariners' 1-2-3 rule or danger area) is a guideline commonly taught to mariners A sailor, mariner, or seaman is a person who navigates water-borne vessels or assists in their operation, maintenance, or service. The term can apply to professional mariners, military personnel, and recreational sailors as well as a plethora of other uses. Etymologically, the name preserves the memory of the time when ships were commonly powered for severe storm A storm is any disturbed state of an astronomical body's atmosphere, especially affecting its surface, and strongly implying severe weather. It may be marked by strong wind, thunder and lightning (a thunderstorm), heavy precipitation, such as ice (ice storm), or wind transporting some substance through the atmosphere (as in a dust storm, snowstorm, (specifically hurricane 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 and tropical storm 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) tracking and prediction. It refers to the rounded long-term NHC/TPC The National Hurricane Center , located at Florida International University in Miami, Florida, is the division of National Weather Service's Tropical Prediction Center responsible for tracking and predicting the likely behavior of tropical depressions, tropical storms and hurricanes forecast errors of 100-200-300 nautical miles The nautical mile is a unit of length corresponding approximately to one minute of arc of latitude along any meridian. By international agreement it is exactly 1,852 metres (approximately 6,076 feet) at 24-48-72 hours, respectively. However, these errors have decreased to near 50-100-150 as NHC forecasters become more accurate. The "danger area" to be avoided is constructed by expanding the forecast path by a radius equal to the respective hundreds of miles plus the forecast wind radii (size of the storm at those hours).[4]

Intensity

See also: Tropical cyclogenesis Tropical cyclogenesis is the technical term describing the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which mid-latitude cyclogenesis occurs. Tropical cyclogenesis involves the development of a warm-core cyclone, due to

Forecasters say they are less skillful at predicting the intensity of tropical cyclones than cyclone track.[5] They attribute the lack of improvement in intensity forecasting to the complexity of tropical systems and an incomplete understanding of factors that affect their development.

An accurate track forecast is essential to creating accurate intensity forecasts, particularly in an area with large islands such as the western north Pacific and the Caribbean Sea, as proximity to land is an inhibiting factor to developing tropical cyclones. A strong hurricane/typhoon/cyclone can weaken if an outer eye wall forms (typically around 80-160 kilometers (50-100 miles) from the center of the storm), choking off the convection within the inner eye wall. Such weakening is called an eyewall replacement cycle The eye is a region of mostly calm weather found at the center of strong tropical cyclones. The eye of a storm is a roughly circular area and typically 30–65 km in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the most severe weather of a cyclone occurs. The cyclone's lowest barometric pressure occurs in the, and is usually temporary.[6]

Dr. Kerry Emanuel created a mathematical model A mathematical model uses mathematical language to describe a system. The process of developing a mathematical model is termed mathematical modelling . Mathematical models are used not only in the natural sciences (such as physics, biology, earth science, meteorology) and engineering disciplines, but also in the social sciences (such as economics, around 1988, called the maximum potential intensity or MPI, to compute the upper limit of tropical cyclone intensity based on sea surface temperature and atmospheric profiles from the latest global model runs. Maps created from this equation show values of the maximum achievable intensity due to the thermodynamics In science, thermodynamics is the study of energy conversion between heat and mechanical work, and subsequently the macroscopic variables such as temperature, volume and pressure of the atmosphere at the time of the last model run (either 0000 or 1200 UTC Coordinated Universal Time is a time standard based on International Atomic Time (TAI) with leap seconds added at irregular intervals to compensate for the Earth's slowing rotation. Leap seconds are used to allow UTC to closely track UT1, which is mean solar time at the Royal Observatory, Greenwich). It does not take vertical wind shear Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere. Wind shear can be broken down into vertical and horizontal components, with horizontal wind shear seen across fronts and near the coast, and vertical shear typically near the surface, into account.[7]

Rainfall

r-CLIPER for Isabel (2003) See also: Tropical cyclone rainfall forecasting Tropical cyclone rainfall forecasting involves using scientific models and other tools to predict the precipitation expected in tropical cyclones such as hurricanes and typhoons. Knowledge of tropical cyclone rainfall climatology is helpful in the determination of a tropical cyclone rainfall forecast. More rainfall falls in advance of the center

Tropical cyclone rainfall forecasting is important, since between 1970-2004, inland flooding from tropical cyclones caused a majority of the fatalities from tropical cyclones in the United States ^ 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.[8] While flooding A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Flooding may result from the volume of water within a body of water, is common to tropical cyclones near a landmass, there are a few factors which lead to excessive rainfall from tropical cyclones. Slow motion, as was seen during Hurricane Danny (1997) Hurricane Danny was the only hurricane to make landfall in the United States during the 1997 Atlantic hurricane season, and the second hurricane and fourth tropical storm of the season. The system became the earliest 5th tropical or subtropical storm of the Atlantic season when it reached tropical storm strength on July 17, and held that record and Hurricane Wilma Hurricane Wilma was the most intense hurricane ever recorded in the Atlantic basin. Wilma was the twenty-second storm , thirteenth hurricane, sixth major hurricane, and fourth Category 5 hurricane of the record-breaking 2005 season, can lead to high amounts. The presence of topography near the coast, as is the case across much 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, Haiti Haiti (pronounced /ˈheɪti/ ; French Haïti, pronounced: [a.iti]; Haitian Creole: Ayiti, Haitian Creole pronunciation: [ajiti]), officially the Republic of Haiti (République d'Haïti ; Repiblik Ayiti) is a Caribbean country. Along with the Dominican Republic, it occupies the island of Hispaniola, in the Greater Antillean archipelago. Ayiti (land, the Dominican Republic Inhabited by Taínos since the 7th century, the territory of the Dominican Republic was reached by Christopher Columbus in 1492 and became the site of the first permanent European settlement in the Americas, namely Santo Domingo, the country's capital and Spain's first capital in the New World. In Santo Domingo stand, among other firsts in the, much of 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, Madagascar Madagascar, or Republic of Madagascar , is an island nation in the Indian Ocean off the southeastern coast of Africa. The main island, also called Madagascar, is the fourth-largest island in the world, Réunion Réunion (French: La Réunion, IPA: [la ʁeynjɔ̃] ; previously Île Bourbon) is a French island of about 800,000 population located in the Indian Ocean, east of Madagascar, about 200 kilometres (120 mi) south west of Mauritius, the nearest island. Since August 2010, the Pitons, Cirques and Remparts of the island, covering more than 40% of its, China China is seen variously as an ancient civilization extending over a large area in East Asia, a nation and/or a multinational entity, and Japan Japan is an island country in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south. The characters that make up Japan's name mean "sun-origin", which is why Japan is acts to magnify amounts due to upslope flow into the mountains. Strong upper level forcing from a trough moving through the Westerlies, as was the case during Hurricane Floyd Hurricane Floyd was the sixth named storm, fourth hurricane, and third major hurricane in the 1999 Atlantic hurricane season. Floyd triggered the third largest evacuation in US history when 2.6 million coastal residents of five states were ordered from their homes as it approached. The Cape Verde-type hurricane formed off the coast of Africa and, can lead to high amounts even from systems moving at an average forward motion. A combination of two of these factors could be especially crippling, as was seen during Hurricane Mitch Hurricane Mitch was the most powerful hurricane of the 1998 Atlantic hurricane season, with maximum sustained winds of 180 mph . The storm was the thirteenth tropical storm, ninth hurricane, and third major hurricane of the season. At the time, Hurricane Mitch was the strongest Atlantic hurricane observed in the month of October, though it has in 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.[9] Therefore, an accurate track forecast is essential in order to produce an accurate tropical cyclone rainfall forecast.[10]

Storm surge

See also: Storm surge 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,

The main storm surge forecast model in the Atlantic basin is SLOSH, which stands for Sea, Lake, Overland, Surge from Hurricanes.[11] It uses the size of a storm, its intensity, its forward motion, and the topography of the coastal plain to estimate the depth of a storm surge at any individual grid point across the United States ^ 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. An accurate forecast track is required in order to produce accurate storm surge forecasts. However, if the landfall point is uncertain, a maximum envelope of water (MEOW) map can be generated based on the direction of approach. If the forecast track itself is also uncertain, a maximum of maximums (MoM) map can be generated which will show the worst possible scenario for a hurricane of a specific strength.[12]

Tornado

The location of most tropical cyclone-related tornadoes is their northeast quadrant in the Northern Hemisphere and southeast quadrant in the Southern Hemisphere.[13] Like most of the other forecasts for tropical cyclone effects, an accurate track forecast is required in order to produce an accurate tornado threat forecast.

Seasonal forecast

By looking at annual variations in various climate parameters, forecasters can make predictions about the overall number and intensity of tropical cyclones that will occur in a given season. For example, when constructing its seasonal outlooks, the Climate Prediction Center The Climate Prediction Center is one of the National Centers for Environmental Prediction, which are a part of NOAA's National Weather Service. It is located in Camp Springs, Maryland in the United States considers the effects of the El Niño-Southern Oscillation El Niño-Southern Oscillation, or ENSO, is a climate pattern that occurs across the tropical Pacific Ocean on average every five years, but over a period which varies from three to seven years, and is therefore, widely and significantly, known as "quasi-periodic." ENSO is best-known for its association with floods, droughts and other, 25-40 year tropical cycle, wind shear Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere. Wind shear can be broken down into vertical and horizontal components, with horizontal wind shear seen across fronts and near the coast, and vertical shear typically near the surface, over the oceans, and ocean surface temperature.[14]

See also: Atlantic multidecadal oscillation The Atlantic multidecadal oscillation is a mode of variability occurring in the North Atlantic Ocean and which has its principal expression in the sea surface temperature (SST) field. While there is some support for this mode in models and in historical observations, controversy exists with regard to its amplitude, and in particular, the and Tropical cyclone#Long-term_activity_trends 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

See also

Tropical cyclones portal 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

References

  1. ^ a b Robert C. Sheets (June 1990). "The National Hurricane Center—Past, Present and Future" (PDF). Monthly Weather Review 5 (2). http://ams.allenpress.com/archive/1520-0434/5/2/pdf/i1520-0434-5-2-185.pdf. Retrieved 2007-12-07.
  2. ^ U. S. Navy. SECTION 1. INFLUENCES ON TROPICAL CYCLONE MOTION. Retrieved on 2007-04-10.
  3. ^ National Hurricane Center. Annual average model track errors for Atlantic basin tropical cyclones for the period 1994-2005, for a homogeneous selection of "early" models. Retrieved on 2006-11-30.
  4. ^ Central Pacific Hurricane Center. Hurricane Awareness Week 2005. Retrieved on 2007-12-24.
  5. ^ National Hurricane Center. Annual average official track errors for Atlantic basin tropical cyclones for the period 1989-2005, with least-squares trend lines superimposed. Retrieved on 2006-11-30.
  6. ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. Frequently Asked Questions: What are "concentric eyewall cycles" (or "eyewall replacement cycles") and why do they cause a hurricane's maximum winds to weaken? Retrieved on 2006-12-14.
  7. ^ Kerry A. Emanuel. Maximum Intensity Estimation. Retrieved on 2006-10-20.
  8. ^ Ed Rappaport. Inland Flooding. Retrieved on 2006-06-24.
  9. ^ "Are You Ready?". Federal Emergency Management Agency. 2006-04-05. http://www.fema.gov/areyouready/hurricanes.shtm. Retrieved 2006-06-24.
  10. ^ William M. Frank. FIFTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES: Topic 2 TROPICAL CYCLONE LANDFALL PROCESSES. Retrieved on 2007-04-17.
  11. ^ FEMA. Sea, Lake, Overland, Surge from Hurricanes. Retrieved on 2007-04-10.
  12. ^ PC Weather Products. Slosh Data... what is it. Retrieved on 2007-04-15.
  13. ^ Roger Edwards. STORM PREDICTION CENTER FORECAST SUPPORT FOR LANDFALLING TROPICAL CYCLONES. Retrieved on 2007-04-10.
  14. ^ Science Friday, National Public Radio, 21 Aug 2009.

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