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Weather Forecasting Models, Methods and Applications AA Iseh

Weather Forecasting Models, Methods and Applications AA Iseh

International Journal of Engineering & Technology (IJERT) ISSN: 2278-0181 Vol. 2 Issue 12, December - 2013

Weather Models, Methods and Applications AA Iseh. A. J.1* Woma. T. Y.1,2 1. Department of Pure & Applied Physics, Federal University Wukari, Taraba State. P. M. B. 1020 Wukari, Taraba State. 2. Department of Pure & Applied Physics, Federal University Wukari, Taraba State. P. M. B. 1020 Wukari, Taraba State.

ABSTRACT data, forecasting methods and modelling is a applications. computer program that provides meteorological information for future 1.0 INTRODUCTION at given locations. In modern forecasting models, Numerical Weather Prediction is mostly applied and this Modern society’s ever-increasing demand means, “a set of simplified equations used for more accurate weather forecasts is to calculate changes in atmospheric evident to most people. The spectrum of conditions”. The act of writing these needs for weather predictions ranges from equations, imposing the boundary the general public’s desire to know if for conditions and solving them using super instance, the weekend will permit an computers, is known as numerical outing at the beach, or an organization’s modelling. An example of such equations rally, or an outdoor wedding reception. Such diverse industries as airlines and fruit is the Hypsometric equation given as PI = growers depend heavily on accurate POexp–gz/RT. Computerized numerical models are designed for different intervals weather forecasts to have an idea of what which are known as global models underIJERT IJERTtheir next schedule of would appear which we have long range forecast and to be or if the weather will be suitable for medium range forecast, and regional harvesting. In addition, in developed models under which we have the short countries, the designs of buildings, and range forecast. The methods include many industrial facilities rely heavily on a persistence, climatologic, looking at the sound knowledge of the . , use of , , use of Weather forecasting can be defined as the forecasting models, analogue and act of predicting future weather conditions . Forecasting could be or an attempt to indicate the weather applied in air traffic, alerts, conditions which are likely to occur. marine, , utility companies, private sector and application. Weather forecasting is the application of Weather forecasting is a complex and and Technology to predict the challenging science that depends on the state of the atmosphere for a future efficient interplay of weather observation, and a given location. Human beings have data analysis by and attempted to predict the weather computers, and rapid communication informally for millennia, and formally system. since at least the nineteenth century. Weather forecasts are made by collecting Key words: Weather, weather qualitative data about the current state of prediction, forecast, forecasting models, the atmosphere and using scientific understanding of atmospheric processes to

IJERTV2IS120198 www.ijert.org 1945 International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 Vol. 2 Issue 12, December - 2013

project how the atmosphere will evolve 2.0 HOW MODELS CREATE within the next few hours. FORECASTS Once, an all-human endeavour based mainly upon changes in barometric 2.1 Data collection , current weather conditions and Since invention of the first weather sky conditions, forecast models are now instruments in the seventeenth century used to determine future conditions. A weather observation has undergone model, in this context, is a computer considerable refinement. Denser program that produces meteorological monitoring networks, more sophisticated information for future times at given instruments and communication systems, positions and altitudes. The horizontal and better-trained weather observers, have domain of a model is either global, produced an increasingly detailed, reliable covering the entire , or regional, and representative record of weather and covering only part of the earth. Regional . In weather forecasting, data models also are known as limited area collection has been divided into two models. Human input is still required to categories namely: pick the best possible forecast model to i. Surface weather observations base the forecast upon, which involves ii. Upper-air weather observations. pattern recognition skills, knowledge of model performance and knowledge of model . The chaotic of the Surface Weather Observations atmosphere, error involved in measuring Surface weather observations are the the initial conditions, an incomplete fundamental data used for safety as well as understanding of atmospheric processes climatological reasons to forecast weather mean that forecast become less accurate as and issue warnings worldwide. They can the difference in current time and the time be taken manually by a weather observer, for which the forecast is being made by computer through observers to augment increases. IJERTIJERTthe otherwise automated . There are a variety of end users to weather Referring to Lutgens and TarBuck (1989), forecasts. Weather warnings are important a vast network of weather stations required forecasts because they are used to protect to produce a weather chart will encompass and property. Forecasts based on enough to be useful for short-range and are forecasts. On a global scale, the World important to agriculture, and therefore to meteorological organization, which commodity traders within stock markets. consists of over 130 nations, is responsible Temperature forecasts are also used by for gathering the needed data and utility companies to estimate demand over producing some general prognostic charts. coming days. On an everyday basis people use weather forecasts to determine what to Surface weather observations of wear on a given day. Since in recent time , temperature, in Uyo – Nigeria for example, outdoor speed and direction, , activities are severely curtailed by heavy are made near the earth’s , forecasts can be used to plan surface by trained observers or automatic activities around these events, and to plan weather stations. The World ahead and survive them. meteorological Organization acts to standardize the instrumentation, observing practices and timing of those observations worldwide. By international agreement, the regular synoptic observations are made every six hours beginning at midnight

IJERTV2IS120198 www.ijert.org 1946 International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 Vol. 2 Issue 12, December - 2013

Greenwish Mean Time (0000GMT, of points where there are processed by a 0600GMT, 1200GMT and 1800GMT) Central weather analysis organization. each day. In addition, observations for Three locations have been designated by aviation purposes are made at many the World Meteorological Organization as airports every hour, or more often if the World Meteorological Centers, these are weather is changing rapidly. Specialized located in Melbourne, Australia; Moscow, observations may also be made under Russia; and Washington, D.C. U.S.A. In certain conditions for agricultural, addition, most countries maintain national industrial, research, or other purposes centers, where the basic weather needs of (Miller and Thompson, 1975). the domestic economy are met. In Nigeria, the National Meteorological Center is located in Abuja. Upper-air weather observations Measurements of temperature, humidity 2.1.1 and and wind above the surface are found by analysis launching on weather In order to do their work, most numerical balloons. is a unit for use in models look at the atmosphere as a series weather balloons that measures various of boxes. In the middle of each box is a atmospheric parameters and transits them point for which the model actually to a fixed receiver. Radiosondes may calculates weather variables and makes operate at a frequency of 403MHz or forecasts. The result of this three 1680MHz and both types may be adjusted dimensional boxing up of the atmosphere slightly higher or lower as required. is known as the grid; the point in the Mohan and Morgan (1991) states that, the middle is the grid point, and the distance instrument transmits to the ground station between one point and another is called the vertical profiles of air temperature, grid spacing (Ackerman and Knox, 2003). pressure, and relative humidity up to an altitude of about 30km. In addition, Grid point models of the atmosphere can at various levels are computed by trackingIJERT IJERTget fussy when the data in the initial the balloons with a radio direction finding conditions is not obtained at exactly the antenna. location of the grid point. Also, the process of creating an evenly spaced data set from Upper-air weather data are also obtained irregularly spaced observations is called by , dropwind sondes, , and interpolation. . Increasingly, data from weather satellites are being used because of their Ackerman and Knox (2003) then say that, almost global coverage. Although their the multiple jobs of interpolating and visible light images are very useful for smoothing the data for use in numerical forecasters to see development of , models are collectively called data little of this information can be used by assimilation. numerical weather prediction models. The During the data assimilation process, data however, can be used as it information gained from the observations gives information on the temperature at is used in conjunction with a numerical the surface and tops. Individual model’s most recent forecast for the time clouds can also be tracked from one time that observations were made, since this to the next to provide information on wind contains information from previous direction and strength at the clouds observations. This is used to produce a steering level. three-dimensional representation of the Miller and Thompson (1975) agrees that, temperature, moisture and wind called a the observations are collected at a meteorological analysis. This is the models estimate of the current state of the

IJERTV2IS120198 www.ijert.org 1947 International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 Vol. 2 Issue 12, December - 2013

atmosphere. Data assimilation proceeds by Referring to the work of Houghton (1986), analysis cycles. In each analysis cycle, the task of writing the equations and the observations of the current (and possibly, boundary conditions in a suitable form and past) state of a system are combined with then of solving them with high speed the result from and mathematical model digital computers is known as numerical (the forecast) to produce an analysis, modeling. By comparing the behaviour of which is considered as “the best” estimate the model with that of the real atmosphere, of the current state of the system. This is the validity of the procedures employed by called the analysis step. Essentially, the the model is tested. The most important analysis step tries to balance the application of numerical modeling is the in the data and in the forecast. development of methods sufficiently The model is then advanced in time and its reliable and sufficiently fast to be used in result becomes the forecast in the next routine weather forecasting. analysis cycle. There are numerous equations employed in 2.1.2 Numerical weather prediction this work of forecasting models one of which is the hypsometric equation which Linacre and Geerts (1997) define can be derived from the hydrostatic Numerical Weather prediction (NWP) as a equation written as simplified set of equations called the g primitive equation used to calculate dP = -P dZ - (1) changes of conditions. Modern weather RT forecasting relies heavily on numerical We can simplify equation (1) by dividing weather prediction. through with P to have According to Lutgens and TarBuck (1989), dP −g the word “numerical” is misleading, for all = dZ - (2) P RT types of weather forecasting are based on some quantitative data and therefore could IJERTIntegrating the right hand side of equation fit under this heading. Numerical weatherIJERT (2) from P to P and the left hand side prediction is based on the fact that the 0 1 from Z0 to Z1, we have: of the atmosphere obey a number of known physical principles. Ideally, these P dP −g Z 1 = 1 dZ + C physical laws can be used to predict the P0 P RT Z0 future state of the atmosphere, given the current conditions. This situation is Let C = 0 analogues to predicting future position of −g InP P1 = Z Z1 the based on physical laws and the P0 RT Z0 knowledge of its current position. Still, the −g large number of variables that must be → InP1 – InP0 = (Z1 – Z0) included when considering the dynamic RT

atmosphere makes this task extremely −g → In (P1/P0) = (Z1 – Z0) - (3) difficult. RT

Manipulating the huge data sets and Taking the exponent of both sides of performing the complex calculations equation (3), we have: necessary to do this (weather prediction) on resolution fine enough to make the −g 푒In(P1 P0) = 푒[ RT (Z1 – Z0)] result useful requires the use of some of the most powerful . −g [ (Z1 – Z0)] P1 P0 = 푒 RT

IJERTV2IS120198 www.ijert.org 1948 International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 Vol. 2 Issue 12, December - 2013

−g [ (Z1 – Z0)] which are too slow to be important in short → P1 = P0푒 RT range weather forecasting. At level, Z = 0. Thus, Meteorological bureaux now regularly 0 provide seasonal outlook, with an accuracy –g Z notably enhanced by increased [ 1 ] P1 = P0푒 RT - (4) understanding of the relevance of the southern oscillation, indicated by the sea Equation (4) is the Hypsometric equation, surface , the strength of the which gives the pressure P of the I , the location of areas of day atmosphere at a particular height Z , 1 convention across the tropical Pacific , and the depth of themocline. Where P0 is the pressure at the sea level, g is acceleration due to gravity. But of all these three types of numerical weather prediction, Mohan and Morgan R is the molar constant and (1991) say that actually, when viewed with the objectivity of statistical analysis, short- T is the temperature at the surface range weather forecasting is surprisingly more accurate probably because of the Mohan and Morgan (1991) agree with short range of time within which this Barry and Chorley (1992) that, some forecast is made for. computerized numerical models of the atmosphere are designed to operate over The most modern models of weather data different spatial scales depending on the processing systems for the two categories forecast range. For medium range forecasts of numerical models are as follows: (up to 10 days), observational data are fed into the computer from all over the globe, Global models: Some of the better-known since within that forecast range a weather global numerical models are: system may travel long distances. On the other hand, for short-range forecasts (up toIJERT IJERT1. (GFS) – 3 days), the model utilizes data drawn Developed by the National from a more restricted region of the globe. Organization for the Atmosphere in Compared to a global model, a regional America. Output is freely available. model offers the advantage of greater 2. NOGAPS – Developed by the US resolution of data over a smaller area of Navy to compare with the GFS interest. 3. Global Environmental Multi-scale As it is, there are basically three types of Model (GEM) – Developed by the numerical weather prediction models meteorological service of Canada namely: short-range forecasts, medium range forecast (as briefly discussed by 4. European Centre for Medium Mohan and Morgan, 1991; and Barry and Range Weather Forecasts Chorley, 1992 above), and long range (ECMWF) – a model run by the forecast. Europeans with limited availability Thus, Linacre and Geerts(1997) describes 5. UKMO – Developed by the United long range forecasts as descriptive Kingdom Meteorological Office. forecasts which are made for times of ten Limited availability, but is hand to thirty days or one to four months (a corrected by professional seasonal outlook). Also, use is made of a forecasters. dynamical numerical weather prediction model which allows for oceanic processes, 6. GME – developed by the German Weather Service

IJERTV2IS120198 www.ijert.org 1949 International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 Vol. 2 Issue 12, December - 2013

7. ARPEGE – developed by the 6. High Resolution Limited Area French Weather Service, Meteo Model (HIRLAM) France. 7. GEM – LAM – Global Environmental Multi-scale Limited 8. Intermediate General Circulation Area Model model (IGCM) – developed by 8. Aladin: The high resolution limited members of the Department of area hydrostatic and non- at the University of hydrostatic model developed Reading. operated by several European and North African countries under the Regional models: Some of the better- leadership of Meteo-France. known regional numerical models are: 9. COSMO: The COSMO Model, 1. The Weather Research and formerly known as LM, aLMD or Forecasting (WRF) Model was LAMI, is a limited area non- developed co-operatively by NCEP hydrostatic model developed and the meteorological research within the framework of the community. WRF has several consortium for small scale configurations including: modelling (Germany, Switzerland, Italy, Poland and Greece). a. WRF – NMM: The ERF www.wikipedia.com. Non-hydrostatic Mesoscale According to Linacre and Geerts (1997), Model is the primary short- the advantage of numerical weather term weather forecast prediction is that it avoids errors of human model for the United State, judgment in deriving the prognosis, and can be steadily improved by enlarging the b. AR-WRF: Advanced amount and reliability of input data, by Research WRF developed new understanding of the Physics of primarily at the United State atmospheric change, and by faster, larger National Center forIJERT IJERTcomputers. (NCAR) 2.1.3 Model Output Post Processing 2. The North American Mesocale Model (NAM) The raw output is often modified before 3. Colorado State University for being presented as the forecast. This can numerical simulations of be in the form of statistical techniques to atmospheric meteorology and other remove known biases (a term used to environmental phenomena on describe a tendency or preference towards scales from metres to hundreds of a particular perspective, ideology or result) kilometres in the model, or its adjustment to take into 4. MMS – The fifth Generation account consensus among other numerical mesoscale model weather forecast. MOS or Model Output 5. The Advanced Region Prediction Statistics is a technique used to interpret System (ARPS) – developed at the numerical model output and produce site- University of Oklahoma. It is a specific guidance. This guidance is comprehensive multi-scale non- presented in coded numerical form, and hydrostatic simulation and can be obtained for nearly all National prediction system that can be used Weather Service reporting stations. for regional scale weather prediction up to the tornadscale simulation and prediction.

IJERTV2IS120198 www.ijert.org 1950 International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 Vol. 2 Issue 12, December - 2013

3.0 FORECASTING PROBLEMS i. Imperfect data: The data of today’s numerical models still An important goal of all scientific includes a large helping of endeavour is to make accurate predictions. radiosonde observations. However, The physicist or chemist who conducts an the number of radiosonde sites in in the laboratory does so in the the World over has actually hope of discovering certain fundamental declined over the past few decades. principles that can be used to predict the Developed countries in the world outcome of other based on today, spend more money in those principles. In fact, most of the laws launching weather satellites than of science are merely very accurate for boring weather balloons. predictions concerning the outcome of data are global in average, certain kinds of experiments. But few but researchers in data assimilation physical scientists are faced with more are still trying to figure out how complex or challenging prediction this data can be “digested” properly problems than the meteorologist. by the models. In addition, In the first place, the meteorological important meteorological features laboratory covers the entire globe, so that still evade detection, especially even the problem of measuring the present over the . The model results state of the atmosphere is tremendous. are only as good as the data in its Furthermore, the surface of the earth is an initial conditions. irregular combination of land and water, ii. Faulty “vision” and “fudges”: each responding in a different way to the Today’s forecasts also involve an – the . Then, too, the inevitable trade-off between atmosphere itself is a mixture of gaseous, horizontal resolution and the length liquid, and solid constituents, many of of the forecast. This is because fine which affect the energy balance of the resolution means lots of point at earth, one of them, water, is continually which to make calculations. This changing its state. Also, the circulations ofIJERT IJERTrequires a lot of computer time. A the atmosphere range in size from forecast well into the future also extremely large ones, which may persist requires millions or billions more for weeks or months, to minute whirls, calculations. If fine resolution is with life spans of only a few seconds. combined with a long range forecast, the task would choke the According to Miller and Thompson (1975) fastest supercomputers today. One and Ayado and Burt (2001) the problem of would not get forecasts for weeks. forecasting then, involves an attempt to Future improvement in computing observe, analyze and predict the many will help speed things up. interrelationships between the solar energy In the meantime, however, some source, the physical feature of the earth, models are still not able to pick or and the properties and motions of the “see” small-scale phenomena such atmosphere. This is the basis on which a clouds, raindrops, and weather forecasts still go wrong today. snowflakes. To compensate for this fuzzy “vision” of models, the Ackerman and Knox (2003) points out computer code includes crude reasons why forecasts still go wrong today approximations of what is not by stating that the limitations which being seen. These are called directly relates to today’s numerical parameterizations. Even though forecast models are as follows: much science goes into them, these approximations are nowhere close to capturing the complicated reality

IJERTV2IS120198 www.ijert.org 1951 International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 Vol. 2 Issue 12, December - 2013

of the phenomena. This is because; when it is steady state, such as during the the smallest scale phenomena are in the . This method often the most daunting to of forecasting strongly depends upon the understand. Therefore, it is not an presence of a stagnant weather pattern. It insult to ’ abilities to can be useful in both short-range forecasts say that parameterizations are and long-range forecasts. “fudges” of the actual phenomena. Persistence forecasts are used by local iii. Chaos: It will be surprising to note forecasters in determining such events as that, even if a which the time of the arrival of a could do quadrillions of that is moving toward their region. calculations each second were to be Persistence forecasts do not account for invented, no better forecasting changes that might occur in the intensity or result would still be gotten. Brute in the path of a weather system, and they force numerical weather do not predict the formation. Because of forecasting with extremely fine these limitations and the rapidity with resolution has its limits. which weather system change in most geographical regions, persistence forecasts The reason for these limits is a break down after twelve hours, or a day at curious property of complex, most. evolving systems like the atmosphere. It is called “Sensitive 4.2 forecasting dependence on initial conditions”, Whereas persistence forecasting is most and is a hallmark of what is accurate over short periods (before factors popularly known as . for change have had time to operate), the Chaos in the atmosphere does not best estimate of the weather a long time mean that everything is a mess; ahead is the average value of past instead, it means that the measurements there at that time of day and atmosphere both in real life and in IJERTyear. a computer model may read veryIJERT differently to initial conditions that Climatology forecast relies on the are only slightly different. observation that weather for a particular day at a location does not change much Because we do not know the from one year to the next. As a result, a atmospheric conditions perfectly at long term average of weather on a certain any time, chaos means that the day or month should be a good guess as resemblance between a model’s the weather for that day or month. The forecast and reality will be less and most obvious climatology forecast in this less with each passing day. part of the world (Nigeria) is, “Cold in December, warm in July (the popular July 4.0 METHODS OF WEATHER break)”. One does not need to be a FORECASTING meteorologist to make that forecast. Of course for weather forecast to exist Today’s numerical forecast methods still there must be methods on which it is done. use climatological statistics as a “reality These methods are as follows: check”. There make sure that the computer 4.1 Persistence forecasting models are not going off the deep end, climatologically speaking. Persistence forecasting is the easiest method of forecasting which assumes a continuation of the present. It relies upon today’s conditions to forecast the weather

IJERTV2IS120198 www.ijert.org 1952 International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 Vol. 2 Issue 12, December - 2013

4.3 Looking at the sky necessitating site-specific forecasts. Along with pressure tendency, use of the Included in this category are sky condition is one of more important , gust fronts, tornadoes, high weather parameters that can be used to winds especially along coasts, over lakes forecast weather in mountainous areas. and mountains, heavy and freezing Thickening of or the invasion precipitation. The development of radar of a higher cloud deck is indicative of networks, new instruments and high speed in the near future. Morning portends communication links has provided a means fair conditions, as rainy conditions are of issuing warnings of such phenomena. preceded by wind or clouds, which prevent Several countries including Nigeria have fog formation. The approach of a line of recently developed integrated satellite and thunderstorm could indicate the approach radar systems to provide information on of a . Cloud free are the horizontal and vertical extent of indicative of fair weather for the near thunderstorms, for example. Such data are, future. The use of sky cover in weather supplemented by networks of automatic prediction has led to various weather stations that measure wind, over the centuries. temperature and humidity. 4.4 Use of a barometer Nowcasting methods use highly automated Using barometric pressure and the pressure computers and image analysis systems to tendency (xthe change of pressure over integrate data from a variety of sources time) has been used in forecasting since rapidly. Interpretation of the data displays th the late 19 century. The larger the change requires skilled personnel and or extensive in pressure, especially, if more than software to provide appropriate 2.54mmHg, the larger the change in information. The prompt forecasting of weather can be expected. If the pressure and hazards at drop is rapid, a low- is airports is one example of the importance approaching, and there is a greater chance IJERTof nowcasting procedures. of rain. Rapid pressure rises are associatedIJERT with improving weather conditions, such 4.6 Use of Forecasting Models as clearing skies. In the past, the human forecasters were 4.5 Nowcasting responsible for generating the entire weather forecast based upon available The forecasting of the weather within the observation. Today, human input is next six hours is often referred to as generally confined to choosing a model nowcasting. In this time range, it is based on various parameters, such as possible to forecast smaller features such model biases and performance. Using a as individual showers and thunderstorms consensus of forecast models, as well as with reasonable accuracy, as well as other ensemble members of the various models, features too small to be resolved by a can help reduce forecast error. However, computer model. A human given the latest regardless how small the average error radar, satellite and observational data will becomes with any individual system, large be able to make a better analysis of the errors within any particular piece of small scale features present and so will be guidance are still possible on any given able to make a more accurate forecast for model run. Humans can use knowledge of the following few hours. local effects, which may be too small in Severe weather is typically short-lived size to be resolved by the model to add (less than two hours) and, due to its information to the forecast. mesoscale character (less than one hundred kilometers), it affects local/regional areas

IJERTV2IS120198 www.ijert.org 1953 International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 Vol. 2 Issue 12, December - 2013

4.7 Analogue Forecasting The main problem with this method may The analogue method is a complex way of well be the lack of complete enough making a forecast, requiring the forecaster information, which also of course, limits to remember a previous weather event the usefulness of numerical weather which is expected to be mimicked by an predictions. upcoming event. The analogue forecaster’s 4.8 Ensemble Forecasting task is to locate the date in history when the weather is a perfect match, or Although a forecast model will predict analogue, to today’s weather. Then the weather features evolving realistically into forecast for tomorrow is simple – whatever the distant future, the errors in a forecast happened in the day after the analogue will will inevitably grow with time due to the be the weather for tomorrow. The forecast chaotic nature of the atmosphere and the for is whatever inexactness of the initial observations. The happened in the second day after the detail that can be given in a forecast analogue, and so forth. therefore decreases with time as these What makes it a difficult method to use is errors increase. These become a point that, there is rarely a perfect analogue for when the errors are so large that the an event in the future. In fact, no two forecast has no correlation with the actual patterns or sequences of weather are ever state of the atmosphere. identical. There may, for example, be five However, looking at a single forecast gives reasonable analogues for a particular no indication of how likely that forecast is month, but examination of the succeeding to be correct. Ensemble forecasting entails weather sequences might show mild, rainy the production of many forecasts in order weather in two cases and cold spells in the to reflect the uncertainty into the initial other three. In the preparation of the state of the atmosphere (due to the errors forecast therefore, many factors, which can in the observations and insufficient affect the weather trends, such as sea sampling). The uncertainty in the forecast temperature and the extent or amount ofIJERT IJERTcan then be assessed by the range of rainfall, have to be taken into different forecasts produced. However, the consideration. simple logic behind ensemble forecasting is that two runs of a model are not enough Some call this type of forecasting pattern to base a forecast upon. recognition. It remains a useful method of observing rainfall over data voids such as Ensemble forecasts are increasingly being oceans, as well as the forecasting of used for operational weather forecasting. precipitation amounts and distribution in Ensemble forecasting requires a the future. A similar method is used in sophisticated understanding of the medium range forecasting, which is known atmosphere and computer models. as – when systems in other locations are used to help pin down the 5.0 APPLICATIONS OF location of another system within the WEATHER FORECAST surrounding regime. Teleconnections are The importance of accurate weather used by forecasters today to make general forecasts cannot be over emphasized as the forecasts months into the future. While in needs for them are always craved for in short term forecasting, the pattern virtually every aspect of life. These recognition is still used by weather forecasts can be applied in the following forecasters to supplement today’s areas: computerized methods. But in the end the complexities of weather, like human personalities, defy simple categorization.

IJERTV2IS120198 www.ijert.org 1954 International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 Vol. 2 Issue 12, December - 2013

5.1 Severe weather alerts and required for takeoff, and to eliminate advisories potential crosswinds. A major part of modern weather 5.3 Marine forecasting is the severe weather alerts and Commercial and recreational use of advisories, which the national weather waterways can be limited significantly by services issue in the case that severe or and speed, wave periodicity hazardous weather is expected. This is and heights, , and precipitation. These done to protect life and property. Some of factors can each influence the safety of the most commonly known severe weather marine transit. Consequently, a variety of advisories are the severe thunderstorm and codes have been established to efficiently warnings, as well as the recent transmit detailed marine weather forecasts warnings about areas that are prone to to vessel pilots through radio, for example in some part of Nigeria by the the MAFOR (Marine forecast). National Meteorological Agency. Other forms of these advisories include 5.4 Agriculture weather, high wind, flood, tropical , and fog. Severe weather Farmers rely on weather forecasts to advisories and alerts are broadcast through decide what work to do on any particular the media, including radio, using day. For example, drying hay is only emergency systems as the Emergency feasible in dry weather. Prolonged periods Alert System, which break into regular of dryness can ruin cotton, wheat, and corn programming. crops. While crops can be ruined by , their dried remains can be used as 5.2 Air Traffic a cattle feed substitute in the form of silage. and freezes play havoc with Because the aviation industry is especially crops both during the and fall. For sensitive to the weather, accurate weather example, peach tree in full bloom can have forecasting is essential considering the factIJERT IJERTtheir potential peach crop decimated by a that a greater number of plane crashes spring freeze. Orange groves can suffer recorded the world over have weather significant damage during frosts and related causes. Just as and icing freezes, regardless of their timing. are significant in flight hazards, thunderstorms are a major problem for all 5.5 Utility companies aircrafts because of severe turbulence due to their updrafts and boundaries, Electricity and gas companies rely on icing due to the heavy precipitation, as weather forecasts to anticipate demand, well as large , strong winds, and which can be strongly affected by the lightening, all of which can cause severe weather. They use the quantity termed the damage to an aircrafts in-flight. Volcanic degree-day to determine how strong of a ash is also a significant problem for use there will be for heating (heating aviation, as aircrafts can lose engine power degree day) or cooling (cooling degree day). These quantities are based on a daily with ash clouds. On a day-to-day basis, 0 0 airliners are routed to take advantage of average temperature of 65 F (18 C). the tailwind to improve fuel Cooler temperatures force heating degree- efficiency. Aircrews are briefed prior to days (one per degree ), while takeoff on the conditions to expect enroute warmer temperatures force cooling degree- and at their destination. Additionally, days. In winter, severe cold weather can airports often change which is cause a surge in demand as people turn up being used to take advantage of a their heating. Similarly, in summer or dry headwind. This reduces the distance season a surge in demand can be linked with the increased use of

IJERTV2IS120198 www.ijert.org 1955 International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 Vol. 2 Issue 12, December - 2013

systems in hot weather. By anticipating a So far, the accuracy of long range surge in demand, utility companies can forecasting has been minimal, but the short produce additional supplies of power or range forecasting has been of immense natural gas before the price increases, or in help and advantage to the world at large some circumstances, supplies are restricted today. through the use of brown outs and blackouts. REFERENCES 5.6 Private Sector Ackerman, S. A. and Knox, J. A. (2003). Increasingly, private companies pay for Meteorology: Understanding the weather forecasts tailored to their needs so Atmosphere. Brooks/Cole USA, pp 362 – 379 that they can increase their profits or avoid large losses. For example, supermarket Aguado, E and Burt, J. E. (2001) chains may change the stocks on their Understanding Weather and shelves in anticipation of different, Climate, Second Edition. Prentice consumer spending habits in different Hall, New Jersey, pp. 348 – 355. weather conditions. Weather forecasts can be used to in the commodity market, Barry, R. G. and Chorley, R. J. (1992). such as futures in oranges, corn, soybeans Atmosphere, , and oil. Also, members of the public use Sixth edition, Routledge, New knowledge of future weather conditions to York, pp. 175 – 184 determine what to put on, on a daily basis. Houghton, J. T. (1986). The Physics Of 5.7 Military applications Atmosphere, Second Edition Similarly to the private sector, military Published by the Press Syndicate of weather forecasters present weather the University of Cambridge, New conditions to the war fighters, community. York, pp. 165 – 188. Military weather forecasters provide pre- flight weather briefs to pilots and provideIJERT IJERTLinacre, E and Geerts, B. (1997). real time resource protection services for and Weather Explained Routledge military installations. London, pp. 321 – 345 6.0 CONCLUSION Lutgens, F. K. and TarBuck, E. J. (1989). The Atmosphere: An Introduction Weather forecasting is a complex and to Meteorology, Fourth edition. challenging science that depends on the Prentice Hall, New Jersey, pp. 299 efficient interplay of weather observation, – 331. data analysis by meteorologists and computers, and rapid communication Miller, A. and Thompson, J. C. (1975). systems. Meteorologists have achieved a Elements of Meteorology, Second very respectable level of skill for short- Edition. A Bell and Howell, range weather forecasting. Further Columbus, Ohio pp. 205 – 233. improvement is expected with denser Mohan, J. M. and Morgan, M. D. (1991). surface and upper air observational Meteorology: The Atmosphere and networks, more precise numerical models Science of Weather, Fourth edition. of the atmosphere, larger and faster Macmillan Ontario, pp. 356 – 381. computers and more are to be realized. However, continued international co- http://www.wikipedia.com/weatherforecast operation is essential, for the atmosphere is ingmodels&applications a continuous fluid that knows no political boundaries.

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