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3 Implications for Operational Meteorology Operational meteorologists will have exciting new opportunities to im- prove weather forecasts and warnings in the 1990s as the National Weather Service (1) inaugurates its Advanced Weather Interactive Processing Sys- tem (AWIPS-90), (2) begins to take advantage of radically new observing systems such as NEXRAD and the Demonstration Wind Profiler Network, and (3) modernizes and restructures its field offices in support of more de- tailed and timely forecasts. These improvements will permit more detailed weather information to be obtained in real time, with easy accessibility and display in a variety of formats including color and animation, and will per- mit more frequent analyses of surface and tropospheric conditions based on intensive use of new data sources. Provided that these opportunities are matched by parallel research efforts and significant upgrading in the educational and training require- ments for NWS personnel, they should lead to more detailed and accurate "nowcasts" and short-range weather forecasts. This chapter describes briefly the potential impacts of increased capa- bilities in mesoscale meteorology. OPERATIONAL DATA BASES Data bases of the future will contain much more detailed information than they do now. The extremely high volume of data that is anticipated will force regular purging of most data after immediate use, yet facilities must be developed to archive data for selected weather situations either because 25
26 they affected the general populace adversely (and thus the data may have use in legal actions) or because they have other research and training value. Forecasters newly arrived at a station will have the opportunity to learn the local peculiarities of the weather if they have the capability to reexamine events in the same sequence as they originally unfolded. HAZARDOUS WEATHER WARNINGS Most weather forecasters acknowledge that radar data provide the most critical information when severe storms threaten. The NEXRAD radars will bring a new dimension to operational forecasting by depicting low-level winds in clear air during the convective season, as well as winds within storms, at all levels that the NEXRAD radar can survey. Warnings will be more specific regarding the location and size of the threatened area, the length of the critical period for severe weather, and the type and intensity of severe phenomena expected. Warnings are also more likely to be issued farther in advance of severe weather occurrences. Visible and enhanced infrared satellite images, portraying the evolution of clouds and cloud systems, will augment the radar information. In winter, satellite images together with radar will depict the mesoscale organization of winter storms. Hourly wind profiler data will show, far better than rawinsonde winds, the temporal evolution of these weather systems. As a result, forecasters will be able to specify short-term variations in the intensities and types of storms and to be more accurate in predicting their locations and times of occurrence. SHORT-TERM WEATHER FORECASTS More accurate warnings of severe or dangerous weather will save lives and avert property damage, but increased accuracy of routine short-term forecasts will also have tremendous value. Instead of "Twenty percent chance of afternoon showers," people should expect to hear, "Thunder- showers are expected to develop southwest of Chicago this afternoon and move northeast across the south side of the city between 4:00 and 5:00 p.m., causing brief heavy rains, small hail, and gusty winds that may cause some minor damage. The storms should weaken rapidly as they cross the Lake Michigan shoreline." Instead of "Turning cloudy, windy, and colder tonight with a chance of rain changing to snow," people should expect to hear, "Mild and breezy prior to midnight, but then turning sharply colder with rapidly falling temperatures. Sprinkles of rain around midnight, changing within an hour to light snow and ending shortly before dawn. An inch of snow on the ground is likely when the rush-hour begins."
27 At present, meteorologists are reluctant to make such detailed fore- casts because their limited information does not instill great confidence in predicting well in advance either the expected timing or sequence of events. Better information sources and improved communication and dis- play capabilities will encourage all weather forecasters (NWS and private) to be more specific. As a basis for detailed forecasts like those above, the provision of hourly numerical guidance is highly desirable, especially beyond the time when simple extrapolation of the existing weather ceases to be useful. WEATHER INFORMATION SERVICES The information industry is burgeoning, and the public demand for weather information is part of the reason. Ten years ago, it was difficult to envision that a 24-hour-a-day television program devoted exclusively to national weather would be a financially rewarding venture. The Weather Channel on cable television and its many commercial sponsors are proof of the success of such a concept. Additionally, the weather report is often the most popular segment of television news programs. Timely collection and dissemination of weather observations and com- puter-generated weather information are critical. Automated collection and quality control of data have assumed greater importance than ever before. Sophisticated interactive systems must give the data analyst ample oppor- tunity to examine and, if necessary, alter weather information products before dissemination without requiring a large expenditure of the analyst's time. Forecasters will benefit from having access to a greater variety of ana- lyzed and predicted meteorological fields with higher spatial and temporal resolution. They will be able to translate this information into more spe- cific public forecasts. Private-sector meteorologists will also benefit from an enhanced ability to tailor products to the individual needs of their clients. Hydrology A NEXRAD algorithm for the calculation of rainfall rate from radar reflectivity data is under active development. Rainfall rates that are de- duced from reflectivity data will be frequently calibrated with automated rain-gauge data. Precipitation runoff models for watersheds can already generate credible estimates of streamflow, given accurate rainfall data. Within reach is the ability to estimate precipitation from a time-history of radar reflectivity over very small areas of a few square kilometers. Such areal estimates, which already agree within a factor of 2 or 3 with point rainfall measurements, will be of great value for flash flood warnings and
28 for water resources management (e.g., deciding whether or not to lower the supply of impounded water in a reservoir). Agriculture Many agricultural losses are unavoidable, such as crop destruction by wind-driven hail or lowered yields in a drought year. Yet many important decisions that can limit such lossesâwhether to spray pesticides, harvest early or late, pump water for irrigation, or protect vulnerable crops from an early or late frostâcan be made with more confidence given better weather forecasts. Increased mesoscale information will improve the timeliness and accuracy of weather information on which the agriculture industry depends for many of its critical decisions. Transportation Transportation is sensitive to short-term changes in the weather. Rapidly deepening extratropical storms are a sudden hazard to shipping in coastal waters and on the Great Lakes, and hurricanes, the paths of which are often difficult to predict, occasionally menace ships along our Gulf and Atlantic coasts. Aviation is highly vulnerable to hourly changes in the weather. Min- imizing fuel consumption depends on accurate en route winds, favorable weather at both terminals, and careful timing of the departure. The safety of crew and passengers depends on avoidance of thunderstorms, icing, and clear-air turbulence en route, as well as avoidance of poor visibility, heavy precipitation, and wind shear during takeoff and landing. Roughly 1000 fatalities annually in general and commercial aviation are weather-related. In 1986 the Aviation Weather Forecasting Task Force made these recommendations, among others, to the Federal Aviation Administration and the NWS (AWFTF, 1986): â¢ Implement an automated aircraft reporting system as one compo- nent of a national meteorological observing system. â¢ Increase the horizontal and vertical resolution of operational weath- er prediction models so as to permit more detail in the initial conditions on which model predictions depend and, in turn, provide forecasts with greater resolution and accuracy. â¢ Update weather analyses and forecasts more frequently. â¢ Provide more precise, timely, and consistent diagnostic and guid- ance products for aviation users. The accuracy of analyses and short-term weather forecasts for aviation will improve as higher-resolution satellite images become available and
29 wind profiles, satellite soundings, and automated aircraft reports provide mesoscale detail in the initial conditions for models. Foul weather associated with mesoscale systems can render road and rail travel hazardous or even impossible within an hour. Accurate and timely forecasts can alert motorists to the risk of sliding on icy highways, hydroplaning in deep puddles, being stranded in a blizzard miles from the nearest shelter, or being swept off the road by a flash flood in a narrow canyon. They can persuade truckers to stay off dangerous or impassable roads for the next 24 hours or to select alternate routes. They can alert snow removal crews in advance of a snowstorm or prevent them from being called out needlessly, and they can alert rail transportation facilities to the need to deice rails and equipment . Hence greater detail and accuracy in predicting the timing and location of significant weather hazards will significantly improve transportation safety and efficiency. Construction The building and paving industries are most concerned with the possi- bilities of precipitation, subfreezing temperatures, and, sometimes, strong winds. Pouring concrete, welding I-beams, excavating for a foundation, painting a house, repairing a roof, and framing exterior walls are all weather-dependent activities. The contractor who sends crews to an out- door job in unexpectedly bad weather, or who loses a partially constructed house to a windstorm, is likely to blame an inaccurate weather forecast. Therefore, more accurate and detailed forecasts will permit construction industries to cope better with adverse weather conditions. Outdoor Recreation A major component of the average person's interest in the weather is connected with outdoor recreation. More accurate forecasts with finer space and time resolution will allow boaters to be warned to return to shore before a squall, swimmers to leave pools, golfers to return to clubhouses, and softball players to vacate playing fields before thunderstorms break. Hunters will be advised in more detail about heavy, early-season snows that could leave them stranded. Skiers who want to avoid travel during heavy snow but be on the slopes as soon as the snow ends will profit from forecasts with better timing of events. All these people will benefit from more accurate and more precise weather information. Furthermore, they will be able to make contingency plans for outdoor activities with greater precision if more accurate forecasts are available.
30 CONCLUDING REMARKS Although some improvement in operational meteorology can reason- ably be expected just from the availability of new observing systems, the im- provement is likely to be very limited unless a systematic scientific program is undertaken to maximize the use of the new observations in increasing understanding of mesoscale weather processes. The resulting increased understanding should, in turn, result in a larger incremental improvement in mesoscale weather predictions and warnings and hence greater benefits to the nation than can be expected from the new observing systems alone.