Page 16of 24Workshop 3: Atmospheric Moisture and Weather - Lecture Tornado warning: A warning issued when a tornado has actually been observed either visually or on a radar screen. It is also issued when the formation of tornadoes is imminent. Tornado watch: A forecast issued to alert the public that tornadoes may develop within a specified area. Weather Forecasting A variety of forecast parameters are used in assessing what’s going to happen over the next several hours. What will the forecaster consider, will the future weather just be the same as the present weather or will that weather system move consistently in the same direction. The forecaster can also look for pattern recognition or weather systems that look familiar with trends from the past to determine the type of prevailing storm type over an area, or even look at it from a climatic point of view to generate a weather forecast The best forecast that can be made based on the data sets available today is just 6 hours. Why is this? Even though there are 75,000 reporting station around the world, the data is not uniformly spread on an even grid over the world.. The reporting locations for the most part are in populated areas. So the data points are clustered. Now if we look at the oceans of the world we have more problems with the lack of data, there are but a few buoys that represent this great area. Even with the fastest computers in the world without consistent distribution of data points the best accurate forecasts we can make is 6 hours. So here are the three types of forecasts; very short-range usually not more than 6 hours, short range that is from 6.5 to 60 hours and long- range up to 16 days To help forecasters handle all the available charts and maps, high –speed data modeling systems using computers are employed. The communication system in use today is the AWIPS (advanced weather interactive processing system). The AWIPS system has data communications, storage, processing and display capabilities. It also has the ability to process and data fuse Doppler radar data into its products. ASOS, Automated surface observation systems, are operational at selected airports and other sites throughout the US. In addition other assets, such as, Geo-stationary and polar-orbiting satellites all have a variety of sensors ( IR, VIS, WV, TEC, and Satellite Sounders ) which allows continue monitoring of time perishable weather environments. (Refer to Assignments section The Weather Desk for online examples) Some of the considerations a forecaster must make before forecasts are issued are to review the past continuity of weather systems from both a macro and local perspective. Once a thorough understanding is obtained, then it is off to review the current data.