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SC.912.E.7.5 Predict future weather conditions based on present observations and conceptual models and recognize limitations and uncertainties of such predictions.

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Earth Systems and Patterns The scientific theory of the evolution of Earth states that changes in our planet are driven by the flow of energy and the cycling of matter through dynamic interactions among the atmosphere, hydrosphere, cryosphere, geosphere, and biosphere, and the resources used to sustain human civilization on Earth.

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questions Some thunderstorms are caused by convection resulting from the collision of two air masses. Which describes the collision involved in this type of thunderstorm? A. Two cold fronts collide. B. Two warm fronts collide. C. A cold front moves into an area with warm air. D. A warm front moves into an area with cold air.

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CHAPTER HOME Meteorologists must gather huge amounts of data in order to make their predictions. They rely on sensing instruments and on computer models to provide the information they need. CHAPTER SECTION OUTLINE VOCABULARY 20.5 Forecasting Weather Weather Visible Satellite Image - Ohio Infrared Satellite Image - Ohio station model

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CHAPTER A compact expression of weather information for an area, including temperature, dew point, weather conditions, wind speed and direction, barometric pressure, and cloud cover. VOCABULARY station model Weather station model

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CHAPTER HOME Meteorologists use the data to make surface weather maps and forecasts. CHAPTER VOCABULARY 20.5 Forecasting Weather Weather Surface Weather Map station model SECTION OUTLINE

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Lightly draw lines connecting identical values of sea level pressure. Remember, these lines, called isobars, do not cross each other. Surface Air Pressure Map

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Isobars can be used to identify "Highs" and "Lows". The pressure in a high is greater than the surrounding air. The pressure in a low is lower than the surrounding air. Label the center of the high pressure area with a large blue "H". Label the center of the high pressure area with a large red "L".

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High pressure regions are usually associated with dry weather because as the air sinks it warms and the moisture evaporates. Low pressure regions usually bring precipitation because when the air rises it cools and the water vapor condenses.

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Where should we expect rain or snow? Where should we expect dry weather? How could we tell if it was rain or snow expectations?

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Surface Temperature Map You will draw lines connecting the temperatures, much like you did with the sea- level pressure map. However, you will also need to interpolate between values. Interpolation involves estimating values between stations which will enable you to properly analyze a map.sea- level pressure map

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Isotherms are used to identify warm and cold air masses. Where is the region with the lowest temperatures? Where is the region with the warmest air?

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Dewpoint Temperature Map This map shows the dewpoint temperature for various locations over the conterminous U.S. The values are in F. Recall, dewpoint is the temperature to which, if the air cooled to this value, then the air would be completely saturated.

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Isodrosotherms are used to identify surface moisture. The closer the temperature and dewpoint are together, the greater the moisture in the atmosphere. As the moisture increases so does the chance of rain. Also, since moist air is lighter than dry air, the greater the moisture, the easier for the moist air to lift into the atmosphere resulting in a better chance for thunderstorms. Typically, dewpoint 70F or greater have the potential energy needed to produce severe weather. What will this information, combined with our previous data sea pressures and temperatures, tell us? Can we predict the actual temperature and precipatation in all areas exactly?

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Surface Pressure Change Map This map shows change in surface pressure (in whole millibars) during the past three hours at various locations.

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Draw lines connecting equal values of pressure change for every two millibars. These lines are drawn for the -8, - 6, -4, -2, 0, +2, +4, +6, +8, etc. values. Remember, like isobars, these lines (called isallobars) are smooth and do not cross each other. Using a blue colored pencil, beginning at any +2 value, lightly draw lines connecting equal values of the +2 millibars pressure change. Remember, you will need to interpolate between values to draw your lines correctly. Draw the remaining "positive" pressure change value(s) at two millibars intervals. Using red colored pencils lightly draw a line connecting equal pressure change values of less than zero (0). Finally, using black, draw a line connecting the zero (0) line.

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Cold fronts are often located in areas where the pressure change is the greatest. The front represents the boundary of different air masses. Cold air is more dense than warm air so when a cold front pass your location, the pressure increases. We analyze for pressure change to look for these boundaries. We can also tell where high pressure and low pressure systems are moving by looking where the greatest change is occurring. Cold air Warm air

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Analyzing maps with the current weather conditions is an essential part of the entire forecast process. Basically, if we do not know what is currently occuring, it is near impossible to predict what will happen in the future. Computers have been able to analyze maps for over 20 years. However, computers cannot interpret what they analyze. There is no substitute for the hand analysis. Analyzing maps by hand causes the forecaster to study every detail in the weather and enables him/her to discern the continuity or "flow" of the weather.

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Great forecasts, the ones that save lives and property, begin with the careful analysis of the current conditions. Conversely, based upon post- analysis, "bad" (or busted) forecasts, the ones most remembered by the public, could have been improved if one did a careful analysis in the beginning. Map analysis is not too unlike drawing in a dot-to- dot coloring book. Just as one would draw a line from one dot to the next, analyzing maps is similar in that we will draw lines of equal values between dots representing various elements of the atmosphere.

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compare, and comment on, the direction the wind blows around high and low pressure (based upon the arrows they drew) compared to the direction of the staffs on the surface map.

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compare, and comment on, the cloud cover under the areas of high and low pressure.

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what type of present weather they see plotted on this map. What type of past weather do the students see?

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