Synoptic Weather Maps

Transcription

1 LAB 38 Synoptic Weather Maps Purpose Materials The purpose of this lab is to have you read and interpret the information displayed on synoptic weather maps. You will also learn the techniques used by meteorologists to analyze weather maps and the weather conditions associated with frontal systems. colored pencils copies of the following surface weather maps available from < current isobar, front, radar, and data surface chart current 500 mb-data upper air chart Procedure A Complete the following steps. 1. On a separate piece of paper, decode and write out the current weather conditions for the ten station models in Figure * FIGURE 38 1 Station Models 144

2 2. On the back of the same piece of paper you used to decode the ten station models, encode the following six current weather conditions in station model format. Station Model A The sky is clear. The wind is from the south at five knots. The barometric pressure is mb and it has risen 2.4 mb in the past three hours. The air temperature is 74 degrees F and the dew point is 66 degrees F. Station Model B The wind is from the northwest at 15 knots. Cloud cover is 25 percent. The present weather is drizzle. There has been.2 inches of rain in the past six hours. The barometric pressure is mb and it has fallen 9.2 mb in the last three hours. The air temperature is 62 degrees F and the dew point is 61 degrees F. Station Model C The sky is totally overcast. The present weather is fog. The air temperature is 76 degrees F and the dew point is 74 degrees F. There has been.6 inches of rain in the past six hours. Barometric pressure is mb and has fallen 3.6 mb in the past three hours. The wind is from the North at 20 knots. Station Model D The sky is 75 percent covered. The wind is from the southeast at 25 knots. The barometric pressure is mb and has dropped 7.2 mb in the past three hours. It is raining and the air temperature is 79 degrees F, and the dew point is 74 degrees F. There has been.5 inches accumulation of rain in the past six hours. Station Model E The sky is clear. The wind is calm. The barometric pressure is mb and rising. The air temperature is 70 degrees F and the dew point temperature is 62 degrees F. The visibility is ½ mile with no precipitation. Station Model F The sky is half covered. Thunderstorms are threatening. There has been.1 inches accumulation of rain. There is a westerly wind at 10 knots. The barometric pressure is mb and has dropped 8.2 mb in the past three hours. The air temperature is 72 degrees F and the dew point is degrees F. Procedure B Complete the following steps. 1. Use the current surface weather map data from the Data Streme Web site to draw the current weather conditions on the blank map in Figure 38 2 with the appropriate colors. Your current weather map should include the locations of the high- and low-pressure centers, fronts, and precipitation. 2. With help from your instructor, use the current 500 mb upper air chart from the Data Streme Web site to locate the jet stream. Upper air maps can be analyzed by drawing an arrow through each wind vane of the individual weather station pointing in the direction the wind is moving. The jet stream can be located by identifying the band of the highest wind velocities. Once you have identified the jet stream s location, draw it in using a green colored pencil on your current weather map. 3. Using the data on your current weather map, the location of the jet stream, and help from your instructor, predict what the weather conditions will be in 24 hours. On the blank map in Figure 38 2, draw the locations of the high and low pressure, fronts, and precipitation to make a forecast map for the next day. 145

3 Current weather Tomorrow's forecast FIGURE 38 2 Weather Forecasts 146

4 Procedure C Using your textbook, fill in the appropriate weather conditions associated with each type of front on Table Air in Front TABLE 38 1 Cold Fronts Warm Air Behind Cross-Section Cloud types Pressure in Front Pressure Behind Frontal Symbol Precipitation 147

5 Conclusions 1. Describe the change in wind direction associated with a low-pressure system moving through your area. 2. What general weather conditions are associated with high-pressure systems? 3. What would you expect the weather conditions to be like if the barometric pressure trend over the past three hours has shown a steady decrease? 4. What is the jet stream, and why is it an important aspect of weather forecasting? 5. Explain what information you need to make accurate weather forecasts. 148