Clear the Fields: Lightning Data From a School Weather Station

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Clear the Fields: Lightning Data From a School Weather Station

Use storm records and lightning sensor data to forecast risk and judge a safety plan.

When and where lightning strikes

Read the passage and study Graph 1. Then answer the questions.

The Station on the Gym Roof

1Harlan Middle School has a weather station on the roof of its gym. Along with wind, rain and temperature sensors, it has a lightning sensor that detects strikes up to 40 km away and estimates how far away each one is. Last year, the weather club and their teacher, Ms. Beatriz Solano, linked the station to a forecast app on the coaches' phones. Their goal was to keep teams on the outdoor fields safe during thunderstorm season.

2Lightning is a giant electric spark between a thunderstorm cloud and the ground, or inside the cloud. It can strike the ground as far as about 15 km from the storm that makes it, even where the sky overhead still looks blue. Thunder is the sound lightning makes. The flash reaches your eyes almost at once, but the sound travels only about 1 km every 3 seconds. In the United States, most people hurt by lightning are outdoors, often because they waited too long to go inside.

3The club averaged 10 years of station records to see when thunderstorms are most common (Graph 1 shows the average for each month). Then they followed five storms last spring and summer (Table 1). For each storm, they recorded how fast it moved toward the school and how many minutes passed between the app's alert and the first strike within 5 km of the school.

4Under the school's plan, the app sends an alert to clear the fields when the sensor detects a strike within 15 km. Everyone must go into a building or a hard-topped vehicle; a dugout or a tree is not a safe place. The club's goal is for everyone to be inside before lightning strikes within 5 km. From the far track field, the team needs about 12 minutes to get everyone into the gym. Practice starts again only after 30 minutes pass with no strike within 15 km. The gym also has lightning rods, which give a strike's electric current a safe path into the ground, and the station's computer has a surge protector that blocks sudden power spikes.

1.

In an average year, how many thunderstorm days does the station record from April through September? days

2.

Which forecast for next year is best supported by Graph 1?

A. September will have more storm days than June, as storms build up all summer.B. July will likely have the most storm days, on dates no one can know yet.C. July will have exactly 11 storm days, on the same dates as this year.D. April will stay free of storms, since it has the fewest on the graph.

3.

During soccer practice, Coach Mbeki-Ross sees a flash of lightning and hears the thunder 24 seconds later. Use paragraph 2.

About how far away was the strike? km

4.

The sky above the soccer field is still blue, and the dark storm clouds are far to the west. What should the team do after the strike in question 3?

A. Go inside now, since the strike was within the 15 km lightning can reach.B. Keep playing until thunder comes less than 3 seconds after a flash.C. Keep playing, since lightning stays under the dark storm clouds.D. Wait under the big oak tree by the field until the storm has passed.

How much warning does the alert give?

Use Table 1 and paragraph 4. In every storm in Table 1, the storm moved 10 km between the alert (a strike within 15 km) and the first strike within 5 km.

Table 1. Five storms: minutes from the alert to the first strike within 5 km
Storm	Speed (km/h)	Warning time (min)
April 18	20	30
May 9	25	24
June 2	40	15
June 27	60	10
July 15	75	8

5.

Which statement best describes Table 1?

A. The faster a storm moved toward the school, the more warning time the alert gave.B. The storms each gave about 15 minutes of warning, whatever their speed.C. The faster a storm moved toward the school, the less warning time the alert gave.D. The storms later in the summer moved more slowly and gave more warning.

6.

A new storm is moving toward the school at 30 km/h. Suppose it acts like the storms in Table 1.

How many minutes of warning would the alert most likely give? minutes

7.

The track team needs about 12 minutes to get from the far field into the gym. Circle every storm in Table 1 that would have reached within 5 km before the team was inside.

8.

The track coach wants a different alert distance for the far field. It must give the team at least 12 minutes before lightning strikes within 5 km, even for a storm moving at 75 km/h, and it must be inside the sensor's range from paragraph 1. Which alert distance meets both needs?

A. A strike within 18 kmB. A strike within 45 kmC. A strike within 15 kmD. A strike within 25 km

Judging the safety plan

Use paragraph 4 and everything you have found.

9.

Match each part of the school's plan to the harm it helps prevent.

10.

On June 2, the last strike within 15 km came at 4:10 p.m., and the sky over the fields cleared at 4:20 p.m. No more strikes came within 15 km. Under the school's plan, when could practice start again?

A. 4:40 p.m., 30 minutes after the last close strikeB. 4:20 p.m., as soon as the sky clearedC. 4:50 p.m., 30 minutes after the sky clearedD. 4:25 p.m., 15 minutes after the last close strike

11.

A parent says, "Lightning is random. Nobody can forecast it, so the sensor and the app are a waste of money. The coaches should just watch the sky." Do you agree? Make a claim, use evidence from Graph 1, Table 1 and the passage, and explain how hazard data can forecast risk and guide technology that reduces harm.