Name Class Date

Laborotory InaestigationChapter 16 What ls Weather? 38lnvestigating Weather MaPs

Background Information

Weather forecasting is made possible through the analysis of detailed information thatdescribes atmospheric conditions from several locations. In the United States, weather datafrom more tnan gOO local weather stations are used to prepare daily weather maps thatpresent an overall picture of the weather throughout the country for a particular time. Adetailed map may contain more than 10,000 items of weather data. Such a maP will becomethe basis for making weather predictions

In this investigation you will prepare a simplified weather map fromyou will analyze the map to discover relationships between atmospheric

Problem

How are weather maps prepared? How can weather maPS be used to better understandrelationships between atmospheric variables?

Materials (per group)

pencilcolored pencils or crayons

ProcedurePart A Information From Observation Stations

l. Figure I illustrates the correct placement of some weather data recorded at anobiervation station. You will plot similar data on a map of the United States.

2. The circle in Figure 1 represents the observation station. Weather data are placed inspecific positions inside and outside the circle.

limited data. Thenvariables.

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Station Circle

Wind speed ' F(about 18 mph)

of cloud cover75% covered)

Temperature ("F) \

Present weather \-

Atmospheric pressure

/ 101e.o mb(30.58 in. of mercury)

Amount(About

I

I

Figure 1

3. Wind direction: You should think of thestation circle as the point of an arrow.Attached to the station circle is a line, whichis the arrow's shaft. The wind direction isrepresented as moving along the arrow'sshaft toward the center of the station circle.Wind directions are given in degrees andrepresent the direction -fro* which the windis blowirg. In Figure 1, the wind is blowirgfrom the southwest toward the northeast.Figure 2 will help you determine winddirection.

\ wind direction

w 270"

(from the southwest)

N

00

NW315"

225"SW

Figure 2

NE45"

1 35"SE

1 80'S

4. Wind speed; Often there are small lines that resemble arrow feathers at the end of theshaft. These lines are symbols for wind speed. Each full line represents an increase inspeed of about i0 miles per hour. Half a line is about 5 miles per hour. If there is onlyone "feather," place it at the end of the arrow if it is a full feather, and slightly farther inif it is a half feather. Although the metric unit of speed is kilometers per hour, miles perhour has been used in this investigation because it is the unit most commonly found onweather maps.

Atmospheric pressure: Look at a weather map in your local newspaper. You will see long,curving lines that have a number attached to them. These lines are called isobars. Someof the curves are closed; some, open. Isobars are linesjoining places on a weather mapthat have the same atmospheric pressure. The numbers associated with these lines are theatmospheric pressure recorded at each observation station. These pressures are measuredin millibars. So isobars are measured in millibars. Look at the column of atmosphericpressures in Figure 6. To determine the pressure in millibars, use only the last threedigits of the pressures listed and omit the decimal point. An example (196) is given inFigure 1.

/D.

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6. Tbmperature; The average dailytemperature is usually recorded in degreesFahrenheit.

7 . Present weather: From the list in Figure 3,select the symbol that most accuratelydescribes the weather existing at eachobservation station listed in Figure 6 whenthe data were collected.

8. Cloud coaerage: [Jsing Figure 4, indicate theamount of cloud cover at each observationstation. This information is enclosed withineach circle. Put this information in thecircles on the map in Figure 7 .

9. Now transfer all the weather informationlisted in Figure 6 ro the specificobservation stations shown in Figure 7 .

Cloud Cover

ooooo

Clear

Partly cloudy (25/. covered)

Partly cloudy (50% covered)

Partly cloudy (75'/. covered)

Completely overcast (1 00Y" covered)

Weather Symbols

Figure 3

Fronts

Cold front

Warm front

Figure 5

Figure 4

Part B Additional Weather Map Information1. In Figure 7 , locate the observation station

with the lowest atmospheric pressure andwrite the word "Low" just above it.Starting at this point, which is the centerof a low-pressure area, draw in the coldand warm fronts. The symbols are shownin Figure 5.

The cold front comes out of the high-pressure center. This front, when placed inFigure 7, will be located between stations where winds change from southwest to northwestand temperatures decrease suddenly. The warm front comes out of the low-pressure center.This front, when placed in Figure 7, will be located between stations where winds changefrom east to southeast and temperatures rise suddenly.

O Rain

--

Fog

,F snow

A.Hail

=Tshowers

7 Thunder-| \ storms

9 Drizzte

^A.sreet

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OBSERVATION STATIONS

Weather Station

Seattle

Bend

San Francisco

Los Angeles

Phoenix

Ely

Dubois

Helena

Medicine Hat

Bismarck

Casper

Pueblo

Roswell

Del Rio

Galveston

Dallas

Oklahoma City

Kansas City

Burwell

M inneapolis

Sioux Lookout

Chicago

Little Rock

New Orleans

Nashville

Cincinnati

Detroit

Sault Ste. Marie

Ert

Quebec

Boston

Buffalo

New York

Hatteras

Charleston

Atlanta

Jacksonville

Tampa

Miami

WindSpeed(mph)

7

10

8

0

11

0

1B

15

20

18

12

B

22

38

5

29

45

0

22

15

20

10

I5

5

7

10

15

5

0

12

7

10

14

15

3

2

2

0

WindDirection

260'

200"

1 35"

50"

225'

31 5"

345"

00

350"

315"

350"

31 5"

225"

31 5"

315"

325"

45'

50"

450

225"

225"

220"

90"

750

45'

1 00"

1 00'

75"

80'

90"

225'

225"

200"

230"

AtmosphericPressure

(mb)

1020.8

1023.5

1020.0

1021 .1

1021 .1

1 025.1

1024.0

1020.0

1 020.1

1014.3

1016.0

1015.3

1016.0

1 012.0

1016.0

1007.9

1007.7

1002.3

1009.3

1008.2

1016.8

1005.2

1009.3

1017.9

1011.1

1009.8

101 1 .9

1013.1

1017.2

1017.0

1018.1

1016.0

1017.6

1 01 9.1

101 7.8

1014.6

101 8.1

1018.0

1019.8

Temperature("F)

42

40

48

41

45

37

38

41

40

48

50

47

48

50

72

60

57

58

52

51

46

58

67

73

68

57

54

50

48

50

52

52

56

60

70

70

73

74

78

Type ofPrecipitation

Thunderstorms

Hail

Thunderstorms

Rain

Rain

Drizzle

Drizzle

Rain

Drizzle

Drizzle

Fog

Drizzle

Fog

Fog

Fog

GloudCover

("/ol

0

0

25

25

0

0

0

0

0

0

0

0

0

100

25

100

100

100

100

100

25

100

25

0

25

100

100

100

0

25

25

100

50

50

25

0

0

25

0

Figure 6

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2. Locate the observation station in Figure 7 with the highest atmospheric pressure andwrite the word "High" just above it. This is the center of an area of high pressure.Draw the following isobars in Figure 7:1004 mb, 1008 mb, l0l2 mb, 1016 mb, 1020mb, and 1024 mb. Draw these isobars so that they point away from the center of thelow-pressure area when they cross cold or warm fronts. Label each isobar. Remembefthat isobars are long, curving lines. They connect locations on a weather map that havethe s-ame atmospheric pressure. It will be helpful to review the atmospheric pressureslisted in Figure 6.

In Figure 7, draw a line around all the locations where precipitation has fallen. Either usea pencil and shade in the area with precipitation or use a colored pencil or crayon and.color in this area.

Observations

Figure 7

Name

3.

4,

\..' \

oSioux Lookout

oErt

Charleston

Jacksonville

Miamt

Bosto

New Yort<

Hatteras

(os oilr:r_..rj'

\nDql RioX

TamPa

Butta\o

;

!In:

\-/n', Irnoeriix.. I\.;'\..-i,.'-

Galveston

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Analysis and Conclusions

l. An area of high pressure is referred to as an anticyclone, and an area of low pressure iscalled a cyclone. According to your weather map, is precipitation generally associated

with a cyclone or an anticyclone?

2. Compare wind

a high-pressure

direction of air around a low-pressure center with wind direction around

3. Compare the type of precipitation associated with the cold front to that associated with

the warm front.

Describe the location of the precipitation associated with the warm front as compared to

the precipitation associated with the cold front.

center.

4.

7D. Describe changes in temperature,

with the passage of a warm front.

wind direction, and atmospheric pressure associated

6. Describe

with the

changes in temperature, wind direction, and atmospheric pressure associated

passage of a cold front.

Gritical Thinking and Application

l. Refer to Figure 7. Assume that the storm center is moving in a northeasterly direction.Describe ail.art three changes in the weather in Cincinnati, Ohio, if the center of thelow-pressure area becomes located directly over Detroit, Michigan.

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2. Identify the error in each of the following observation station reports.

l+6

Date

?..

b' gl ,^fi ( t7s

q6

)f

ilt

3. Is it possible for yesterday's weather map to help you to predict tomorrow's weather?

Explain your answer.

Going Further

1. Wind speed is normally given in miles per hour on a weather map. Change all the windspeeds listed in Figure 6 to kilometers per hour.

2. There are four major types of air masses that affect the weather in the United States.Each of them brings different weather conditions. Look up information in the libraryabout these air masses. Then label the areas on your weather map behind the cold front,in front of the cold front, and in front of the warm front with the appropriate air masssymbol. The names and symbols for these air masses are continental polar (cP),continental tropical (cT), maritime tropical (mT), and maritime polar (mP).

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