Observations of Observations Weather Over the Oceans

III: WEATHER MAP WATCH

I N T H I S S E C T I O N O F ‘ W E A T H E R W I S E ’ Y O U W I L L L E A R N A B O U T W E A T H E R M A P S A N D F O R E C A S T I N G .

z z What is a Weather Map ? Well, that’s a simple question. It’s a map that shows us weather! But how? What are all those lines on a weather map? And what about the symbols? Often on maps we see large H’s and L’s, blue and red lines with triangles and half- circles. What does all that mean? And how do we know where to draw all those lines? I’m here to explain A solar-powered Surface all these puzzles to Automated Measurement you. We will also take a trip back in time to year 1922. Do you think (SAM) site. Photo from NOAA photo weather maps were different back then? Remember, we didn’t have library. computers!

In order to make accurate weather forecasts, we also need observations of Observations weather over the oceans. These come from buoys and ships. The surface The ﬁrst step towards making a weather observations are most relevant to us, so map is having observations. There are let’s discuss these ﬁrst. All surface thousands of weather stations all over observations are coordinated and taken the world that collect measurements of at the same time. Observations are also atmospheric pressure, temperature, collected and recorded in the same precipitation, wind, and cloudiness. manner for consistency. Surface data are Most surface observations are taken in recorded using a ‘station model’. areas that are densely populated.

III.1 Station Model Have you ever wondered how weather 4. To show the wind direction, we draw a line information is recorded? And how was it away from the circle in the direction in which the recorded 100 years ago? wind is coming from: It turns out that surface weather measurements North are being recorded in the same way as 100 years ago, using a station model. A station model is a West East diagram which uses a combination of numbers 55 012 and drawings to describe the weather. Today you will learn about a simplified station model that In the above case, the wind is coming from the North-East. shows only cloud cover, temperature, pressure, wind direction, and wind speed. 5. Finally we show the wind speed by adding 1. To draw a station model, we start with a circle: ‘barbs’ and flags to the wind direction line: Each full barb represents winds of 10 knots, each half barb is 5 knots, etc. (1 knot of wind is a little less 2. We leave the circle empty if the sky is clear and than 1 mile per hour of wind.) For example, the color it in in proportion to the cloudiness. For picture below depicts wind strength of 25 knots: example: if we can’t see the sky anymore because clouds are everywhere, we fill in the circle 10 knots entirely: +10 knots + 5 knots 55 012 = 25 knots 3. We then write down the temperature to the left of the circle (above the center line) and the If the winds are strong we use a flag to mark 50- pressure to the right of the circle: knot winds. So the wind in the following picture is 55 012 60 knots: 50 knots temperature pressure +10 knots 55 1012 On the map you will see on the next page, = 60 knots pressure is reported in inches of mercury, and the DEN first digit is skipped. So ... 012 means 30.12 and if the number starts with a 9 the pressure is 29.XX. Finally, we note the name of the station with a So, 987 means pressure of 29.87 inches of three letter symbol. The Denver airport station mercury. It’s a little confusing, I know! has a symbol DEN.

III.2 Decipher the Weather Code ! In this fun game you will practice decoding the NOW, let’s play another game: station model observations. Work in groups of 3! 1. Pick one girl scout in your three-person group DIAGRAM 1 to write down the weather (it can be from Decode the following station model: anywhere or you can make it up): Cloudiness:! ______

Temperature:! ______Pressure:! ______50 015 Wind Speed:! ______Wind dir. from ______

Write down the following: 2. Have the other two group members draw a station model of the weather in the space below. Cloudiness:! ______

Temperature:! ______

Pressure:! ______Wind Speed:! ______

Wind Direction: from ______

DIAGRAM 2 Decode the following station model: 3.Repeat the above 2 steps: Cloudiness:! ______88 995 Temperature:! ______Pressure:! ______

Wind Speed:! ______Wind dir. from ______Station model:

Cloudiness:! ______

Temperature:! ______

Pressure:! ______Wind Speed:! ______

Wind Direction: from ______

III.3 The following picture shows a fewRead selected surface the observations Map collected 1 over the United States at one time on Feb 1, 2006. y r s e w alue v it is v e r the e he high or lo r he d). is w gions w gions of e e e r ssur cle e totally ﬁlle e , cir r s ar ke y mostly in r cle , high pr r cir mbe the e me r e he ? R e y (w ith a GREEN mar stion: Is it cloud ssur e 2. W cloud Que pr start with a ‘0’. ______

UE ss than s of z he s le

alue v e ssur e r than 30 inc ead station models. On te pr a e r the s g cle alue , cir r v e y (starting with a 9) and BL ke ssur cur r e pr Read the Map me

cle z s of y (starting with a 0) r cir he ith a RED mar ke cur e is an opportunity for you to r r Her the above map: 1. W 30 inc mar me

III.4 Drawing a Weather Map You have learned now how to record surface weather observations. It’s time now to learn how they are transformed into a weather map! LOOK AT ALL THOSE SYMBOLS! On page 3 you looked at a weather map with only selected surface observations collected over the United States. Now, let’s take a look at ALL of the observations taken at that time.

Look at all those symbols! You can hardly see anything! There must be a better way to look at observations! You’re absolutely right! There is a better way and it involves contouring.

z z Contouring ! Contouring is a process similar to playing ‘connect-the-dots’: each contour connects places where a given quantity is the same. On a weather map we typically contour pressure or temperature.

The map below is a contour map of pressure created from the observations shown on the previous page. Do you understand now what the blue ‘H’s’ and red ‘L’s’ represent? Compare this to your map! The ‘H’s ‘ on a weather map mark L regions of higher atmospheric pressure, and the ‘L’s’ mark regions of lower atmospheric pressure. Where do you see stormy (rainy/snowy) weather? Is it near regions of low or high pressure? ______

______

That’s right! Bad weather is usually associated with regions of LOW atmospheric pressure. That’s why meteorologists are very concerned with accurately measuring pressure.

III.5 Historical Perspective Weather maps today are made with the help of EATHER TATION computers. Computers today can draw contours W ‘S ’ and generate colorful weather maps. But do you In Norway back in the early 1900’s, weather know how this was done in the 1920’s? ofﬁces were quite different to what they are today. Instead of a fancy ofﬁce building, meteorologists sometimes used the upstairs of their home as a place to work. The crucial working equipment consisted of large tables on which weather maps were drawn by hand.

Information from various weather stations was transmitted via telegraphs throughout the world. It took meteorologists about two hours to prepare a hand-drawn weather map and issue a forecast. The meteorologists were not drawing the station models on the maps - that was the job of the Jacob Bjerknes, year 1920 Bergen, Norway Photo courtesy of Mel Shapiro assistants. Meteorologists would draw the maps, and based on that map and previous maps they PORTRAIT OF A WEATHERMAN would make a forecast for the next days. IN 1920 The above photo depicts Jacob Bjerknes - a pioneer of modern weather forecasting. He was the ﬁrst to introduce the concept of fronts into the model of winter storms. He also explained the association of clouds and rain to fronts. Jacob lived in Norway, and came to America in the 1940’s to become a meteorology professor at the University of California at Los Angeles. Later on Tor Bergeron (l) Jacob Bjerknes (r) and assistant at work 1919. in his career he discovered El Nino. Bergen, Norway Photo courtesy of Mel Shapiro

MileHi Girl Scout Council, you Does it look different in will ﬁnd in it a copy of a comparison to the modern HAND-DRAWN map from weather maps? If you Bonus:picked up the 1958. Can you believe how WeatherWise Kit from the smoothly this map is drawn?

III.6 Temperature Map: Although meteorologists are very concerned with air pressure, most people typically want to know the air temperature. After all, this in large part determines what clothes we are going to wear! The map on the right shows contours of the surface air temperature corresponding to the maps shown on the previous pages. Not surprisingly, warmer temperatures are found in the southern portion of the United States and coldest temperatures are in the north. Note that temperature contours are drawn in 5F intervals. Hence, on a map we see the following contours: ... 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105 .. 3. Using a PENCIL, draw a contour, separating z z Try Contouring ! the circles of different color. Note that temperatures higher than 60F are on one side of the contour, and temperatures Let’s have some fun and let’s draw a pretty weather lower than 60F are on the other side! map! Hope you have lots of colorful markers! On the next page you will ﬁnd another copy of a 4. Pick another marker color! Now, with it circle map with selected surface observations. This time temperatures between 40F and 49F. we’re going to look at the temperature which is noted 5. Using a pencil or a marker, draw a contour, to the left of the circles on the station models. To separating the circles of different color. make things easy we will draw contours every 10F, so the contours will be: 70, 60, 50, 40, 30, 20. To get 6. Pick another marker color! Now, with it circle you started the 70F contour has already been drawn temperatures between 30F and 39F. for you. 7. Using a pencil or a marker draw a contour, WHAT TO DO? separating the circles of different color. 1. Pick a marker color! Look above the 70F contour 8. Pick another marker color! Now, with it circle and circle all the temperatures between 60F and 69F. temperatures between 20F and 29F. 2. Pick another marker color! Now, with it circle 9. You’re almost done - now shade the areas temperatures that are between 50F and 59F. between the pencil contours with markers of the same color as your circles!

III.7 The following picture shows a fewRead selected surface the observations Map collected 2 over the United States at one time on Feb 1, 2006. 70F 60F 30F 50F - 20F - ! ! ! ! 70F 40F 60F - 30F - ! ! ! ! 80F 50F 70F - 40F - e z

o the right ar e range with : T t forget which color es. evious page, contour cle each temperatur e ranges that you will mark with e on the above map. HINT uctions on the pr Contour the Map

ent colors. Cir 70F esents which temperatur z fer epr Using instr temperatur the temperatur dif your marker of choice so you don’ r

III.8 More Symbols? By now you understand most of the features of a typical weather map. Are there more symbols on it that puzzle you? What about the red lines with half-circles and blue lines with triangles? Those mark ‘fronts’. z Fronts z

A FRONT IS A BOUNDARY BETWEEN TWO AIR MASSES OF DIFFERENT TEMPERATURES

When a cold air mass (e.g., air from On the other hand, if a warm Sometimes air masses don’t Alaska) is approaching a region of air mass is approaching a cold move very fast. When an cold warm air (for example from the air mass, the transition region air mass meets a warm air Gulf of Mexico), we see a region of is called a warm front. Warm mass and they are just sitting transition on the boundary between air masses, and hence warm next to one another, we call the the two air masses. We call that fronts, come from the transition region between them region a cold front. Cold fronts southwest and move towards a stationary front. typically move from the northwest the northeast. towards the southeast, as that’s Cold Air where the cold air comes from. Mass Cold Air Mass Warm Air Mass Cold Air Warm Air Stationary Front Mass Mass Warm Front Warm Air Mass A stationary front is marked Cold with blue triangles and red Front half-circles. The triangles point Warm fronts are marked with a in the direction in which the Cold fronts are marked with a blue red line with red half-circles. cold air wants to move and the line with blue triangles. The pointy The round side of the half- circles point in the direction in side of the triangles shows the circles shows the direction in which the warm air wants to direction in which the front is which the front is moving. moving. move.

III.9 Eventually, the cold front catches up to the warm z One more front ...z front, and an occluded front forms where the warm and cold front met: There is one more type of front that we need to discuss: the ‘occluded front’. This type of front is Occluded often associated with big storms crossing the Front United States. An occluded front occurs when a cold front catches up to a warm front. How does that happen? Warm and cold fronts usually occur near one Cool Air another when there is a low pressure system, or Very Cold Air an area of low pressure: Warm Air Cool Air

Very Cold Warm An occluded front is marked with a purple line Air Air with triangles and half-circles.

z z In this case we have then really cold air behind Front Skills the cold front, we have very warm air in front of the cold front and behind the warm front, and we Here is your chance to practice what you have learned about fronts! have cool air in front of the warm front. Cold fronts tend to move a lot faster than warm fronts, Look at a weather map and see if you can so after some time, the cold front is closer to the identify the different types of fronts that you warm front: learned about. What is the most common type of front? ______

Cool Air ______Very Cold Air Look for areas of low and high pressure. Are they Warm typically near fronts? Describe. Air ______

______

III.10 z Forecasting z z Predict the Weather z Weather forecasting is quite a difficult skill. It takes a lot of practice to master it! Do you want to Now it’s time for you to become a meteorologist! try? Remember, even the professional meteorologist don’t get the forecast right all the time! 1. Pick a place for which you would like to make a forecast: ______The first step towards forecasting the weather is understanding why we have the current weather. Go 2. Write down the weather today: ______back to the weather map on page 4 - can you ______explain why it is rainy and stormy in some areas, and nice in others? 3. Write down why do you think we’re having that weather: ______Let me give you one additional hint: ______Clouds and rain come from water in the ______atmosphere. Air has the greatest amount of moisture where there is a lot of surface water: for ______example, over the oceans and over large lakes. ______Therefore, a cold front coming from the Pacific Ocean towards Seattle is likely to cause a lot of rain 4. On a newspaper or TV weather map, look to there. A cold front, passing through Colorado the northwest and southwest of your location. Are usually will bring cold temperatures and strong there any cold or warm fronts approaching? winds, but not so much rain. ______‘Weather Map Watch’ is a part of ‘WeatherWise’ - a learning kit designed to teach ba- ______sics of weather, weather instrumentation, and atmospheric science related careers to Girl Scouts. ______5. Make a forecast for the next day: ______For more information visit: http://cires.colorado.edu/education/k12/weatherwise/ ______or contact Jadwiga (Yaga) Richter at [email protected] 6. Next day: Check if your forecast was correct. If you weren’t exactly right, listen to a meteorologist WeatherWise was created as part of the Education on TV explaining the forecast and try to figure and Research Visiting Fellowship at the Cooperative Institute for Research in Environmental Sciences at out what you missed. ______the University of Colorado at Boulder by Jadwiga ______(Yaga) Richter. ______

Repeat steps 4 through 6 and don’t forget to have fun!

III.11