INTRODUCTION TO DRAWING ISOPLETHS
Upon completion of this unit, students will be expected to know:
- How to recognize changes in weather patterns based on analyzed
- How to analyze weather maps by drawing isopleths.
- How to draw isopleths using raw data.
- How isopleth information can be used in forecasting weather
- How significant weather changes can change their lives and the
lives of those around them to include crops, livestock, and wildlife.
- Students should be given an understanding of how significant
weather patterns can affect even migration habits of wildlife
including insects, and even sometimes the transfer of diseases.
The following Colorado Model Content Standards for Science will
be met or exceeded: (Unless otherwise noted, the standards for grades
5 through 8 are used.)
Standard 1, 2.1, 2.2, 3.1, 3.3, 4.1,4.2, 5, 6,
The following Texas Essential Knowledge and Skills for Science
will be met or exceeded: (Unless otherwise noted, the TEKS for Middle
School Science are used.)
TEKS 6.1A,B, 6.2A,C,D,E 6.3A,B,C,D 6.4A,B, 6.9A, 7.1A,B, 7.2A,B,C,D,E,
7.3A,C,D, 7.4A,B, 7.12C, 7.14A,B, 8.1A,B, 8.2A,B,C,D,E 8.3A,C,D,E,
8.4A,B, 8.5A,B,C, 8.10B, 8.12B
Other standards from other specific subject areas and grade levels
are also covered.
Isopleths are simply lines that connect measurements of equal value.
They may be isopleths of equal temperature (isotherms), pressure
(isobars), altitude or almost any other measurement including precipitation
and snow cover. In short, they graphically represent a constant
measurement or value.
A change in the measured value represents a gradient. When the
isopleths are close together, a large change takes place and the
gradient is said to be large. This could represent a significant
change in weather over a small area, a steep slope on a topographic
map, or a large difference in precipitation amounts. Isopleths spread
out indicate a small change and the gradient would be small, so
would represent a gradual slope, or small weather-related change.
Large pressure and temperature gradients represent dramatic, sometimes
dangerous changes in the weather, so meteorologists are very concerned
with how the isopleth patterns and contours shape up each day.
Drawing isopleths on a map may be somewhat confusing, challenging,
and difficult at first, but with practice, one can become good at
it and actually enjoy studying the changes and analysis of a map;
it can be quite satisfying to solve the daily weather puzzle.
The following guidelines will help you get started:
- No isopleth lines will ever cross each other.
- Isopleth lines form curved lines not corners.
- Estimates must be made between point values. (Example 66 is
closer to 70 than 60, so you must adjust where you draw your line.)
ISOPLETH ACTIVITY 1
In this activity, be flexible. You can have students work individually,
or in groups up to 4 students. It will give them an idea of how
variable rainfall amounts are by using colored confetti. Each individual
or team will draw isopleths based on how many pieces of "confetti
snow" land in their cup and the cups of the other groups/individuals.
It should be explained to students that precipitation patterns affect
where people live, build their homes, what different animals live
in different climates and environments with different precipitation
amounts, and how a sudden downpour or severe snow event can affect
the lives of both people and wildlife.
- A substantial amount of different colors of paper confetti (confetti
snow) which may simply be small pieces of colored construction
- Paper cup for each group/individual placed in a grid. (For instance
if you have 12 students make a grid of cups of 3 cups by 4 cups,
or 25 students, make it 5 by 5, etc.)
- Grid paper marked off similar to the cup grid you have made.
- PENCIL and eraser.
- Colored pencils (optional).
- worksheet HTML version,
1. Place the cups in the grid on the floor. (See examples below.)
O O O O
O O O O
O O O O
(3 X 4 GRID
FOR 12 STUDENTS)
O O O O O
O O O O O
O O O O O
O O O O O
O O O O O
(5 X 5 GRID
FOR 25 STUDENTS
2. Scatter the "confetti snow" all over the grid randomly.
3. Have the students count the pieces of confetti in their cup and
write that number on their grid paper where their cup was. They
will also need to share with the other students/groups what their
count was in order for each group to complete their grid paper.
One idea would be to put a sample grid on the board or overhead
and write in it for them to copy.
4. Have the students color the grid points with equal numbers a
certain color. (For instance, all the 5's are red, the 4's are green,
5. Have the students connect the grid points of equal values with
each other in smooth lines.
6. (Optional) have the students color in areas of equal value over
the entire grid paper, much like a weather map with areas of equal
7. For the students more gifted in art, you might want them to shade
from light to dark.
Just like the "snow confetti", precipitation patterns
may seem very random over an area. We have all heard of heavy rain
on one side of the road and a sprinkle on the other, or a severe
hail storm on one side of town with tremendous damage, and no hail
on the other side of town.
It is important that when we build a home, we make certain that
it is above a flood plain, or if we purchase a farm that it is not
likely to be washed away the next time we have a downpour. It is
equally as important to our wildlife that they build their homes
accordingly. Students should be aware of this, and what happens
when unusual precipitation occurrences happen.
ISOPLETH ACTIVITY 2
TODAY'S ISOTHERM PATTERN
In this activity, students will learn to draw isotherms using a
current weather map with temperatures. They will begin to understand
how weather patterns form according to temperature gradients, and
how to analyze where a cold front or warm front may be located.
It may work best if the students work in groups of two, but depending
on the class, it may be better to work individually.
Temperature patterns affect the lives of almost every living organism
and the economy of each area and should be discussed when doing
- Select different colors for temperatures that have the same
first digit. (Examples: all the 50's are green 60's are blue-green,
70's blue etc.)
- Put a colored dot at each station that matches the proper color
for that station's temperature.
- Draw isopleths at 10 degree intervals (gradients) based on the
different colors. (Always use a pencil and have an eraser when
first drawing isopleths. You can go over your lines with a dark
pen when you have satisfactorily finished.)
- Color in each of the gradients with the corresponding colors.
(Artistic students shade from light to dark. Example: low 50's
would be light green, high 50's dark green. It makes a very attractive
- Analyze the gradients. If there is a large gradient, there is
a significant change in the weather over a small area. This would
indicate a cold or warm front. (Go to http://dstreme.comet.ucar.edu/images/sfc_adv.gif
to find where the fronts are for today.
- Never be upset if your analysis is not exactly the same as another's!
Temperature patterns are very important for most of us. They can
help us decide what to wear tomorrow, or possibly help a foreman
decide if he will send his construction crew out tomorrow. These
and other ideas should be discussed after the students have completed
their maps successfully.
ISOPLETH ACTIVITY 3
DRAWING TODAY'S ISOBARS
Isobars are lines of equal barometric pressure. They are valuable
to the meteorologist in determining many factors of a weather forecast
such as wind speed and wind direction. The larger the pressure gradient,
the faster the wind will blow, and it will always blow from areas
of high pressure to areas of low pressure. This is a bit more challenging.
Have patience with yourself and students!
- Have the students start with a pressure of 1012, and highlight
all pressures between 1012 and 1015 orange, pressures 1016 and
above red, pressures between 1008 and 1011 yellow, pressures between
1004 and 1007, blue, and pressures below 1004 green.
- Have the students make isobar lines of 1004, 1008, 1012, and
- Have the students determine where the large and small pressure
Large pressure gradients (large change/small area) are usually indicators
of unsettled and stormy weather.
Small pressure gradients (small or no change/large area) are usually
indicators of fair or nice weather.
Look at today's weather map and see where the stormy and calm weather
are and compare it to your maps.
You may want to discuss with your class how the behavior of animals
(even students) seem to change with the change of a pressure system.
ISOPLETH ACTIVITY 4
ANALYZING PRECIPITATION PATTERNS
Now that your students are showing an understanding of drawing isopleths,
a nice challenge is to analyze precipitation patterns using CoCoRaHS
maps. These patterns can be very important to farmers, construction
sites, schools, and the list would be never ending. The patterns
indicate where flooding is or may be occurring downstream, where
mosquito populations will increase, what schools will take a snow
day, what crops will be destroyed, where mudslides will happen,
and once again, the list goes on.
Depending on the time of year, geographic location etc., precipitation
patterns will many times be very random and unpredictable, while
at other times of the year, they may be very general. In areas just
east of the Rockies, precipitation patterns present a special problem
for forecasters because of their unpredictability and sudden changes
that sometimes can lead to disaster. (Copy the article located at
www.cocorahs.org/pdfs/Coco4pg.pdf and make it available to students.
You may want the students to read the article aloud in class.)
Find a CoCoRaHS archived map for precipitation, hail, or snowfall
and have students draw isopleths according to them and give possible
conclusions of the results and consequences of such a weather event.