This is the basic step by step process of How to Read A Weather Map. You can see here in a nice presentation the basic knowledge how to analyze a weather map AKA Synoptic charts.

1. HOW TO READ A WEATHER
MAP
Ezra Dave C. Ignacio
MT31FA2

2. 1. Understand general concepts of precipitation. What
most people are concerned with is precipitation,
in meteorology (the study of weather), is any form of
water that falls onto the Earth's surface. Forms of
precipitation include rain, hail, snow, and sleet.

3. 2. A major aspect of weather interpretation involves
being able to understand the actions caused by
differences in air pressure. High pressure implies dry
weather and low pressure is usually associated with
humid air-perhaps precipitating.

4. 3. Study a weather map. Watch out for one on the TV
news, online, or in your local newspaper. Newspapers
are a convenient method to find a weather map as
are cheap, reliable, and can be cut apart so you can
carry them with you while learning to interpret the
symbols.

5. 4. Analyze a small portion of your weather map. If
possible, find a map covering a smaller area – these
can be easier to interpret. Focusing on a larger scale
may be difficult for a beginner. On the map, notice
location, lines, arrows, patterns, colors, and numbers.
Every sign counts and all are different.

6. 5. Understand what air pressure measures. This is the
weight or pressure the air exerts on the ground and is
measured in millibars. It is important to be able to
air pressure because pressure systems are associated
with certain weather patterns.

7. 6. Learn the air pressure symbols. To read air pressure
on a surface analysis weather map, check for isobars
(iso = equal, bar = pressure) – plain, curved lines that
indicate areas of equal air pressure. Isobars play a
major role in determining the speed and direction of
wind.

8. 7. Learn how to interpret a Low Pressure System
(Cyclone). These storms are characterized by increased
cloudiness, winds, temperatures, and chance of
precipitation. They are represented on a weather map by
isobars that are close together with arrows traveling
clockwise (Southern Hemisphere) or counter-clockwise
(Northern Hemisphere).

9. 8. Learn how to interpret a High Pressure System.
These conditions indicate clear, calm weather with
reduced chance of precipitation. Drier air usually
results in a greater range of high and low
temperatures.

10. 9. Observe the types and movement of fronts. These
mark the boundary between warmer air on one side
and colder air on the other. If you are close to a front
and you know the front is moving towards you, you
can expect a change in weather when the front
boundary passes over you.

11. 10. Analyze a Cold front. With these weather patterns,
rainfall can be torrential and wind speeds can be high.
Blue lines with triangles on one side represents cold
fronts on weather maps. The direction the triangles
point is the direction in which the cold front is

12. 11. Analyze a Warm front. These often bring a gradual
increase in rainfall as the front approaches, followed by
prompt clearing and warming after the front passes. If the
warm air mass is unstable, the weather might be
characterized by prolonged thunderstorms. A red line
semi-circles on one side represents warm fronts.

13. 12. Study an Occluded front. These are formed when a
cold front overtakes a warm front. They are associated
various weather events (possibly thunderstorms)
depending on whether it is a warm or cold occlusion. A
purple line with semi-circles and triangles both on the
side represents occluded fronts.

14. 13. Analyze a Stationary front. These indicate a non-
moving boundary between two different air masses.
fronts have long continuous rainy periods that linger for
extended periods in one area and move in waves. A semi-
circle bordering one side and triangles along the opposite
side represents that the front is not moving in any

15. 14. Read the station models at each point of
observation. If your weather map has station
models, each one will plot the temperature, dew-
point, wind, sea level pressure, pressure tendency,
and ongoing weather with a series of symbols.

16. 15. Study the lines on the weather map. There
are many other lines on weather maps. Two of
the most important kinds of lines indicate
isotherms and isotachs.

17. 16. Analyze the pressure gradient. A number on the
isobars, such as "1008", is the pressure (in millibars)
along that line. The distance between isobars is
referred to as the pressure gradient. A large change in
pressure over a short distance (i.e. close isobars)
indicates strong winds.

18. 17. Analyze wind strength. Wind barbs point in the
direction of the wind. Lines or triangles coming off
the main line at an angle indicate wind strength:
knots for every triangle, 10 knots for every full line,
5 knots for every half line