Photo credit: Ametsoc.org
How to Read a Weather Station Model Plot
WXobservation is a site all about weather observation and the tools that help us automate the process and make it easy to share with others in the community. It seems like we’re constantly discussing how to upload weather data to the web. We even have an article telling you how to find weather stations nearby that share weather data. But, what good is all that if don’t know how to read a weather station model? I figured it was about time to go over some weather station symbols so you can understand the maps if you don’t already.
Station Plot Example
As you can see in this example, there are symbols and numbers set up that offer all the weather data observed and recorded including temperature, wind speed and direction, pressure, pressure trend, sky cover, dew point, and the general weather conditions. Station model plots in the United States typically report data in Imperial units, whereas metric units are used in much of the rest of the world.
Common Weather Station Symbols and Their Meanings
Here are some of the common readings and symbols you’ll find around a weather station plot or on a weather map. Note, this list is not exhaustive as some maps show even more information, but this covers the basics without getting too deep into the weeds. We’ll go around the station plot example above in a clockwise fashion.
I think the temperature is pretty self-explanatory. This is the temperature at the time of the observation or at the last update.
Wind Speed and Direction
I think this is the most fun symbol on a station plot. Wind is indicated with a flag-shaped pattern. The direction the flag comes into the center circle is the direction the wind is going. To make sure I said that clearly, the direction of the flag in relation to the circle is the direction the wind is coming from.
The lines and flags on the post indicate the wind speed in knots. For those unfamiliar, 10 knots is equivalent to 12 mph. A flag represents 50 knots, a line is 10 knots, and a half line is 5 knots. So, a post with a flag, a line, and a half line would indicate 50 + 10 + 5 = 65 knots. If the winds are calm, this would be indicated with another circle around the center circle. Here are some more examples.
The sea-level pressure show is in tenths of millibars (mb), however the first digit or two is always left off. It will always be a 9 or 10 in front of the 3 digits, whichever gets the number closer to 1000. For example, 107 is actually 1010.7 mb. The 10 is added to the front since 1010.7 is closer to 1000 than 910.7 is. For those not used to millibars, 30 in-HG is about 1015.9 mb.
The pressure trend is shown in symbols that indicate changes over the most recent three hours. Here are the symbols commonly used for pressure trend. In some station plots, you’ll see a number next to the trend. In this case, the number indicates how much the pressure has risen or fallen during the past 3 hours.
The center circle is the location of the observation, but the symbol itself also indicates what kind of sky cover was present during the observation. The symbol is filled according to the estimated amount of cloud cover in the sky. Here are some common depictions.
Again, like the temperature, the dew point is indicated just by a number. This reading is the temperature at which the air would cool enough to be saturated with water. For this reason, the dew point temperature will never be higher than the air temperature. Additionally, you can get an idea of relative humidity through this dew point temperature. As the dew point temperature becomes increasingly close to the air temperature, this means that air is gaining moisture and thus, the relative humidity is also higher. The humidity is likely becoming uncomfortable as this dew point temperature increases past 65 degrees F.
This one is interesting to me. These common weather station symbols represent the current weather conditions. A dot is used for rain and an asterisk for snow, with the number of dots or asterisks indicting to what extent it is happening. For example, 2 dots is light rain, 3 dots is moderate rain, and 4 dots means there is heavy rainfall. See below for a list of examples or visit NOAA’s Aviation Weather Center for a more comprehensive list of common weather station symbols and their meaning.
We hope you enjoyed this short lesson, or refresher, depending on your previous exposure. You should better understand how to read a weather station model now. We’ve covered measurements and common weather station symbols and explained what they all mean and how they look. Here’s a page full of active station plots. Take a minute to go zoom in on your area and test out your new knowledge!
Interested in making your own observations? Check out our best home weather station page for ideas where to start!