A Meteorologist’s Guide to Forecasting
Written by Shannon Brady
Last updated 10/16/2023, 4:01:29 PM
Have you ever wondered how meteorologists forecast the weather? It’s not all cloud watching and guessing. Meteorologists are actually atmospheric physicists! There is a plethora of maps, math, and measuring and analyzing data that is done before any meteorologist releases a forecast for the day. Every scientist has to take credit for his/her forecast, putting their name on everything.
One of the first things your local meteorologist will look at when making a forecast is a surface analysis map. This map details temperatures, dew point temperatures, wind speeds and directions, and present weather conditions at over 100 weather stations across the United States. Each of these stations across the US reports their present weather and a map is manually created based on that data. A surface analysis is made and released every six hours (NOAA) by a forecaster at the National Weather Service and reveals where weather fronts are and where high and low pressure systems are, which help to determine current weather and predict future weather conditions.
Forecasters also analyze a series of constant pressure maps. A few of these maps include the 500mb pressure map, the 700mb, and the 250mb pressure map. Each of these maps have their own purpose and their own “special” things to look for. When looking at a 500mb constant pressure map, meteorologists are analyzing where the troughs and ridges are, areas of low and high pressure respectively. This pressure shows the general air flow of the atmosphere and can help forecasters predict where storms might move. At the 700mb level, meteorologists are looking for shortwaves which are uplift mechanisms, meaning they can influence the development of storms. Depending on the time of year, meteorologists will look at the 200-300mb pressure maps to determine upper air flow and winds, determining where jet max’s are. A jet max is an area of maximum wind speeds in the jet stream. Finding these jet max areas as well as where upper level air is diverging, or spreading out, helps to determine which areas have secondary uplift mechanisms which help to produce storms.
In addition to these maps of constant pressure, radar and satellite imagery is extremely helpful in forecasting. Satellite imagery has developed and dramatically increased in quality in the last 10-15 years. Meteorologists like to look at the visible, the enhanced infrared, and the enhanced water vapor satellite imagery. Visible satellite imagery helps to show where low level clouds are.
Enhanced infrared shows temperature, specifically cold and high cloud tops. These cold and high cloud tops reveal storm severity. When analyzing the satellite imagery, areas of red and yellow have the coldest temperatures and areas that are black have warmer temperatures.
When looking at enhanced water vapor imagery, scientists are looking at how much water vapor is in the atmosphere. When looking at this data, it’s important to note that it is not known if the water vapor is located in the upper or lower atmosphere. By converging evidence, meteorologists can decipher where that moisture is located. Knowing if its low-level moisture is important when forecasting storms. Areas that are colored brown mean the air is very dry and when the area is in color, there is more moisture in the air.
In addition to these visual maps, math and numerical modeling is used every day to forecast short and long term weather. Meteorologists don't entirely rely on technology; many models are run and then are compared against each other and analyzed by a meteorologist based on observable data, knowledge, and experience (NWS). Although computer models do a good job analyzing data and creating an analysis/forecast and much of weather follows a pattern that we can mathematically calculate, weather can still be very unpredictable and requires real human forecasters to interpret all the data.
These are just a few products your local meteorologist analyses every day to give you the best weather forecast. Meteorologists are hard at work to keep communities safe and informed about present and future weather conditions.
You can take a look at some of these products yourself on weatherTAP.com and try to make your own forecast!