GFS Forecast Model: Precipitable Water and 500mb Height Contours - Real-time

To predict where it will rain or snow, meteorologists look at two things: where the storms are moving and how much "fuel" they have to work with. This dataset combines 500mb Height Contours (the steering currents) with Precipitable Water (the available moisture).

The colorful shading represents Precipitable Water. Think of this as a measurement of all the water vapor in a vertical column of air from the ground to the edge of space.

• Blues/Purples (High Moisture): These areas have a high concentration of water vapor. If all that vapor condensed and fell at once, it would result in significant rainfall.
• Reds/Yellows (Low Moisture): These areas represent dry air, where the "fuel" for rain is scarce.

The lines on the sphere are 500mb Height Contours, representing the "middle" of the atmosphere at roughly 18,000 feet, also called the "upper-air chart."

• These lines show the ridges (mounds of warm air) and troughs (dips of cold air) that guide moisture around the planet.
• Notice how the moisture often bunches up and moves along these contour lines like a river following a canyon.

This visualization is powered by the Global Forecast System (GFS). By calculating how these moisture plumes interact with the atmospheric troughs, the model can project where heavy precipitation is most likely to occur over the next 7.5 days.

GFS column precipitable water and 500 mb geopotential height are taken from GRIB2 output of NOAA's Global Forecast System, obtained through NCEP NOMADS. The animation maps moisture through the atmospheric column with 500 mb height contours overlaid. The visualization is updated once per day and shows a 180-hour forecast sequence. Python was used to process and visualize these fields.

• Time frame: Real-time, updated once per day
• Range: 180 hours (7.5 days)>/li>
• Variable: 500 mb height contours, Precipitable water (mm)
• Color Scale: Blue/Purple = High moisture (wet); Red/Orange = Low moisture (dry).