Pressure tendency

Also called pressure change, 3-hour tendency, barograph

Station model. What an observer recorded, not a weather-app forecast.

Pressure tendency meaning

Pressure tendency on a station model is the change over three hours: an amount in tenths, and a symbol for whether it rose or fell. It is not the pressure itself.

At a glance

System: NOAA station model
Used for: The three-hour pressure change
Not the same as: The sea-level pressure code, or a front

How pressure changed in the last three hours. Not the sea-level pressure code, and not a front.

The name. The tendency is the three-hour pressure change, a number in tenths plus a symbol for the shape of the change.

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Where it comes from

The Weather Prediction Center describes the tendency as the three-hour change in tenths of a millibar, plotted with a symbol. The three-digit sea-level pressure nearby is a different code, the one that turns 103 into 1010.3. This page does not redraw every tendency symbol in the plotting handbook. The rising stroke in the drawing is a reading aid for “pressure rose,” not a claim that one diagonal is the whole code.

The line drawing is original to this cabinet. It is not an agency logo, a vendor icon, or the emoji for the same idea.

Weather

What it means

The barometer’s recent behavior at that station. Rising and falling are the part a reader can use without the full symbol set: the air column was gaining or losing. A front on a map is a boundary between air masses. A tendency can agree with a front’s approach and still not be the front. The isobar is the line of equal pressure. The tendency is the change at a point.

Variants

The symbol set

Steady, then rising, falling then rising, and the other shapes are why the code is a set. If you are plotting, use the handbook. If you are reading, trust the number’s sign and the legend on that map.

Questions

What is the pressure tendency on a station model?

The Weather Prediction Center plots the three-hour change in tenths of a millibar, plus a symbol for how the trace behaved. It is not the three-digit sea-level pressure.

Does a falling tendency mean a low is coming?

It means pressure fell at that station. A low on the map is a pressure center. The two are often discussed together. They are not the same symbol.

Often confusedIsobarAn isobar joins equal pressures on a map. The tendency is one station’s change.

Often confusedStation modelThe three pressure digits are the pressure. The tendency sits with them and means the change.

Near this

Sources

Named when the entry depends on a text, a date, or a standard. Catalog numbers are not invented.

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symbol.wiki, edited as Sigilla. Last reviewed 18 October 2026. A reading of public tradition, not a ruling.