Definition
A meteorological term describing a decrease in the central atmospheric pressure of a low-pressure system (a cyclone or trough) over time. As the central pressure falls, the pressure gradient around the system steepens, generally producing stronger winds and more vigorous weather.
Plain English
A low-pressure weather system is getting stronger because the pressure at its center is dropping. The lower the center goes, the more intense the system becomes.
Context Anchor
Seen in aviation weather forecasts and weather briefings when discussing developing lows, fronts, and storm systems.
Derivation
From the everyday word 'deep.' In weather, a low is described as getting 'deeper' the further its central pressure falls below surrounding pressure — like a basin getting deeper. 'Deepening' simply means that process is happening.
Why Pilots Care
A deepening low indicates the system is strengthening, often bringing stronger winds, lower ceilings, and more turbulence.
Grounding Statement
If a low-pressure system is deepening, expect the weather around it to become more active rather than settle down.
Intuition Check
Deepening does not mean clouds are getting physically deeper. Here it means the pressure at the center of a low-pressure system is dropping.
Example Sentence 1
The forecaster noted that the low over the Great Lakes was deepening rapidly, so we delayed our departure until the front passed.
Example Sentence 2
Pilots delayed departure because the deepening trough was expected to bring strong crosswinds.