Definition
In a METAR, PO is the weather phenomenon code reported when well-developed dust or sand whirls are observed at or near the station. These are small, rotating columns of air made visible by the dust or sand they pick up from the surface, typically forming on hot, dry days when strong surface heating creates rising air that begins to spin. They are reported under the present weather group of the METAR.
Plain English
PO is the code used in a weather report to say that small spinning columns of dust or sand are forming on the ground near the airport.
Context Anchor
Seen in the present-weather part of a METAR, where short codes describe weather observed at or near the airport.
Derivation
PO comes from the French "poussière," meaning "dust." Aviation weather codes were standardized internationally, and several abbreviations trace back to French because of its historical role in international aviation and meteorology.
Why Pilots Care
These whirls can suddenly reduce visibility and create brief but sharp changes in wind near the runway, affecting takeoff and landing safety.
Grounding Statement
Picture a sunny desert ramp on a hot afternoon: a small, swirling column of dust suddenly lifts off the ground and dances across the airfield -- that is what PO reports.
Intuition Check
Do not read PO as a general warning for dusty air everywhere. In a METAR, PO specifically means dust or sand is being lifted in rotating whirls.
Example Sentence 1
The METAR included PO in the present weather, alerting the pilot to dust whirls forming on the field.
Example Sentence 2
Ground observers reported PO near the airport, prompting the crew to delay departure until the whirls dissipated.