A triple point is the intersection of three distinct boundaries at the surface, most often a warm front, a cold front, and a dryline meeting near a surface low. Because three air masses are in contact at the same place, the convergence there is stronger than along any single boundary, and the horizontal shift in wind through the small area is sharper.
How it forms
In a classic Plains setup, a surface low anchors the intersection. A cold front trails southwest from the low, a warm front extends east or southeast, and a dryline pushes south into the moist sector on the warm side. Where the three boundaries meet, low-level flow curls around the low and locally maximizes convergence and low-level rotation.
The exact geometry varies. Two outflow boundaries can meet a synoptic front and form a triple point of their own. On a supercell scale, the point where warm inflow, forward flank rain-cooled air, and rear flank downdraft all meet is also sometimes called a triple point, because the same three-way convergence idea applies at storm scale.
How forecasters use it
Forecasters watch triple points because they combine three things a storm wants at once: focused lift from converging boundaries, deep moisture from the warm sector, and enhanced low-level turning from the pressure minimum overhead. Storms that initiate at or near a triple point often become the day's most organized cells.
On radar and satellite, the triple point shows up as a bend or kink in a fine line, a shift in cloud texture, or a change in wind barbs on a mesonet. Locating it accurately usually requires blending several tools rather than trusting any single analysis.
Important limits
Triple points move. Under strong low-level flow and steady frontal motion, the intersection can drift tens of kilometers over a few hours, and storms that anchor to it will move with it rather than with the mean wind. Chasing an initiation-time triple point after storms are up often ends behind the action.
The triple point does not guarantee a tornadic supercell. It provides the lift and the low-level shear, but cap strength, storm-scale interactions, and how quickly cells pull away from the intersection all shape the outcome. If you are in the threatened region, have a plan to take shelter if a warned storm approaches you.