Radar resolution is the smallest separation, either along the beam or across it, at which two features can be distinguished as separate returns rather than merged into a single sample volume. It sets the finest detail the radar can honestly show, no matter how the data are colored or interpolated on screen.
Range resolution and azimuthal resolution
Range resolution is the ability to separate two targets along the same radial. It is fundamentally set by pulse length, and is roughly half that pulse length. The WSR-88D uses range gates of about 250 meters, which is why fine along-beam structure inside a storm typically resolves at that scale.
Azimuthal resolution is the ability to separate two targets side by side across the beam. It is set by beamwidth, and it degrades with range because the same one-degree beam covers more physical width the farther out it goes. Close to the radar, two circulations 500 meters apart may resolve cleanly; at 100 nautical miles they may merge into one sample.
How forecasters use it
Forecasters treat resolution as a limit on what a single radar can claim. Fine-scale features like tornado vortex signatures, tight gate-to-gate shear, and thin boundary lines are only trustworthy when they are inside the range where the beam is still narrow enough to resolve them.
Super-resolution products on modern WSR-88D radars use 0.5 degree azimuthal spacing on lower tilts, which sharpens low-level velocity signatures at close and moderate ranges. Even so, physical beamwidth is what actually sets the resolvable scale.
Where resolution misleads
A storm at long range paints as a coarse patch of large pixels, so a real hook or a real couplet inside it may not appear at all. Users unfamiliar with beam geometry sometimes read the smoother distant picture as a calmer storm, when the storm may simply be too far away to resolve its important features.
Pulling in a nearer radar, checking adjacent tilts, and cross-checking against surface reports are the standard ways to compensate. Composite products help visually but do not add new information that was not in the raw volume scan.