Weather Glossary – Q


QPF– Quantitative Precipitation Forecast

QG Forcing– Upward vertical velocity generated by low level convergence or upper level divergence. Example of phenomena that produce upward QG forcing include low level warm air and moisture advection, positive differential vorticity advection, and the right rear and left front quadrant of a jet streak. If QG forcing is in reference to sinking air, example that cause this are low level cold air and dry air advection, negative differential vorticity advection, and the left rear and right front quadrants of a jet streak.

QVECTORS (QVEC, DIVQ)– A mathematical entity (Q-vectors do not exist in the atmosphere) that allows forecasters to better identify areas of vertical motion. Q-vectors essentially show vertical motions arising from the combination of differential vorticity advection (changes of advection with height) and temperature (thickness) advection. Areas where Q-vectors converge implies upward motion and Qvector divergence (DIVQ) implies an area of sinking motion. Note: Negative Q-vector divergence is the same mathematically as Q-vector convergence, so the statement “…negative divq…” means Q-vector convergence.