A Global Positioning System (GPS) scintillation channel model for the disturbed low-latitude ionosphere is developed by combining first-principles physics-based simulated low-latitude ionospheric irregularities together with an electromagnetic wave propagation model. Using this combined model, basic channel parameters, that is, phase variance, decorrelation length, decorrelation time, and coherence bandwidth, are computed and are favorably compared with recent ground-based low-latitude GPS experimental observations.