Suppose that the 500mb geostrophic relative vorticity at Prescott is increasing at a rate of 1×10−6 s−1 per 3 h. If the wind is from the southwest at 25 m s−1 and the relative vorticity is decreasing toward the northeast at a rate of 4×10−6 s−1 per 100 km, estimate the horizontal divergence at Prescott using the quasi-geostrophic vorticity equation. Use β=1.6×10−11 m−1 s−1 and f0=1×10−4 s−1