This work is now seeing major demand from solar developers who are scrambling to meet new ramp rate requirements. Any new utility-scale power plant operator needs to commit to limiting changes in output (‘ramps’) to 10% per minute - a tall order for PV where a single PV panel could fluctuate over 70% per second. The model - originally published in 2011 and since validated at Sempra Generation’s 48 MW PV plant in Nevada was recently enhanced by accounting for cloud speed. Model application is simple: input plant layout high resolution measurements from a single ground sensor and NOAA cloud speed. The wavelet variability model (WVM) then accurately simulates the ramps experienced by a power plant. Cloud speed can be obtained for the entire US and much of the Carribean from NOAA numerical weather prediction data. Applications: For example simulations for Hawaii show that a closely-packed quadratic 20MW plant would exceed the 10% per minute limit (corresponding to a 2MW change in power output per minute) on average 37 times per day. The maximum 1-min ramp rate over a year would be 8.6MW per minute.