Diagnostics of Tropical Variability for Numerical Weather Forecasts

Abstract Tropical precipitation and circulation are often coupled span a vast spectrum of scales from few to several thousands kilometers hours weeks. Current operational numerical weather prediction (NWP) models struggle with representing the full range tropical phenomena. Synoptic planetary particular importance because improved skill in representation larger-scale features such as convectively equatorial waves (CCEWs) has potential reduce forecast error propagation tropics midlatitudes. Here we introduce diagnostics recently developed variability toolbox, where focus on two recent versions NOAA’s Unified Forecast System (UFS): GFSv15 forecasts experimental GFSv16 April October 2020. The include space–time coherence spectra identify preferred coupling between precipitation, pattern correlations Hovmöller diagrams assess model zonal precipitating features, CCEW assessment, plus diagnostic aimed at evaluating moisture–convection tropics. Results show that slightly more realistic than their dynamics synoptic scales, modest improvements moisture convection coupling. However, this performance does not necessarily translate traditional scores. results highlight utility these pursuit better understanding NWP tropics, while also demonstrating challenges translating advancements into skill.