Real-time Applications of The Variational Version of The Local Analysis and Prediction System (vlaps)

Abstract

The accurate and timely depiction of the state of the atmosphere on multiple scales is critical to enhance forecaster situational awareness and to initialize very short-range numerical forecasts in support of nowcasting activities. The Local Analysis and Prediction System (LAPS) of the Earth System Research Laboratory (ESRL)/Global Systems Division (GSD) is a numerical data assimilation and forecast system designed to serve such very fine scale applications. LAPS is used operationally by more than twenty national and international agencies, including the National Weather Service, where it has been operational in the Advanced Weather Interactive Processing System (AWIPS) since 1995. Using computationally efficient and scientifically advanced methods such as a multi-grid technique that adds observational information on progressively finer scales in successive iterations, GSD recently introduced a new, variational version of LAPS (vLAPS). Surface and 3D analyses generated by vLAPS were tested in the Hazardous Weather Testbed (HWT) to gage their utility in both situational awareness and nowcasting applications. On a number of occasions, forecasters found that the vLAPS analyses and ensuing very short range forecasts provided useful guidance for the development of severe weather events, including tornadic storms while in some other cases the guidance was less sufficient.