Atmospheric River Reconnaissance Dropsonde Data Impact in the NCEP Operational GFS

Vijay Tallapragada

NOAA/NWS/NCEP Environmental Modeling Center

Tuesday, Sep 08, 2020, 2:00 pm
Webinar

Abstract

Atmospheric Rivers (ARs) are crucial to precipitation and water supply for the West Coast of the United States. AR Reconnaissance (Recon) campaign is a collaborative effort led by Center for Western Weather and Water Extremes (CW3E), Scripps Institution of Oceanography, University of California San Diego involving several partners in the U.S. and abroad, with experts on mid-latitude dynamics, ARs, airborne reconnaissance, and numerical modeling. Environmental Modeling Center of the National Weather Service (NWS) National Centers for Environmental Prediction (NCEP) has developed a Research and Operations partnership with CW3E, US Naval Research Laboratory, National Center for Atmospheric Research, European Center for Medium Range Weather Forecasts and other academic partners to support improved prediction of landfalling ARs in the U.S. West Coast.

In this study we used NCEP GFS version 15 (GFSv15) to examine the impact of the AR supplemental observations dropsonde data on GFS forecasts. The dropsonde data used were from the AR Recon campaigns, including 17 intensive observation periods from 2020. Global control and denial experiments were conducted by using or denying the dropsonde data in the GFS. Preliminary analysis indicates that there is systematic improvement for the precipitation prediction over the U.S. West Coast when the dropsonde data are used. This is associated with improvement of the water vapor transport forecasts and better representation of large-scale circulation. The AR supplemental observations have helped to fill the data gap that is needed for the data assimilation to provide better initial conditions for GFS. In this presentation, the overall GFSv15 performance and the associated dropsonde data impact on AR forecasts will be examined.