Tracking 2012 Atlantic Hurricanes Using NASA’s GEOS-5 AGCM

Abstract:

On average, the Atlantic Hurricane Season consists of 11 named storms, including six hurricanes. However, the 2012 hurricane season tied with the 1887, 1995, 2010, and 2011 seasons for having the third-most named storms on record, with 19 named storms, 10 of which were hurricanes. Seven of these systems made landfall in North America, including Hurricane Isaac and "Super-Storm" Sandy. This active season also included Hurricane Nadine, the fourth longest-lived Atlantic hurricane on record. The structure and life cycle of these severe storms can be viewed through the detailed meteorological analyses and forecasts that the Global Modeling and Assimilation Office (GMAO) conducts on a routine basis with our GEOS-5 Atmospheric General Circulation Model (AGCM) system. GMAO routinely produces five-day forecasts twice daily, at 0000 and 1200 UTC, using the GEOS-5 AGCM. The GEOS-5 atmospheric data assimilation system is used to generate near real-time analyses of the atmosphere over the globe every six hours. These analyses provide the initial conditions for the GEOS-5 forecasts. Following the abnormally active 2012 Atlantic hurricane season, one focus has been on the skill of the GEOS-5 forecasts of tropical storms in the Atlantic, East Pacific, and West Pacific.

In this presentation it’s shown the results for two of the most destructive storms of the Atlantic season: Hurricanes Isaac and Sandy, and the 2012 Season’s Track Forecast Error. The primary impetus for investigating these two storms was the opportunity to test the ability of the model to reproduce their track and intensity forecast. We observe several features associated with the morphology and inner core of these storms indicative of the capability of the model to reproduce these tropical systems. GEOS-5 predicted Sandy's intensity to within a few hectopascals over much of the life of the storm. The model also predicted some of the finer details of Sandy’s evolution. The forecast from 12z 26Oct2012 appeared to perform the best at forecasting Sandy's intensity. This same forecast correctly predicted the location of Sandy's landfall. Furthermore, this study also shows how the model rapidly creates a closed circulation from a tropical wave up to 24 hours before these TCs are detectible in nature, without any vortex relocation information.