Environmental influences on the wind and precipitation distribution in Hurricane Irene (2011)

In August 2011, Irene made landfall on the east coast of the United States, first in North Carolina as a category one hurricane and then in New Jersey and near New York City as a strong tropical storm about a day later. A few days prior to its landfall in North Carolina, Irene underwent structural changes, evolving into a broad wind field that lacked deep inner-core convection. Due to the limited capability of current tools to reliably predict structural changes in tropical cyclones, the intensity of Irene was over-predicted. In this study, environmental influences such as relative humidity, vertical wind shear, and instability are retrospectively explored in the context of the prediction of Irene's wind field and rainfall distribution. Among the tools used here are satellite-derived wind vectors, and analyses and forecasts from the National Center for Environmental Prediction's (NCEP) Global Forecast System (GFS). The primary environmental influences, and their effects on the numerical forecasts will be presented.