James I. Belanger

A Revised Model for Radial Profiles of Hurricane Winds

Abstract A revision to the Holland parametric approach to modeling the radial profile of winds in hurricanes is presented. The approach adopted uses information readily available from hurricane archives or in hurricane warning information and the profile can be readily incorporated into existing parametric models of the hurricane surface wind field. The original model utilized central and environmental surface pressures, maximum winds, and radius of maximum winds. In the revision a capacity to incorporate additional wind observations at some radius within the hurricane circulation was included. If surface observations are used, then a surface wind profile will result, obviating the need for deriving a boundary layer reduction from the gradient wind level. The model has considerably less sensitivity to data errors compared to the original and is shown to reproduce hurricane reconnaissance and surface wind profiles with high accuracy.

Predictability of North Atlantic Tropical Cyclone Activity on Intraseasonal Time Scales

Abstract Recent work suggests that there may exist skill in forecasting tropical cyclones (TC) using dynamically based ensemble products, such as those obtained from the ECMWF Monthly Forecast System (ECMFS). The ECMFS features an ensemble of 51 coupled ocean–atmosphere simulations integrated to 32 days once per week. Predicted levels of TC activity in the North Atlantic Ocean with these monthly ensemble forecasts is compared with the observed variability during the months of June–October during 2008 and 2009. Results indicate that the forecast system can capture large-scale regions that have a higher or lower risk of TC activity and that it has skill above climatology for the Gulf of Mexico and the “Main Development Region” on intraseasonal time scales. Regional forecast skill is traced to the model’s ability to capture the large-scale evolution of deep-layer vertical shear, the frequency of easterly waves, and the variance in 850-hPa relative vorticity. The predictability of TC activity, along with the ...

Extended Prediction of North Indian Ocean Tropical Cyclones

AbstractThis analysis examines the predictability of several key forecasting parameters using the ECMWF Variable Ensemble Prediction System (VarEPS) for tropical cyclones (TCs) in the North Indian Ocean (NIO) including tropical cyclone genesis, pregenesis and postgenesis track and intensity projections, and regional outlooks of tropical cyclone activity for the Arabian Sea and the Bay of Bengal. Based on the evaluation period from 2007 to 2010, the VarEPS TC genesis forecasts demonstrate low false-alarm rates and moderate to high probabilities of detection for lead times of 1–7 days. In addition, VarEPS pregenesis track forecasts on average perform better than VarEPS postgenesis forecasts through 120 h and feature a total track error growth of 41 n mi day−1. VarEPS provides superior postgenesis track forecasts for lead times greater than 12 h compared to other models, including the Met Office global model (UKMET), the Navy Operational Global Atmospheric Prediction System (NOGAPS), and the Global Forecasti...

Extended Prediction of North Indian Ocean Tropical Cyclones Using the ECMWF Variable Ensemble Prediction System

This analysis examines the predictability of several key forecasting parameters using the ECMWF Variable Ensemble Prediction System (VarEPS) for tropical cyclones (TCs) in the North Indian Ocean (NIO) including: tropical cyclone genesis, pre-genesis and post-genesis track and intensity projections and regional outlooks of tropical cyclone activity for the Arabian Sea and the Bay of Bengal. Based on the evaluation period from 2007 to 2010, the VarEPS TC genesis forecasts demonstrate low false alarm rates and moderate to high probabilities of detection for lead-times of one to seven days.