| Description |
Accurate prediction of hurricane track and intensity is a challenging problem in numerical weather prediction (NWP). Evaluation of the performance of a forecast model is an important step in guiding model improvements. In this study, a statistical evaluation of track and intensity forecasts has been performed for the Navy Global Environmental Model (NAVGEM) during June 2014 to November 2014 for the Atlantic, East Pacific, and West Pacific basins. Results show that: 1) the averaged track errors of NAVGEM range from 100 km at day 1 to 460 km at day 5 and 2) the NAVGEM model has good skill in forecasting intensity trends, although the predicted intensifications lag the observed intensifications in many cases. Then, a notable recent hurricane, Hurricane Joaquin (2015) is used to evaluate the ability of NAVGEM analysis and forecasts to represent the atmospheric conditions in both the large-scale environment and the vortex core region of the hurricane. In order to do this, a series of high-resolution mesoscale numerical simulations of Hurricane Joaquin is performed with an advanced research version of the Weather Research and Forecasting (WRF or WRF ARW) model, and the outcomes are compared with NAVGEM largescale forecasts. Specifically, since there was considerable uncertainty in the Hurricane Joaquin NWP track forecast, five groups of sensitivity experiments with different cumulus, boundary layer, and microphysical schemes as well as different initial and boundary conditions and initial times in WRF simulations have been performed to investigate the large-scale environment and hurricane inner-core structures related to the best-track simulation of Joaquin. It is found that the midlevel steering flows and the thermal structure of the hurricane core region are crucial for track and intensity forecasts. A comparison between the NAVGEM forecasts and the WRF simulation during 1200 UTC 30 September 2015 to 0000 UTC 4 October 2015 shows that NAVGEM makes a fairly good track forecast with reasonable representation of hurricane environmental conditions at its resolution. |
