Publication Date

2014-12-10

Availability

Open access

Embargo Period

2014-12-10

Degree Name

Master of Science (MS)

Department

Meteorology and Physical Oceanography (Marine)

Date of Defense

2014-11-04

First Committee Member

Sharan Majumdar

Second Committee Member

Brian Mapes

Third Committee Member

Michael Brennan

Abstract

Over the past 20 years, tropical cyclone (TC) track forecasts have improved significantly while intensity forecasts have improved little. Part of the reason for this lack of improvement in intensity forecasts is a lack of understanding behind the physical mechanisms that control the size and structure of a TC. Previous studies on TC structure have largely focused on wind shear, or have been conducted using idealized TC simulations. This study examines the influence of synoptic-scale vorticity interactions and moisture on the structural evolution of a real hurricane. Simulations were conducted using the Advanced Weather Research Weather Research and Forecasting Model (WRF-ARW) in which the initial conditions were perturbed in order to examine which features may have played a role in the structural evolution of Hurricane Irene (2011). Irene was chosen as a case study given the unique forecasting challenges of this storm in which the track was very well forecast, while the intensity and structure were forecast with skill below the five-year average. The experiments showed that Irene showed little structural sensitivity to vorticity perturbations (except in cases of very strong perturbations), indicating that Irene was not exceptionally sensitive to the larger scale synoptics within the model. Irene did however show significant sensitivity with respect to moisture, where even a small perturbation in the core moisture of Irene led to noticeable changes in the track, intensity, and structure of the storm. This study concludes that even storms in which there is little sensitivity to larger scale synoptic features, significant sensitivity may still exist in other fields, most notably, moisture. This sensitivity emphasizes the importance of properly observing and initializing moisture fields within forecast models.

Keywords

hurricane; tropical cyclone; wrf; meteorology; weather; synoptic

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