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Sensitivity of intensifying Atlantic hurricanes to vortex structure
Author(s) -
Brown Bonnie R.,
Hakim Gregory J.
Publication year - 2015
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.2540
Subject(s) - climatology , environmental science , eye , weather research and forecasting model , storm , forcing (mathematics) , sensitivity (control systems) , convection , meteorology , tropical cyclone , atmospheric sciences , geology , geography , electronic engineering , engineering
Sensitivity analysis is performed in order to determine objectively the role of storm structure during periods of rapid intensification in a sample of five Atlantic hurricanes. Weather Research and Forecasting (WRF) model 24 h forecasts for 96 member ensembles provide the basis for analyses of hurricanes Bill (2009), Earl (2010), Igor (2010), Katia (2011) and Ophelia (2011). Ensemble sensitivity analysis is used to investigate which patterns in the analysis have a strong influence on the forecast intensity and then a novel sensitivity compositing technique is used to identify common patterns that affect the forecast intensity. We find a common response for increasing intensity associated with an initial increased primary and secondary circulation, an increased warm core, an elevated tropopause and moistening of the rain‐band region. Perturbed initial‐condition experiments show a linear response for modest initial amplitude and also signs of nonlinearity for large perturbations, indicating that these sensitivity patterns are robust for limited additional strengthening of the hurricane. When initial perturbations are partitioned into dry and moist variables, we find that most of the forecast change is achieved by the dry dynamics. Further investigation into convective indicators reveals that simulations in which only moist variables are perturbed experience less convective development in the eyewall throughout the forecast.