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Yi Dai, Sharanya J. Majumdar, and David S. Nolan

. Frank and Ritchie (2001) argued that the upper-level warm core was ventilated by the environmental flow, leading to top-down weakening by hydrostatic adjustment of low-level pressure. In addition to the midlevel ventilation, the environment shear can also result in a low-level ventilation by downward flushing of low-entropy air from the middle levels to the boundary layer (e.g., Tang and Emanuel 2010 ; Riemer et al. 2010 ). However, TCs can sometimes intensify under moderately strong shear (5

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Jie Feng and Xuguang Wang

for the Atlantic basin in 2016 has a smaller error than the forecast at the 2-day lead time in 1990 ( Katz and Murphy 2015 ). Despite the substantial improvement in TC track forecasts, the progress in TC intensity forecasts is relatively limited ( Harnos and Nesbitt 2011 ; DeMaria et al. 2014 ). Various studies have reported that the accuracy of TC intensity forecasts for the past few decades has little or even no improvements (e.g., Harnos and Nesbitt 2011 ; Zhang and Tao 2013 ). Current

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William A. Komaromi and James D. Doyle

most stronger (weaker) storms in the sample, but with a large degree of variability ( Fig. 4b ). Fig . 4. Scatterplot of azimuthal-mean quantities for all cases with a current intensity ≥30 kt (see Table 1 ). Included are (a) the cold-point tropopause pressure difference (hPa) between the mean from r = 0 to 100 km and the mean from r = 400 to 600 km, with negative values indicating a higher tropopause over the TC center, and (b) the cold-point tropopause temperature difference (°C) between the

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Robert G. Nystrom and Fuqing Zhang

environmental conditions—and the actual low practical predictability of Patricia’s intensity from operational real-time forecasts presents an apparent contradiction and will be explored within this study. Given the large errors by all forecast models in Patricia’s intensification and peak intensity, and given the large divergence among operational forecast guidance, the current study focuses on key uncertainties that may have limited the practical aspects of the predictability of Patricia–despite favorable

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Benjamin C. Trabing, Michael M. Bell, and Bonnie R. Brown

inflowing boundary layer, with the upper-tropospheric “outflow temperature” formally providing an upper and outer thermodynamic boundary condition on a parcel erupting from the boundary layer in the eyewall. Conceptually, the outflow temperature determines the thermodynamic efficiency of the TC heat engine and can be regarded as the temperature of a radiative heat sink for the system. The steady-state assumption in PI theory implies that a TC is in some statistical or radiative–convective equilibrium

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David R. Ryglicki, James D. Doyle, Yi Jin, Daniel Hodyss, and Joshua H. Cossuth

negative ways. Vertical wind shear can weaken a TC through ventilation of the warm core aloft ( Frank and Ritchie 2001 ; Knaff et al. 2004 ); through the midlevel entrainment of dry air ( Simpson and Riehl 1958 ; Cram et al. 2007 ; Tang and Emanuel 2010 ; Ge et al. 2013 ); through the interruption of moist inflow at low levels through flushing of the boundary layer with cold pools ( Riemer et al. 2010 ); by upper-level convergence on the upshear side of the storm ( Xu and Wang 2013 ); or via a

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Xu Lu and Xuguang Wang

. D. Marks , A. Mehra , and V. Tallapragada , 2018 : Role of eyewall and rainband eddy forcing in tropical cyclone intensification . Atmos. Chem. Phys. Discuss. , , in press . 1 The turbulent layer is currently defined as the updraft greater than a certain critical value (e.g. 0.4 m s −1 in this study) above the boundary layer height. Therefore, in the non-deep-convection zone, the vertical diffusivity profile in the modified PBL scheme is

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Nannan Qin and Da-Lin Zhang

fact, it is well known that our ability to predict hurricane intensity and intensity changes, especially for rapidly intensifying hurricanes, has been severely hampered partly by the lack of high-resolution observations to improve the quality of the model initial conditions, especially over vast tropical oceans where few upper-air observations are available, and partly by deficiencies in the current numerical weather prediction (NWP) models, including the model horizontal and vertical resolutions

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Daniel J. Cecil and Sayak K. Biswas

repeatable from one flight to the next. As the temperature variations evolve, so do these systematic errors. For HIRAD, the systematic errors are much greater in magnitude than the random errors. Design considerations have been identified that could greatly reduce those errors in the future, but data from the current experimental version of the instrument require substantial postprocessing to reduce the artifacts resulting from those errors.The initial scene construction follows standard techniques for

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Russell L. Elsberry, Eric A. Hendricks, Christopher S. Velden, Michael M. Bell, Melinda Peng, Eleanor Casas, and Qingyun Zhao

) field. Model dynamics will then adjust the mean and asymmetric wind fields, which in the lower model levels will take into account the planetary boundary layer frictional effects and enthalpy fluxes. Whereas these internal adjustments will determine the intensity change, the TC vortex dynamics and physics prediction are expected to also improve the interaction between the vortex and its environment in conjunction with the better depiction of the outflow jets from the high temporal and spatial

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