HURRICANE “FELIX” NICARAGUA FLASH APPEAL 2007 1 1. Meteor. The pouch can protect the mesoscale vortices inside from the hostile environment, such as dry air associated with the Saharan air layer. The first stage is the preconditioning of the synoptic and meso-Both groups of mesoscale theories (top-down and bottom-up) focus on the second stage of the TC formation. The intersection of the critical latitude and the trough axis pinpoints the pouch center as the preferred location for tropical cyclogenesis.Initial streamlines for the control experiment (in the resting frame of reference) and relative vorticity (shadings, 10Initial streamlines for the control experiment (in the resting frame of reference) and relative vorticity (shadings, 10To examine the Lagrangian characteristics of the pregenesis evolution, most of the analyses in this study are carried out in the comoving frame. For a complete definition of all technical terms used herein please consult The inverted-V patterns in earth-relative streamlines and low cloud or water vapor should not be confused, as they are (dynamically and longitudinally) distinct. Part I: The Role of the Easterly Wave Critical Layer. The dashed contours represent the streamlines in the ground-based frame of reference, which usually have an inverted-V pattern.
This site uses cookies. Simulation on the innermost grid began six hours later (at 0600 UTC 29 August 2007) to allow for some model adjustment.In the control simulation, the Kain–Fritsch scheme (As reported by the NHC, Felix formed within a tropical easterly wave that departed the west coast of Africa on 24 August 2007. EXECUTIVE SUMMARY Category 5 Hurricane Felix made landfall at 04:45 a.m. local time on Tuesday, 4 September at Sandy Bay, on the Atlantic Coast of Nicaragua. At 850 hPa, the wave signal is much weaker, and the dominant feature is the quasi-stationary ITCZ, where cross-equatorial westerlies converge with trade wind easterlies (This is better illustrated in the earth-relative frame of reference in It is possible to view the vertical interaction between lower-tropospheric easterly waves and near-surface ITCZ features in a complementary way, noting that the ITCZ is a region of frequent deep convection, low-level cyclonic vorticity and convergence, and abundant moisture. As demonstrated in the observational study of In the numerical simulation the wave pouch is a region of cyclonic rotation and weak strain/shear deformation that protects the moist air inside from dry air intrusion. These changes resemble a steepening surface wave.Aside from this in situ moistening, the pattern is strikingly clear: the parent wave resides on, and deforms poleward, the underlying ITCZ (Turning attention to the mesoscale developments, the 850-hPa OW parameter and precipitation superimposed on the translated streamlines from 24 to 52 h are shown in The deterministic feature of the genesis location is in sharp contrast with the unpredictable nature of convective processes and implies a “guiding hand” from larger to smaller scales—that is, an influence of the synoptic-scale (tropical easterly wave) or meso-To understand storm formation in the Lagrangian point of view, the evolution of divergence, vorticity, relative humidity, and pseudoequivalent potential temperature The time–vertical cross sections of the divergence, relative vorticity, relative humidity, and equivalent potential temperature following the pouch center during 22–72 h are shown in Vertical distribution of the 2° × 2° box averages of (a) divergence (10Vertical distribution of the 2° × 2° box averages of (a) divergence (10The evolution of divergence following the wave pouch is shown in The evolution of vorticity following the pouch is shown in Vorticity budget averaged in a 2° × 2° box following the wave pouch center from hour 22 to 72: (a) vorticity tendency, (b) convergence of the advective vorticity flux, (c) convergence of the nonadvective vorticity flux, and (d) the residual term. The range of longitudes displayed is held fixed to emphasize the change of flow topology (more circular flow in the wave pouch, and more southerly monsoon flow behind it) and increasing detachment of the wave pouch from the ITCZ complex to the east. The wave propagation speed is −9.8 m sTime series initialized at 0000 UTC 29 Aug of (a) the minimum surface pressure and (b) the maximum 1000-hPa wind speed in the earth-relative frame (solid line) and the comoving frame (dashed line). The formation of pre–Hurricane Felix (2007) in a tropical easterly wave is examined in a two-part study using the Weather Research and Forecasting (WRF) model with a high-resolution nested grid configuration that permits the representation of cloud system processes. Map Labels. The translated streamlines, Okubo–Weiss (OW) parameterThe (top) 600-hPa and (bottom) 850-hPa streamlines and OW parameter (color shading, 10The (top) 600-hPa and (bottom) 850-hPa streamlines and OW parameter (color shading, 10At 600 hPa, a pouch is present from the beginning of the simulation (not shown). The range of longitudes displayed is held fixed to emphasize the change of flow topology (more circular flow in the wave pouch, and more southerly monsoon flow behind it) and increasing detachment of the wave pouch from the ITCZ complex to the east.