An environmental synoptic analysis of tropical transitions in the central and Eastern North Atlantic

Horizontal kinetic energy analysis of tropical transition simulations with the WRF and HARMONIE‐AROME models

“…The distribution seems to be inverted at the mesoscale (Figure 5), with negative values for the middle and upper troposphere and a contribution from APE to HKE in the lower troposphere and the stratosphere. The positive C A→h values for the low levels could be related to the direct forcing of APE by the latent heating, of major importance in these kinds of system (Calvo-Sancho et al, 2022). Similar results in the tropospheric C A→h behaviour are shown by Peng et al (2015a;2015b), who studied the spectral energy budget associated with WRF baroclinic wave simulations and indicated that the energy conversion of APE to HKE is mainly promoted by moist processes, which take place at all the mesoscale and synoptic wavelengths below 1,000 km.…”

“…Upper tropospheric disturbances have the potential to develop TTs in environments characterized by low sea-surface temperature (McTaggart-Cowan et al, 2015;Calvo-Sancho et al, 2022) and moderate-to-high vertical wind shear (Bracken and Bosart, 2000;Molinari et al, 2004;McTaggart-Cowan et al, 2008Calvo-Sancho et al, 2022). Therefore, a TT is the process whereby a baroclinic extratropical or subtropical cyclone, commonly presenting high-to-moderate vertical wind shear, is transformed into a warm-core, low vertical wind shear tropical cyclone.…”

“…Furthermore, extratropical transition of ex-Hurricane Ophelia severely affected Ireland (Moore, 2021). Calvo-Sancho et al (2022) analysed 30 TT events over the central and eastern North Atlantic basin during the period 1979-2019, studying their synoptic environments to highlight their common features and differences. In this study, the importance of potential vorticity redistribution and latent heat release on the transition time is emphasized.…”

“…Since the skill to reproduce the theoretical power-law dependence spectra is regularly shown as evidence of the accuracy of the formulation, implementation, and configuration of an atmospheric model (Skamarock et al, 2014), in the current study the HKE spectra for several high-energetic atmospheric systems, such as TTs, is evaluated using two NWP models. The most severe TTs analysed by Calvo-Sancho et al (2022) are selected and simulated using two NWP models: the mesoscale Weather Research and Forecasting (WRF) and the HARMONIE-AROME. The ERA5 climatology of the HKE spectra is used as a reference curve to compare against in this study, highlighting the value of high-resolution simulations in the spectrum results and how the models assume and manage the atmospheric energy in the simulation.…”

“…One of the possible disturbances can be a tropical transition (TT). The TT is a form of tropical cyclogenesis associated with extratropical precursors in which a baroclinic cyclone evolves and mutates into a tropical cyclone when affected by an upper tropospheric disturbance originating in midlatitudes (Davis and Bosart, 2003, 2004; Hulme and Martin, 2009; Galarneau et al ., 2015; McTaggart‐Cowan et al ., 2015; Bentley et al ., 2017; Calvo‐Sancho et al ., 2022). The upper tropospheric disturbance is frequently formed in conjunction with breaking Rossby waves (McIntyre and Palmer, 1983; Thorncroft et al ., 1993; Martius et al ., 2008), which can arise in an assortment of phenomena: cut‐off lows (Palmén and Newton, 1969; Nieto et al ., 2005), potential vorticity streamers (Martius et al ., 2008; Galarneau et al ., 2015), and tropical upper tropospheric trough cells (Sadler, 1976; Ferreira and Schubert, 1999; Patla et al ., 2009).…”