The study of extratropical cyclones has provided the basis for vigorous scientific debates within the meteorological community for at least the past 150 years In her monograph entitled The Thermal Theory of Cyclones: A History of Meteorological Thought in the Nineteenth Century, Kutzbach (1979) documents the interest of the leading European and American meteorologists of the 19th and early 20th centuries in providing a description of the weather and airflow associated with cyclones and identifying the physical processes that contribute to their development In the 19th century, the emergence of the so-called “thermal theory of cyclones” (see Fig 61) was based, to a large degree, on the work of Espy, who believed that the decrease of surface pressure in storms is related primarily to the release of latent heat in the ascending air near the storm center By the early 20th century, the theoretical work of Margules and V Bjerknes and the observational studies by Dines (which indicated extratropical cyclones were cold core systems) led to a more dynamically based perspective on cyclogenesis The energy conversions and low-level convergence associated with instabilities in regions marked by significant temperature gradients (especially in the lower troposphere) were recognized as important contributing factors in the development of extra tropical storms

Processes Contributing to the Rapid Development of Extratropical Cyclones

The results from several idealized and case studies are drawn together to form a comprehensive picture of “downstream baroclinic evolution” using local energetics. This new viewpoint offers a complementary alternative to the more conventional descriptions of cyclone development. These additional insights are made possible largely because the local energetics approach permits one to define an energy flux vector which accurately describes the direction of energy dispersion and quantifies the role of neighboring systems in local development. In this view, the development of a system's energetics is divided into three stages. In Stage 1, a pre-existing disturbance well upstream of an incipient trough loses energy via ageostrophic geopotential fluxes directed downstream through the intervening ridge, generating a new energy center there. In Stage 2, this new energy center grows vigorously, at first due to the convergence of these fluxes, and later by baroclinic conversion as well. As the center matures, it begins to export energy via geopotential fluxes to the eastern side of the trough, initiating yet another energy center. In Stage 3, this new energy center continues to grow while that on the western side of the trough decays due to a dwinding supply of energy via fluxes from the older upstream system and also as a consequence of its own export of energy downstream. As the eastern energy center matures, it exports energy further downstream, and the sequence begins anew. The USA “Blizzard of'93” is used as a new case study to test the limits to which this conceptual sequence might apply, as well as to augment the current limited set of case studies. It is shown that, despite the extraordinary magnitude of the event, the evolution of the trough associated with the Blizzard fits the conceptual picture of downstream baroclinic evolution quite well, with geopotential fluxes playing a critical role in three respects. First, fluxes from an old, decaying system in the Pacific were convergent over the west coast of North America, creating a kinetic energy center there and modifying the jet, resulting in a large extension of the overall kinetic energy center well into Mexico. Second, energy fluxes from this extension of the northwesterly flow were strongly convergent east of the trough, producing explosive growth of kinetic energy over the northwestern Gulf of Mexico, with baroclinic conversion following shortly thereafter. Lastly, the kinetic energy generated by the vigorous baroclinic conversion in the cold advection on the west side of the trough was very effectively transferred to the energy center on the east side of the trough via geopotential fluxes. DOI: 10.1034/j.1600-0870.1995.00108.x

https://onlinelibrary.wiley.com/doi/pdf/10.1034/j.1600-0870.1995.00108.x

Stages in the energetics of baroclinic systems

Sensitivity of WRF to boundary layer parameterizations in simulating a heavy rainfall event using different microphysical schemes. Effect on large-scale processes

The North Pacific and Bering Sea regions represent loci of cyclogenesis and storm track activity. In this paper climatological properties of extratropical storms in the North Pacific/Bering Sea are presented based upon aggregate statistics of individual storm tracks calculated by means of a feature-tracking algorithm run using NCEP–NCAR reanalysis data from 1948/49 to 2008, provided by the NOAA/Earth System Research Laboratory and the Cooperative Institute for Research in Environmental Sciences, Climate Diagnostics Center. Storm identification is based on the 850-hPa relative vorticity field (ζ) instead of the often-used mean sea level pressure; ζ is a prognostic field, a good indicator of synoptic-scale dynamics, and is directly related to the wind speed. Emphasis extends beyond winter to provide detailed consideration of all seasons. Results show that the interseasonal variability is not as large during the spring and autumn seasons. Most of the storm variables—genesis, intensity, track density...

/pdf/characteristics-and-variability-of-storm-tracks-in-the-north-ged3l7uixp.pdf

Characteristics and Variability of Storm Tracks in the North Pacific, Bering Sea, and Alaska*

Impact of different IFS microphysics on a warm conveyor belt and the downstream flow evolution

A diagnostic energetics analysis is used to study the effects of moisture-related processes on two numerically simulated cases of extratropical cyclone development Model output is derived from moist and dry versions of the Drexel University Limited Area Mesoscale Prediction System (LAMPS) Both kinetic and available potential energy budgets are partitioned into zonal and eddy quantities in order to focus more effectively on cyclone-scale processes Results from the LAMPS forecasts show that the baroclinic aspects of cyclone development are significantly enhanced by both convective and stable latent heat release Although generation of available potential energy (GE) is an important source of eddy available potential energy (AE), diabatic heating produces substantial modifications to eddy energy conversion terms Transformation of zonal available potential energy (AZ) to AE is strengthened in the moist forecasts through increased horizontal eddy transport of sensible heat Although conversion of 

F. R. Robertson

Papers

The Impact of Model Moist Processes on the Energetics of Extratropical Cyclones