Southerly Low-Level Jet in the Winter Cyclones of the Southwestern Great Plains

Djurić, Dušan; Ladwig, David Scott

doi:10.1175/1520-0493(1983)111<2275:slljit>2.0.co;2

Cited by 20 publications

(16 citation statements)

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“…If). As the airflow associated with a drytrough develops, the strong southerly flow ahead of the drytrough leads to the formation of a southerly low-level jet (Bonner 1968;Djuric and Ladwig 1983). This jet enhances the transport of warm, moist air northward (Fig.…”

Section: Nonclassic Cyclonic Features Included In the New Conceptuamentioning

confidence: 99%

“…These include lee troughs (Carlson 1961;Steenburgh and Mass 1994), dry lines (Fujita 1958;McGuire 1960;Schaefer 1974Schaefer , 1986, low-level jets (Bonner 1968;Djuric and Damiani 1980;Djuric and Ladwig 1983), arctic fronts (Wexler 1936;Showalter 1939;Wang et al 1995), elevated mixed layers (Carlson et al 1983;Benjamin and Carlson 1986), and cold fronts aloft (Holtzmm 1936;Lichtblau 1936;Lloyd 1942;Omoto 1965;Hobbs et al 1990). In our conceptual model, these features are viewed as interdependent phenomena, produced by synoptic-scale waves moving eastward over the Rocky Mountains and interacting with warm, moist subtropical air from the Gulf of Mexico and cold, dry air from the Canadian Arctic.…”

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confidence: 99%

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A New Conceptual Model for Cyclones Generated in the Lee of the Rocky Mountains

Hobbs¹,

Locatelli²,

Martin³

1996

Bull. Amer. Meteor. Soc.

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When a shortwave trough moves eastward over the Rocky Mountains and into the central United States, the following important features may form: a drytrough (i.e., a lee trough that also has the characteristics of a dryline), an arctic front, a low-level jet, and two synoptic-scale rainbands (called the cold front aloft rainband and the pre-drytrough rainband) that can produce heavy precipitation and severe weather well ahead of the drytrough. These features are incorporated into a new conceptual model for cyclones in the central United States. Use of this model can aid the interpretation of observational data and numerical model output, and it may also help to improve short-range forecasting in the central United States. Introductory remarksDespite the fact that the Norwegian Cyclone Model was based on maritime cyclones making landfall in northwestern Europe (Bjerknes and Solberg 1922), it has been applied essentially unchanged to cyclones in the central United States for 70 years (Friedman 1989;Mass 1991). This is not without some justification, since one of the main features of the Norwegian model are fronts demarcating airmasses, which are also a characteristic of cyclones in the central United States. However, in view of the unique geography of the central United States, it would not be surprising if cyclones in this region displayed structural differences from those in Europe.In this paper we present a new conceptual model for the structure and evolution of cyclones in the cen- Locatelli et al. (1989Locatelli et al. ( , 1995, Martin et al. (1990Martin et al. ( , 1995, Hobbs et al. (1990), andWang et al. (1995), as well as on regular observations of cyclones in the central United States. It is important to note that we are not proposing that all cyclones that form in the lee of the Rocky Mountains are described by our model. However, many cyclones that form in the winter, spring, and even into early summer, in the lee of the Rockies, and move eastward into the central United States, appear to be described better by the conceptual model presented here than by the Norwegian model. Our conceptual model highlights a number of important nonclassic features associated with cyclones in the central United States, some of which have been known for many years. These include lee troughs

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Section: Nonclassic Cyclonic Features Included In the New Conceptuamentioning

confidence: 99%

mentioning

confidence: 99%

A New Conceptual Model for Cyclones Generated in the Lee of the Rocky Mountains

Hobbs¹,

Locatelli²,

Martin³

1996

Bull. Amer. Meteor. Soc.

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“…While the quiescent LLJ is found at the base of the decoupled boundary layer, the LLJs associated with synoptic-scale cyclogenesis are somewhat deeper. The core of the jet tends to lie at the base of an inversion, which has been identified as a subsidence inversion (Djurić and Ladwig 1983), the remnants of the old cold front (Djurić and Ladwig 1983), or the base of the EML (Martin et al 1995). Lanicci and Warner (1991) note that the LLJ composite maps of Djuric and Ladwig closely match their own EML/lid composites.…”

Section: Introductionmentioning

confidence: 92%

“…Here we refer to this environment as ''active'' rather than ''quiescent.'' In the typical evolution, as described by Djurić and Damiani (1980) and Djurić and Ladwig (1983), a southerly wind first forms over the central Plains in response to the formation of a lee trough. During the next day, as the upper-level trough and surface front approach from the west, the low-level southerlies become widespread over the Plains of Oklahoma and Texas.…”

Section: Introductionmentioning

confidence: 99%

“…This process also leads to the formation of a surface dryline (Schaefer 1974) where the warm, dry airstream from the west meets the moist airstream from the south. Often during the return flow, a southerly low-level jet (LLJ) develops which rapidly transports the modified air northward (Djurić and Damiani 1980). The development of the LLJ over the southern Plains and the western Gulf of Mexico during the return flow cycle is the primary focus of this paper.…”

Section: Introductionmentioning

confidence: 99%

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Low-Level Jet Development during a Numerically Simulated Return Flow Event

Igau¹,

Nielsen‐Gammon²

1998

Mon. Wea. Rev.

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The evolution of the southerly low-level jet (LLJ) during a return flow event is studied using output from the Penn State/NCAR Mesoscale Model (Version 4). Three geographically different southerly LLJs develop in the simulation: one over the southern Plains of the United States, a second southwest of Brownsville, Texas, and a third over the western Gulf of Mexico. The LLJ over the Plains is found to form first as an inertial oscillation and later as a response to lee troughing and an elevated mixed layer that develops over the region. Over Mexico, the temperature structure over the Altiplanicie Mexicana (Mexican High Plain) is responsible for a locally intense low-level pressure gradient east of the High Plain which remains nearly stationary over two diurnal cycles. The LLJ over the western Gulf of Mexico results largely from topographic blocking of the low-level southerly flow by the eastern end of the Neovolcanic Cordillera northwest of Veracruz, Mexico.The evolution of the lower troposphere over the southern Plains resembles the Carlson and Ludlam conceptual model for a severe storm environment, but the structure of the return flow is complex. When midlevel westerlies are weak, mesoscale and boundary layer processes govern the development of LLJs. As the west and southwesterly winds increase with an approaching upper-level disturbance, synoptic influences overwhelm the mesoscale processes leading to a single, larger-scale LLJ.

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The influence of climate change on low‐level jet characteristics over the South‐Central Plains as simulated by CMIP5 models

Wimhurst

Greene

2020

Intl Journal of Climatology

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Previous studies have projected the Central Plains low‐level jet (LLJ) to form more frequently over the South‐Central Plains region in the future, with limited projected changes in its speed and height. This work's objective was to assess future LLJ characteristics with wind speed outputs obtained from the Phase 5 of the Coupled Model Intercomparison Project (CMIP5) suite of models. Improvements in model resolution and simulation of climate dynamics relevant to LLJs were made in CMIP5, and a multi‐model study that focuses specifically on the LLJ's future state using these models is yet to be done. Occurrences of LLJs were identified by applying an LLJ definition based on wind shear to six‐hourly vertical wind profiles derived from the model outputs. Changes in future LLJ speed, frequency, and height versus a historical control were subsequently calculated on seasonal and diurnal temporal scales. As seen in previous work, the largest expected changes in LLJ characteristics are those of its frequency, especially in summer, autumn, and at night. Evidence was also found for large increases in frequency in the northern half of the study region, consistent with previous expectations. CMIP5 models with finer horizontal and vertical resolutions tended to project greater increases in LLJ frequency than those with coarse resolutions. Projected changes in LLJ speed and height were by contrast largely insignificant, also consistent with previous findings. However, these characteristics, along with frequency, exhibited notable diurnal variability in historical and future simulations, especially in winter. An increase in cold‐season LLJ variability could have implications for the consistency of synoptically driven LLJs. This finding, along with the projected warm‐season poleward shift in the LLJ's frequency maximum over the study region, elucidates the LLJ's future state as projected by a selection of CMIP5 models, and the consequences for processes that depend upon the LLJ's consistency.

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Southerly Low-Level Jet in the Winter Cyclones of the Southwestern Great Plains

Cited by 20 publications

References 0 publications

A New Conceptual Model for Cyclones Generated in the Lee of the Rocky Mountains

A New Conceptual Model for Cyclones Generated in the Lee of the Rocky Mountains

Low-Level Jet Development during a Numerically Simulated Return Flow Event

The influence of climate change on low‐level jet characteristics over the South‐Central Plains as simulated by CMIP5 models

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