Dryline Position Errors in Experimental Convection-Allowing NSSL-WRF Model Forecasts and the Operational NAM

Coffer, Brice E.; Maudlin, Lindsay C.; Veals, Peter G.; Clark, Adam J.

doi:10.1175/waf-d-12-00092.1

Cited by 20 publications

(29 citation statements)

References 57 publications

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“…This particular =q y was chosen in order to be consistent with previous dryline studies (Schaefer 1974b;Hoch and Markowski 2005;Coffer et al 2013). The second and third criteria were chosen because they are commonly observed near drylines over the SGP (e.g., Ziegler and Hane 1993;Miao and Geerts 2007;Geerts 2008), although the second criterion also acts as a means of removing strong eastward-moving cold fronts.…”

Section: B Selection Of Casesmentioning

confidence: 99%

Characteristics and Synoptic Environment of Drylines Occurring over the Higher Terrain of Southeastern Wyoming

Bergmaier

Geerts

2015

Weather and Forecasting

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Commonly observed over the broadly sloped terrain of the southern Great Plains (SGP), drylines are frequent loci of warm season deep convection and have been the focus of numerous observational, theoretical, and climatological studies over last half century. In this study, a 3-yr (2010-12) analysis of the characteristics and synoptic environment of drylines occurring elsewhere, over the high terrain in southeastern Wyoming just east of the Rocky Mountains, is presented. Observed on ;11% of the days between May and August of the years examined, southeastern Wyoming drylines were often associated with large moisture gradients [;5-10 g kg 21 (100 km) 21 ], large horizontal virtual potential temperature differences (;2-5 K), and convergent zonal wind flow at the surface. The synoptic conditions leading to their formation and their relationship to thunderstorm activity are also explored in an effort to aid local forecasters in anticipating the development and convective impact of drylines across the region. Similarities exist between these drylines and those found over the SGP, especially with regard to their strength and close relationship to deep convection. However, the frequency at which they occur, some characteristics of their diurnal motion, and the synoptic conditions driving their formation differ noticeably.

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Section: B Selection Of Casesmentioning

confidence: 99%

Characteristics and Synoptic Environment of Drylines Occurring over the Higher Terrain of Southeastern Wyoming

Bergmaier

Geerts

2015

Weather and Forecasting

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“…The Control simulations demonstrated that the WRF produced reasonable atmospheric moisture gradients and precipitation patterns compared to observations. While differences were noted, these were typical to the WRF modeling system shown by previous studies [61]. Sensitivity simulations modifying soil moisture were completed to quantify the impacts of soil moisture on the dry line location during the study period.…”

Section: Discussionmentioning

confidence: 99%

“…by Coffer et al [61] that found an eastward bias of the dry line in the operational NSSL-WRF system. Surface fields were also well represented by the Control simulations, with each simulation incurring small perturbations to the surface temperature and moisture fields.…”

Section: Wrf-arw Modeling Case Studies and Sensitivity Simulationsmentioning

confidence: 91%

“…This figure indicates two areas of preferred dry line locations, over the central to west central portion of the state and in the northwest portion of the state into the panhandle. Coffer et al [61] mentioned in their analysis of model dry line position errors that 2011 was an active year with frequent passages of shortwave troughs across the central Plains. Hane [62] states that dry lines that form in active synoptic regimes propagate further to the east during the day than those that develop during quiescent periods because the increased westerly momentum associated with the synoptic disturbance aids the vertical turbulent mixing in shifting the boundary towards the east.…”

Section: Dry Line Analysismentioning

confidence: 99%

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The Effect of the Dry Line and Convective Initiation on Drought Evolution over Oklahoma during the 2011 Drought

Flanagan

Basara

Illston

et al. 2017

Advances in Meteorology

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Observations from the Oklahoma Mesonet and high resolution Weather Research and Forecasting model simulations were used to evaluate the effect that the dry line and large-scale atmospheric patterns had on drought evolution during 2011. Mesonet observations showed that a "dry" and "wet" pattern developed across Oklahoma due to anomalous atmospheric patterns. The location of the dry line varied due to this "dry" and "wet" pattern, with the average dry line location around 1.5∘ longitude further to the east than climatology. Model simulations were used to further quantify the impact of variable surface conditions on dry line evolution and convective initiation (CI) during April and May 2011. Specifically, soil moisture conditions were altered to depict "wet" and "dry" conditions across the domain by replacing the soil moisture values by each soil category's porosity or wilting point value. Overall, the strength of the dry line boundary, its position, and subsequent CI were dependent on the modification of soil moisture. The simulations demonstrated that modifying soil moisture impacted the nature of the dry line and showed that soil moisture conditions during the first half of the warm season modified the dry line pattern and influenced the evolution and perpetuation of drought over Oklahoma.

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“…A potential reason for the delayed CI within CI3 in CNTL is the westward bias in the placement of the surface dryline (Fig. 17); CNTL does not mix Other studies have found that convection-permitting models mix the dryline too far to the east (Coffer et al 2013). The present case is different in that the dryline is not associated with a synoptic-scale low pressure system, thus its evolution is likely more sensitive to PBL estimates of vertical mixing.…”

Section: E Discussionmentioning

confidence: 99%

Assimilating Surface Mesonet Observations with the EnKF to Improve Ensemble Forecasts of Convection Initiation on 29 May 2012

Sobash

Stensrud

2015

Monthly Weather Review

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Surface data assimilation (DA) has the potential to improve forecasts of convection initiation (CI) and short-term forecasts of convective evolution. Since the processes driving CI occur on scales inadequately observed by conventional observation networks, mesoscale surface networks could be especially beneficial given their higher temporal and spatial resolution. This work aims to assess the impact of high-frequency assimilation of mesonet surface DA on ensemble forecasts of CI initialized with ensemble Kalman filter (EnKF) analyses of the 29 May 2012 convective event over the southern Great Plains.Mesonet and conventional surface observations were assimilated every 5 min for 3 h from 1800 to 2100 UTC and 3-h ensemble forecasts were produced. Forecasts of CI timing and location were improved by assimilating the surface datasets in comparison to experiments where mesonet data were withheld. This primarily occurred due to a more accurate representation of the boundary layer moisture profile across the domain, especially in the vicinity of a dryline and stationary boundary. Ensemble forecasts produced by assimilating surface observations at hourly intervals, instead of every 5 min, showed only minor improvements in CI.The 5-min assimilation of mesonet data improved forecasts of the placement and timing of CI for this particular event due to the ability of mesonet data to capture rapidly evolving mesoscale features and to constrain model biases, particularly surface moisture errors, during the cycling period.

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Dryline Position Errors in Experimental Convection-Allowing NSSL-WRF Model Forecasts and the Operational NAM

Cited by 20 publications

References 57 publications

Characteristics and Synoptic Environment of Drylines Occurring over the Higher Terrain of Southeastern Wyoming

Characteristics and Synoptic Environment of Drylines Occurring over the Higher Terrain of Southeastern Wyoming

The Effect of the Dry Line and Convective Initiation on Drought Evolution over Oklahoma during the 2011 Drought

Assimilating Surface Mesonet Observations with the EnKF to Improve Ensemble Forecasts of Convection Initiation on 29 May 2012

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