scholarly journals LLAP Band Structure and Intense Lake-Effect Snowfall Downwind of Lake Ontario: Insights from the OWLeS 7–9 January 2014 Event

2020 ◽  
Vol 59 (10) ◽  
pp. 1691-1715
Author(s):  
Philip T. Bergmaier ◽  
Bart Geerts
Keyword(s):  
Doppler Radar ◽  
Model Simulation ◽  
Lake Ontario ◽  
Radar Data ◽  
Heat Fluxes ◽  
Secondary Circulation ◽  
Land Breeze ◽  
Surface Heat Fluxes ◽  
Lake Effect ◽  
Axis Parallel

AbstractModeling and observational studies stemming from the 2013–14 Ontario Winter Lake-Effect Systems (OWLeS) field campaign have yielded much insight into the structure and development of long-lake-axis-parallel (LLAP) lake-effect systems over Lake Ontario. This study uses airborne single- and dual-Doppler radar data obtained during two University of Wyoming King Air flights, as well as a high-resolution numerical model simulation, to examine and contrast two distinctly different LLAP band structures observed within a highly persistent lake-effect system on 7–9 January 2014. On 7 January, a very cold air mass accompanied by strong westerly winds and weak capping aloft resulted in a deep, intense LLAP band that produced heavy snowfall well inland. In contrast, weaker winds, weaker surface heat fluxes, and stronger capping aloft resulted in a weaker LLAP band on 9 January. This band was blocked along the downwind shore and produced only light snowfall closer to the shoreline. Although the two structures examined here represent opposite ends of a spectrum of LLAP bands, both cases reveal a well-organized mesoscale secondary circulation composed of two counterrotating horizontal vortices positioned on either side of a narrow updraft within the band. In both cases, this circulation traces back to a shallow, baroclinic land-breeze front originating along a bulge in the lake’s southern shoreline. As the band extends downstream and the low-level baroclinity weakens, buoyancy increases within the band—driven in part by cloud latent heating—leading to band intensification and a deeper, stronger, and more symmetric secondary circulation over the lake.

scholarly journals The OWLeS IOP2b Lake-Effect Snowstorm: Dynamics of the Secondary Circulation

2017 ◽  
Vol 145 (7) ◽  
pp. 2437-2459 ◽  
Author(s):  
Philip T. Bergmaier ◽  
Bart Geerts ◽  
Leah S. Campbell ◽  
W. James Steenburgh
Keyword(s):  
Doppler Radar ◽  
Vertical Plane ◽  
Wrf Model ◽  
Lake Ontario ◽  
Radar Data ◽  
Secondary Circulation ◽  
Land Breeze ◽  
Lake Effect ◽  
Axis Parallel ◽  
Convergence Zones

Intense lake-effect snowfall results from a long-lake-axis-parallel (LLAP) precipitation band that often forms when the flow is parallel to the long axis of an elongated body of water, such as Lake Ontario. The intensity and persistence of the localized precipitation along the downwind shore and farther inland suggests the presence of a secondary circulation that helps organize such a band, and maintain it for some time as the circulation is advected inland. Unique airborne vertical-plane dual-Doppler radar data are used here to document this secondary circulation in a deep, well-organized LLAP band observed during intensive observing period (IOP) 2b of the Ontario Winter Lake-effect Systems (OWLeS) field campaign. The circulation, centered on a convective updraft, intensified toward the downwind shore and only gradually weakened inland. The question arises as to what sustains such a circulation in the vertical plane across the LLAP band. WRF Model simulations indicate that the primary LLAP band and other convergence zones observed over Lake Ontario during this IOP were initiated by relatively shallow airmass boundaries, resulting from a thermal contrast (i.e., land-breeze front) and differential surface roughness across the southern shoreline. Airborne radar data near the downwind shore of the lake indicate that the secondary circulation was much deeper than these shallow boundaries and was sustained primarily by rather symmetric solenoidal forcing, enhanced by latent heat release within the updraft region.

scholarly journals Understanding Heavy Lake-Effect Snowfall: The Vertical Structure of Radar Reflectivity in a Deep Snowband over and downwind of Lake Ontario

2016 ◽  
Vol 144 (11) ◽  
pp. 4221-4244 ◽  
Author(s):  
Dan Welsh ◽  
Bart Geerts ◽  
Xiaoqin Jing ◽  
Philip T. Bergmaier ◽  
Justin R. Minder ◽  
...  
Keyword(s):  
Vertical Velocity ◽  
Doppler Radar ◽  
Lake Ontario ◽  
Radar Reflectivity ◽  
Distribution Data ◽  
W Band ◽  
Lake Effect ◽  
X Band ◽  
Axis Parallel ◽  
Frictional Convergence

Abstract The distribution of radar-estimated precipitation from lake-effect snowbands over and downwind of Lake Ontario shows more snowfall in downwind areas than over the lake itself. Here, two nonexclusive processes contributing to this are examined: the collapse of convection that lofts hydrometeors over the lake and allows them to settle downwind; and stratiform ascent over land, due to the development of a stable boundary layer, frictional convergence, and terrain, leading to widespread precipitation there. The main data sources for this study are vertical profiles of radar reflectivity and hydrometeor vertical velocity in a well-defined, deep long-lake-axis-parallel band, observed on 11 December 2013 during the Ontario Winter Lake-effect Systems (OWLeS) project. The profiles are derived from an airborne W-band Doppler radar, as well as an array of four K-band radars, an X-band profiling radar, a scanning X-band radar, and a scanning S-band radar. The presence of convection offshore is evident from deep, strong (up to 10 m s−1) updrafts producing bounded weak-echo regions and locally heavily rimed snow particles. The decrease of the standard deviation, skewness, and peak values of Doppler vertical velocity during the downwind shore crossing is consistent with the convection collapse hypothesis. Consistent with the stratiform ascent hypothesis are (i) an increase in mean vertical velocity over land; and (ii) an increasing abundance of large snowflakes at low levels and over land, due to depositional growth and aggregation, evident from flight-level and surface particle size distribution data, and from differences in reflectivity values from S-, X-, K-, and W-band radars at nearly the same time and location.

scholarly journals The Influence of a Lake-to-Lake Connection from Lake Huron on the Lake-Effect Snowfall in the Vicinity of Lake Ontario

2018 ◽  
Vol 57 (7) ◽  
pp. 1423-1439 ◽  
Author(s):  
Carrie E. Lang ◽  
Jessica M. McDonald ◽  
Lauriana Gaudet ◽  
Dylan Doeblin ◽  
Erin A. Jones ◽  
...  
Keyword(s):  
New York ◽  
New York State ◽  
Lake Ontario ◽  
Heat Fluxes ◽  
Lake Huron ◽  
Atmospheric Conditions ◽  
Near Surface ◽  
Surface Heat Fluxes ◽  
Wind Speeds ◽  
Lake Effect

AbstractLake-effect storms (LES) produce substantial snowfall in the vicinity of the downwind shores of the Great Lakes. These storms may take many forms; one type of LES event, lake to lake (L2L), occurs when LES clouds/snowbands develop over an upstream lake (e.g., Lake Huron), extend across an intervening landmass, and continue over a downstream lake (e.g., Lake Ontario). The current study examined LES snowfall in the vicinity of Lake Ontario and the atmospheric conditions during Lake Huron-to-Lake Ontario L2L days as compared with LES days on which an L2L connection was not present [i.e., only Lake Ontario (OLO)] for the cold seasons (October–March) from 2003/04 through 2013/14. Analyses of snowfall demonstrate that, on average, significantly greater LES snowfall totals occur downstream of Lake Ontario on L2L days than on OLO days. The difference in mean snowfall between L2L and OLO days approaches 200% in some areas near the Tug Hill Plateau and central New York State. Analyses of atmospheric conditions found more-favorable LES environments on L2L days relative to OLO days that included greater instability over the upwind lake, more near-surface moisture available, faster wind speeds, and larger surface heat fluxes over the upstream lake. Last, despite significant snowfalls on L2L days, their average contribution to the annual accumulated LES snowfall in the vicinity of Lake Ontario was found to be small (i.e., 25%–30%) because of the relatively infrequent occurrence of L2L days.

scholarly journals The OWLeS IOP2b Lake-Effect Snowstorm: Shoreline Geometry and the Mesoscale Forcing of Precipitation

2017 ◽  
Vol 145 (7) ◽  
pp. 2421-2436 ◽  
Author(s):  
W. James Steenburgh ◽  
Leah S. Campbell
Keyword(s):  
New York ◽  
Large Scale ◽  
Model Simulation ◽  
System Development ◽  
Wrf Model ◽  
Lake Ontario ◽  
Land Breeze ◽  
Primary Role ◽  
The North ◽  
Lake Effect

Long-lake-axis-parallel (LLAP) lake-effect precipitation systems that form when the flow is parallel to the long axis of an elongated body of water frequently produce intense, highly localized snowfall. Conceptual models of these LLAP systems typically emphasize the role of thermally forced land breezes from the flanking shorelines, with low-level convergence and ascent centered near the lake axis. In reality, other factors such as shoreline geometry and differential surface roughness can strongly influence LLAP systems. Here a WRF Model simulation is used to examine the mesoscale forcing of lake-effect precipitation over Lake Ontario during IOP2b of the Ontario Winter Lake-effect Systems (OWLeS) field campaign. In the simulation, the large-scale flow, shoreline geometry, and differential surface heating and roughness contribute to the development of three major airmass boundaries. The first is a land-breeze front that forms along a bulge in the south shoreline between St. Catharines, Ontario, Canada, and Thirty Mile Point, New York; extends downstream over eastern Lake Ontario; and plays a primary role in the LLAP system development. The second is a land-breeze front that forms along the southeast shoreline near Oswego, New York; extends downstream and obliquely across the LLAP system near Tug Hill; and influences inland precipitation processes. The third is a convergence zone that extends downstream from the north shoreline near Point Petre, Ontario, Canada; and contributes to the intermittent development of lake-effect precipitation north of the primary LLAP system. These results highlight the multifaceted nature of LLAP system development over Lake Ontario, especially the contributions of shoreline geometry and mesoscale airmass boundaries.

Doppler Radar Analysis of the Eyewall Replacement Cycle of Hurricane Matthew (2016) in Vertical Wind Shear

2021 ◽  
Author(s):  
Ting-Yu Cha ◽  
Michael M. Bell ◽  
Alexander J. DesRosiers
Keyword(s):  
Wind Shear ◽  
Doppler Radar ◽  
Vertical Wind Shear ◽  
Radar Data ◽  
Secondary Circulation ◽  
Vertical Wind ◽  
High Temporal Resolution ◽  
Radar Observations ◽  
Eyewall Replacement Cycle ◽  
Replacement Cycle

AbstractHurricane Matthew (2016) was observed by ground-based polarimetric radars in Miami (KAMX), Melbourne (KMLB), and Jacksonville (KJAX) and a NOAA P3 airborne tail Doppler radar near the coast of the southeastern United States during an eyewall replacement cycle (ERC). The radar observations indicate that Matthew’s primary eyewall was replaced with a weaker outer eyewall, but unlike a classic ERC, Matthew did not reintensify after the inner eyewall disappeared. Triple Doppler analysis was calculated from the NOAA P3 airborne fore and aft radar scanning combined with the KAMX radar data during the period of secondary eyewall intensification and inner eyewall weakening from 19 UTC 6 October to 00 UTC 7 October. Four flight passes of the P3 aircraft show the evolution of the reflectivity, tangential winds, and secondary circulation as the outer eyewall became well-established. Further evolution of the ERC is analyzed from the ground-based single Doppler radar observations for 35 hours with high temporal resolution at a 5-minute interval from 19 UTC 6 October to 00 UTC 8 October using the Generalized Velocity Track Display (GVTD) technique. The single-Doppler analyses indicate that the inner eyewall decayed a few hours after the P3 flight, while the outer eyewall contracted but did not reintensify and the asymmetries increased episodically. The analysis suggests that the ERC process was influenced by a complex combination of environmental vertical wind shear, an evolving axisymmetric secondary circulation, and an asymmetric vortex Rossby wave damping mechanism that promoted vortex resiliency despite increasing shear.

scholarly journals The Evolution of Lake-Effect Convection during Landfall and Orographic Uplift as Observed by Profiling Radars

2015 ◽  
Vol 143 (11) ◽  
pp. 4422-4442 ◽  
Author(s):  
Justin R. Minder ◽  
Theodore W. Letcher ◽  
Leah S. Campbell ◽  
Peter G. Veals ◽  
W. James Steenburgh
Keyword(s):  
Vertical Structure ◽  
Lake Ontario ◽  
Radar Data ◽  
Horizontal Distance ◽  
Field Campaign ◽  
Lake Effect ◽  
X Band ◽  
Liquid Precipitation ◽  
K Band

Abstract A pronounced snowfall maximum occurs about 30 km downwind of Lake Ontario over the 600-m-high Tug Hill Plateau (hereafter Tug Hill), a region where lake-effect convection is affected by mesoscale forcing associated with landfall and orographic uplift. Profiling radar data from the Ontario Winter Lake-effect Systems field campaign are used to characterize the inland evolution of lake-effect convection that produces the Tug Hill snowfall maximum. Four K-band profiling Micro Rain Radars (MRRs) were aligned in a transect from the Ontario coast onto Tug Hill. Additional observations were provided by an X-band profiling radar (XPR). Analysis is presented of a major lake-effect storm that produced 6.4-cm liquid precipitation equivalent (LPE) snowfall over Tug Hill. This event exhibited strong inland enhancement, with LPE increasing by a factor of 1.9 over 15-km horizontal distance. MRR profiles reveal that this enhancement was not due to increases in the depth or intensity of lake-effect convection. With increasing inland distance, echoes transitioned from a convective toward a stratiform morphology, becoming less intense, more uniform, more frequent, and less turbulent. An inland increase in echo frequency (possibly orographically forced) contributes somewhat to snowfall enhancement. The XPR observations reproduce the basic vertical structure seen by the MRRs while also revealing a suppression of snowfall below 600 m AGL upwind of Tug Hill, possibly associated with subcloud sublimation or hydrometeor advection. Statistics from 29 events demonstrate that the above-described inland evolution of convection is common for lake-effect storms east of Lake Ontario.

Radar Data Assimination in WRF Model to Forecast Heavy Rainfall at Ho Chi Minh City

2018 ◽  
Vol 34 (1S) ◽  
Author(s):  
Tran Duy Thuc ◽  
Cong Thanh
Keyword(s):  
Heavy Rainfall ◽  
Doppler Radar ◽  
Initial Conditions ◽  
Model Simulation ◽  
Wrf Model ◽  
Cold Start ◽  
Radar Data ◽  
Warm Start ◽  
South Vietnam ◽  
Better Than

Abstract: This article using high resolution WRF model simulation on a heavy rainfall in summer at Hochiminh city by using radar data to assimilation initial conditions with 3DVAR method, the WRF3Dvar running simulation with two modes: cold start and warm start combine with three cases: only Reflectivity of radar; Reflectivity and Doppler radar radial wind observations; Reflectivity, Doppler radar radial wind, and GTS data. The background error used was CV7 created from 6 months forecast in South Vietnam. Radar data before assimilation was quality control and thinned to remove noise and create the best observation. 24 station rainfall in South Vietnam using to an evaluation of WRF model simulation. Results show assimilation only reflectivity will affect to variable qcloud, qvapor and qrain on the initial condition of model and assimilation only Doppler radar radial wind improve wind. Compare each case show warm start simulation precipitation better than the cold start, assimilation both Doppler radar radial wind observations, the reflectivity of radar and GTS better than another case. Key words: WRFDA,RADAR

scholarly journals Thunderstorm Characteristics during the Ontario Winter Lake-Effect Systems Project

2018 ◽  
Vol 57 (4) ◽  
pp. 853-874 ◽  
Author(s):  
Scott M. Steiger ◽  
Tyler Kranz ◽  
Theodore W. Letcher
Keyword(s):  
Boundary Layer ◽  
Wind Turbines ◽  
Winter Season ◽  
Primary Source ◽  
Lake Ontario ◽  
Field Campaign ◽  
Lake Effect ◽  
Lightning Detection ◽  
Axis Parallel ◽  
And Behavior

AbstractThe Ontario Winter Lake-Effect Systems (OWLeS) field campaign during the winter season of 2013/14 provided unprecedented data with regard to the structure and behavior of long-lake-axis-parallel (LLAP) lake-effect storms. One of the interesting characteristics of LLAP storm bands is their ability to initiate lightning. The OWLeS datasets provide an opportunity to examine more thoroughly the kinematics and microphysics of lake-effect thunder-snowstorms than ever before. The OWLeS facilities and field personnel observed six lake-effect thunderstorms during December–January 2013/14. Most of them produced very little lightning (fewer than six cloud-to-ground strokes or intracloud pulses recorded by the National Lightning Detection Network). The 7 January 2014 storm had over 50 strokes and pulses, however, which resulted in 20 flashes over a 6-h period (0630–1230 UTC), making it the most electrically active storm during the field campaign. Relative to the 18 December 2013 storm, which only had three flashes, the 7 January 2014 case had a deeper boundary layer and greater instability. Also, 45% of the lightning during the 7 January storm was likely due to flashes initiated by wind turbines or other man-made antennas, along with all of the lightning observed during 18 December. No lightning was documented over Lake Ontario, the primary source of instability for these storms.

scholarly journals Lake-Effect Mode and Precipitation Enhancement over the Tug Hill Plateau during OWLeS IOP2b

2016 ◽  
Vol 144 (5) ◽  
pp. 1729-1748 ◽  
Author(s):  
Leah S. Campbell ◽  
W. James Steenburgh ◽  
Peter G. Veals ◽  
Theodore W. Letcher ◽  
Justin R. Minder
Keyword(s):  
New York ◽  
Weather Forecasting ◽  
Lake Ontario ◽  
Short Wave ◽  
Operational Forecasts ◽  
Radar Echoes ◽  
Lake Effect ◽  
Axis Parallel ◽  
Upper Level ◽  
Precipitation Enhancement

Improved understanding of the influence of orography on lake-effect storms is crucial for weather forecasting in many lake-effect regions. The Tug Hill Plateau of northern New York (hereafter Tug Hill), rising 500 m above eastern Lake Ontario, experiences some of the most intense snowstorms in the world. Herein the authors investigate the enhancement of lake-effect snowfall over Tug Hill during IOP2b of the Ontario Winter Lake-effect Systems (OWLeS) field campaign. During the 24-h study period, total liquid precipitation equivalent along the axis of maximum precipitation increased from 33.5 mm at a lowland (145 m MSL) site to 62.5 mm at an upland (385 m MSL) site, the latter yielding 101.5 cm of snow. However, the ratio of upland to lowland precipitation, or orographic ratio, varied with the mode of lake-effect precipitation. Strongly organized long-lake-axis parallel bands, some of which formed in association with the approach or passage of upper-level short-wave troughs, produced the highest precipitation rates but the smallest orographic ratios. Within these bands, radar echoes were deepest and strongest over Lake Ontario and the coastal lowlands and decreased in depth and median intensity over Tug Hill. In contrast, nonbanded broad-coverage periods exhibited the smallest precipitation rates and the largest orographic ratios, the latter reflecting an increase in the coverage and frequency of radar echoes over Tug Hill. These findings should aid operational forecasts and, given the predominance of broad-coverage lake-effect periods during the cool season, help explain the climatological snowfall maximum found over the Tug Hill Plateau.

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