scholarly journals The Association of the Elevated Mixed Layer with Significant Severe Weather Events in the Northeastern United States*

2010 ◽  
Vol 25 (4) ◽  
pp. 1082-1102 ◽  
Author(s):  
Peter C. Banacos ◽  
Michael L. Ekster
Keyword(s):  
United States ◽  
Mixed Layer ◽  
Trajectory Analysis ◽  
Source Region ◽  
Warm Season ◽  
The United States ◽  
Severe Weather ◽  
Lapse Rate ◽  
Northeastern United States ◽  
Weather Events

Abstract The occurrence of rare but significant severe weather events associated with elevated mixed-layer (EML) air in the northeastern United States is investigated herein. A total of 447 convective event days with one or more significant severe weather report [where significant is defined as hail 2 in. (5.1 cm) in diameter or greater, a convective gust of 65 kt (33 m s−1) or greater, and/or a tornado of F2 or greater intensity] were identified from 1970 through 2006 during the warm season (1 May–30 September). Of these, 34 event days (7.6%) were associated with identifiable EML air in regional rawinsondes preceding the event. Taken with two other noteworthy events in 1953 and 1969, a total of 36 significant severe weather events associated with EML air were studied via composite and trajectory analysis. Though a small percentage of the total, these 36 events compose a noteworthy list of historically significant derechos and tornadic events to affect the northeastern United States. It is demonstrated that plumes of EML air emanating from the Intermountain West in subsiding, anticyclonically curved flows can reinforce the capping inversion and maintain the integrity of the EML across the central United States over a few days. The EML plume can ultimately become entrained into a moderately fast westerly to northwesterly midtropospheric flow allowing for the plume’s advection into the northeastern United States. Resultant thermodynamic conditions in the convective storm environment are similar to those more typically observed closer to the EML source region in the Great Plains of the United States. In addition to composite and trajectory analysis, two case studies are employed to demonstrate salient and evolutionary aspects of the EML in such events. A lapse rate tendency equation is explored to put EML advection in context with other processes affecting lapse rate.

scholarly journals Impact of Assimilating Dropsonde Observations from MPEX on Ensemble Forecasts of Severe Weather Events

2016 ◽  
Vol 144 (10) ◽  
pp. 3799-3823 ◽  
Author(s):  
Glen S. Romine ◽  
Craig S. Schwartz ◽  
Ryan D. Torn ◽  
Morris L. Weisman
Keyword(s):  
United States ◽  
Initial Conditions ◽  
Positive Impact ◽  
The United States ◽  
Early Morning ◽  
Severe Weather ◽  
Synoptic Scale ◽  
Ensemble Forecasts ◽  
Forecast Performance ◽  
Weather Events

Over the central Great Plains, mid- to upper-tropospheric weather disturbances often modulate severe storm development. These disturbances frequently pass over the Intermountain West region of the United States during the early morning hours preceding severe weather events. This region has fewer in situ observations of the atmospheric state compared with most other areas of the United States, contributing toward greater uncertainty in forecast initial conditions. Assimilation of supplemental observations is hypothesized to reduce initial condition uncertainty and improve forecasts of high-impact weather. During the spring of 2013, the Mesoscale Predictability Experiment (MPEX) leveraged ensemble-based targeting methods to key in on regions where enhanced observations might reduce mesoscale forecast uncertainty. Observations were obtained with dropsondes released from the NSF/NCAR Gulfstream-V aircraft during the early morning hours preceding 15 severe weather events over areas upstream from anticipated convection. Retrospective data-denial experiments are conducted to evaluate the value of dropsonde observations in improving convection-permitting ensemble forecasts. Results show considerable variation in forecast performance from assimilating dropsonde observations, with a modest but statistically significant improvement, akin to prior targeted observation studies that focused on synoptic-scale prediction. The change in forecast skill with dropsonde information was not sensitive to the skill of the control forecast. Events with large positive impact sampled both the disturbance and adjacent flow, akin to results from past synoptic-scale targeting studies, suggesting that sampling both the disturbance and adjacent flow is necessary regardless of the horizontal scale of the feature of interest.

An Analysis of Subdaily Severe Thunderstorm Probabilities for the United States

2020 ◽  
Vol 35 (1) ◽  
pp. 107-112 ◽  
Author(s):  
Makenzie J. Krocak ◽  
Harold E. Brooks
Keyword(s):  
United States ◽  
Spatial Scales ◽  
The United States ◽  
Severe Weather ◽  
Severe Thunderstorm ◽  
Probabilistic Information ◽  
Weather Events ◽  
Single Location ◽  
Spatiotemporal Scales ◽  
Definition Of

Abstract One of the challenges of providing probabilistic information on a multitude of spatiotemporal scales is ensuring that information is both accurate and useful to decision-makers. Focusing on larger spatiotemporal scales (i.e., from convective outlook to weather watch scales), historical severe weather reports are analyzed to begin to understand the spatiotemporal scales that hazardous weather events are contained within. Reports from the Storm Prediction Center’s report archive are placed onto grids of differing spatial scales and then split into 24-h convective outlook days (1200–1200 UTC). These grids are then analyzed temporally to assess over what fraction of the day a single location would generally experience severe weather events. Different combinations of temporal and spatial scales are tested to determine how the reference class (or the choice of what scales to use) alters the probabilities of severe weather events. Results indicate that at any given point in the United States on any given day, more than 95% of the daily reports within 40 km of the point occur in a 4-h period. Therefore, the SPC 24-h convective outlook probabilities can be interpreted as 4-h convective outlook probabilities without a significant change in meaning. Additionally, probabilities and threat periods are analyzed at each location and different times of year. These results indicate little variability in the duration of severe weather events, which allows for a consistent definition of an “event” for all locations in the continental United States.

scholarly journals Tropopause-Penetrating Convection from Three-Dimensional Gridded NEXRAD Data

2016 ◽  
Vol 55 (2) ◽  
pp. 465-478 ◽  
Author(s):  
David L. Solomon ◽  
Kenneth P. Bowman ◽  
Cameron R. Homeyer
Keyword(s):  
United States ◽  
Three Dimensional ◽  
Warm Season ◽  
The United States ◽  
Lapse Rate ◽  
High Plains ◽  
Annual Cycles ◽  
Weather Radars ◽  
The North ◽  
The Stability

AbstractA new method that combines radar reflectivities from individual Next Generation Weather Radars (NEXRAD) into a three-dimensional composite with high horizontal and vertical resolution is used to estimate storm-top altitudes for the continental United States east of the Rocky Mountains. Echo-top altitudes are compared with the altitude of the lapse-rate tropopause calculated from the ERA-Interim reanalysis and radiosondes. To sample the diurnal and annual cycles, tropopause-penetrating convection is analyzed at 3-h intervals throughout 2004. Overshooting convection is most common in the north-central part of the United States (the high plains). There is a pronounced seasonal cycle; the majority of overshooting systems occur during the warm season (March–August). There is also a strong diurnal cycle, with maximum overshooting occurring near 0000 UTC. The overshooting volume decreases rapidly with height above the tropopause. Radiosonde observations are used to evaluate the quality of the reanalysis tropopause altitudes and the dependence of overshooting depth on environmental characteristics. The radar–radiosonde comparison reveals that overshooting is deeper in double-tropopause environments and increases as the stability of the lower stratosphere decreases.

scholarly journals The Seasonal Nature of Extreme Hydrological Events in the Northeastern United States

2015 ◽  
Vol 16 (5) ◽  
pp. 2065-2085 ◽  
Author(s):  
Allan Frei ◽  
Kenneth E. Kunkel ◽  
Adao Matonse
Keyword(s):  
United States ◽  
Extreme Precipitation ◽  
Extreme Event ◽  
Warm Season ◽  
The United States ◽  
Cold Season ◽  
Northeastern United States ◽  
Extreme Precipitation Events ◽  
Extreme Hydrological Events ◽  
Precipitation Events

Abstract Recent analyses of extreme hydrological events across the United States, including those summarized in the recent U.S. Third National Climate Assessment (May 2014), show that extremely large (extreme) precipitation and streamflow events are increasing over much of the country, with particularly steep trends over the northeastern United States. The authors demonstrate that the increase in extreme hydrological events over the northeastern United States is primarily a warm season phenomenon and is caused more by an increase in frequency than magnitude. The frequency of extreme warm season events peaked during the 2000s; a secondary peak occurred during the 1970s; and the calmest decade was the 1960s. Cold season trends during the last 30–50 yr are weaker. Since extreme precipitation events in this region tend to be larger during the warm season than during the cold season, trend analyses based on annual precipitation values are influenced more by warm season than by cold season trends. In contrast, the magnitude of extreme streamflow events at stations used for climatological analyses tends to be larger during the cold season: therefore, extreme event analyses based on annual streamflow values are overwhelmingly influenced by cold season, and therefore weaker, trends. These results help to explain an apparent discrepancy in the literature, whereby increasing trends in extreme precipitation events appear to be significant and ubiquitous across the region, while trends in streamflow appear less dramatic and less spatially coherent.

scholarly journals Extreme Weather and Forest Management in the Mid-Atlantic Region of the United States

2003 ◽  
Vol 20 (2) ◽  
pp. 61-70 ◽  
Author(s):  
David R. DeWalle ◽  
Anthony R. Buda ◽  
Ann Fisher
Keyword(s):  
Climate Change ◽  
United States ◽  
Forest Management ◽  
The United States ◽  
Extreme Weather ◽  
Severe Weather ◽  
Extreme Weather Events ◽  
Forest Land ◽  
Atlantic Region ◽  
Weather Events

Abstract Projected climate change could have major effects on forest management because of the potential for increased frequency, duration, and/or severity of extreme weather events. We surveyed public and private forestland management groups in the Mid-Atlantic region of the United States to better understand current interactions between extreme weather events and forest land management and to help predict future impacts. Our questionnaire addressed the importance and types of problems created by extreme weather events, the coping strategies employed to mitigate problems, and the overall economic effects of extreme weather. Responses were received from 322 forest managers/users (54% response rate) primarily representing state natural resources agencies, forestry consulting firms, large industrial forestry companies and smaller logging companies. Overall, respondents rated the impacts of extreme weather on their operations as low to modest; however, over 20% experienced “major” effects because of extreme weather over the past 10 yr. The highest rated impacts were: (1) reduced access to forestland because of flooding, deep snow, or wind- and ice-damaged trees; (2) increased costs for road and facility maintenance, and (3) direct damage to trees by wind, snow, or ice and subsequent effects on timber supplies and market prices. Mitigation strategies most commonly mentioned were switching of silvicultural systems and changing site preparation and planting schemes, but most respondents had not altered their management due to extreme weather. When asked about effects of a hypothetical 25% increase in severe weather, the most common mitigation strategy was increased investment in new equipment and facilities. Short-term economic impacts of severe weather varied between “supply increasing” conditions associated with increased tree damage and salvage operations and “supply decreasing” conditions related to reduced access to forest land. Increased severe weather due to climate change can be expected to have small to modest effects on forest management and users overall, but areas subjected to hurricanes and ice storms within the Mid-Atlantic region appear to be more sensitive to impacts of severe weather. North. J. Appl. For. 20(2):61–70.

Coleopteran Pests: Family Scarabaeidae

2020 ◽  
pp. 161-173
Author(s):  
Patricia J. Vittum
Keyword(s):  
United States ◽  
The United States ◽  
Southwestern United States ◽  
Northeastern United States ◽  
White Grubs ◽  
Large Complex ◽  
The Family ◽  
Major Pest ◽  
General Appearance

This chapter studies Coleopteran pests. The larvae of turfgrass-infesting species of the family Scarabaeidae constitute a large complex whose members (white grubs) are similar in general appearance, in habits, and in the turfgrass damage they cause. At least 10 species of scarabs, belonging to five subfamilies, are pests of turfgrass in the United States. The larvae of this family are known also as grubs, a term applied to the larvae of several Coleoptera (beetles) and Hymenoptera (ants, bees, and wasps) in general. Grubs of the Scarabaeidae are the most serious turfgrass pests in the northeastern United States, and are considered a major pest in the Midwest, Southeast, and parts of the southwestern United States. Their subterranean habits make them among the most difficult of turfgrass insects to manage.

scholarly journals Shifts in Precipitation Accumulation Extremes During the Warm Season Over the United States

2018 ◽  
Vol 45 (16) ◽  
pp. 8586-8595 ◽  
Author(s):  
Cristian Martinez‐Villalobos ◽  
J. David Neelin
Keyword(s):  
United States ◽  
Warm Season ◽  
The United States

scholarly journals A Radar-Based Climatology of Mesoscale Convective Systems in the United States

2019 ◽  
Vol 32 (5) ◽  
pp. 1591-1606 ◽  
Author(s):  
Alex M. Haberlie ◽  
Walker S. Ashley
Keyword(s):  
United States ◽  
Agricultural Land ◽  
Gulf Coast ◽  
Warm Season ◽  
The United States ◽  
Corn Belt ◽  
High Plains ◽  
Convective System ◽  
Aquifer Recharge ◽  
Mesoscale Convective

Abstract This research applies an automated mesoscale convective system (MCS) segmentation, classification, and tracking approach to composite radar reflectivity mosaic images that cover the contiguous United States (CONUS) and span a relatively long study period of 22 years (1996–2017). These data afford a novel assessment of the seasonal and interannual variability of MCSs. Additionally, hourly precipitation data from 16 of those years (2002–17) are used to systematically examine rainfall associated with radar-derived MCS events. The attributes and occurrence of MCSs that pass over portions of the CONUS east of the Continental Divide (ECONUS), as well as five author-defined subregions—North Plains, High Plains, Corn Belt, Northeast, and Mid-South—are also examined. The results illustrate two preferred regions for MCS activity in the ECONUS: 1) the Mid-South and Gulf Coast and 2) the Central Plains and Midwest. MCS occurrence and MCS rainfall display a marked seasonal cycle, with most of the regions experiencing these events primarily during the warm season (May–August). Additionally, MCS rainfall was responsible for over 50% of annual and seasonal rainfall for many locations in the ECONUS. Of particular importance, the majority of warm-season rainfall for regions with high agricultural land use (Corn Belt) and important aquifer recharge properties (High Plains) is attributable to MCSs. These results reaffirm that MCSs are a significant aspect of the ECONUS hydroclimate.

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