An Assessment of the Subseasonal Predictability of Severe Thunderstorm title Environments and Activity using the Climate Forecast System Version 2

The prospect for skillful long-term predictions of atmospheric conditions known to directly contribute to the onset and maintenance of severe convective storms remains unclear. A thorough assessment of the capability for a global climate model such as the Climate Forecast System Version 2 (CFSv2) to skillfully represent parameters related to severe weather has the potential to significantly improve medium- to longrange outlooks vital to risk managers. Environmental convective available potential energy (CAPE) and deep-layer vertical wind shear (DLS) can be used to distinguish an atmosphere conducive to severe storms from one supportive of primarily nonsevere ordinary convection. As such, this research concentrates on the predictability of CAPE, DLS, and a product of the two parameters (CAPEDLS) by the CFSv2 with a specific focus on the subseasonal timescale. Individual month-long verification periods from the Climate Forecast System reanalysis (CFSR) dataset are measured against a climatological standard using cumulative distribution function (CDF) and area-under-the-CDF (AUCDF) techniques designed mitigate inherent model biases while concurrently assessing the entire distribution of a given parameter in lieu of a threshold-based approach. Similar methods imposed upon the CFS reforecast (CFSRef) and operational CFSv2 allow for comparisons elucidating both spatial and temporal trends in skill using correlation coefficients, proportion correct metrics, Heidke skill score (HSS), and root-meansquare- error (RMSE) statistics. Key results show the CFSv2-based output often demonstrates skill beyond a climatologically-based threshold when the forecast is notably anomalous from the 29-year (1982-2010) mean CFSRef prediction (exceeding one standard deviation at grid point level). CFSRef analysis indicates enhanced skill during the months of April and June (relative to May) and for predictions of DLS. Furthermore, years exhibiting skill in terms of RMSE are shown to possess certain correlations with El Ni˜no-Southern Oscillation conditions from the preceding winter and concurrent Madden Julian Oscillation activity. Applying results gleaned from the CFSRef analysis to the operational CFSv2 (2011-16) indicates predictive skill can be increased by isolating forecasts meeting multiple parameter-based relationships

Crosslinking of epoxy-polysiloxane system by reactive blending

(PAMS) containing pendant amino groups and diglycidyl ether of Bisphenol A (DGEBA). The initially immiscible blend is compatibilized during the reaction and crosslinked. Network formation, dynamics of the system and evolution of morphology were determined by dynamic mechanical analysis and light scattering techniques. The grafting epoxy-amine reaction involves a high extent of cyclization resulting in a high fraction of the sol in the networks. Dynamic light scattering data analysis reveals fast and slow relaxation modes of reacting species in the pregel and one single mode in the post-gel state. The network with a stoichiometric composition shows the most homogeneous morphology with a single glass transition temperature. On the contrary, the networks with excess of PAMS are strongly phase-separated exhibiting the unreacted PAMS-rich phase, PAMS phase partly grafted with epoxide and PAMS-DGEBA crosslinked phase.The authors acknowledge financial support of the European Commission through a Marie Curie Training Site contract No. HPMT-CT-2001-00396 and of the Grant Agency of Academy of Sciences of the Czech Republic (A4050008).Publicad

A C-Band, Dual-Polarimetric Radar Analysis of a Tornadic Mesoscale Convective System: The 25 May 2011 Northern Illinois and Indiana Tornado Event

During the morning hours of 25 May 2011, at least six tornadoes struck a narrow corridor of Northeast Illinois and Northwest Indiana. Two tornadoes were rated EF0, three EF1, and one EF2. These tornadoes occurred in conjunction with a mesoscale convective system (MCS) that traveled northeast across the region during the early to mid-morning hours, between 1200 UTC and 1500 UTC. The tornadoes occurred at least 65 km away from the nearest NEXRAD WSR-88D radar site. The confirmed tornadoes from this event occurred without severe thunderstorm or tornado warnings likely due to the fact that (1) the squall-line was oriented parallel to the radar beam, (2) there were minimal real-time spotter reports, (3) embedded circulations were shallow, and (4) the tornado-producing storms did not exhibit classic radar signatures at the nearest NEXRAD locations. The tornadoes occurred anywhere from approximately 50-75 km from the C-band dual-polarimetric radar located on the campus of Valparaiso University in Valparaiso, IN. In this presentation, we examine the data gathered from the C-band, dual-polarimetric radar at Valparaiso University. We review the data in hopes of revealing methods that could have better detected the tornadoes produced during this event

Measurements of Differential Reflectivity in Snowstorms and Warm Season Stratiform Systems

The organized behavior of differential radar reflectivity (ZDR) is documented in the cold regions of a wide variety of stratiform precipitation types occurring in both winter and summer. The radar targets and attendant cloud microphysical conditions are interpreted within the context of measurements of ice crystal types in laboratory diffusion chambers in which humidity and temperature are both stringently controlled. The overriding operational interest here is in the identification of regions prone to icing hazards with long horizontal paths. Two predominant regimes are identified: category A, which is typified by moderate reflectivity (from 10 to 30 dBZ) and modest +ZDR values (from 0 to +3 dB) in which both supercooled water and dendritic ice crystals (and oriented aggregates of ice crystals) are present at a mean temperature of −13°C, and category B, which is typified by small reflectivity (from −10 to +10 dBZ) and the largest +ZDR values (from +3 to +7 dB), in which supercooled water is dilute or absent and both flat-plate and dendritic crystals are likely. The predominant positive values for ZDR in many case studies suggest that the role of an electric field on ice particle orientation is small in comparison with gravity. The absence of robust +ZDR signatures in the trailing stratiform regions of vigorous summer squall lines may be due both to the infusion of noncrystalline ice particles (i.e., graupel and rimed aggregates) from the leading deep convection and to the effects of the stronger electric fields expected in these situations. These polarimetric measurements and their interpretations underscore the need for the accurate calibration of ZDR.United States. Federal Aviation Administration (Air Force Contract FA8721-05-C-0002

Dynamic Critical Phenomena of Polymer Solutions

Recently, a systematic experiment measuring critical anomaly of viscosity of polymer solutions has been reported by H. Tanaka and his co-workers (Phys.Rev.E, 65, 021802, (2002)). According to their experiments, the dynamic critical exponent of viscosity y_c drastically decreases with increasing the molecular weight. In this article the kinetic coefficients renormalized by the non-linear hydrodynamic interaction are calculated by the mode coupling theory. We predict that the critical divergence of viscosity should be suppressed with increasing the molecular weight. The diffusion constant and the dynamic structure factor are also calculated. The present results explicitly show that the critical dynamics of polymer solutions should be affected by an extra spatio-temporal scale intrinsic to polymer solutions, and are consistent with the experiment of Tanaka, et al.Comment: 17 pages, 2 figures, to be published in J.Phys.Soc.Jp

North Pacific - North American circulation and precipitation anomalies associated with the Madden-Julian oscillation

The Madden-Julian Oscillation (MJO) has been associated with extreme precipitation events in western North America. However, the mechanisms for, and predictability of, these associations are not clear. We have examined the influence of the MJO on North Pacific - North America (NPNA) circulation and precipitation anomalies during the boreal winter. We constructed composites of MJO events during 1979-2005 determined from the Wheeler RMM1/RMM2 index of MJO activity. Our analyses of NPNA anomalies were based primarily on the National Centers for Environmental Prediction reanalysis data set. We focused our investigations on the impacts on NPNA circulation and precipitation of: (1) the location and amplitude of the convective and subsidence components of the MJO; (2) the season of MJO occurrence; and (3) concurrent El Nino (EN) or La Nina (LN) events. We found that the NPNA response to the MJO is sensitive to the location of both the convective and subsidence components of the MJO, the season of MJO occurrence, and to the existence of concurrent EN or LN events. EN or LN events affect the extratropical response to the MJO by altering the equatorial Rossby-Kelvin wave response to the components of the MJO. This in turn affects the anomalous extratropical wave trains initiated by the MJO, and alters the strength and location of the resulting NPNA precipitation anomalies. Our results have allowed us to identify characteristic patterns associated with the MJO that can be related to the location and intensity of extreme NPNA precipitation. MJO events are relatively persistent phenomena. Thus, increased understanding of the mechanisms by which they impact the extratropics has the potential to improve extratropical extended range forecasting. Our results provide a substantial foundation for improving forecasts of NPNA circulation and precipitation.http://archive.org/details/northpacificnort109452953Approved for public release; distribution is unlimited

An Assessment of the Subseasonal Predictability of Severe Thunderstorm Environments and Activity using the Climate Forecast System Version 2

The prospect for skillful long-term predictions of atmospheric conditions known to directly contribute to the onset and maintenance of severe convective storms remains unclear. A thorough assessment of the capability for a global climate model such as the Climate Forecast System Version 2 (CFSv2) to skillfully represent parameters related to severe weather has the potential to significantly improve medium- to long-range outlooks vital to risk managers. Environmental convective available potential energy (CAPE) and deep-layer vertical wind shear (DLS) can be used to distinguish an atmosphere conducive to severe storms from one supportive of primarily non-severe ‘ordinary’ convection. As such, this research concentrates on the predictability of CAPE, DLS, and a product of the two parameters (CAPEDLS) by the CFSv2 with a specific focus on the subseasonal timescale. Individual month-long verification periods from the Climate Forecast System reanalysis (CFSR) dataset are measured against a climatological standard using cumulative distribution function (CDF) and area-under-the-CDF (AUCDF) techniques designed mitigate inherent model biases while concurrently assessing the entire distribution of a given parameter in lieu of a threshold-based approach. Similar methods imposed upon the CFS reforecast (CFSRef) and operational CFSv2 allow for comparisons elucidating both spatial and temporal trends in skill using correlation coefficients, proportion correct metrics, Heidke skill score (HSS), and root-mean-square-error (RMSE) statistics. Key results show the CFSv2-based output often demonstrates skill beyond a climatologically-based threshold when the forecast is notably anomalous from the 29-year (1982-2010) mean CFSRef prediction (exceeding one standard deviation at grid point level). CFSRef analysis indicates enhanced skill during the months of April and June (relative to May) and for predictions of DLS. Furthermore, years exhibiting skill in terms of RMSE are shown to possess certain correlations with El Niño-Southern Oscillation conditions from the preceding winter and concurrent Madden Julian Oscillation activity. Applying results gleaned from the CFSRef analysis to the operational CFSv2 (2011-16) indicates predictive skill can be increased by isolating forecasts meeting multiple parameter-based relationships

Solar Eclipse Radiosonde Launch Project

On August 21, 2017, the United States experienced a total solar eclipse from coast to coast for the first time in 38 years. This event provided a unique opportunity to study the vertical profile of the atmosphere during the duration of a solar eclipse through the deployment of instrumented balloons capable of measuring temperature, wind speed and direction, and humidity. Six students and three faculty members from Valparaiso University worked in cooperation with the University of Montana in an effort to coordinate radiosonde launches across the path of totality in North America. Four launches were conducted in Coulterville, Illinois measuring the state of the atmosphere before, during, and after the event. Goals of this project centered on the eclipse’s impact on temperature, barometric pressure, humidity, and wind variations from the surface to the middle of the troposphere. Key discoveries include a decrease in both surface temperature and dew point coincident with an increase in wind speed, particularly during and after eclipse totality. Temperature was measured in ten minute intervals with an eclipse-driven minimum temperature observed two minutes after totality. Winds near the surface continually increased between the first and third launches while a slight decrease was measured after the fourth launch. It is hypothesized the fluctuations in wind speed are a consequence of temperature changes within the boundary layer

Solar Eclipse Radiosonde Launch Project

On August 21, 2017, the United States experienced a total solar eclipse from coast to coast for the first time in 38 years. This event provided a unique opportunity to study the vertical profile of the atmosphere during the duration of a solar eclipse through the deployment of instrumented balloons capable of measuring temperature, wind speed and direction, and humidity. Six students and three faculty members from Valparaiso University worked in cooperation with the University of Montana in an effort to coordinate radiosonde launches across the path of totality in North America. Four launches were conducted in Coulterville, Illinois measuring the state of the atmosphere before, during, and after the event. Goals of this project centered on the eclipse’s impact on temperature, barometric pressure, humidity, and wind variations from the surface to the middle of the troposphere. Key discoveries include a decrease in both surface temperature and dew point coincident with an increase in wind speed, particularly during and after eclipse totality. Temperature was measured in ten minute intervals with an eclipse-driven minimum temperature observed two minutes after totality. Winds near the surface continually increased between the first and third launches while a slight decrease was measured after the fourth launch. It is hypothesized the fluctuations in wind speed are a consequence of temperature changes within the boundary layer