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Oklahoma is a region that is well known for its high frequency of severe thunderstorms, which vary in activity, mode, and coverage. In particular, this region experiences a significant number of highly organized supercell thunderstorms that pose hazards such as high winds, large hail, and tornadoes. This demonstration study focuses on the development and analysis of a 10-yr sample of supercell storms resulting from organized severe weather events in Oklahoma. Geographic information systems (GIS) were used as the primary tool to develop and analyze the 10-yr supercell dataset. The use of GIS technologies within the field of meteorology has increased dramatically in recent years and will likely continue as additional atmospheric science data formats become available in popular GIS software packages such as the Environmental Systems Research Institute's ArcGIS series. For this specific study, GIS served as a critical component for developing individual georeferenced storm features and analyzing the life span and characteristics of 943 supercell thunderstorms. The results of a series of spatial storm frequency, initiation, termination, and direction analyses are presented. Results revealed that for the period spanning 1994-2003 supercell storms resulting from organized severe weather events were most frequent across several regions, including eastcentral Oklahoma, southwest Oklahoma, and west-central through northeast Oklahoma, with an overall mean track from the southwest to northeast. Supercell tracks were predominantly southwesterly during the first 5 months of the year, northwesterly from June through September, and once again southwesterly from October through the end of the year. A final set of analyses and examples illustrate the utility of storm feature-based climatologies.

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ABSTRACT:Severe thunderstorms are an important and relatively common component of the annual weather across the State of Oklahoma. Such weather brings hazardous features such as, large hail, damaging winds, and tornadoes, while also providing beneficial precipitation vital to the state's agricultural and hydrological needs. In any given year, severe weather activity is dictated by seasonal and monthly changes in atmospheric conditions, which frequently determine the type and severity of subsequent storms.This study focuses on a 10-year period between 1994 and 2003 to quantify the spatial and temporal characteristics of severe squall line storms across Oklahoma. A squall line is a linearly organized set of storms that has a sharp radar reflectivity gradient at its leading edge typically followed by a less intense stratiform region. Squall line storms are one of the most significant storm modes observed in Oklahoma due to their large aerial extent, long durations, high winds, heavy rains, and hail. For this study, geographic information systems (GIS) were used to store geo-referenced storm data and spatially analyse storm events across varying timescales. The analysis revealed that squall lines were most predominant across eastern Oklahoma with a decreasing westward gradient. The annual averaged storm track was from the west to east, while the monthly mean squall line tracks were oriented from southwest to northeast from January through April, from west to east during May, from northwest to southeast from June through September, and from southwest to northeast through the end of the year. In addition, high-resolution analyses of squall line initiation and termination locations revealed important geographical variability in typical storm lifecycle.

This paper examines past drought and assesses future drought scenarios for the Arkansas Red River Basin using two common drought indexes, the Standardized Precipitation Index (SPI) and Palmer Drought Severity Index (PDSI). Historical climate data within the 1900-2009 time frame were used to derive the past drought index estimates. The projected climate data under two greenhouse gas emission scenarios from 16 global climate models (GCMs) after bias correction and statistical downscaling were applied in drought occurrence frequency and affected area projection. The results derived from the SPI and PDSI show that widespread droughts mainly took place in the 1910s, 1930s, 1950s, and 1960s in the Arkansas Red River Basin, which agrees well with the historical climate record. Both the SPI and PDSI project that more frequent and severe droughts will appear in the second part of the 21st century under both of the emissions scenarios. Future PDSI projects that more severe droughts will occur in the western parts of this basin under one scenario.

Since the Oklahoma Mesonet (the state’s automated mesoscale weather station network) was established in 1994, it has served a number of diverse groups and provided public services to foster weather preparedness, education, and public safety, while also supporting decision-making in agricultural production and wildland fire management. With 121 monitoring stations across the state, the Oklahoma Mesonet has developed an array of technologies to observe a variety of atmospheric and soil variables in 5- to 30-min intervals. These consistent observations have been especially critical for predicting and preparing for extreme weather events like droughts, floods, ice storms, and severe convective storms as well as for development of value-added tools. The tools, outreach programs, and mesoscale data have been widely utilized by the general public, state decision-makers, public safety officials, K–12 community, agricultural sector, and researchers, thus generating wide societal and economic benefits to many groups. Based on practical application examples of weather information provided by the Oklahoma Mesonet, this paper analyzes both benefits generated by Oklahoma Mesonet information to the public and decision-makers and ripple effects (spreading amplified outcomes/implications) of those benefits in the short and long term. The paper further details ongoing and anticipated Oklahoma Mesonet innovations as a response to changing needs for weather-related information over time, especially as a result of technological developments and weather variability.

Since 1997, the Oklahoma Mesonet (the state’s automated mesoscale weather station network) has served a community of more than 1,400 public safety officials (emergency managers, fire officials, law enforcement, etc.) across Oklahoma through a weather data and training program called Oklahoma’s First-Response Information Resource System using Telecommunications (OK-First). OK-First provides free weather and radar data interpretation classes to eligible public safety officials and, following successful completion of training, password-protected access to weather data tools including a website and software. The objective of OK-First when it began was to fill significant gaps in weather product training and data access for Oklahoma’s public safety community. Though the core mission remains the same 20 years later, many aspects of OK-First have evolved over time, including participant membership, training curriculum, formats of training, training requirements, website and software technology, and program feedback. The purpose of this paper is to provide an update on the Mesonet’s OK-First program, with a particular focus on training, tools, and the impact it has had on the public safety community.

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