Twenty-eight predecessor rain events (PREs) that occurred over the United States east of the Rockies during 1995–2008 are examined from a synoptic climatology and case study perspective. PREs are coherent mesoscale regions of heavy rainfall, with rainfall rates ≥100 mm (24 h)−1, that can occur approximately 1000 km poleward of recurving tropical cyclones (TCs). PREs occur most commonly in August and September, and approximately 36 h prior to the arrival of the main rain shield associated with the TC. A distinguishing feature of PREs is that they are sustained by deep tropical moisture that is transported poleward directly from the TC. PREs are high-impact weather events that can often result in significant inland flooding, either from the PRE itself or from the subsequent arrival of the main rain shield associated with the TC that falls onto soils already saturated by the PRE. The composite analysis shows that on the synoptic-scale, PREs form in the equatorward jet-entrance region of a 200-hPa je...

Predecessor Rain Events ahead of Tropical Cyclones

This study evaluates rainfall estimates from the Next Generation Weather Radar (NEXRAD), operational rain gauges, Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA), and Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks Cloud Classification System (PERSIANN-CCS) in the context as inputs to a calibrated, distributed hydrologic model. A high-density Micronet of rain gauges on the 342-km2 Ft. Cobb basin in Oklahoma was used as reference rainfall to calibrate the National Weather Service’s (NWS) Hydrology Laboratory Research Distributed Hydrologic Model (HL-RDHM) at 4-km/l-h and 0.25°/3-h resolutions. The unadjusted radar product was the overall worst product, while the stage IV radar product with hourly rain gauge adjustment had the best hydrologic skill with a Micronet relative efficiency score of −0.5, only slightly worse than the reference simulation forced by Micronet rainfall. Simulations from TRMM-3B42RT were better t...

http://hydro.ou.edu/files/publications/2011/Hydrologic%20Evaluation%20of%20Rainfall%20Estimates%20from%20Radar,%20Satellite,%20Gauge,%20and%20Combinations%20on%20Ft.%20Cobb%20Basin,%20Oklahoma.pdf

Hydrologic Evaluation of Rainfall Estimates from Radar, Satellite, Gauge, and Combinations on Ft. Cobb Basin, Oklahoma

Since 2007 the advancement of the National Weather Radar Testbed Phased-Array Radar (NWRT PAR) hardware and software capabilities has been supporting the implementation of high-temporal-resolution (∼1 min) sampling. To achieve the increase in computational power and data archiving needs required for high-temporal-resolution sampling, the signal processor was upgraded to a scalable, Linux-based cluster with a distributed computing architecture. The development of electronic adaptive scanning, which can reduce update times by focusing data collection on significant weather, became possible through functionality added to the radar control interface and real-time controller. Signal processing techniques were implemented to address data quality issues, such as artifact removal and range-and-velocity ambiguity mitigation, absent from the NWRT PAR at its installation. The hardware and software advancements described above have made possible the development of conventional and electronic scanning capabil...

High-Temporal-Resolution Capabilities of the National Weather Radar Testbed Phased-Array Radar

Assimilation of remotely sensed precipitation observations into numerical weather prediction models can improve precipitation forecasts and extend prediction capabilities in hydrological applications. This paper presents a new regional ensemble data assimilation system that assimilates precipitation-affected microwave radiances into the Weather Research and Forecasting Model (WRF). To meet the challenges in satellite data assimilation involving cloud and precipitation processes, hydrometeors produced by the cloud-resolving model are included as control variables and ensemble forecasts are used to estimate flow-dependent background error covariance. Two assimilation experiments have been conducted using precipitation-affected radiances from passive microwave sensors: one for a tropical storm after landfall and the other for a heavy rain event in the southeastern United States. The experiments examined the propagation of information in observed radiances via flow-dependent background error auto- and...

Assimilation of Precipitation-Affected Radiances in a Cloud-Resolving WRF Ensemble Data Assimilation System

This paper evaluates, for the first time, flash-flood guidance (FFG) values and recently developed gridded FFG (GFFG) used by the National Weather Service (NWS) to monitor and predict imminent flash flooding, which is the leading storm-related cause of death in the United States. It is envisioned that results from this study will be used 1) to establish benchmark performance of existing operational flash-flood prediction tools and2)to provideinformation toNWSforecastersthatrevealshow theexistingtools canbe readilyoptimized. Sources used to evaluate the products include official reports of flash floods from the NWS Storm Data database, discharge measurements on small basins available from the U.S. Geological Survey, and witness reports of flash flooding collected during the Severe Hazards Analysis and Verification Experiment. Results indicated that the operational guidance values, with no calibration, were marginally skillful, with the highest criticalsuccessindexof0.20 occurringwith3-h GFFG.Thefalse-alarm ratesfell andtheskill improvedto0.34 when the rainfall was firstspatially averaged within basins and then reached 50% of FFG for 1-h accumulation and exceeded 3-h FFG. Although the skill of the GFFG values was generally lower than that of their FFG counterparts,GFFGwascapableofdetectingthespatialvariabilityofreportedflashfloodingbetterthanFFG was for a case study in an urban setting.

/pdf/evaluation-of-tools-used-for-monitoring-and-forecasting-41tqpo69vr.pdf

Evaluation of Tools Used for Monitoring and Forecasting Flash Floods in the United States

Atlantic Tropical Depression Five (2007) briefly strengthened into Tropical Storm Erin over the western Gulf of Mexico shortly before making landfall as a tropical depression near Corpus Christi, Texas, on the morning of 16 August 2007. During the overnight hours of 18–19 August 2007, nearly 3 days after landfall, Erin's remnant circulation strengthened over western Oklahoma, where sustained winds near the circulation's center exceeded 18 m s−1 for more than 3 h—the strongest reported during Erin's entire life cycle. Likewise, station pressure values reduced to sea level were lower at several measurement sites on 19 August than those recorded while Erin was classified by the National Hurricane Center as a tropical cyclone. During this period of lowest pressure, Erin developed an eye, an eyewall structure, and spiral bands, as observed by radar. The reintensification occurred within the domain of multiple observing networks and platforms, which provided rich detail on the near-surface behavior of Erin and ...

Observations of the Overland Reintensification of Tropical Storm Erin (2007)

Chapter 23 : Southern Great Plains. Impacts, Risks, and Adaptation in the United States: The Fourth National Climate Assessment, Volume II

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 man...

Benefits and Beneficiaries of the Oklahoma Mesonet: A Multisectoral Ripple Effect Analysis

A minimum temperature of −31°F (−35°C) was recorded at Nowata, Oklahoma, on 10 February 2011. This exceeded the previous record minimum temperature for Oklahoma of −27°F (−32.8°C). The Nowata station is in the Oklahoma Mesonet network. High pressure was centered over Oklahoma on the morning of the record with clear skies, calm winds, and a fresh snow cover of 38 cm at Nowata. A State Climate Extremes Committee (SCEC) examined the record, including the siting of the station, calibration of the thermometer, and depth of snow. The SCEC voted unanimously to approve the reading as the new lowest minimum temperature record for Oklahoma.

Gary McManus

Papers

Observations of the Overland Reintensification of Tropical Storm Erin (2007)

Chapter 23 : Southern Great Plains. Impacts, Risks, and Adaptation in the United States: The Fourth National Climate Assessment, Volume II

Benefits and Beneficiaries of the Oklahoma Mesonet: A Multisectoral Ripple Effect Analysis

A New Minimum Temperature Record for Oklahoma

A new minimum temperature record