William E. Lewis

RECORDED PRESSURE DISTRIBUTION IN THE OUTER PORTION OF A TORNADO VORTEX

Abstract Records are presented from nine barographs located in a small area close to the path of a tornado. The pressure profile in the range from 720 to 2,300 feet from the path of the tornado center as determined from the barograph records was found to be in good agreement with calculations based on a simple model consisting of a frictionless vortex with in-flow.

Geostationary Doppler Radar and Tropical Cyclone Surveillance

AbstractThe potential usefulness of spaceborne Doppler radar as a tropical cyclone observing tool is assessed by conducting a high-resolution simulation of an intense hurricane and generating synthetic observations of reflectivity and radial velocity. The ground-based velocity track display (GBVTD) technique is used to process the radial velocity observations and generate retrievals of meteorologically relevant metrics such as the maximum wind (MW), radius of maximum wind (RMW), and radius of 64-kt wind (R64). Results indicate that the performance of the retrieved metrics compares favorably with the current state-of-the-art satellite methods for intensity estimation and somewhat better than current methods for structure (i.e., wind radii).

FORECASTING 700-MB. DEWPOINT DEPRESSION BY A 3-DIMENSIONAL TRAJECTORY TECHNIQUE

Abstract Quasi 3-dimensional forecasts of 700-mb. dewpoint depression are made for periods up to 36 hours using observed 700-mb. charts and initial and 12-hr. forecast vertical motion charts from the JNWP Units “thermotropic model.” Results show that moisture can be successfully forecast by this technique. Through establishment of a relationship between 700-mb. dewpoint depression, instantaneous vertical velocity, and large-scale weather, a forecast scheme is devised using forecast 700-mb. dewpoint depression and forecast vertical motion from the thermotropic model as arguments. Preliminary results of some experimental forecasts are favorable.

Assimilation of High-Resolution Satellite-Derived Atmospheric Motion Vectors: Impact on HWRF Forecasts of Tropical Cyclone Track and Intensity

AbstractIt is well known that global numerical model analyses and forecasts benefit from the routine assimilation of atmospheric motion vectors (AMVs) derived from meteorological satellites. Recent studies have also shown that the assimilation of enhanced (spatial and temporal) AMVs can benefit research-mode regional model forecasts of tropical cyclone track and intensity. In this study, the impact of direct assimilation of enhanced (higher resolution) AMV datasets in the NCEP operational Hurricane Weather Research and Forecasting Model (HWRF) system is investigated. Forecasts of Atlantic tropical cyclone track and intensity are examined for impact by inclusion of enhanced AMVs via direct data assimilation. Experiments are conducted for AMVs derived using two methodologies (“HERITAGE” and “GOES-R”), and also for varying levels of quality control in order to assess and inform the optimization of the AMV assimilation process. Results are presented for three selected Atlantic tropical cyclone events and comp...

Assessing the Accuracy of the Cloud and Water Vapor Fields in the Hurricane WRF (HWRF) Model Using Satellite Infrared Brightness Temperatures

AbstractIn this study, cycled forecast experiments were performed to assess the ability of different cloud microphysics and cumulus parameterization schemes in the Hurricane Weather Research and Forecasting (HWRF) Model to accurately simulate the evolution of the cloud and moisture fields during the entire life cycle of Hurricane Edouard (2014). The forecast accuracy for each model configuration was evaluated through comparison of observed and simulated Geostationary Operational Environmental Satellite-13 (GOES-13) infrared brightness temperatures and satellite-derived tropical cyclone intensity estimates computed using the advanced Dvorak technique (ADT). Overall, the analysis revealed a large moist bias in the mid- and upper troposphere during the entire forecast period that was at least partially due to a moist bias in the initialization datasets but was also affected by the microphysics and cumulus parameterization schemes. Large differences occurred in the azimuthal brightness temperature distributio...