DeMaria, Zehr, Knaff, Dostalek

A manuscript entitled, "Annular Hurricanes" by J. A. Knaff, J. P. Kossin, and M. DeMaria, was submitted to Weather and Forecasting. The paper documents the existence of major hurricanes with large eyes that are nearly symmetric and have little or no outer rainband activity. The paper also documents the environment in which these storms occur and an objective method for identifying them in an operational setting. An example of one of these storms (Luis 1995) is shown in Figure 1. See past quarterly reports for greater detail. Click on images to enlarge.

A manuscript entitled "Statistical, Five-Day Tropical Cyclone Intensity Forecasts Derived From Climatology and Persistence" was submitted to Weather and Forecasting. The paper describes the development and performance of statistical tropical cyclone intensity forecasting models designed for the Atlantic, eastern North Pacific and the western North Pacific. The model uses climatology and persistence (CLIPER) as a basis. CLIPER models are primarily run operationally for evaluation of other forecast models as part of the year-end verification process. These 5-day forecast models replace older 3-day forecast models in the operational suit at the National Hurricane Center and the Joint Typhoon Warning Center as these forecast centers evaluate the issuance of 5-day tropical cyclone forecasts. Independent operational performance of the models in the Atlantic and eastern Pacific basins are comparable to their predecessors, while the model developed for the western North Pacific produced forecast that were between 5 and 20% better than its predecessor, as shown in Figure 2.

Figure 2: Homogeneous comparison of mean absolute intensity forecast errors for the western North Pacific tropical cyclone basin during 2001 between the official Joint Typhoon Warning Center Forecast (JTWC), the Statistical Typhoon Intensity Forecasts (STIFOR) and the new 5-day STIFOR forecast.

A proposal entitled "Development of Tropical Cyclone Wind Speed Probabilities" has been submitted to the Insurance Friends of the Hurricane Center, Inc. The proposed research will determine the error properties associated with the NHC official track, intensity and wind radii forecasts in order to create a map of probabilities of the wind exceeding various thresholds.

Two progress reports and "Year 2" proposals and funding requests for a Joint Hurricane Test-bed (JHT) projects were submitted. The first of these projects is to improve tropical cyclone intensity forecasts using satellite data. Preliminary results show that ocean heat content data derived from satellite altimetry and GOES infrared data have the potential to improve the operational Statistical Hurricane Intensity Prediction Scheme (SHIPS). An experimental version of SHIPS with these new satellite data sources will be run in real-time during the 2002 Atlantic hurricane season for evaluation by the Tropical Prediction Center. The second project involving CIRA and CIMSS describes methods to estimate tropical cyclone intensity and wind radii using the AMSU instrument.

Case studies of 2001 Atlantic Tropical Storm Chantal and Hurricanes Erin, Felix, Iris, and Michelle, are partially completed. The vertical shear and satellite observed cloud asymmetry, along with their relationship to intensity change, were analyzed. Some of those results are included in an Extended Abstract, entitled "Vertical Wind Shear Characteristics with Atlantic Hurricanes During 2001" by R. Zehr. It was submitted to the AMS 25th Conference on Hurricanes and Tropical Meteorology to be held April 29 - May 3, 2002 in San Diego, CA. This ongoing project is evaluating independent measurements of environmental vertical wind shear using numerical model analyses, high-density satellite winds, and IR cloud asymmetry. The goal is to improve the quantitative representation of vertical wind shear forcing on observed hurricane intensity changes.

A manuscript entitled, "Three Approaches to Quantitative Observations of Environmental Vertical Wind Shear with Hurricane Bertha," was submitted to Weather and Forecasting.

New images from the late 2001 Season and the 2002 Southern Hemisphere season have been added to the CIRA Infrared Tropical Cyclone archive. As of March 15, 2002, there are approximately 200 tropical cyclones in the archive, with over 50,000 images on 30 CDs. Images are extracted from the 4 km resolution Mercator remaps archived by Tropical RAMSDIS. All images are reviewed for quality and if necessary re-sectorized. Matt McClurg (CIRA hourly) continues to provide support in saving Tropical RAMSDIS images to CD, writing IR Archive images to CD, and assisting with data processing.

Datasets for studying global tropical cyclones are being collected and archived in a real-time basis. Routine datasets include high-density cloud drift winds, and QuikScat winds, hurricane reconnaissance, surface and upper air reports, and AMSU quick look data sets.

Programming support was provided for Mark DeMaria and post doctorate researcher Jim Kossin for a project involving the initialization of tropical storms in models. A grib-to-ASCII conversion program was written for use with AVN model data in sigma coordinates.

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