Principal Investigator: Peter Dodge
Sam Houston
Collaborating scientist(s):
Colin McAdie (National Tropical Prediction Center)
Dr. Frank Marks, Jr.
Objective: Analyze the three-dimensional wind structure of landfalling tropical cyclones by combining airborne Doppler radar data collected by NOAA research aircraft with Doppler data archived by National Weather Service WSR-88D coastal radars.
Rationale: NOAA will soon complete deployment of land-based Doppler (WSR-88D) radars along the coast of the continental US. The WSR-88D's measure only one component of the wind, towards or away from the radar. However, if a NOAA P-3 flies an appropriate track relative to the hurricane and WSR-88D, then data from the two platforms can be analyzed with dual-Doppler algorithms to yield a time-series of three-dimensional wind fields. HRD designed the Tropical Cyclone Windfields Near Landfall experiment, part of the Hurricane Field Program, to gather flight-level wind data and make surface wind estimates to improve real-time and post-storm surface wind analyses in tropical storms and hurricanes (see REAL-TIME HURRICANE DAMAGE MITIGATION). One of the objectives of this experiment is to collect airborne Doppler radar data to combine with WSR-88D radar data.
Method: If a tropical cyclone with sufficient radar scatterers to define the vortex moves within 230 km (Doppler range) of a WSR-88D, then a NOAA P-3 will fly on tracks defined by the WSR-88D and the storm center. Because the airborne Doppler radar scans in a vertical plane perpendicular to the aircraft track, the airborne and land-based Doppler rays will be nearly orthogonal, optimal for dual-Doppler analyses. During the storm, the WSR-88D will record base data. After the storm HRD will obtain the WSR-88D data from the National Climatic Data Center and process the two Doppler data sets.
Accomplishment: On 1 August, 1995, a NOAA AOC P-3 recorded airborne Doppler radar data in Hurricane Erin near the time of landfall on the East Coast of Florida. From 2235 UTC to 0204 UTC on 2 August, the aircraft made several penetrations through the eye when the storm was within Doppler range of the Melbourne WSR-88D (FIGURE 1). The aircraft track was aligned along a radial from the WSR-88D. Our first attempt will be to generate an analysis of Erin's wind field derived from airborne and WSR-88D Doppler data collected at 0150 UTC, when the center of circulation was ~170 km from the Melbourne radar. At 0154 UTC the 0.5 deg WSR-88D Doppler scan (FIGURE 2) shows a typical Doppler velocity couplet, with flow > 40 m/s towards the radar in the northeast part of the eye, and flow > 16 m/s away from the radar in the southwest part. P3 Doppler radar data at 3.5 km elevation ( the approximate height of the 0.5 deg 88D radar beam at this distance ) (FIGURE 3), has a maximum of ~ 30 m/s Doppler velocity in the Northwest side of the storm. When these two data sets are combined (stay tuned!) we should have a good estimate of the winds in the forward half of the storm.
Key reference:

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