Objective Determination of Hurricane Tracks from Aircraft Observations

Hugh E. Willoughby National Hurricane Research Laboratory, NOAA/AOML, Coral Gables, FL 33146

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Marcy B. Chelmow National Hurricane Research Laboratory, NOAA/AOML, Coral Gables, FL 33146

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Abstract

An algorithm for location of hurricane centers by least squares using aircraft data has been developed. As the aircraft traverses the eye, lines of position normal to the wind are constructed each 100 m along its track. An additional line of position is constructed normal to the track at the closest point of approach to the center. The center coordinates are then chosen such that the sum of the squares of the normal distances from the center to the lines of position is minimized. A cubic spline storm track is first constructed using centers based on winds in a coordinate system fixed to the earth. A track based upon winds in moving, storm-centered coordinates may be obtained by transformation of the winds into such a coordinate system and iterative redetermination of the centers.

For intense hurricanes, the centers can be located with an accuracy of 3 km and the mean motion over a period of four to six hours determined to within 4° of direction and 0.5 m s−1 of speed. The details of the track oscillations analyzed by this techique agree with those observed simultaneously by land-based radar. The technique is used routinely to prepare storm-centered composites and has potential for real-time operational application.

Abstract

An algorithm for location of hurricane centers by least squares using aircraft data has been developed. As the aircraft traverses the eye, lines of position normal to the wind are constructed each 100 m along its track. An additional line of position is constructed normal to the track at the closest point of approach to the center. The center coordinates are then chosen such that the sum of the squares of the normal distances from the center to the lines of position is minimized. A cubic spline storm track is first constructed using centers based on winds in a coordinate system fixed to the earth. A track based upon winds in moving, storm-centered coordinates may be obtained by transformation of the winds into such a coordinate system and iterative redetermination of the centers.

For intense hurricanes, the centers can be located with an accuracy of 3 km and the mean motion over a period of four to six hours determined to within 4° of direction and 0.5 m s−1 of speed. The details of the track oscillations analyzed by this techique agree with those observed simultaneously by land-based radar. The technique is used routinely to prepare storm-centered composites and has potential for real-time operational application.

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