Extended Abstract (4.8M)2D.3
Hurricane Risk in Hawaii. Part 1: Steering flow analysis in the central north pacific
Anthony Reynes-Figueroa, University of Hawaii at Manoa, Honolulu, HI; and D. Stevens and S. H. Houston
Central Pacific tropical cyclone tracks are investigated, with an emphasis on the satellite era. Our purpose is to better understand the environmental influences and climatology of hurricane risk over the Hawaiian region and to apply this knowledge in seasonal and short-term outlooks. The relative paucity of events increases the challenge, making inferences from observational studies difficult. We report the results of a study conducted in two stages. First, we investigate the behavior of tropical cyclones and the relation of their tracks to the environmental steering flow . Using NWS track data and NCEP/NCAR reanalysis, we seek to determine an optimal layer mean environmental steering flow. Second, we apply our empirical layer mean concept to a set of virtual storms in the central Pacific, using forward and backward trajectories to develop risk dependencies for the residents of Hawaii. We consider sensitivity to initial position, track bifurcations, and the beta gyre effect. Dependence of intensity on sea surface temperature and vertical shear are also investigated. Fifty storm cases in the central Pacific have been analyzed. We have found that, of 28 different candidates for steering layers, the deepest ones show the smallest absolute error in both storm speed and angle error. A deep layer mean steering layer of 850 to 300 mb is a leading prospect for tropical cyclone steering layer in the central Pacific. Possible extensions of this work to other basins are addressed.
Session 2D, Tropical Cyclone Motion (Parallel with Sessions 2A, 2B, & 2C)
Monday, 29 April 2002, 2:00 PM-3:15 PM
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