Extended Abstract (500K)16A.4
What are Annular Hurricanes?
John A. Knaff, CIRA/Colorado State Univ., Fort Collins, CO; and J. P. Kossin and M. DeMaria
This study introduces and examines the occurrence of a symmetric category of tropical cyclone, which the authors call "Annular Hurricanes". The structural characteristics and formation of this type of hurricanes are examined using satellite and aircraft reconnaissance data. The formation is shown to be rather systematic resulting from what appears to be asymmetric mixing of eye and eyewall components of the storms. Flight level thermodynamic data supports this contention, as qe is rather uniform inside the radius of maximum winds of the storms. The flight level winds however show evidence of continued mixing - local, small-scale variations in angular velocity inside the radius of maximum wind during the period that storms have annular characteristics. Intensity tendencies of annular hurricanes are examined using the best track dataset and shows that these intense tropical cyclones maintain their intensities longer than the average hurricane and therefore present a significant intensity forecasting challenge. Using NCEP numerical analyses and Reynold's SST, these storms are shown to exist in a unique set of environmental conditions, which are found 3% , 0.3% of the time in the East Pacific and Atlantic tropical cyclone basins, respectively. Using the findings of this investigation two methods of objectively identifying these storms, one using satellite signatures and the other using environmental conditions are developed
Session 16A, Tropical Cyclone Observations and Structure V (Parallel with Sessions 16B and 16C)
Friday, 3 May 2002, 8:30 AM-10:30 AM
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