Extended Abstract (768K)4D.5
Multiple eyewall structure of Hurricane Juliette 2001
Brian D. McNoldy, Colorado State University, Fort Collins, CO; and M. D. Eastin, C. M. Rozoff, and W. H. Schubert
Concentric eyewalls are relatively rare and ephemeral; only about 10% of all tropical cyclones (TCs) develop them, and once formed, they typically are not maintained for longer than about twelve hours. Multiple eyewalls are more commonly observed in intense TCs as compared to weaker storms and are identified by finding two or even three distinct annuli of intense convection encircling the central eye. This can be done via aircraft reconnaissance, ground-based radar if the storm is near land, or space-based microwave imagery if a satellite happens to pass over the storm at an opportune time.
An interesting example of multiple eyewalls occured during 25-26 September 2001 in the East Pacific basin. Category 4 Hurricane Juliette was observed not only by GOES-10, but also by Hurricane Hunter aircraft and by microwave imagers onboard TRMM and DMSP satellites, and for a period on 26 September, triple eyewalls were observed.
Eyewall cycles began in Juliette just prior to reaching maximum intensity (63 m/s and 923 hPa), but the triple eyewall configuration formed as the storm was deteriorating, although still very intense (48 m/s and 930 hPa). In this case however, the triple eyewall did not result in one dominant eyewall after the replacement cycle; instead, the entire inner core deteriorated due to a combination of increasing vertical wind shear, decreasing sea surface temperature, and proximity to land.
Supplementary URL: http://einstein.atmos.colostate.edu/~mcnoldy/tropics/juliette/269/
Session 4D, tropical cyclone observations and structure II
Monday, 3 May 2004, 3:45 PM-5:15 PM, Napoleon III Room
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