Extended Abstract (164K)5D.5
Aircraft data from rapidly-moving Hurricane Juan south of Nova Scotia
Chris Fogarty, Canadian Hurricane Centre, Dartmouth, NS, Canada
Near midnight September 29th, 2003, Hurricane Juan struck the Nova Scotia coastline just west of the capital city of Halifax as an 85-knot category-2 hurricane. The hurricane was moving very rapidly northward near 30 knots over 18oC sea surface temperatures. Significant damage from storm surge and wind was inflicted on the coastline near but mostly east of landfall. There were hundreds of thousands of downed trees, many occurring as large tree blow-downs in wooded areas due to localized extreme gusts. The hurricane spread a swath of wind damage as far north as Prince Edward Island. Rainfall amounts were uncharacteristically light for a hurricane - less than 35 mm - since the storm was moving so quickly and due to the lack of cloud/convection on the southern side of the storm.
The Canadian Search and Rescue Secretariat have funded a 2-year research project into Atlantic hurricanes affecting Canadian interests. The primary goals of the project are to collect data from tropical cyclones undergoing extratropical transition in order to better quantify the threats, as well as to improve the understanding of the structure and predictability of these systems. Two flights were conducted in the Fall of 2003 using the National Research Council Convair-580 aircraft: the first into the remnants of Hurricane Isabel over southern Ontario, and the second into Hurricane Juan just prior to landfall in Nova Scotia.
Data from the Huricane Juan flight will be presented in this talk. There were two transects through the storm (two eye penetrations) at approximately 6500 m; one from north to south and the other from southwest to northeast parallel to the coast of Nova Scotia. Dropsondes were deployed along both legs, 11 along the north-south leg and 13 along the coastal leg. Vertical profiles of radar data were also collected from this flight. Wind data showed very strong deep-layered winds above the boundary layer on the east side of the hurricane, not unlike an earlier mission into Hurricane Michael in 2000. Very large wind shears in the boundary layer were observed with surface winds as low as 50% of the top-of-boundary layer winds. A large portion of the south side of the storm was void of convection and precipitation, possibly owing to dry air entrainment from over land. Thermodynamic data revealed a pronounced core of high equivalent potential temperature (350 K+) that appeared to tilt northward in the direction of increasing shear.
Data and imagery available at http://www.novaweather.net/Hurricane_Juan.html
Supplementary URL: http://www.novaweather.net/Hurricane_Juan.html
Session 5D, tropical cyclone observations and structure III
Tuesday, 4 May 2004, 8:00 AM-9:45 AM, Napoleon III Room
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