JP7.12
Propagating patterns in 6.7 µm imagery in re-intensifying tropical-to extratropical cyclone transitions
PAPER WITHDRAWN
John A. Knaff, NOAA/NESDIS, Fort Collins, CO
Tropical cyclones often transition to extra-tropical cyclones when they move from the subtropics to the mid-latitudes. This process is commonly referred to as extra-tropical transition (ET). The forecasting of ET is important because it often occurs in the latter part of the hurricane season when the number of ships at sea, particularly near coastal areas, is the greatest. During the ET process cyclones commonly accelerate and while the wind field is observed to expand, thus they can affect large areas in relatively short periods of time. Occasionally such events re-intensify following ET to hurricane strength further exacerbating the forecast problem. The phasing between the mid-latitude troughs and tropical cyclones has been shown to be important to the future evolution of the resulting extra-tropical cyclone, but remains relatively difficult to forecast because of the rapid and complex nature of those interactions. To examine the utility of geostationary water vapor imagery (6.7µm) in potentially better anticipating the re-intensifying ET case, the evolution of several re-intensifying ET cases is studied using complex empirical orthogonal functions (CEOF). The CEOFs will provide the spatial patterns that explain the most variability in the 6.7µm imagery as well as the mean temporal evolution of those patterns. Finally the CEOF form a basis that potentially can be used to better predict the evolution of other ET cases. The results of the CEOF analysis, the diagnosis of the patterns that are related to re-intensification of these ET cases and possibly the diagnosis of a case from the 2008 hurricane season will be presented.
Joint Poster Session 7, Natural Hazards
Wednesday, 14 January 2009, 2:30 PM-4:00 PM, Hall 5
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