Thursday, 1 May 2008
Palms ABCD (Wyndham Orlando Resort)
A number of studies have shown that the moisture content in the environments of tropical cyclones affects intensity changes. For example, the Saharan Air Layer (SAL) is characterized by very low mid-level relative humidity and high vertical shear compared to a typical Atlantic tropical sounding. SAL outbreaks typically move off the west coast of Africa during the hurricane season, and have the potential to slow the intensification of tropical cyclones if this air is entrained into the storm circulation or when it impedes a storm's moisture source. Mid-latitude dry air intrusions are another type of dry layer that can negatively impact tropical cyclone intensity via these same mechanisms. One method for identifying these various dry layers is to examine the total precipitable water (TPW) structure around a storm. A significant advantage of using TPW is that it is derived using microwave channels, and can therefore provide a robust representation of the low- to mid-level atmospheric moisture in both clear and cloudy conditions. In this study, a 10-year sample of a satellite-based TPW product is examined to quantitatively estimate the effect of moisture information on Atlantic tropical cyclone intensity prediction. The TPW product is retrieved from SSM/I, TMI, and AMSR-E data, and is available at 6 hour intervals. Parameters from the TPW product are used as input to the Statistical Hurricane Intensity Prediction Scheme (SHIPS) to determine if they provide additional predictive information relative to what is already included in the model.
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