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A CASE STUDY
OF HURRICANE FORMATION IN STRONG SHEAR: CLAUDETTE (2003)
» Kay Shelton - University at Albany/SUNY
The storm that was to become Hurricane Claudette evolved from an easterly wave in the Caribbean Sea in early July 2003. The storm experienced strong shear throughout the majority of its existence, forcing convection to remain downshear of the storm centre. On 9th July, convection pulsed repeatedly over the storm centre, but became sustained over the centre throughout the morning of 10th July. The storm intensified to a hurricane at 12UTC on 10th July as the shear reached 16ms-1 (850-200hPa). The shear had increased further to 16.7ms-1 six hours later, by which time almost no trace of even a tropical storm strength circulation could be found.
The intensification of Claudette to a hurricane and the subsequent rapid weakening is investigated using USAF reconnaissance data. These data reveal a storm initially composed of a small warm-core circulation embedded within a larger-scale wave at both 850hPa and 700hPa. As the hurricane spun up, an eyewall developed (indicated by saturated, high θe air) with the warm, dry air indicative of an eye trapped inside. However, dry air is seen to have persisted at 700hPa, just outside the eyewall on the upshear side and subsequently both to the left and right of the shear vector. Rapid weakening occurred over a period of about 90 minutes.
It is hypothesized that advection of the dry air from upshear, around the storm to downshear, by the storm's own circulation brought about the weakening. The presence of the dry air downshear allowed cold downdrafts to occur, which then acted to erode the surface-based warm pool on which the convection had been feeding, effectively killing the storm.
A further hypothesis regarding how the hurricane actually managed to form under such high shear will be presented in the talk. Additional figures can be found on my Claudette page.
» Direct link to an animation of IR satellite imagery for Claudette
» The presentation. [Powerpoint]
» Return to North-East Tropical Cyclone Workshop page
» Kay Shelton - University at Albany/SUNY
The storm that was to become Hurricane Claudette evolved from an easterly wave in the Caribbean Sea in early July 2003. The storm experienced strong shear throughout the majority of its existence, forcing convection to remain downshear of the storm centre. On 9th July, convection pulsed repeatedly over the storm centre, but became sustained over the centre throughout the morning of 10th July. The storm intensified to a hurricane at 12UTC on 10th July as the shear reached 16ms-1 (850-200hPa). The shear had increased further to 16.7ms-1 six hours later, by which time almost no trace of even a tropical storm strength circulation could be found.
The intensification of Claudette to a hurricane and the subsequent rapid weakening is investigated using USAF reconnaissance data. These data reveal a storm initially composed of a small warm-core circulation embedded within a larger-scale wave at both 850hPa and 700hPa. As the hurricane spun up, an eyewall developed (indicated by saturated, high θe air) with the warm, dry air indicative of an eye trapped inside. However, dry air is seen to have persisted at 700hPa, just outside the eyewall on the upshear side and subsequently both to the left and right of the shear vector. Rapid weakening occurred over a period of about 90 minutes.
It is hypothesized that advection of the dry air from upshear, around the storm to downshear, by the storm's own circulation brought about the weakening. The presence of the dry air downshear allowed cold downdrafts to occur, which then acted to erode the surface-based warm pool on which the convection had been feeding, effectively killing the storm.
A further hypothesis regarding how the hurricane actually managed to form under such high shear will be presented in the talk. Additional figures can be found on my Claudette page.
» Direct link to an animation of IR satellite imagery for Claudette
» The presentation. [Powerpoint]
» Return to North-East Tropical Cyclone Workshop page