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The Hurricane Rainband and Intensity Change Experiment (RAINEX) was performed by Shuyi Chen, Robert A. Houze, Wen-Chau Lee, Robert F. Rogers, James A. Moore, Gregory J. Stossmeister, Michael M. Bell, Jasmine Cetrone, Wei Zhao, and S. Rita Brodzik in 2005. The project sought to improve hurricane intensity forecasting via measuring interactions between rainbands and the eyewalls of tropical storms. RAINEX was planned in advance for years to be ready to fly in the midst of the 2005 Atlantic hurricane season. Some notable storms included Hurricane Katrina and Hurricane Rita during that season.

The four stages of cyclone eyewall replacement: (i) rainbands rotate around the center of a low pressure system (ii) distinct eyewall and strengthening rainbands visible (iii) rainbands form a new eyewall (iv) new eyewall replaces old eyewall and weakens storm

File:P3 tarmac

P3 aircraft on the tarmac at MacDill Air Force Base in Tampa, Florida

Background

RAINEX’ main purpose was to accomplish this task via studying the fluctuations of storm intensity as they are influenced by interactions between the eye, eyewalls, and rainbands of a tropical storm. Most hurricanes exhibit a definitive eyewall and spiral rainbands outside of the eye. These spiral rainbands were known to be complex structures that possess deep convective cores enmeshed in low altitude precipitative clouds.

Experimental Design

Equipment

The experiment entailed a high-resolution numerical model of the internal structure of the vortex and collection of data by three P3 Orion aircraft equipped with Doppler radar and intensive dropsonde coverage. These aircraft were based at the National Oceanic and Atmospheric Administration (NOAA) Aircraft Operations Center (AOC) at MacDill Air Force Base in Tampa, Florida. All flights were controlled from The Rosenstiel School of Marine and Atmospheric Science (RSMAS) at the University of Miami (UM). The aircraft were equipped with dual-beam Electra Doppler Radar and dropsondes. Postanalysis was to include high-resolution model simulations of the data collected in flight at the RSMAS atmosphere-wave-ocean modeling system.

Project Communications

As data was collected in the field, satellite communications relayed the information from aircraft to the RAINEX Operations Center at RSMAS. In order to determine which days were suitable for flight, principal investigators, forecasters, pilots, and facility engineering staff held a daily conference call originating from the RSMAS center in Miami. Based on the forecast of evolution of the tropical storm throughout the proposed time of flight, principal investigators would develop a plan of flight for the day. Flight patterns typically followed one of two plans accepting special cases. The plans are shown in the image. Plan A was usually selected when aircraft were to arrive during a time without eyewall replacement. Plan B was employed when eyewall replacement was expected to occur during flight. For instance, during flight into Hurricane Rita a second eyewall was forming and Plan B was executed.

Notable Hurricanes

Hurricane Katrina

Because RAINEX was planned in advance of the 2005 Atlantic Hurricane Season. Therefore, RAINEX did fly in to Hurricane Katrina among other storms. Hurricane Katrina followed a very similar track to a later storm in this season (Hurricane Rita); however, Katrina did not undergo eyewall replacement during its time in the Gulf of Mexico.

Hurricane Ophelia

Hurricane Ophelia was an interesting storm to document due to its long duration and considerable fluctuations in strength throughout its existence.

Hurricane Rita

Hurricane Rita was not a welcome site in the Gulf of Mexico following the devastating, Katrina. Hurricane Rita underwent eyewall replacement while in the Gulf of Mexico where the storm went from a category 5 on the Saffir-Simpson Hurricane Wind Scale to a category 3 storm by landfall.

Previous Experiments

Potential Vorticity

Potential vorticity is the primary physical principal behind hurricane the eyewall replacement cycle. One of the advancements that were able to be made by RAINEX data was the connection between potential voracity and the formation of second eyewalls in major hurricanes. One such additional study used high-resolution, full-physics-model forecast fields from Hurricanes Katrina and Rita. The comparison between the two hurricanes was important because Hurricane Rita developed a second eyewall Rainband and Hurricane Katrina did not. The relationship between vortex Rossby wave (VRW) and potential vorticity (PV) explains the difference.

References

1. Houze, R. a, Chen, S. S., Smull, B. F., Lee, W.-C., & Bell, M. M. (2007). "Hurricane intensity and eyewall replacement." Science (New York, N.Y.), 315(5816), 1235–1239.

2. Houze, R. A., Chen, S. S., Lee, W. C., Rogers, R. F., Moore, J. A., Strossmeister, G. J., … Brodzik, S. R. (2006). The hurricane rainbrand and intensity change experiment. Bulletin of the American Meteorological Society, 87(11), 1503–1521.

3. Judt, F., & Chen, S. S. (2010). Convectively Generated Potential Vorticity in Rainbands and Formation of the Secondary Eyewall in Hurricane Rita of 2005. Journal of the Atmospheric Sciences, 67(11), 3581–3599.