Location and Date:

Coast Guard Air Station Borinquen, Puerto Rico in August/September 2005.


The Field Research Division, along with scientists from the University of Hawaii and the University of New Hampshire, participated in the RAINEX experiment that was conducted at the Coast Guard Air Station Borinquen near the town of Aguadilla in northwestern Puerto Rico. FRD smart balloons were deployed in an effort to better characterize the evolution of the energy content of the marine boundary-layer inflow to hurricanes and its relationship to hurricane boundary layer structure and hurricane intensity changes. The study was funded by AIRMAP and the Targeted Wind Sensing Program.


Both smart balloons in hanger waiting to be released.


The objectives of RAINEX are to use airborne observations to examine simultaneously the dynamic and thermodynamic structures of hurricane inner core and outer rainband regions where the positive potential vorticity associated with deep convective cores are located. Numerical models will be used to investigate the interactions of the rainbands and primary hurricane vortex circulation and their role in hurricane intensity change. RAINEX is the first experiment using three- Doppler-aircraft flying in hurricanes. Airborne Doppler radar will be used to observe both eyewall and rainband internal vorticity structures simultaneously. Dropsondes and smart balloon data will be used for thermodynamic environment of hurricane rainbands and eyewall to support both analysis and modeling/forecasting. Use model to determine how the vorticity features evolve and storm intensity changes.


Two NOAA smart balloons were launched from Puerto Rico in an effort to place the balloons into a hurricane during the RAINEX experiment. Balloon 1 was launched at about 0120 hours (GMT) on September 8th, 2005. It tracked to the northwest in the direction of Hurricane Ophelia. After tracking the balloon for nearly a day and half, the solar panel stopped working. This failure was diagnosed by monitoring the solar radiation reading from the solar pyranometer, while the solar panel charging current remained at zero as the battery voltage decreased over time. The balloon data were monitored for a few hours and when it was determined beyond doubt that the batteries were not going to charge, the balloon flight was terminated. We may have been able to track the balloon for several hours longer, however we decided to terminate the flight while battery power was good and so we could ensure the balloon did drop into the ocean. The balloon position and altitude were tracked until it went into the water.

Balloon 2 was launched approximately 4 hours after the termination of balloon 1 at about 1838 hours (GMT) on September 9th, 2005. The balloon started heading mostly to the west, over the Dominican Republic then over Cuba (which was not in the direction that we wanted). After going across Cuba the balloon headed directly toward the Yucatan Peninsula. After flying for a little over three days the elevation of the balloon was changed from 2600 meters to around 700 meters. Balloon 2 then flew for a few more hours, with everything working just fine, when communications to the balloon failed and was never established again.

Map of the 2 smart balloons during RAINEX. Red dots path of balloon 1, blue dots path of balloon 2.


The hurricane balloon effort during August and September 2005 provided important logistical and practical experience for the smart balloon team. The significance of the smart balloons to RAINEX is that they provided critical data in the boundary layer, where relatively little in situ data are available from other sources.


RAINEX homepage:



Roger Carter
1750 Foote Dr.
Idaho Falls, ID 83402
email: Roger.Carter@noaa.gov

Modified: March 1, 2011
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