September 7, 2013
Global Hawk Dropsondes Help With Tropical Storm Gabrielle Forecasting
[ Watch the Video: NASA’s Global Hawk Aircraft and the Dropsonde System ]
April Flowers for redOrbit.com - Your Universe OnlineOne of NASA’s Global Hawk unmanned aircraft recently dispersed dropsondes, which are expendable weather reconnaissance devices designed to accurately measure tropical storm conditions as the device falls from an aircraft to the ground. Data from those dropsondes assisted forecasters at the National Hurricane Center (NHC) when analyzing the environment of newly formed Tropical Storm Gabrielle at 11 p.m. EDT on Sept. 4.
NASA has two Global Hawks, one of which flew over Tropical Depression Seven on September 4. Tropical Depression Seven organized into Tropical Storm Gabrielle.
"During this flight, the National Hurricane Center upgraded the tropical system to Tropical Storm Gabrielle and acknowledged the data that they are getting real time from our aircraft on their website," said Chris Naftel, Global Hawk Project Manager at NASA Dryden Flight Research Center. A record 80 dropsondes were dropped by the Global Hawk during the mission.
NHC’s second discussion of Tropical Storm Gabrielle at 11pm, September 4, noted that a small area of very deep convection was present near and northeast of the surface center of the depression while the convective bands had largely dissipated over the past few hours. That is when the NHC researchers classified Tropical Depression Seven as Tropical Storm Gabrielle.
The second discussion noted: Data gathered from the NASA Global Hawk suggests that the circulation of Gabrielle is tilted to the northeast with height. This was combined with a mid-level circulation seen in data from the San Juan wsr-88d Radar. The University of Wisconsin Cooperative Institute for Meteorological Satellite Studies and other analyses showed the tilted structure being consistent with southerly to southwesterly vertical shear of 5 to 10 knots.
The dropsonde data also showed dry air in the mid-levels of the atmosphere around Gabrielle. The scientists do not expect much strengthening of the storm in the short term given the environment and the somewhat disorganized state of the circulation within the storm, possible land interaction and the presence of the large area of disturbed weather northeast of Gabrielle.
NASA is planning two further Global Hawk flights over Tropical Storm Gabrielle this weekend on September 7 and 8. NASA 872 is expected to fly over the storm on September 7, and 871 will investigate on September 8.