Use of Global Sounding Balloons to Augment Tropical Cyclone Over-Ocean, Near -Environment Observations from the Surface Boundary Layer to the Tropical Tropopause

Global Sounding Balloons (GSBs) observe temperature, humidity, pressure, wind speed and wind direction. They are remotely controlled to profile the atmosphere from the near-surface boundary layer to the tropopause and stratosphere near 20 km, at approximate 3-hour intervals for 5-6 days. This paper describes two sample cases illustrating the manner in which the GSB balloons complemented the aircraft dropsonde sampling for developing tropical depression systems over the eastern and central Atlantic in the vicinity of the TC Main Development Regions (MDR).

GSBs were first deployed during a portion of the 2022 Atlantic Hurricane season and most of the 2023 hurricane season from Cabo Verde, Puerto Rico and Gainesville, FL for use within and around tropical disturbances and Tropical Cyclones. Windborne GSBs were used to augment aircraft Inner Core dropsondes for improved Tropical Cyclone 3-D environmental mapping and intensity prediction. An initial series of four balloons (W-344, W-345, W-346 and W-347) were launched from Sal Island, Cabo Verde (CV) during the passage of a tropical disturbance on 09-10 Aug, 2022. Joint dropsonde measurements from two NOAA GIV aircraft flights deploying ~18 dropsondes on the first flight and 30 sondes on the second flight, together with four Windborne balloons were then made over two days.

Subsequently, a tropical disturbance, which became pre-Earl, was sampled by 4 balloons (W-424, W-425, W-426 and W-427) deployed from Puerto Rico over 5 days beginning 27 Aug, executing 62 soundings in the NW quadrant of the depression at a radius interval of 500-900 nm, documenting the large area of dry air ahead of the depression. These observations complemented NOAA N42RF WP-3D flights on 30-31 Aug and 01-02 Sep which deployed ~20 dropsondes per flight over the inner core of the 4 flights within 150 nm of the circulation center, for a total of ~80 dropsondes. Two additional GSB balloon flights, W-430 and W-436, on 2-5 Sept, illustrated the monitoring of the large outflow region associated with the development of pre-Earl north of Puerto Rico.