Mission Plan :

The mission is to conduct a TDR experiment into Tropical Storm Earl, with a secondary goal of collecting DWL observations. The system is located off the coast of Belize and moving west at about 8 knots (Figure 1). It is located between a gradient of westerly shear with 5 knots to its west ranging to ~20 knots on the eastern side (Figure 2). Satellite presentation shows increased convection in all quadrants indicating a possible strengthening of the storm.

Track guidance agree that Earl will continue to travel west until making landfall in Belize. The majority of models suggest that Earl will maintain its strong tropical storm strength, however a few forecast bring it up to a Category 1 hurricane (Figure 3).

Figure 3. TS Earl forecast intensity

Figure 4a. Proposed track Figure 4b. Actual track

Given the long transit time and proximity to land, the plan calls for a TDR pattern with an initial point (IP) in the north quadrant. A butterfly pattern will be flown and completed in the northeast quadrant (Figure 4a). Upon completion of the mission, the plane will return to MacDill AFB.

Mission Summary :

A butterfly pattern was flown, however the IP was shifted to the NW quadrant (Figure 4b). Upon completing the first cross section, the downwind leg arched between the eyewall and a newly forming rainband up to the NE quadrant (shown in a lower fuselage radar image in Figure 5). This was a relatively cloud free, precipitation free area making it ideal for the DWL and close enough to the areas of precipitation to collect TDR observations. The EP was to the north of the storm. This flight was responsible for upgrading Earl to a category 1 hurricane. The strongest surface and flight level winds were located in the NNW. Radar composites show increased convection, especially in the eastern portion of the storm, with a more vertically aligned vortex (Figure 5).

The mission was completed at 0107Z with a recovery at MacDill airport. A total of 14 GPS sondes were dropped.

Figure 5. TS Earl on LF radar

Mission Evaluation:

The GPS/INS initialized properly on the DWL during this mission. DWL observations were captured en route to Earl and within Earl. Within the storm, the DWL collected wind profiles both above and below the plane (2 conical scans downward, 1 upward). A calibration flight over the everglades was not performed due to storms in the targeted area.

It was hypothesized that the DWL caused the plane oscillations in the pervious afternoon flight and tests were conducted. The plane was flown at a similar speed and altitude and the DWL was positioned similarly to the day before. While the oscillations as they occurred did not repeat themselves, smaller brief oscillation did occur. It was recommended that the DWL not be place in a forward facing position during takeoff and ascent.

Three radar analyses were completed and transmitted. One sonde stopped transmitting at 946 mb and one drop had an early launch.

Problems :

No problems were encountered on this flight.

Lisa Bucci
October 18, 2016