Mission Plan :

A mission into Tropical Storm Kyle. Though the central pressure had increased 15 hPa since the previous day, NHC continued to forecast Kyle to intensity into a hurricane. The plan is for a figure-4 pattern and then Ocean Winds.

Mission Summary :

Because of the disorganized state of Kyle, the initial approach toward the IP was well south of where it should have been. Thus, the flight track (see Fig. 1 above) showed a large jog to the north to get near the flight-level center. During the first passage through the center, it because evident that Kyle was very tilted, likely due to shear, with the surface wind speed minimum, the flight-level wind speed minimum, and the extrapolated surface pressure minimum all displaced from each other by more than 25 nmi (Fig. 2). In addition, the strong asymmetry with the sharpest gradients on the east side was clearly evident. The tilt with height can clearly be seen in the realtime radar analyses sent from the plane (Fig. 3).

Just to the east of the center, a curious feature was observed (Fig. 4). Flight-level wind speeds rose quickly once the aircraft entered the region of convection displaced east of the center, and lightning because visible. Just after midnight UTC, the surface wind speed rose suddenly to near 70 kt, and a 6 hPa dip in the extrapolated surface pressure occurred nearby. The flight-level wind speed also rose to near 62 kt in this region. The data suggest that the aircraft encountered a mesovortex, but without any associated vertical velocity maximum.

Two more passes through the center were completed. The vortex tile decreased in time, and the direction changed from a northeastward tilt from the surface to more of a northward tilt as time progressed (Fig. 5 and Fig. 6).

Problems :

The mission began late because a number of AOC crewmember were at the 120-h 30-day limit for flying and needed to get waivers to fly the mission. AOC did not realize this beforehand since this was only the second time the limit was reached during hurricane operations.

Sim Aberson
Nov. 19, 2008

Mission Data :