Saturday, July 9, 2005

The N42RF tasked mission took off from San Jose at 05 UTC the previous night. Dennis had emerged from the coast of Cuba and had weakened substantially to a Category 1. Infrared satellite imagery indicated that deep convection had disappeared, although a tight core was still evident from the curvature in the clouds. Upon reaching the storm, we found that Dennis was quite weak. The pattern called for a standard figure- 4 pattern, oriented SW-NE-NW-SE. The wind field was highly asymmetric, with the shortest radii on the SW side and the largest on the NE side. The eye was open on the SW side. SFMR gale-force winds extended 25 nm on the SW side and more than 105 nm on the NE side, while hurricane-force winds were not observed the SW side and 12 nm on the NE side. Minimum central pressure was 970 mb. On the next inbound leg, the gale-force (hurricane-force) wind radii was 116 (32) nm on the NW side, and unknown (18) nm on the SE side. Radar and satellite imagery indicated that the storm was beginning to get better organized. Deep convection had redeveloped on the SE and E side, and the eye appeared to be closing off again. Maximum surface winds were 85 kts on the SE side. The storm had deepened by 3 mb, to 967 mb, while we were in it. At the completion of that leg we headed for Jacksonville.

N43RF had a research mission they were going to conduct, takeoff at 14 UTC from San Jose. Originally N43RF was going to fly a coordinated mission with the ER-2, but the ER-2 crew did not want to have to land during the afternoon hours, so they pushed their takeoff up to 11 UTC.

During the nighttime hours it became evident that Dennis was deepening rapidly, and it regained major hurricane status by 11 PM . The plan for the following day called for a landfall research mission into Dennis to be flown by N43RF. Originally N42RF was going to return to San Jose, but it was decided that, since it appeared that Dennis could be making landfall as a Category 4 hurricane, this would be an ideal opportunity to fly N42RF on a post-landfall decay module for John Kaplan and Peter Dodge. N43RF would takeoff at 14 UTC while N42RF would takeoff at 21 UTC. The takeoff of each plane was timed so that the aircraft would be in the storm before landfall (in the case of N43RF) and just at or after landfall (for N42RF).

With the missions planned for the following day, the flights into Dennis will have covered portions of the entire lifecycle, with flights beginning when Dennis had just become a depression, all the way through to development to a Category 4 storm, then weakening over land, the reintensification to a Category 4, then to landfall and nearly 6 h after landfall. The temporal frequency of the observations for the entire lifecycle was around 24 h.

Rob Rogers
HRD Field Program director