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Hurricane Research 

IFEX daily log

Friday, September 16, 2005

There are areas of note in the Atlantic basin. The first is Tropical Storm Ophelia, seen in a water vapor image (Fig. 142) off the North Carolina coast. The second system is 95L Invest, which is a mass of clouds oriented southwest-northeast approaching 55 W, while the third system is an area of deep convection located north or Puerto Rico associated with an upper-level cyclonic circulation.

The cloud signature in Ophelia is indicative of a system undergoing extratropical transition. N42RF is currently flying this system for the extratropical transition experiment. It had a takeoff time of 14 UTC from Macdill Air Force Base, and it was expected to be in the system by about 17 UTC. The plan called for N42RF to fly a figure-4 pattern at 10,000 ft through the center of the storm (Fig. 143) and then sample the environment at about 18,000 ft altitude. The plane would then recover in Portsmouth, NH. At the same time, the Aerosonde took off from Wallops Island to sample Ophelia in the low-levels. Its plan was to fly in the periphery of the system, sampling the wind speed, direction, temperature, and moisture, and then penetrate the core of the storm. The majority of the pattern would be flown at 2500 ft, though some of the time it would operate at 1500 ft.

Figure 142. GOES-East water vapor image valid 1215 UTC September 16.

Figure 143. Proposed flight track for N42RF on September 16, 2005. Green line denotes flight track, green dots denote locations of GPS dropsondes, and red dots denote locations of rawinsonde observations.

As can be seen from a plot of flight-level winds from each aircraft (Fig. 144), both aircraft were in the storm at the same time. N42RF was providing Doppler radar and dropsonde coverage from 10,000 ft to the surface, while the Aerosonde was providing flight-level measurements of wind, temperature, and moisture at 1500-2500 ft. This is the first time ever that an unmanned aircraft has flown into a tropical cyclone, and it is the first time that is has flown in a tropical cyclone at the same time a research aircraft was also flying it. This demonstrates the possibility of having coordinated low- level and mid-level research flights in tropical cyclones in the future.

Figure 144. Flight-level winds (barbs, kt) from N42RF (red) and Aerosonde (blue) in Tropical Storm Ophelia on September 16.

System 95L Invest continues to show significant areas of deep convection (Figs. 145, 146. The primary area of activity is in the southwest region of the line of convection. There is some indication of rotation in the visible image in Fig. 145, though it is not clear is this rotation is in the low levels or the mid levels. This rotation is collocated with relatively cold cloud tops indicative of deep convection, and it is further confirmed by satellite microwave and radar measurements (Fig. 147). The shear is also light over the system (Fig. 148), i.e., less than 10 kt. Some of the GFS ensemble members are also developing a system east of the Leeward Islands in the next few days (Fig. 149). For these reasons, it appears that there is a good chance that this system will become a tropical depression soon.

Figure 145. GOES-East visible image valid 1115 UTC September 16.

Figure 146. GOES-East infrared image valid 1115 UTC September 16.

Figure 147. TRMM TMI/PR overpass valid 0720 UTC September 16.

Figure 148. CIMSS-derived 850-200 hPa vertical shear (shaded, kt) valid 09 UTC September 16.

Figure 149. Plot of detection of vortices in GFS ensemble members for model runs initialized at 00 UTC 16 September 2005.

The final system of interest is located at around 21 N 63 W (Fig. 150). There is a region of fairly concentrated convection located just east of an upper-level cyclonic circulation. The proximity to the upper-level circulation makes development of the system unlikely in the next few days. If the upper-level circulation moves away from the area of convection, there is some chance that this could develop.

Figure 150. GOES-East infrared image valid 1215 UTC September 16.

Rob Rogers
HRD Field Program director

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