Hurricane Gabrielle (13-16 September 2001)

A very good set of missions! Good coordination with the groundbased radars and the research aircraft. Storm structure was very interesting as it got organized on the 13th, made landfall on the W coast of FL on the 14th, and became entangled with a mid-latitude trough. At landfall the storm intensified rapidly and the mobile groundbased radars were able to document a mesocyclone signature near the center of circulation and 35 m s-1 w inds at 1-2 km altitude.

On the 15th the storm moved off the east coast of Florida and was reorganizing despite ingestion of dry air into the circulation. The storm stucture had little deep convection, with the only d eep convective features NE of the center about 120 nm from the center where the cloud tops were near 15 km and the reflectivity was near 50 dBZ. The surface circulation was well S and E of the flight-level center (20-25 nm). The region S and E of the cent er was very dry with only small convective clouds. However, the sea state S and E of the center indicated a region of strong surface winds 18-25 m s-1 surrounding a broad center 50 nm across. It appeared the storm was moving right over the Gulf Stream axis. AXBTs revealed that the SST was running between 28.5-29.0 C over a large domain that the storm was over. By the time we left the storm the convection was getting more vigorous and it appeared the storm was much better organized than when we arrived, certainly deserving tropical storm status. This flight represents the best documentation of a reintensifying tropical storm.

On the 16th the storm was better organized as it raced to the NE passing between Cape Hatteras and Bermuda. The storm structure was much better organized that the previous data, with intense c onvection still to the NE of the center, but closer to the center. The major rainband was also closer to the storm center, but there was still significant tilt to the vortex with a 20 nm displacement from the surface center to the flight level center at 1 4 kft. During the flight a new center seemed to be forming closer to the convection and our last center drop actually recorded hurricane force winds near the surface. Coordinated legs were flown with N42RF and the ER-2 through the deep convection NE of th e center, followed by some spirals dropping GPS sondes along the inside and outside of the major rainband.

The analysis of these flight will prove very useful in diagnosing how a storm gets better organized out over open water with relatively high SSTs. The phenomenal GSP sonde coverage over such a large area from N42RF, DC-8, and G-IV, combined with the A XBT coverage will provide a great data set for air-sea interaction and trough interaction studies of a slowly intensifying storm.

Storm/ Date	Aircraft (Duration)	Altitude	Experiment/ Pattern	Comments (expendables)
Gabrielle
13 September	N49RF GPS dropsondes	45 kft	Synoptic Surveillance	Gabrielle becomes a tropical storm during mission. N49RF recovers in Savannah, GA.
14 September	WC-130 N49RF (9 h) GPS dropsondes	5000 ft 45 kft	Windfields at Landfall experiment along west coast of Florida Synoptic Surveillance	Tropical Storm Gabrielle reaches near hurricane strngth at landfall. SMART-R and MIPS set up at Venice, FL airport during landfall. XPOL failed to collect any data because of water leaks. Researchaircraft flights cancelled because of close proximity of storm to MacDill AFB and Jacksonville NAS. N49RF recovers in Ft. Lauderdale.
15 September	N42RF (8.9 h) mission summary(572 Kb) one minute listing GPS dropsondes DC-8 (9 h) mission summary GPS dropsondes WC-130 N49RF (9 h) mission summary(476 Kb) GPS dropsondes	14 kft 37-39 kft 1500 ft 45 kft	2-plane XCDX/QPE Experiment. N42RF, DC-8 within 250 nm radius of center. Synoptic Surveillance	Tropical Storm Gabrielle . (18 AXBT, 48 GPS sondes) N49RF recovers at MacDill AFB. ER-2 can not participate because of strong cross winds at Jacksonville NAS.
16 September	N42RF (8.9 h) mission summary(72 Kb) one minute listing GPS dropsondes ER-2 (7 h) WC-130	14 kft 65 kft 1500 ft	2-plane XCDX/QPE Experiment. N42RF, ER-2 within 100 nm radius of center.	Gabrielle became hurricane during mission. (18 AXBT, 35 GPS sondes) DC-8 cancels flight with engine problem.