The last hurricane

CAMEX team wrapping up campaign with flights into Georges

Sept. 21, 1998: (this is the 18th in a series of stories covering the ongoing CAMEX mission to hunt hurricane data in a way not done since the 50s. Other stories are linked in below.)

Two NASA research aircraft - the DC-8 Airborne Laboratory and the ER-2 - took off about 10 a.m. EDT today to study a compact hurricane that is hammering the Windward Islands.

Hurricane Georges is smaller than Bonnie, the hurricane that NASA and its partners closely studied earlier this season, but is still quite deadly.

Right: Georges as seen shortly after midnight by the Advanced High Resolution Radiometer on board the NOAA-14 polar-orbit weather satellite. (Links to 874x980-pixel, 203KB GIF. Courtesy of the Ocean Remote Sensing Group at the Applied Physics Laboratory, The Johns Hopkins University, Laurel, Md.)

The ER-2 and DC-8 should arrive at Hurricane Georges in the St. Croix area at about 1 p.m. EDT. Plans call for the two aircraft to rendezvous with one of the NOAA WP-3D aircraft for a joint study of the eye wall where the winds are the strongest.

Georges will give the Convection and Moisture Experiment (CAMEX-3) a busy conclusion. From its first calibration flight on Aug. 13 through this Wednesday (Sept. 23), the CAMEX-3 team - which includes aircraft from the National Oceanic and Atmospheric Administration and coordination with the U.S. Air Force Hurricane Hunters - has studied Hurricanes Bonnie, Danielle, Earl and now, Georges.

Overnight, Hurricane Georges weakened to a Category 2 hurricane (152 km/h [95 mph] winds) after passing over the Windward Islands, in particular Antigua and Montserrat. The weakening may have been due to the inflow of drier middle to upper level air to the west, apparent in the 6 p.m. Sunday San Juan sounding and in the water vapor imagery.

Left: Georges as seen this morning in infrared light by the GOES-8 weather satellite. The intensity rises from blue at the edges of the storm to red at the center around the eye. Current images are available from the Global Hydrology Center's Interactive GOES viewer. (Links to 600x400-pixel, 21KB JPG.)

Another possible reason for the weakening appears in the satellite imagery: the center point of the cirrus shield is to the east of the circulation center. This suggests westerly shear. However the circulation was larger and cloud tops higher today than yesterday, and cloud top temperatures down to -85 °C (-121 °F).

The National Hurricane Center official track and the Florida State University ensemble track have Georges moving over Puerto Rico and along the northern shores of the Dominican Republic, at about 26 mph (16 mph). By evening, its eye is expected to be at 18.00°N, 65.20°W, right over St. Croix, U.S. Virgin Islands. The storm is expected to contract and intensify; maximum sustained winds should be 168 km/h (105 mph).

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Later afternoon Tuesday, Georges should be about 110 km (69 mi) east of the eastern border of Haiti (about 71.75°W), and its intensity should be about the same, i.e. Category 3. The official track keeps Georges just north of Hispaniola, although there is considerable uncertainty. The low-level storm inflow will be affected by the island's topography, therefore the details of Georges' approach to the island are important to the storm's further track and intensity.

Wednesday, the last official science day for CAMEX-3, Georges should move just north of Haiti, between eastern Cuba and the Bahamas (Great Exuma Island), still at Category 3.

Finally, one more tropical storm is brewing off Africa. Tropical Storm Ivan is expected to move to the northwest and probably will not become a hurricane. Hermine has weakened to a tropical depression and is moving inland across the Florida-Alabama-Mississippi Gulf Coast.

Note: More details are available in the NASA press release describing CAMEX-3. Check back as hurricane season progresses. We will post science updates as the campaign develops. PIX: High resolution scans of 35mm camera photos from the CAMEX-3 campaign are available from Public Affairs Office at NASA headquarters. Please call the NASA Headquarters Photo Department at 202-358-1900, or contact Bill Ingalls at bingalls@hq.nasa.gov. CAMEX Series Headlines August 12: Overview CAMEX story , describes the program in detail. August 13: CAMEX maiden flight , for calibration of TRMM satellite instruments August 14: CAMEX test flights , CAMEX flies over tropical storm weather in successful calibration run August 18: CAMEX aircraft make second flight with TRMM , second calibration run for TRMM August 20: CAMEX may get first chance at a tropical storm , later this week  August 21: Here comes Bonnie! , CAMEX scheduled to fly over T.S. Bonnie  August 22: West by Northwest , CAMEX team may have to evacuate to Georgia  August 24: Eye-to-eye, and Bonnie winks, CAMEX team makes first flight through eye  August 25: Snow in August, Bonnie surprises the hurricane team  August 26: Camera of many colors Hurricane hunters using advanced scanner to peer into storms   August 28: Preparing for Danielle NASA team takes break as Bonnie fades away August 31: Quite a Windfall Hurricane team completes first half of unique science campaign. Includes listing of August flights and aircraft and spacecraft used in CAMEX-3. September 2: Bonnie Cuts a Towering Figure Satellite radar shows mountainous cloud chimney September 4: Hurricane team studies Earl Four aircraft probe storm September 10: NASA team awaits next hurricane September 16: Hurricane season passing its prime Thunderstorm studies continue as a new hurricane candidate wends its way from Africa. September 18: Two new storms brewing for hurricane research team Scientists fly 4 out of 5 days, clear air sampled over the Bahamas, oceanic convection data collected east of Cape Canaveral September 21: The last hurricane - CAMEX team wrapping up campaign with flights into Georges (this story) September 21:The last hurricane - CAMEX team wrapping up campaign with flights into Georges September 23: Hurricane Georges puts on a light show - CAMEX team treated to purple sprites and weird lightning NCAR has an extensive writeup on the GPS dropsondes used in CAMEX-3 and other atmospheric campaigns. A new study - not related to CAMEX-3 - by the Arizona State University suggests a link between hurricanes in the northwest Atlantic and air pollution.

CAMEX-3 - the third Convection and Moisture Experiment - is an interagency project to measure hurricane dynamics at high altitude, a method never employed before over Atlantic storms. From this, scientists hope to understand better how hurricanes are powered and to improve the tools they use to predict hurricane intensity.

An overview story (Aug. 12, 1998) describes the program in detail. The study is part of NASA's Earth Science enterprise to better understand the total Earth system and the effects of natural and human-induced changes on the global environment. A midterm story (Aug. 31, 1998) reviews the first month of operations and the windfall of data.

Measuring distance and speed

Because meteorology and aeronautics first used modified nautical charts, their data bases are in nautical miles and knots (nautical miles per hour). In these stories, we use Standard International ("metric") units first, and give more familiar measurements in English units and the original measurements in nautical units. Because of rounding and because the wind speeds originally are expressed in knots, km/h speeds to knots may be slightly different from the numbers in the story.

Standard International Units: 

km - kilometer (1 km = 0.62 smi = 0.54 nmi) 

km/h - kilometers per hour 

English (or US) units: 

mi, or smi - miles (statute miles; 1 smi = 0.87 nmi = 1.61 km)
mph - (statute) miles per hour 

Nautical units: 

nmi - nautical miles (1 nmi = 1.15 smi= 1.85 km) 

kts - knots (nautical miles per hour) 

 

Web Links

CAMEX-3 home page contains links to daily flight operations and instrument descriptions. Lightning Imaging Sensor aboard the TRMM satellite observes lightning from above the clouds - and my lead to better warnings on the ground. MACAWS uses the Doppler effect (red and blue shifts) to measure wind velocity. SPARCLE is a Space Shuttle experiment set for 2001 to demonstrate laser wind measurement from space.