Snow in August
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Weather researchers taking part in NASA's CAMEX-3 hurricane study found Monday that Hurricane Bonnie is still not a classic storm, and is full of surprises - including snow in the middle of August.
An armada of five aircraft took part in the second flight into Bonnie as the hurricane continued northwest at less than 16 km/h (10 mph). Joining the NASA ER-2 high-altitude jet and the converted NASA DC-8 airliner, NOAA increased its study team to two WP-3D Orion turboprop airplanes and the U.S. Air Force added a C-130 Hercules cargo plane to measure the season's first hurricane. The NASA airplanes left their staging point at Patrick Air Force Base, Fla., for the eight-hour mission at 3:30 p.m. EDT, returning at 11:30 p.m. EDT.
| What looks like abstract art at right is a detailed microwave image of water - as rain and as ice - distributed along a strip 40 by 160 km (25 x 100 mi) inside Hurricane Bonnie (click for image showing
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). It was made Sunday by the Advanced Microwave Precipitation Radiometer (AMPR) aboard the high-altitude ER-2. Every object emits a little bit of radiation; the frequency depends on the temperature and other factors. AMPR is tuned to microwaves - at 10.7, 19.35, 37.1, and 85.5 gigahertz (GHz) - unique to water. By scanning the scene below the ER-2, AMPR produces images of water distribution in the atmosphere. AMPR is similar to instruments aboard polar-orbit weather satellites and the Tropical Rainfall Measuring Mission (TRMM). In observing Bonnie, AMPR shows convection and storm intensity, eye wall structures, rain distribution. During landfall, it will be able to map changes in convection and show the relationship of electrification to signal storm intensity changes. More information on AMPR is available on its page at the CAMEX-3 web site and at the AMPR home page. |
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 Click on the picture to go to an animated infrared view of Bonnie! |
Mission Scientist Robbie Hood from NASA's Marshall Space Flight Center in Huntsville, Ala., stressed that the nation's weather researchers will greatly benefit from the large body of information being collected at one time at distinct levels of a single hurricane. The ER-2 aircraft flew up to an altitude of 21 km (69,000 ft), the DC-8 at 10.6 km (35,000 ft), with the NOAA Orions at 4.6 and 1.5 km (15,000 and 5,000 ft), and the Air Force Hercules in the storm at 3 km (10,000 ft). |
"We could all communicate and know what parts of the storm we were studying, our timing was perfect," she said. The collection of aircraft made six passes through the hurricane. "The NOAA and Air Force aircraft really helped the study because we had a better idea of what was happening below us," she added.
Left: A GOES-8 image this morning depicts Bonnie's strength by showing cold areas (growing colder from blue to yellow to red) which indicate where clouds are highest in the atmosphere.
"I saw a large, domed cloud that looked like a mini-hurricane swirling out of the top of Bonnie about 70 miles (112 km) north of the eye at about 55,000 feet (16.8 km)," Broda said.
"These storms are usually very symmetrical, but Bonnie is nothing like what we would expect," said Texas A&M University weather scientist Ed Zipser. While hurricanes normally display a pattern of wind flow that pulls winds in at the base of the hurricane, up through the eye, and out at the top of the storm, Bonnie apparently doesn't work that way.
"We found winds coming into the hurricane from the southwest at 40-50 knots (74-93 km/h) at our altitude, and winds and moisture being pumped out of the chimney that Ken saw flowing to the Northwest. As we flew to the boundary of the winds, the moisture blown out through the chimney turned to snow and fell into the DC-8 flight path - this was very spectacular," Zipser said. Instruments also recorded wind shear along the wind flow boundary.
The researchers will not fly today, and are considering a mid-day flight Wednesday in concert with NOAA as the hurricane approaches a possible landfall.
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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. 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.
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.
- km - kilometer (1 km = 0.62 smi = 0.54 nmi)
- km/h - kilometers per hour
- mi, or smi - miles (statute miles; 1 smi = 0.87 nmi = 1.61 km)
mph - (statute) miles per hour
- nmi - nautical miles (1 nmi = 1.15 smi= 1.85 km)
- kts - knots (nautical miles per hour)
- Standard International Units:
- English (or US) units:
- Nautical units:
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