West by Northwest

Bonnie now a hurricane, stays on track

Aug. 22, 1998: (This is the seventh 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.)

Tropical storm Bonnie graduated to Hurricane Bonnie overnight, and stayed on a track that could make the CAMEX-3 team evacuate Patrick Air Force Base, Fla., for Warner Robbins Air Force Base south of Macon, Ga.

Right: A GOES-8 image of Bonnie as it churns the Atlantic Ocean north of the Windward Islands. Current images are available through the interactive viewer at the Global Hydrology and Climate Center. (links to 532x443-pixel, 252KB JPG showing more of the U.S.)

"It is ironic that what we came to Florida to study, might just drive us to our alternate staging base," said Robbie Hood, mission scientist from the Global Hydrology and Climate Center at NASA's Marshall Space Flight Center in Huntsville, Ala.

Despite the impending move, the CAMEX-3 team has started its science campaign.

Getting ready

The team stayed on the ground Wednesday to have more time to prepare for flight operations. On Thursday, the NASA DC-8 and the University of North Dakota Citation took off at noon EDT from Patrick 5-hour flight to study a wide band of maritime rain off Cape Canaveral. Both aircraft performed spiraling maneuvers down through the rain to study the sizes of cloud ice crystals and raindrops. The aircraft also flew under the Tropical Rainfall Measuring Mission (TRMM) satellite at 2:42 EDT.

On Friday, DC-8 flew a long synoptic flow mission ahead of what was still Tropical Storm Bonnie. The ER-2 could not take off due to high winds at Patrick AFB.

The DC-8 flew part of the mission with the NOAA Gulfstream IV. The Lidar Atmospheric Sensing Experiment (LASE) from NASA's Langley Research Center had a very successful mission. Ed Browell, who was the DC-8 mission scientist for this flight, was very impressed with the variety of aerosols and water vapor conditions encountered during the flight.

Left: NASA/Langley's Lidar Atmospheric Sensing Experiment (LASE) sits on a special pallet inside the DC-8 research aircraft. The black cylinder houses the optics that aim the laser into the air and receives the return signal. (links to 468x441-pixel, 93KB JPG.) Photo by Bill Ingalls, NASA

The total time for the DC-8 mission should have been 8 hours. but the actual time was over 9 hours. The mission was lengthened because of unfavorable wind conditions at the landing time. The DC-8 was forced to circle Patrick AFB until the landing conditions improved.

The current plan for today is for the NASA and NOAA WP-3 Orion aircraft to have a "no fly" day. The NASA DC-8 and ER-2 may be asked to leave Patrick if the hurricane forecasts predict unfavorable 92 km/h (58 mph, or 50 kt; see the note below on measurements) winds of Bonnie to reach Patrick within 48 hours. If the aircraft are asked to leave, then a mission over Bonnie will be attempted before recovering the aircraft at Warner Robbins AFB. The first meeting to discuss this possibility was scheduled for 9 am EDT at Patrick.

Collecting science data

To date, CAMEX-2 has concentrated on measuring tropical thunderstorms.

"We have achieved three multi-plane under-passes of the TRMM satellite, and have collected significant information," said Ed Zipser, lead scientist for the thunderstorm investigation portion of CAMEX.

Right: Dr. Ed Zipser (left), Tropical Rainfall Measuring Mission, Field Campaign Lead, Texas A&M University, College Station, TX. (Links to 540x323-pixel, 62KB JPG) Photo by Bill Ingalls, NASA

CAMEX forecaster J. Halverson, in the daily CAMEX forecast, wrote that hurricane reconnaissance aircraft report Bonnie has a closed eyewall, and flight level winds of 140 km/h (87 mph, 76 kts) and minimum pressure of 987 mb (lower pressures mean stronger storms). Its direction is west-northwest (300 deg) at 28 km/h (17 mph, 15 kts), and reflects a slow turning toward the northwest. The latest large-scale models suggest a weakening of the ridge and steering flow, and approach of a shortwave trough. This argues for more of a turn toward the northwest and deceleration of the storm.

The NOAA Geophysical Fluid Dynamics Laboratory's (GFDL) forecast track continues to the left of the ensemble, but its 72-hour period has ended up to the left of the actual track. The official NOAA track forecast is now to the right of the GFDL. Further strengthening is likely with excellent upper level outflow and an eye is now becoming visible. Bonnie is forecast to become a major hurricane, with winds 184 km/h (115 mph, 100 kts) or greater by Sunday night and has the potential to become a Saffir-Simpson Category 3 storm.

A new wave 1300 km (805 smi, 700 nmi) east of the Windward Islands is organizing, moving west at 28 km/h (17 mph, 15 kt), and may be upgraded to Tropical Depression #4 today (TD-03 became Tropical Storm Charlie which now is moving across Texas).

Expecting Bonnie

In Florida, the Cape morning sounding shows deep moisture and easterly flow. Morning, scattered convection has prevailed along the east coast. East winds of 28 km/h (17 mph, 15 kts) will prevail at Patrick today. With the approach of Bonnie, subsidence in advance of the vortex center will begin to induce drying through the middle and upper troposphere. This will begin to suppress convection across the eastern half of the peninsula late today and into tonight. Winds will also begin to shift around to northeasterly at about 18 km/h (12 mph, 10 kts) late tonight.

Over the next 48 hours, look for gradually more suppressed conditions as subsidence dries out the atmosphere ahead of Bonnie's northeastern quadrant, and an increase in northeasterly winds to 28-37 km/h (17-23 mph, 15-20 kts). By the end of this forecast period Bonnie will be located about 110 km (69 smi, 60 nm)s east of the Bahamas and will likely attain strong hurricane status. Sea swell will also begin to build along the Atlantic coast with associated dangerous rip currents.

Left: A composite of two National Hurricane Center maps depicts the locations of Bonnie and Charlie on Saturday morning. (Links to 937x549-pixel 204KB JPG).

During the next 48 to 72 hours (through Tuesday), look for suppressed conditions (i.e. lack of convection across the Florida peninsula) to prevail with clear, hot skies and stiff northerly winds. The official (11 a.m.) NHC forecast places Bonnie due east of Cape Canaveral (76.5 W, 29.5 N) by 8 a.m. EDT (12 UTC) Tuesday, and with winds at 184 km/h (115 mph, or 100 kt.).

Over the next 3 to 5 days, as Bonnie passes to the north and east of Central Florida, winds will gradually shift through westerly and then southwesterly and weaken. Deep layer moisture should return as subsidence relaxes, and we will see a return to sea-breeze induced convection. But what could go wrong? Bonnie could slow or stall offshore to our north. Tropical Depression 4 (which would become Danielle) could develop and threaten the southeast again.

Welcome to hurricane season in Florida!

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 (this story) 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 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 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.

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.

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.

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