Preparing for Danielle

NASA team rests after "quite incredible" work with Bonnie

Aug. 28, 1998: (this is the eleventh 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.)

NASA researchers are taking Thursday and Friday off to rest themselves, recalibrate their instruments, and then plan their research over hurricane Danielle which is gaining power to the east of Florida.

To date the Convection and Moisture Experiment (CAMEX-3) team has made four sets of flights around, through, and over Hurricane Bonnie as part of a major effort to understand how hurricanes intensify and, eventually, to be able to predict what their strength will be.

"This is certainly the most complete data set that we've ever had of a hurricane, any one day would have been the most complete," said Dr. Ed Zipser of Texas A&M University, lead scientist for the Tropical Rainfall Measuring Mission (TRMM) field validation experiment and a major participant in the CAMEX-3 campaign. "But we had three days ... this is quite incredible. And then it was topped off by the TRMM overflights" on Wednesday.

At right: A colorized GOES-8 image shows Bonnie as it staggers northeast into the Atlantic Ocean. (Links to 600x508-pixel, 55KB JPG.)

"We studied the atmosphere in front of this very large hurricane, spent two days flying through Bonnie's eye wall out at sea, and then catch her in a landfall situation," said Robbie Hood, the mission scientist from NASA's Marshall Space Flight Center in Huntsville, Ala. "It was our sheer luck to be able to catch the storm in many different phases. This is a powerful data set that will help NOAA [National Oceanic and Atmospheric Administration] in its predictions of intensity and direction to help save lives and money."

CAMEX operates out of Patrick Air Force Base, Fla., and uses NASA's DC-8 and ER-2 research aircraft in conjunction with NOAA's WP-3D Orion hurricane hunters. In addition, the study uses data from weather satellites and has timed its flights to coincide with observations by the Tropical Rainfall Measuring Mission (TRMM) satellite. Wednesday's flights, for example, matched three passes by TRMM, exactly the sort of coordinated measurements that the team wanted.

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Bonnie's progress is seen in color images from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite. The images here show Bonnie, from left to right, top to bottom, on Aug. 24 (Monday) through Aug. 27 (Thursday). Each image links to a larger JPG up to 1,000 pixels wide and 200 to 226 KB in size.

The first CAMEX-3 research flight set (DC-8 and ER-2 plus NOAA aircraft) was in the relatively calm weather ahead of Bonnie as the hurricane approached the U.S. coast. This let scientists measure conditions that would affect Bonnie's growth, which they measured with two flight sets through the hurricane and its eye and then one more (Wednesday) as Bonnie waded ashore in North Carolina.

"I think we are in the era of what I hope will be a well-organized national weather research program," Zipser said, "because NASA, NOAA, the [National] Science Foundation, and the university community have shown they can cooperate in a multi-agency, multi-aircraft mission and I think that holds great promise, not just in hurricanes, but all kinds of natural disasters."

The first stage in studying Danielle will be a synoptic flight ahead of the storm to measure winds and other conditions ahead on Saturday.

Weather forecast

Bonnie continued to pummel the Carolina outer banks, but is expected to begin recurving toward the north, albeit along the U.S. coast. On Friday morning it had moved back over the Atlantic and picked up energy, turning itself from a tropical storm back into a hurricane.

Hurricane Danielle, currently at an intensity of 148 km/h (92 mph, 80 kts), is moving nearly due west at 31 km/h (20 mph, 17 kts). Minimum pressure is 993 mb, on the high side for winds of 148 km/h (92 mph, 80 kts). Danielle is fighting shear generated by an upper low to its west, but models forecast this shear to break down, and Danielle should slowly intensify. All models tightly agree on the predicted continued westward track, around the southern flank of a strong 500 mb anticyclone located east of Bermuda. Then the models gradually track Danielle toward the northwest, then north, on a similar track to Bonnie.

Over Florida, weak south-southwest winds prevail over the peninsula. A weak high is projected to build westward across Florida tonight, with the ridge axis initially located over southern Florida. This should keep the area in a southwesterly regime for the next 24-36 hours. Morning soundings at Cape Canaveral and Tampa are dry in the mid-levels, although water vapor imagery shows increasing mid- and upper-level moisture is advecting into the region. Today, the probability of thunderstorms is low as the atmosphere slowly recovers from the dry, subsident environment in the wake of Bonnie. Scattered, short-lived showers are possible along both sea breeze fronts, with the west coast breeze propagating inland through the afternoon. Surface winds will be southwesterly at 19 km/h (12 mph, 10 kts).

Over the next day to two days, look for gradual moistening through the column and slightly increased thunder storm probabilities. The wind regime will be light southerly, changing to a southeasterly regime. Thus the probability of afternoon thunder storms is equally likely inland of both sea breeze fronts. Danielle's 48-hr forecast position is some 500 km (311 mi) north of Hispaniola with an intensity of 176 km/h (109 mph, 95 kts).

Left: NASA/Marshall's Lightning Imaging Sensor observed Hurricane Bonnie as the TRMM spacecraft flew over the storm several times in the last few days. The image at left shows intense lightning as Bonnie nears the North Carolina coast in observations made Thursday. (Links to 756x680-pixel GIF)

For the next 2 to 3 days, Danielle's forecast position by 72 hrs is 28.0 N, 73.5 W, or 650 km (404 mi) east of PAFB, with gentle recurvature toward the northwest, and an intensity of 222 km/h (138 mph, 120 kts).

Finally, for the next 3 to 5 days, thunderstorm activity over the peninsula should again become suppressed over the peninsula as Danielle skirts by us offshore.

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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. 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)