The plan called for 30 dropsondes, and the crew released a few during the long flight down to the convection zone and then picked up the pace as the plane headed west.

A brief whooshing noise was the only indication that a sonde had been released. The cylindrical tubes, which weigh about a pound, are simply sucked out of the plane by the difference in pressure between the cabin and the outside air, and quickly sink when they hit the water about 15 minutes later.

Data starts streaming in almost immediately once a dropsonde leaves the plane, and is displayed in real time on a few of the several computer screens in the cabin, including the one manned by Richard Henning, the other flight director. Mr. Henning, who like Mr. Holmes is a meteorologist, makes sure the data is clean — with his practiced eye, he can quickly tell if a sensor has malfunctioned or the sonde has otherwise provided unusable data — before sending it off in several forms, including a condensed format that can be immediately fed into models around the world.

Elsewhere in the cabin, crew members made sure all the plane’s electronics were running properly and monitored the Doppler radar. Mr. Holmes, Dr. Spackman and the aircraft commander, Ron Moyers, talked from time to time about course changes designed to get closer to the convection to obtain better data.

After two and a half hours of flying west, it was time to turn to the northeast and head back to Honolulu, still three hours away. The pace of work slowed again, with only a few dropsondes left to release.

Mr. Henning and Dr. Spackman took time to look over some of the dropsonde data. They saw winds coming out of the top of the convective cell and blowing toward the northwest. Earth’s rotation, Dr. Spackman said, would make that wind curve to the east, where it would no doubt join up with the Pacific jet stream that was affecting the West Coast.

Dr. Spackman seemed pleased despite the change in plans. “We did a lot of good science today,” he said.