First in an occasional series.

ABOVE THE NORTH PACIFIC - Eight miles up, in a mysterious region where the atmosphere harbors some of its most dangerous secrets, Cmdr. Jeff Hagan was taking in the ironies aboard a Gulfstream IV jet.

The mesmerizing view of a dense cloud mass outside the cockpit window on Thursday suggested an endless white beach and a sky-blue sea. But Hagan knew such a calm was illusory. Behind the clouds were violent winds taking aim at the United States.

The in-flight meteorologist, Willow Grove native Jessica Williams, was analyzing data that help fuel the world's weather forecasts. She and the Gulfstream crew were hurtling over nature's storm factory, home to the winds that have brewed a winter of floods in California and the Philadelphia region's record snows. Jet-stream winds even had a hand in this weekend's heavy rains.

Solving the jet stream's riddles could immensely improve short-term and long-term forecasts, yielding economic benefits and giving power companies and emergency managers a heads-up on major storms. It would be a boon to airline safety. Scientists see the jet stream, too, as a bellwether for gauging the future course of Earth's climate.

"If you want to understand the creating, development, and translation of winter storms, you have to understand jet flow," said Louis Uccellini, the director of the National Centers for Environmental Prediction.

But here above the North Pacific, that flow is in a blind spot, so far from land and traditional weather-tracking tools that it can be mined only by Williams and the crew on the plane.

"This," she said, "is a weather nerd's dream job."

Aboard the high-altitude jet, she and the rest of the National Oceanic and Atmospheric Administration (NOAA) crew, clad in blue jumpsuits with "Hurricane Hunter" patches, were looking for trouble.

From a rear hatch, they were dropping data "bombs" - miniature weather stations no bigger than an extra-large hoagie roll, packed with instruments that record what is going on as they float down, slowed by "square-cone" parachutes, through chaotic air to the agitated, whitecapped sea. One of the probes dropped on Thursday measured a wind speed of 161 m.p.h.

Hagan, a former Coast Guard pilot who lives in Tampa, Fla., mused that he had been trained to avoid bad weather. That changed when he joined NOAA 16 years ago.

"You go to NOAA, and they tell us to fly through it," he said. "It's kind of ironic."

Hagan, who flew into every hurricane in the stormy years of 2004 and 2005 - including six trips into Katrina - now is flying missions for the Winter Storm Reconnaissance program.

This $875,000 project's aim is to relay data that can't be captured any other way. Since January, the jet has dropped 492 instrument packs into the Pacific on flights from Tokyo, Honolulu, and Anchorage, said project manager Nancy Ash. For the next several days, the data from the "bombs" dropped on Thursday will be used in computer models all over the world for weather forecasts.

And in the longer term, that data will help researchers come to a deeper understanding of the powerful jet-stream winds that are crucial to the weather out here, in Philadelphia, and all over the world.

The potent winds form over the clashing boundaries of warm and cold, inciting storms and moving them around the planet.

These are the powerful winds, noticed by a Japanese researcher in the 1920s, that bedeviled World War II bomber pilots, causing their planes over Europe and the Pacific to burn precious fuel and their bombs to miss targets, and contributed to a horrifying incident in the woods of Oregon.

The winds have been particularly ferocious this winter, with the unusually warm El Niño waters over the tropical Pacific simmering the overlying air and sharpening the temperature contrasts.

Aboard the Gulfstream IV, engineer Charles Lynch was dropping the instrument "bombs" from an airtight hatch in the rear of the craft. They were thin cylinders, about 18 inches long, encapsulating a computer board. Brief gasps of air went through the cabin as Lynch opened the hatch and ejected the devices called dropsondes.

They work like upside-down weather balloons, reading wind, pressure, and temperature from the top down, rather than the bottom up. A tiny square parachute slows the descent, said technician Mark Rogers.

The dropsonde sends back readings every half-second during its 13-minute descent to the waves.

The Gulfstream was stalking a deep upper-air system behind a cold front the shape of a dragon's tail about to lash the West Coast. The cylinders had wild and erratic rides through the layers of winds, as so many of those World War II bombs must have had.

The dropsonde data were relayed to in-flight meteorologist Williams, an Upper Moreland High School alumna, who screened them for "outlier" readings that would skew the data that were about to be sent to the rest of the world via satellite. Unusual jumps in air pressure and temperatures might indicate a problem with the transmitter.

Williams' love of weather science goes back. She remembers when, as a lifeguard at the Upper Moreland Swim Club, she would pass the tedious hours admiring the reflected clouds floating across the pool.

Thursday's first "bomb" turned out to be a dud, failing to relay any signals. But the next 16 sent back portraits of an atmosphere in a frenzy.