In 1986 Yossi Koren saw his baby come to life. And the next year, that baby "knew" someone else and begot another baby, and then that baby begot another baby. So it went for 12 years until the family grew to almost 1,000 members.

Now, after almost 13 years of knowing and begetting, it's time for a bar mitzvah.

The "baby" is the East Bay Community Youth Experience in Israel, sponsored by the Jewish Federation of the Greater East Bay.

Koren is the patriarch of these trips. He conceived the idea and brought it to life with the help of Ami Nahshon, executive vice president of the federation, and financial support from the Jewish community.

On Saturday, Nov. 28, the federation will celebrate 13 years of successful teen trips. According to Riva Gambert, the federation's director of education and culture, all of the past emissaries are coming from Israel. About 350 trip alumni are expected out of a total of 1,000.

There will be food, a disc jockey, dancing, a collage video of all the trips and a lot of shmoozing.

In addition, the group will remember Marika Winheld, a counselor on the 1989 trip who died in a fall while hiking at Ein Gedi, a nature preserve.

Former emissary and trip leader Kobi Sharon proposed a bar mitzvah reunion before he left the Bay Area to return to Israel. Nitzan Aviv, the leader of last year's trip, and federation staff have been putting it together.

"We've been working on collecting phone numbers since last December," says Gambert. "The biggest challenge has been to find people. They go all over the world."

Although the community trip is now well established, it was Koren who designed the first itinerary.

"I thought it would be good for these kids to see Israel through my eyes," Koren said by phone from Israel. So he took them to where he grew up, went to school and served in the army. At Yad Vashem, the Holocaust museum, he showed them the memorials to his family. "This was not a Jewish Disneyland. I wanted to show another way of being a Jew far away from Oakland."

The first trip was difficult to plan.

"It was probably the worst year to organize a trip to Israel," says Nahshon. "That was the year [Moammar] Khadafy and Libya were going crazy with bombing and hijacking."

Koren knew he would have to sell the trip to kids and their parents.

"I decided to sell them a challenge," Koren says. "Each teen would have to study a half year in pretrip sessions about themselves, Judaism and Israel."

The trip was a success — 17 youngsters made the first foray — and the teens took over marketing it to their peers. The next year, 52 signed up.

"It was the cool thing to do," says Koren.

According to Nahshon, now about 80 percent of the teens enrolled in East Bay Midrashot, the federation's high school program, take the trip.

Although the itinerary is modified and refined every year, Koren's basic philosophy remains intact. The trip is very much a hands-on experience and whenever possible, groups of Israeli and American teens interact.

In addition to seeing the usual sites, the kids do the sorts of things an Israeli teen might do — witnessing army life, living and working on kibbutzim, camping in the desert, spending a night in a Bedouin community and even hitting the discos.

The biggest change over the years has been the size of the trip. Last summer, a total of 187 East Bay teens went on two trips to Israel, including one funded by the Koret Foundation.

And at the end of every summer, when the World Zionist Organization evaluates all teen trips from around the country, the East Bay's consistently rates first or second in all categories.

"You can't imagine what pressure there was on me," says Aviv, discussing his concerns before coming to Oakland to head last year's trip. But the previous emissaries were on hand to help guide him.

Over the past 13 years, "the Israel trip has transformed the landscape of the East Bay Jewish community," says Nahshon. It keeps teens in religious school after their bar and bat mitzvahs and strengthens their ties to the Jewish community locally and in Israel.

In the last two years the trip has gone high-tech with photos, journal entries and updates posted on a Web site and a real-time broadcast from the top of Masada featuring all the teens.

Nov. 28 will also mark the kick-off dinner for the Israel scholarship drive to establish an endowment fund to assist teenagers and college students needing financial help for the Israel trip. In the past, scholarship funds have come from the federation, Koret and local synagogues. The goal is to raise $2.5 million to $3 million and use the interest for scholarships.

So what does Koren think about his legacy?

"I'm very proud of being a small part of it."