For half a century, the United States has pursued a policy of isolating Cuba in the vain hope that doing so would lead to the downfall of the island's Communist regime. Today that policy is one of the last great historical anachronisms of the Cold War, outliving the Berlin Wall and the Soviet Union, despite the fact that it has never accomplished what it was supposed to do. Political realists such as Henry Kissinger have argued for years that the policy undercuts U.S. diplomatic efforts on a host of fronts because it is so widely disliked by other countries, especially in the Western Hemisphere. (It is one of Venezuelan President Hugo Chávez's most successful talking points.) Human rights groups like Amnesty International have long pointed out that the embargo is an obstacle to improving human rights conditions, not an aid. Meanwhile, greater trade with the United States has led to better lives and greater--if not necessarily complete--freedoms for the citizens of other countries with Communist governments, such as China and Vietnam. And yet, thanks to intransigent conservative ideology and the outsized electoral influence of Florida's Cuban American voters, the policy of near-complete isolation has endured.

For the last several months, however, the Obama administration has moved slowly, step by incremental step, away from the policy. In March, the president signed a budget bill easing Bush-era restrictions on how often Cuban Americans can visit the island and how much remittance money they can send to relatives there. In April, he eliminated such restrictions altogether, and also gave U.S. telecom firms permission to pursue licensing deals with Cuba to expand cell phone, broadband, and other communications services. Then, in May, his administration offered to resume direct mail service to the island for the first time in decades, and to begin negotiations on issues involving migration--offers the Cuban government readily accepted. Finally, in June, Secretary of State Hillary Clinton brokered a deal to allow Cuba to rejoin the Organization of American States if it meets key benchmarks of democratic reform. (Cuba was not so quick to take up that offer.) Meanwhile, the White House has been watching with interest efforts on Capitol Hill to repeal the law that bans American tourists from visiting the island--efforts that stand a surprisingly decent chance of garnering majority support in both the House and Senate by this fall.

The next logical step--and by far the biggest and most controversial--would be to end the United States's forty-seven-year-old trade embargo on Cuba. When he was a state senator, Obama called for doing exactly that. But he backtracked four years later, as presidential candidates inevitably do. In a speech in Miami to the Cuban American National Foundation, a bastion of support for the existing policy, Obama promised to end the restrictions on Cuban American travel and remittances to Cuba but said, "as president I'm not going to [end] the embargo; it's an important inducement for change." This is more or less his position today.

But the president and his senior advisers also understand a key political fact: on November 6, 2008, Obama won Florida with only 35 percent of the Cuban American vote. In fact, he is the first U.S. president since the Cuban Revolution who is not beholden to that voting bloc for his victory in the state. In other words, he is the first president to have the political running room to lift the embargo.

And here's the most interesting part: he doesn't necessarily need Congress's support to do it. Under the right conditions, he can lift the embargo unilaterally. Those conditions are dictated by, of all things, the weather.

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By dint of its location, Cuba is a nearly perennial target of tropical storms. Last year saw Cuba absorb four direct hits by hurricane-force storms, wiping out a third of the island's agricultural production, damaging or destroying a third of its housing, devastating its electrical grid, and eliminating 20 percent of its GDP. It was, many experts say, the worst storm season ever.

In the wake of that disaster, the Cuban government was somehow able to patch together enough international credit to avert mass starvation. It did so only by importing enough food to increase its monthly ration from 50 percent of the nation's calories to 75 percent. Indeed, reports from the island suggest that Havana had to choose between importing food and importing building materials: much, if not most, of the housing that was damaged in the 2008 storms has yet to be rebuilt. And with tourism down, nickel prices down, and last year's tobacco crop flattened--and with Venezuela, Cuba's most important regional ally and budget subsidizer, reeling from the drop in oil prices--Havana's sources of cash are not keeping up with its mounting debt.

This year the National Hurricane Center predicts fourteen named storms and up to seven major hurricanes in the Atlantic basin. In its present weakened condition, just a single direct hit by a major hurricane could overwhelm the Cuban government's ability to meet the basic needs of its people. A storm like last year's Hurricane Ike--which came ashore as a Category 3 storm and chewed up the length of the island from east to west--could be catastrophic.

If Cuba were any other country, the United States would efficiently arrange assistance through the U.S. Agency for International Development. However, as the Bush administration learned last September, Cuba will not accept direct humanitarian assistance from the United States. The Cubans' rationale, one has to admit, has a certain logic: if a man is being choked, does it make sense for him to accept a glass of water from the person who's choking him?

That's where things get interesting. If, by extraordinarily bad luck, Cuba does get severely battered, the government may not be able to deliver enough food, reconstruction aid, and, frankly, coercion to prevent the people from voting with their boats. Before long, we could see a wave of seagoing humanity motoring, paddling, and floating the ninety miles to the coast of South Florida. After all, it's happened before, twice--once in 1980, and again in 1994.

If a major storm hits, President Obama will face a choice. Like George Bush, he could offer assistance. Like Bill Clinton, he could wait for the Cuban people to take to the sea and then order the Navy and Coast Guard to scoop up rafters and try to send them back. Or he could use the crisis to forge a bold new policy.

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Here's how. In a little-known corner of the United States Code, the 1961 Foreign Assistance Act, Congress gave the president extraordinary authority in times of humanitarian disaster: "[N]otwithstanding any other provision of this chapter or any other Act, the President is authorized to furnish assistance to any foreign country, international organization, or private voluntary organization, on such terms and conditions as he may determine, for international disaster relief and rehabilitation."

"Notwithstanding ... any other Act" means the president is not constrained by any other law passed by Congress as he responds to a disaster. And that gives the president the opportunity to convert a perfect storm into a strategic watershed: instead of offering the Cuban government direct assistance, which it will only reject, he could lift the embargo itself.

Structured properly--say, for a term of 180 days, during which the Cuban government and people could purchase nonmilitary items on the American market for cash or credit--the Obama administration could avert a humanitarian nightmare, win the goodwill of the Cuban people, provide significant economic stimulus to the southeastern United States, tie Hugo Chávez in knots, and make it possible for Congress to repeal the embargo at the end of the 180 days, when it is clear that America's national interests are best served by a policy of confident and generous strategic patience.

The president's chief of staff, Rahm Emmanuel, is famous for saying that one should never let a good crisis go to waste. One hopes that it would not take a significant uptick in human suffering to force a change in an antiquated piece of U.S. policy--but if it does, this might just be how it happens.