Washington ? There’s no phenomenon quite like Washington in a whirlwind. These cyclones, endemic to the political climate here, have dangers all their own. In the past, these storms have brought two red scares that compromised the very values authorities were seeking to preserve, a debate over who lost China that was misleading and distracting, and a general uneasiness about the espionage arts that may have contributed to last fall’s terrorist tragedies.

Now there’s heavy weather brewing over intelligence failures that led to the attacks of Sept. 11. The public itself is skeptical; a new Wall Street Journal/NBC News Poll shows that 58 percent of Americans fear that an investigation might be unproductive and too political. But if an intelligence inquiry can be run soberly, the country might be served and made safer.

The very nature of the failure a systemic breakdown over two administrations actually increases the chances that an intelligence inquiry might be profitable. The bad news is that so many agencies share so much blame. The good news is the same thing. “The nice thing about everybody having some of the blame is that no one is eager to point fingers,” says Loren B. Thompson, a defense analyst at the Lexington Institute, a nonpartisan think tank. “It would be different if all the blame were concentrated in one place, but we know better.”

As Washington fights about who conducts this inquiry either a group composed of members of the House and Senate intelligence committees, which is the administration preference, or an independent panel, which some prominent lawmakers of both parties want here are some of the questions that might usefully be asked by any group conducting an investigation:

l What is the “stovepipe,” and what role did it play in Sept. 11? The new metaphor of choice in intelligence circles is the stovepipe, which describes how information flows in various agencies responsible for surveillance and espionage. The long-standing complaint at the Pentagon is that the flow of information from these sources tends to run straight up, like hot air, with twin negative results: Intelligence is seldom analyzed or synthesized. And the people at the top of the pipe are deluged with so much information that they cannot process it.

This is precisely what happened in the months leading to the attacks on Washington and New York. FBI agents were looking at the activities of foreign nationals here. The CIA was tapping into al-Qaida overseas. Nobody was drawing this information together or drawing conclusions from it.

l Who really does a better job of collecting information? There are a dozen major intelligence agencies, each with different skills. It would be useful to know which agencies are best suited to the new challenges facing the United States. In Afghanistan, for example, an inquiry may well conclude that the National Security Administration did a good job of penetrating the Taliban but performed less well with al-Qaida. Discovering whether that is true will help U.S. authorities know where to place their emphases in the terrorism war and may provide hints about how to tap into new threats.

l Is this really a matter for American foreign-intelligence services? The fact that the threat came from foreigners who were bankrolled by foreigners in support of a cause with foreign roots would suggest that it is. But not so fast. Some intelligence experts believe that the chances of gathering information abroad on what a group like al-Qaida will do in the United States is very low. Indeed, much of the intelligence about al-Qaida came from the FBI, from computers seized by foreign law-enforcement agencies or in Afghanistan, and from information provided by foreign intelligence services friendly to the United States. “You won’t ever penetrate al-Qaida,” says R. James Woolsey, former director of central intelligence, “because it is a terrorist organization and it’s very well compartmentalized.”

l What did we really know and, of course, when did we know it? This question, first posed in the Watergate inquiry, has become something of a facile weapon in Washington; the very asking of the question now implies dishonesty, wrongdoing or failure. But Sen. Howard H. Baker Jr., the Tennessee Republican who first posed it more than a quarter-century ago, was onto something, at least in how that question can be applied to U.S. intelligence failures. A sober reply to that query will provide a useful answer to the two real questions: Is al-Qaida really clever? Or were American intelligence agencies really incompetent? If the answer to the last question is yes, then there is action that political leaders and spy masters can take, and fast.

l What precautions should be in place during this investigation? First, assure that the inquiry doesn’t compromise American assets further; U.S. intelligence services made breakthroughs by intercepting Osama bin Laden’s satellite-telephone calls and reading al-Qaida’s e-mails, but once those capacities were publicized, they became worthless. Second and most important, assure that the purpose of the investigation is to learn information to avoid the next failure, not to ascribe responsibility for the last one. “We didn’t do our best last summer,” says Stansfield Turner, another former director of central intelligence. “We’d be remiss if we didn’t try to fix things.”

David Shribman is a columnist for The Boston Globe.