The outpouring of support and sympathy was seen around the world, but it was particularly strong in the United States, stoked by social media publicity and the large size of the Filipino population, the second-largest Asian-American group in the country. Some aid groups reported generous pledges from the New York area, reflecting what they called the sympathy effects caused by Hurricane Sandy a year ago.

The United Nations relief agency said on its website that as of Monday, 9.8 million people had been affected across the Philippines and more than 659,000 were displaced from their homes. But Mr. Ging and other top relief officials at the United Nations and elsewhere said they could not yet calibrate the full scope of the death and devastation because they simply did not have enough facts.

Charities with long experience in the Philippines said they were not waiting for guidance.

“At this early stage, the big issue for us is moving people and aid supplies to the affected area,” Natasha Reyes, the Philippines emergency coordinator for Doctors Without Borders, the Paris-based medical aid organization, said in an emailed update. Dr. Reyes also said: “Right now we’re operating in a relative black hole of information. We know from the very little we can see that the situation is terrible. But it’s what we don’t see that’s the most worrying.”

Bob Kitchen, the global emergency director of the International Rescue Committee, one of the oldest aid groups, said it was already assuming that transportation was going to be the biggest challenge in delivering help. “If we can’t get to the communities affected because the road systems are down, we’re going to have to up our game,” he said.

Even with the best planning, advance notice of storms and the lessons learned from previous calamities, the prospect of an initially confused relief effort was difficult to avoid. “There are always unique circumstances in these disasters,” said Elizabeth Ferris, a senior fellow and expert on natural disasters at the Brookings Institution in Washington. “It’s hard to prepare for these really big storms.”

Still, Ms. Ferris and other experts said the Philippines was relatively well positioned to handle the crisis, even as it evoked images of the devastation wrought on impoverished countries by the December 2004 Indian Ocean tsunami and the January 2010 Haiti earthquake.