There were some warnings yesterday afternoon about the storm headed to New York: the sky turned steel-gray, emails from utility providers alerted people of possible outages, and amber illuminated signs over the freeways and bridges warned of rain and flooding. But after a summer of record rainfalls, no one seemed to be on high alert. Hurricane Henri had come and gone — what was another tropical storm? But at 9 p.m., phones across the city lit up with a flash-flood warning — the first ever for New York City. Then the deluge: more than 7 inches of rain in some parts of the city, and a record-smashing 3.15 inches in one hour in Central Park. Subway stations were filled with torrents, the BQE and FDR were brimming, and even a ramp to the Brooklyn Bridge flooded. The water that surged into basements in Queens and Brooklyn trapped and killed at least eleven people.