As Hurricane Irene trundles toward the densely populated cities of the U.S. Northeast, residents and officials in municipalities large and small have been preparing for a full-force tropical cyclone. "All implications point to this being a historic hurricane," President Barak Obama said in a speech Friday morning.

Some 50 million people along the eastern seaboard are likely to be affected by the storm, and the Federal Emergency Management Agency (FEMA) is poised with water, meals and cots and blankets for millions.

For all of their harbor-side advantages, low-lying coastal cities, such as New York, are particularly vulnerable when it comes to major storms, which are predicted to become more powerful with climate change. New York State has initiated long-term plans to build sea walls and discourage waterside development as a means to decrease future high-water threats, but these preparations are still years and decades away. In the meantime, the city is poised to undergo a complete shutdown of mass transit systems and has already evacuated some hospitals and nursing homes. In the event that Irene makes landfall in the city as a category 2 or greater, millions of residents could face flooding on Sunday.

An interactive map of New York City evacuation zones (courtesy of WNYC) shows the areas at risk of flooding in the event of various hurricane categories.

Those battening down the hatches in urban areas face a special set of challenges in preparing for what Obama said is "likely to be an extremely dangerous and costly storm." Extra supplies can be troublesome to acquire and store, and keeping away from windows in a small apartment can be next to impossible. New York City hurricane preparation guidelines offer some counterintuitive advice for urban dwellers, such as advising those who live in high-rise buildings to take shelter below the 10th floor (if they live in a high-rise and have not been ordered to evacuate altogether).

Numerous Web sites (including Stormpulse and The New York Times) as well as a handful of mobile apps (including Hurricane and iHurricane HD for iPhone users and Hurricane Software for Android) are available to track the storm's path and intensity—at least as long as internet, cell networks and electricity hold out.

Update [8/26/2011, 5:50 p.m.]: On Friday afternoon, New York Mayor Michael Bloomberg issued an evacuation order for the more than quarter of a million residents who live in evacuation zone A, closest to low-lying coastlines. The city's subway system along with commuter rail lines will be closed down starting at noon Saturday. The system, which reportedly cannot operate safely with sustained winds of more than 35 miles per hour and battles groundwater on a daily basis even on sunny days, would not likely fare well with the rain, 75- to 97-mph winds and four to five-foot storm surges that come typically accompany a category 1 hurricane.

The standard advice for emergency at-home and "go-bags" still applies. The usual, clean drinking water, nonperishable foods, first aid kit, batteries, flashlights, battery-operated or crank-powered AM/FM radio, telephone that plugs directly into a wall jack and requires no electricity (doesn't plug in, is non-portable), supplies of medications and whistle are always a good idea. To that list, we might humbly add: a few back issues of the magazine (so you can spend those long days and nights finally figuring out quantum physics), supplies for some at-home science activities and, as one New York Times commenter reminded us, especially in the case of a short-term emergency, water doesn't have to be the only beverage in your stockpile. But in case of a longer disruption, just be prepared to take your drinks neat.