This image shows water vapor in the atmosphere around the 700 millibar level, or around 10,000 feet above sea level. Warmer colors show dry air, which is conductive to calm weather and clear skies, while progressively cooler colors show deep atmospheric moisture and likely where showers and thunderstorms are occurring.
This afternoon's water vapor image shows the strengthening nor'easter sitting east of the New Jersey coast. A batch of rain and thunderstorms are developing along the warm and occluded fronts near the low, while the cold front leads the charge of cool, dry air surging southeast into the Atlantic. The low pressure center is wrapping the dueling air masses around one another, creating the tsunami-like "wave" in the water vapor imagery.
It's the twenty-first century version of seeing things in the clouds. Here's a less dramatic looking view at the visible satellite imagery for the same time. The effects of the moist and dry air are still pretty clear:
[Images: NASA, WPC]