Today's weather III: Wrap-around cloud and moisture

The map at left shows that the mP air that is affecting Vermont today is wrapping around a low pressure system parked off the coast of New England. The circulation around this system is counter-clockwise as indicated by the dark blue arrow (arrow ends over Vermont). This advects in cloud and cool moist air from the North Atlantic (remember, advection refers to wind transporting an air mass). This mass of cloud and moisture is called "wrap around" becasue it appears to curve around the center of the low pressure system.

Note that the blob of cloud off the coast of Newfoundland is the remnants of tropical storm Isaac. The wrap-around today is particularly moist because it taps into the huge amount of cloud and water vapor associated with this storm.

You can view an animation of this system for the past few days by clicking here. Pay attention to the dates at the bottom left of the images.