Stationary Front over New England

Fronts are usually analyzed at the leading edge of cold air. The past few days have seen a stationary front stalled over New England leading, with a moist polar air mass lying to the north and a moist tropical air mass lying to the south . High humidity in these air masses combined with the front itself has given us lots of rain over the past few days.
The image at left shows temperatures taken at 3PM Monday, July 21 2008. Northern New England and Southern Quebec are in a uniform polar air mass where most temperatures (with a few exceptions in the Burlington VT area) lie in the 70's. South of the front, temperatures are more tropical (generally in the 80's).

The station analysis (click on image below for better view) for 18Z (2 PM EDT) on the same date shows dewpoints (green numbers) in the 60's almost everywhere in the northeast, indicating an abundant supply of water vapor. These high humidity conditions make for sticky, uncomfortable weather everywhere. The nightime temperatures are not likely to sink below the dewpoint, meaning warm, clammy nights where you constantly have to flip your pillow to get the cold side (grrrr ... ).


A stationary front extends along the temperature gradient (the area of contrasting temperatures) across New York State and Connecticut. The strong temperature gradient is actually north of the front. Very weak lows associated with cloud and thundershowers are shown over Massachusetts, southern Ontario, and southern Michigan. Weak winds around these systems blow across the stationary front, leading to warm and cold advection. These weak systems are typical of the summer, when extratropical cyclone development is not as well defined as in the winter, making these systems difficult to track. Tropical cyclones, as we will see this week, are much more frequent and obvious at this time of year!