This web page shows the passage of a cold front over the northeastern portion of the U.S.   By using today’s technology with satellite weather images, downloaded from the Internet, and the graphing capabilities of a computerized weather station, I am able to totally demonstrate not only the start of the high pressure system way up in the Canadian arctic, but the actual passage of the cold air mass as it swept over Chelsea, Vt. and my weather station.

The first four images are surface analysis charts from Canadian weather stations showing the beginning of a high pressure bubble of cold air way up in the arctic.   I have circled this high as it proceeded to flow southward.
The next four images are daily weather charts from the Weather Channel site that shows the high pressure coming down out of Canada and sweeping into the U.S.   And at the same time pushing a trailing cold front ahead of it.

The two graphs are from my computerized weather station located in Chelsea, Vt.   The different colored lines represent different parameters that were automatically measured every second and were stored in the computer in five minute increments.   The first graph shows the measurement of the barometric pressure in black and the temperature in yellow, with their vertical scales on either side of the graph, temperature on the left and pressure on the right in inches of mercury.   The bottom scale on the graphs represent the flow of time and the graph shows three days worth of measurements stating on the 15th of November.
As can be seen in the middle of the graph one of the characteristics of a cold front passage and the arrival of the cold air mass is the sudden abrupt turn around of both the pressure and temperature.   The barometric pressure has bottomed out and suddenly starts to shoot upward and at the same time the temperature starts its plunge downward.

Another characteristic of the passage is the shifting of the wind shown in the second graph.   Most cold fronts follow the passing of a low pressure system and their winds are usually out of the south, southeast.   Upon the entrance of the colder air mass the winds will suddenly pick up in strength and shift around to the west coming up out of the southwest at first.   As the colder air sweeps in and the temperature falls the winds will shift further northward eventually coming straight down from the north, ushering in much cooler conditions.

The second graph shows this shift nicely.   The white jagged lines represent the peak gusts and the purple lines the wind direction.   You can see that the prevailing winds on the 15th were out of the south and almost exactly on the rising of the barometric pressure (the black line) the winds picked up in strength and began to shift around to the west.   By the time the pressure has peaked again, and the temperature has fallen 36 degrees into the twenties, the winds are coming straight down from the north and thankfully have also died down considerably.