Fronts and the Evolution of a Midlatitude Cyclone
A surface weather analysis is shown for a 24 hour period from Jan 9-10, 2013. The isolines of pressure are shown along with the location and types of fronts. Let us focus on the Pacific Northwest. In the initial map we find a surface low pressure located over northern Vancouver Island with a warm front extending southeastward toward Moscow. This weather system had its origins in the Gulf of Alaska, and while cold, is generally much warmer and wetter than the air mass located over the interior western US and Canada. By contrast, the air mass west of the surface low north of Minnesota is likely of continental origin and much colder and drier.
The passage of the warm front through the Palouse results in a more moderate air mass (not warm by any means since this in January). What sort of precipitation (intensity) might be expected in Moscow during this time period?
The passage of the warm front through the Palouse results in a more moderate air mass (not warm by any means since this in January). What sort of precipitation (intensity) might be expected in Moscow during this time period?
The surface weather analysis 12 hours later shows that the center of the surface low have moved eastward and the cold front moving through the North Cascades and Portland, Oregon. Note the strong gradient in surface pressure near Moscow. What direction are the winds blowing from at this time? Do you think the wind direction is consistent with being in the warm sector of a storm? Note the change in the intensity of the center of the surface low between this time period and 12 hours earlier. Did the system strengthen or weaken?
Finally, a surface weather plot 12 hours later shows the surface low centered over southern Alberta. The cold front has now passed through Moscow. What direction are the winds blowing from in Moscow at this time? How do you think temperatures changed over the previous 12 hours?
Log in to BBLearn, and under Module 5 and complete "Assignment 5.6: Air masses" AND "Assignment 5.7: Midlatitude Cyclones"