Thomas is an avid weather enthusiast, landscaper and organic gardener. This blog is dedicated to Northeast and tropical weather forecasting. Enjoy!
By: sullivanweather , 12:22 AM GMT on March 06, 2014
So, what went wrong with the snowstorm for the Northeast on Sunday/Monday? There were several key factors which led into a much further southward track with the storm; two of which were strong confluent flow over New England and one of the coldest March outbreaks of arctic air over the northern US in the last 140 years thanks to an unusually strong 1050mb surface high pressure sagging south over the northern Plains.
Selection of all-time March records for cold broken during arctic outbreak
This surface high also had a eastward extending ridge axis which extended over eastern Canada and resulted in strong wedging down the east side of the Appalachians. The combination of the confluent flow and surface high pressure led to strong subsidence and vast amounts of dry air becoming entrained into the front-end of the storm in the ageostrophic flow east of the Appalachians. These two factors severely cut down the precipitation arriving with the first system on Sunday behind the arctic front. However, the main 500mb trough still hung back to the west over Texas and surface low pressure with the developing storm was still back in the mid-Mississippi Valley. What led to the main storm also taking a detour south from expectations which held for nearly a week?
One of many consistent model runs of expected storm for Monday, March 3rd showing southern stream shortwave moving out ahead of northern stream trough.
Final solution showing the southern stream shortwave obviously left behind by rapidly advancing northern stream shortwave.
Just some minor shifts in the longwave pattern, it turns out. Large scale features, such as the North American center of the polar vortex, were slightly removed from the regions in which they were modeled to be in, with small changes in the configuration of individual vorticity centers within the core of the vortex and subsequent changes in the resulting orientation of minor trough axes (oddly enough, that is the correct spelling of the plural of "axis"). What ensued was a faster northern stream of the jet from the southwestwardly placed center of the polar vortex over eastern Canada. This helped to move a minor trough axis (A Rossby wave, really) through the North American northern stream flow out in front of the Pacific-origin system in the southern stream by the time it emerged out in the southern Plains. The height falls associated with the passage of the northern stream Rossby wave out ahead of the southern stream system essentially put in place an atmospheric wall which kept the southern stream system from penetrating too far north.
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