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"Zonal Flow" Sets up For New England This Week; Here's What That Means

This is one of those posts for people who want to know WHY the weather will be the way it is, not just WHAT it will be


There are no high-impact weather events in store for New England through much of the upcoming week, though a couple disturbances will likely trickle through the region. This is thanks to a strong zonal flow pattern. Zonal flow occurs when the jet stream is in a more stable state, lying "flat" across the United States. This allows for a strong west-to-east motion when it comes to weather events moving across the country.


A strong west-to-east motion allows for weather systems to move across the country fairly quickly. This also prevents large-scale, strong storms from crossing the country as the motion of the jet stream moves systems quickly across the country without stalling or gaining too much strength.


A zonal flow is the opposite of what's called meridional flow, which is a stronger north-to-south motion. This is the pattern that is synonymous with larger-scale, more powerful storm systems. This is when the jet stream takes on much more of a wavy pattern, allowing for blocking of systems. This pattern also allows for more extreme temperature contrasts, an important factor for (non-tropical) storms to strengthen. This is the pattern that often sets up New England for blizzards and arctic blasts in the winter.




The jet stream setup through much of the next week will be pretty much identical to the zonal flow image above, with some minor fluctuations (the jet stream is always moving and is never truly static in one place for extended periods of time). This will lend New England a low-impact weather week.


While much of the upcoming week will be nice and quiet, it doesn't automatically mean the weather will be perfect with sunny skies and seasonable temperatures the entire time. As stated above, zonal flow lends itself to disturbances moving quickly through the area.



This will be the case starting this weekend as a series of "shortwave" disturbances ripple through New England. This will continue through the week, bringing the chance for precipitation. With this zonal flow in place, the systems will pass to the north of New England. This will, naturally, lead to higher precipitation chances in northern New England.


The highest precipitation chances will be Saturday to Sunday morning (for the northern third of New England), Tuesday (again, mainly for northern New England) and Wednesday night through Friday (for most of New England). These systems are looking to be overall low-impact with mainly scattered showers (and some frozen precipitation possible, details are yet to be worked out this far in advance). Some areas will not be impacted by these disturbances at all, remember, these are not large-scale, region-wide storms.


Temperatures will be swinging this week as well with near to below average temps on Sunday and Monday, swinging to above average on Tuesday as the system to New England's north will likely place the region in the warm sector. That system's cold front will likely be dragged across the region for Wednesday, setting up a cooler Wednesday through the end of the week. These rapid swings can be seen as weather systems move quickly through instead of stalling or slowing down in New England.




A deeper trough may to develop later in the week, bringing a chance for more widespread precipitation to New England by the end of next week. With zonal flow in place, the system should move through fairly quickly as the mid-level jet stream is currently looking to be directly overhead late next week. This would lend itself to another low-impact storm.


The timing of all of this needs to be worked out. A big issue for forecasting in a zonal flow setup is that models can have a very difficult time trying to get a handle on timing of these disturbances. There is usually a wide spread in the models in regards to timing whenever zonal flow sets up, and this week is no different.


Overall, next week is looking pretty nice, especially for southern New England, with some small hiccups possible.



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