A look at the changing pattern and quick look at the week ahead.

We have a ridge out over Western North America with a deep trough over the East. As we go through the next several days, the western ridge will move eastward. At the same time, we have an upper-level low over the Canadian Maritimes, that is rotating cooler air into the Northeast and Middle Atlantic.  The air temperature over the Northeast is below average, during this week, we’re probably going to see the first snow of the season over parts of Eastern Canada.  While the Northeast into Middle Atlantic won’t see snow, frost and freeze will be an issue for parts of our region.

The Pacific has seen a very active tropical season; this is now going to have an impact on the pattern over North America.  We have Typhoon Choi-Wan in the West Pacific, this is going to track closer to Japan, before turning northeast and recurving away for the Island. If you’ve been following me for a while, you know That I say western Pacific typhoons recurving toward Alaska, lead to cold outbreaks in the Eastern half of the US.  

We have an upper-level-low over Siberia, that is going to be tracking south and east. As what’s left of Choi-Wan gets into the North Pacific both of these are going to interact and merge; making for a much stronger upper-level-low. This will move into the Aleutian Islands. The result will be a major snowstorm for Alaska into Northwest Canada. Then all of this will be a pumping up of an Alaskan Ridge.  

We’re entering the time of year where Long-waves (Rossby waves) adjust their wavelength.  Rossby waves are those big dips you see on the 500 mb charts. During the Summer long-waves have a shorter wavelength, due to the northern jet being weaker and the zonal flow being stronger, the shortwaves moving across the long-waves are faster. Zonal Flow is the west to east movement of air. This promotes stability and mild weather patterns. However, during the winter, the wavelength of the Rossby waves gets longer. As a result, meridional flow becomes a much bigger deal, this type of flow involves air movement running along a north-south axis, this type of pattern can lead to persistent cold snaps, or intervals of heat, or prolonged precipitation due to the slow wave propagation.  That’s enough of atmospheric waves 101.

Because of the ridge over Alaska, we’re going to see a trough develop over the Western CONUS (Contiguous United States). Because of what I talked about above, this will be a deep trough. As a result, a tall ridge will develop over the Eastern CONUS. This will ensure the West will see a big cool down and the East will warm up, as we move deeper into October.  

This pattern is also going to strengthen the subtropical Jet across the Southern CONUS, While the Northern Pacific Jet will direct storms into the Pacific Northwest and California setting up a active storm track. The Setup will also lead to a lot of cold air blocking keeping the northern tier of the US warmer with occasional shots of cool to colder air. This should end up being the predominate pattern over the coming winter.

 

Surface Chart, Radar and Satellite

 

 

Today

It has been unseasonable cool and breezy.  We have a few rain showers across New York State ahead of a cold front, this cold front will be pushing into Eastern New York State by Monday morning

The rest of the week.

The cold front move into New England by noon, behind the front west-northwesterly winds will become very blustery. This will usher in a much cooler airmass into the region.  So, Monday and Tuesday will be very chilly. Tuesday night will see the greatest chance for a frost and freeze.  A widespread frost and higher elevation freeze are likely across the northern half of the region. This will mark the end of growing season for those areas. So, any plants you want to save will have to be brought inside. On Wednesday and thru the rest of the workweek, temperatures will climb to above average.

A weak cold front will move through on Thursday, it really won’t affect temperatures too much, any rain should be very isolated.  Friday and Saturday look to be mainly dry and sunny. At this time Sunday is also looking to be mainly dry, so the Columbus Day holiday weekend shouldn’t be too bad.

Tropics

For several days, I have been talking about the chance of something developing in the Gulf.

We will have low pressure forming along the tail of a stalled front draped across the southern Gulf and Bay of Campeche.  Right now, the NHC is giving this area a 40% chance of tropical development. Those in eastern Texas, and especially from Louisiana and points eastward will want to keep an eye on this!