Monday, November 9, 2015

Monday Morning Weather Discussion: A Late Month Pattern Change?

Good morning everyone. Well we really had a bonus week of weather last week. Who is going to complain when temperatures are in the 70's in November. Now the natural question on everyone's mind is will this continue or will things start to cool down. I will start off by saying things will start to cool down but the jury is still out on if we actually see a pattern change that would actually make it a winter like pattern.

This week will actually start off above normal but not nearly as warm as last week. Expect high temps in the high 50's to low 60's all week. We will have some possible to deal with as we head into tomorrow afternoon as a low pressure system moves just off shore to our south..

Don't expect too much rain with this, most of it will stay off shore tomorrow. But in any event it will not be the nicest day.

Moving on, We then focus on another storm system Friday that will pass to our west. This will bring showers along with it on Thursday.

The big factor this system will contribute however will be the cold air it is going to pull in for the weekend..

You can see on the image above the blue colors which represent colder air flowing towards our area Friday. This is due to the cold front from the system that effects us Thursday. As a result, by the time we get into this weekend it will really feel like mid November. 

High temps should struggle to get into the low 50's with highs in the 40's in spots for Saturday and Sunday before it warms up a little by early next week. 

Our attention now turns to the long range. We have one big factor supporting a pattern change but another that is fighting against it. Let me explain by the image below..

The image above shows areas of high and low pressure or cool and warm air for early next week. The reason I show this is because it represents the flow of the pattern. Based on the configuration determines if we have warm and mild or cold and stormy conditions. To start off, looking near Greenland I highlighted an area of high pressure. This supports colder weather as it causes cold air to try to funnel south as I show by the yellow arrow. This is called the negative phase of the NAO.

However, sometimes you need more than that and in the case above there is a big factor that is fighting against the NAO which is the big area of blue or low pressure in the gulf of Alaska. The reason this does not allow the pattern to change is that it lets pacific air flow into the country which fights back against the blocking over Greenland.  This results in variability in the weather and swings in temps from cooler to warmer vice versa.

The biggest factor I have been keeping an eye on is will the ridging or red pull back west. If that was to happen with the blocking we have over Greenland then boom you have a brand new winter pattern. The models have been back and forth with this. But we need to see the vortex over AK go away. 

So what is the bottom line? I think that between the 19th and 30th of November we see this pattern start to flip. This is based on the idea that the jet stream will shift  based on its seasonal variation. In English that means the ridging or reds shifts north and the blue or cooler conditions are underneath.

Do not be surprised to see a big storm somewhere along the eastern 1/3 of the country when this shift occurs. Some models have been showing this idea and I will go as far as saying I can see it happening sometime after this week.  

More commentary to come this week. 


  1. Hey Willy, good stuff, thanks for getting us started on the upcoming winter season. But as to the NAO getting the fun going . . . well, the Atlantic SSTA pattern off the Maritime Provs still looks like it did last winter, which helped to keep the NAO in check last season (which would have been a block-buster for us like it was for Boston, had the NAO been more of a factor). I took a quick look at the ESRL telecon projection for the next 2 weeks and it shows an NAO back-off to neutral but then a bounce back positive, no negative trend yet. As to the north Pacific driving a cold air pattern here, sure, that whole situation is extremely dynamic, all the more so with the Nino boiling away below. Thanks for the great chart, gonna be interesting to see if the Ridiculously Resilient Ridge sets back up over the west coast. With all the Nino energy in the mix, though, the situation might get into chaos theory territory --- anything and everything could happen!! I'm sure you'll keep us posted. Jim G

  2. Jim we got the shot at stuff to get very interesting middle to end of thanks giving week. Big negative EPO w all sorts of energy on the field..if that trough is more east look out. I discussed this today.

  3. Jim we got the shot at stuff to get very interesting middle to end of thanks giving week. Big negative EPO w all sorts of energy on the field..if that trough is more east look out. I discussed this today.