September Pattern Update

September Pattern Update
Summer weather is essentially over and a thing of the past other then perhaps eeking out one more day of warmer weather which would be today. Signs of fall weather on the way and perhaps some very chilly air arriving right on time at the start of the fall season around the 22nd of this month.

Lets look at the PNA to start this off..

As one can see when looking at the chart above the PNA is very positive. When the PNA is positive such as it is this is usually pretty indicative of troughiness being somewhere in the continental USA. One thing at this time that I am not seeing happening is the substantiated drop from such a positive PNA to the opposite side of the spectrum in neutral to negative at the end of the period.

The reason for not believing it is that the EPO is expected to be pretty much negative at the occurrence of the dropping of the PNA. When the EPO goes negative that means that high pressure will generally sit itself off the West coast or along the west coast and cause the Jet stream to lift into Canada and then dive back down into the USA carving a trough out along the east coast. This is exactly what we see occurring in the 00z ECM last night as high pressure causes that ridge to form (-EPO) and this would allow the PNA to stay quite positive with an impressive trough along the east coast. Hence the reason why i do not believe that the PNA is going to drop to neutral to negative.
Both the 00z ECM & operational 12 Z GFS from today support the indexes teleconnecting the way I think they should go..
During this time period the NAO is expected to remain somewhat positive to a neutral position..

So essentially over the next week we should be expecting to see seasonal to slightly below seasonal but there after look for a more below normal regime when it comes to the temperatures. Also look for the potential of wet weather and coastal storm scenarios to possibly effect the region. This pattern that we have now gone back into with the start of mid month (right on time as well) is the pattern to watch for thruout the winter season. I will be making a post in the winter thread sometime this afternoon..