Teleconnections creating USA Cold.

Hello and welcome, it's probably in the front news at the moment that large swathes of the USA are experiencing below average temperatures and Snowfall early this year. the "Arctic plunge " of cold air is the culprit right? let's all blame the Polar air descending, after all most Tweets i have read on Twitter refer to " a PV disruption causing chaos". however what do the feedbacks from teleconnections say?

Firstly let's look at the NAO.

Positive NAO (CURRENT as of november 9th)

We can see that we are in the positive phase of the North Atlantic Oscillation right now with a warm anomaly ( ridging in the Atlantic and a suggested high scandinavian blocking pattern looking likely into wk 3/4 of November.

Hang on David that has eastern seaboard with a warm Anomaly? correct but remember this is one feedback..

Now let us take a look at the current AO Pattern

Positive AO ( Arctic Oscillation)

OK looking at the graphs above and given current weather patterns in the Conus what would you say the current index is? NEGATIVE? Incorrect the current pattern suggests AO is slightly positive after returning from a brief negative spell.

Again this is one feedback, it is in favour albeit the feedback currently is small.

So let us take a look at more feedbacks, firstly the WPO (West Pacific Oscillation).

WPO Negative phase

The above is current WPO index forecast for 9th November through to 25th November however as the WPO has remained negative (exceptions above) it is likely it will remain throughout Nov/Dec However we are looking at current index. You will notice that during the Negative phase Parts of central and most of Eastern regions of USA experience below average Temperatures for the months of November December.

AHH David but this is one feedback as you keep saying it is not coupled.. ok let's now look at the PNA Pattern, (Pacific North American Pattern).

Positive North American Pattern (PNA)

We can see from the above Climatology forecast that currently the PNA is in a Positive Pattern index and apart from minor fluctuations has been so for some time,

You will notice from the 500hpa heights we have ridging (positive) in western Canada and the extreme western united states with below average Temperature in the Eastern USA. We can also see during the positive phase an enhanced Jet stream with an eastward shift ( a drop in subtropical jet) bringing cold Arctic air south, it is important to stress at this point that it is not POLAR air merely a southern departure of Arctic air mass.

I will not go into detail about the brief PV disruption that took place earlier in November as i feel this has received enough air time on many platforms to the point of obsession, looking at the 10hpa heights it is highly likely there WILL be another disruption around 25- end of November but again this will be confined to the US.

THIS WILL NOT BE A SINGLE EVENT to the USA and may continue beyond week 3 with lower than average Temperatures and snowfall to mid/eastern regions AND A POSSIBILITY to produce Nor'easters.

Obviously patterns can change rather quickly however it is not an INSTANT feedback.

So there we have it folks we have 2 couples indexes, the PNA and the WPO with borderline AO.

Does this have an effect on the UK? YES but that is for another blog!

thanks for stopping by

David.