The NAO and AO is going to hit the bottom of the tank over the next 7 days and it’s uphill from there but the recovery will be slow given that the index is near -3.

What does this mean for the UK, Ireland and Europe? Expect the mean trough position over the next 10 days to hold firmly over the NE Atlantic. The UK will be on the west side of that trough so systems will be active keeping us frequently wet and at times windy. The return to somewhat milder air last night starts this cycle of chillier storminess rather than mild. In other words our flow is northwesterly rather than west or southwesterly. A cold rain and wind will effect low levels whil snows could become more common over higher ground.

The week ahead looks unsettled with several fronts swinging a cold rain and wind down across Scotland and all parts of the UK. The northwest flow draws polar-maritime air down from Greenland and Iceland keepings days 1-3C below normal. In between weather systems, expect cold and frosty nights with a risk of ice. This regime is Atlantic driven still but more of a polar-maritime rather than maritime of sub-tropical-maritime.

This weather regime is fairly typical for late October, early November and this should last through at least the first week of November.

As of now, the NAO is firmly negative but according to recent runs of the ensembles, recovery appears on it’s way into the second week of November. However, given recent trends and the difficulty in getting the index positive means this may get delayed till later in the month. I would be foolish to deny that possibility. However, it’s got to flip sometime along with the AO in order for cold air to reload in it’s source region. I believe this is highly likely and so this would support my idea of a mild but stormy period during November (see recent posts relating to autumn and winter by holding your mouse over the ‘Winter 2012-13’ tab and click ‘UK-Europe’ to find out why i think Nov shouldn’y be dominated by cold). Many are hyping a very cold, blocked pattern throughout November however history doesn’t suggest this. Unfortunately many out there WANT to see a certain pattern but don not understand the atmosphere and the role of feedback during a transitionary period in the atmosphere. Paying to much attention to models and leaning on individual runs eventually catches you out.

The fly in the ointment which leaves little guidance for November which MAY result in a colder November, is the fact the cold mode in the Pacific and warm mode in the Atlantic have never been as strong at the same time.This is a sense throws out analog years whicj forecasters go by as a guide. So I am open to the idea of potentially a colder month than expected.

As for when the NAO SHOULD at least recover to nearer neutral, this current period in which colder air is more readily available in the mid-latitudes, which lows impacting us, can tap, this means we must keep an eye on cold blasts coming down on the backsides of lows. In other words, November may not only see a period of enhanced storminess but you ask the question, why? It’s because colder air and warmer air is closer together, this increases the speed of the jet stream and as lows deepen and expand their windfield, they pull warmth from the south and cold from the north. In other words, a temperature rollercoaster is likely with mild surges ahead of storms and cold surges on the backside. This will depend up the amplification of the pattern and it should flatten, becoming more zonal or west-east once the NAO goes from the current -3 to 0 or +.

Rather than appearing to sit on the fence, I am really trying to explain what’s going on and why there are various possibilities onj the table. We all see various theories on facebook, twitter or on forums but these are often put out without any reasoning, explaination and if you ask the why behind the what, it’s often “because the latest model says so”. While I believe recovery is on it’s way once we hit the 2nd week of November and the flow flattens and more active, stronger storminess kicks in bringing an active period of gales or damaging, severe gales accompanied by flooding rains, I have explained why this may be delayed. The power of ocean heat contnent, feedback is a vital player which many don’t look at. Here you get a look at ALL sides of possibility including an expanitory post of what can go wrong with the winter forecast. If you haven’t read it, please do so. That is just as important as what I do think will happen.

The latest NAO/AO ensembles.

 

 

 

 

 

 

 

 

Here’s the setup with a -NAO

+NAO

Here’s the latest ECMWF upper charts through next Tues… Note the systems tracking southeast from Iceland to the UK beneath the cold upper trough.