Jack Wales

I notice a lot more mention of ‘Stratospheric Anomalies’ on the forum this year, particularly regarding of the possible effects on our weather at the surface. The analysis and modelling of Stratospheric Anomalies has also formed part of a lot of winter LRF’s this year. I have done some research and there is a definate correlation between stratospheric warming events and cold anomalies occurring at the surface approximately 3 – 6 weeks later. Conversely when the stratosphere is cold this leads to more zonal weather at the surface with a similar time lag. The attached chart (Stratospheric Warming) for the JFM period in 2006 shows this clearly. The stratosphere in the NH being cold in Dec 05 entered a warming phase at the beginning of January 06 and remained anomalously warm until early Feb (and beyond in the lower layers). The cold kicked in properly at the surface (in the UK) around early February and remained until April so a clear correlation is visible there. There is also a correlation with Stratospheric zonal wind conditions which generally turn negative during warming phases with similar time lags affecting temperatures at the surface, see attached (Stratospheric zonal wind) chart. It is clearly evident that we entered warming phase about a week ago and the signs are that warming is taking place down to the mid layers of the stratosphere (40 hpa), considering the rate of warmth you would expect to see an exponential increase in temperature anomalies in the lower layers over the coming days. Factoring in a four week time lag for this event to take effect at the surface, can we expect to be engulfed in an arctic air mass when the surface synoptics ‘flip’ in early January? I very much doubt it but with the AO likely to enter a more prolonged neutral/negative phase you would assume that the chances of colder weather would be greater. The above analysis merely reflects anomalies for the Northern Hemisphere alone. When you break this down it actually shows that the stratospheric warming is taking place over Canada/Alaska with UK/Europe remaining in a cold phase. Link So I have three questions: 1, Does this mean that any blocking would only occur over N America with W Europe remaining in a zonal pattern? 2, What correlation is there (if any) to the amplitude of the height’s field waves to surface level blocking? 3, What are the caveats which could inhibit stratospheric anomilies from affecting weather at the surface? I’d be grateful if anyone could shed more light on this. Stratospheric_Warming.xls Stratospheric_Zonal_Wind_Anomaly.xls

I note from the cryosphere site the develpoment of a large hole (polyna) to the north of Franz Jozef in the arctic basin. This is an unusual event in itself but I thought such a development would be impossible at this time of the year. It may just be a a quirk of the cryosphere system but I'd be interested to hear anyones views.

Thanks for the welcome, I look forward to future discussions across the MB.

I'm fairly new to the MB and there are undoubtedly many on here who are more knowledgeable than me but I would like to 'chip in' on this one if it's ok. The ensembles will never give you any degree of accuracy as they are positively and negatively weighted to varying degrees, so there is bound to be scatter in FI. It's like driving your car in a straight line and then doing it again but turning the steering wheel slightly, after 10 meters the car will be in pretty much the same position as before after 100 meters your position will be considerably different and it's the same with the ensembles The object of the ensembles is firstly to be indicative of the accuracy of the control run. If there is a wide scatter from the start, it means that confidence in that particular run is low, alternatively if there is a wide correlation in the ensembles the chances of the control run synoptics coming off are more likely. Secondly the ensembles do help identify trends. If you look in FI during the summer and you note that one of the ensembles is out on its own predicting 18C at 850hpa. You would normally dismiss this as an outlier and rightly so, however the following day two members are taking the same route and the next day three members etc. How many times have we seen patterns like this evolve over the summer for heat and for winter cold. If anything there is nothing wrong with the ensembles, it's us as human beings who need to improve our ability to read them both mathematically and visually. As for predicting our weather with 75% accuracy, it depends how strictly you set your targets and measure results. I could predict the next 10 winter CET’s to be between 2.5C and 5.5C and be confident of meeting the 75% success rate! Without wanting to sound flippant I'm just emphasising how such a target would be difficult to measure or quantify. The beauty of meteorology is that it's an evolving science. Whereas Maths and Physics are right/wrong, black/white etc, meteorology will never be that. We will continue to improve in our quest for better accuracy and to do this we need ensembles, LRF's, alternative theories etc. It's easy to dismiss something because it doesn't sound right at the time (i.e the world is round etc) but we need to keep our minds open. Apologies if I've waffled on, I think I need a drink now! Regards Adrian