summer blizzard

JAS ONI came in at +1.3. To update our list and ranking. Our updated list for AMJ. 1957: +1.3 1972: +1.4 1976: +0.4 1986: +0.4 2002: +0.9 2009: +0.6 2014: 0.1 2018: 0.2 2023: +1.3 We remain joint second. To update on our ENSO trades index, September weakened a little to -0.3 but remained net westerly. https://www.cpc.ncep.noaa.gov/data/indices/cpac850 To compare to our primary analogue list since 1979 (standardised): 1986: -0.4 2002: -1.0 2009: +0.4 2014: -0.1 2018: -0.7 2023: -0.3 Remember that our analysis last month showed a corellation between how early the event coupled and eventual strength so this may be another sign that the models are OTT (i still lean in the +1.3 to +1.7 range).

04OCT2023: Nino3: 1.9 , Nino3.4: 1.5 , Nino4: 1.2

Actually quite lovely in the sun.

While it is theoretically possible to sustain a perverse outcome of mild southerlies, I don't see the model support for that to sustain as things stand. While subject to change, the two key things by day 9 on the GFS, GEM and Euro are.. 1) They all shift the vortex away from the Atlantic as they ride our block north, eventually they'd dump into Russia. This basically reduces pressure on our block. 2) By day 9, they all have a second low by the Azores putting energy into the southern stream. So long as you don't have weird GFS style fizzle out then it's likely to either undercut or encourage the high to retrogress. Either outcome is good in our bid for surface cold and frosts. So long as the modelling does not change drastically then yes, it would suggest that the Euro weeklies were right for week 2.

We are forecast 3C on Sunday morning which could be interesting.

Very similar to the GEM evolution but a day or two slower. We'd likely see the hight hold out since it's fairly far north and linked (no path over for the low) which would hopefully see the low attempt more of an undercut.

I think it had a handful of unexceptional events. I recall Boxing Day producing via a secondary low and something in February which was probably the same event.

GEM would be pretty fantastic if it were January. Atlantic is being pulverised. Days 8 and 10.

Did not expect to say this because it normally is wrong but I think the Euro weeklies and Met Office are onto a winner. We are about to couple in just about the best position tropically for a +PNA/-AO pattern. Blocking to the north and east likely in the final third though we should beware.. - +PNA over warm SST's could just juice the jet - Always a risk of west based -NAO response - Blocking centered to north and east can always sag and we can still draw warm uppers.

Do we have the January and February and March charts.

Essentially it just depends where you set the bar. Winter 09/10 was cold throughout and the coldest winter in 31 years with a sub-zero mid Dec to mid-Jan period. Equally though, Dec 10 and Jan 13 were exceptional. More recently, Dec 22 was the coldest since 2010 and the first half was the 12th coldest on record. Jan 21 had the first half of January the coldest since 2010. The second half the coldest since 2013. The first half of February 21 was the coldest since 2012.

The question is essentially how you define cold winter's. 05/06, 08/09 and 12/13 were all cool.

While it did feature a persistent +AO, it did feature high pressure either west or at mid-lattitudes which meant that while the hemispheric pattern was very different, our experience was basically a poor man's versions of winter 06. Weak north westerlies or blocking until quite late on. We did get a pretty zonal spell around early January though.

It did propagate to be fair (or the second burst did) but it was just quite late on. It was also not really a strong thumb but rather a succession of hits from late Jan, that just happened to cross the line. That's probably why it was not the best propogator.

It has got some very anomalous months correct but has gotten a tonne of inconspicuous months wrong. That suggests there might be a signal that very hot/cold months out that it can detect but broad patterns it's still pretty poor with.

Jan 21 had a CET of 3.1C and the first half of February was the coldest since 2012. Apparently, not all areas got much snow though.

Interesting. Produced the highest number of attempted (mostly frontal) snow events since 2013 here (albeit no significant depths).

You were not a fan of winter 21?

Do they produce 200hpa vorcity charts for the seasonals, that would indicate if things have changed radically in the Indian Ocean.

My early analysis pointed towards you potentially having a colder and snowier December and March but probably being largely mild and dry through January and February (of course, I imagine in your part of the world that's minima around 0C rather than -20C).

While a high amplitude IOD is not good, it's not currently functioning in the same way. In 2019 we were basically in a +IOD event that gave the east Pacific enough scraps to be near El Nino, this meant that we saw persistent convection through Autumn in the Indian Ocean. (Sadly i only posted one of these charts once in the Nino thread that Autumn) Basically the reality was that waves started strong in the Indian Ocean and then got a bit weaker than that forecast as they progressed. Contrast that to this Autumn where even if the Nino is fighting the PDO and Nina legacy (struggling to couple strongly), it is a Nino driven pattern and the Indian Ocean is dead (the IOD is producing convection but well west of 2019, over Africa). Dominant forcing here is over the west Pacific rather than Indian Ocean. .. We probably still have to worry about the IOD but its clear that the forcing is being driven elsewhere this time.

The strongest coorrelation is week 4 of September through week 3 of October.

Euro takes until Thursday to push the cold front through. GEM is the same to complete. GFS is pretty messy, dumping the very warm uppers early but never completing. - The complicating feature for the models is a small low that forms over the weekend and moves a dead cold front south. It pushes the proper warmth near the south coast where it then festers a few days. You can see its impact on the airmass above despite warm uppers hanging around.

I don't believe it was forecast but there was snow on the ground as i was leaving for Middle School. FAX charts suggest the 31st as i recall a storm a day or two previously and they show a north westerly afterwards (a mighty secondary low - it was the thing without a number undernearth 972mb). Strengthens from about 1004mb to 976mb as it approaches Ireland. Then it merges into the wider cyclonic complex. But yeah, as it passed through on the morning of the 31st it must have produced.

For the UK it was basically an average December and January and mild February before a cold March. Applying an extra degree for climate change and it would be a fairly poor winter and then perhaps a SSW causing spring cold.