summer blizzard

No 20C here as yet, not especially late though. Hopefully a signal.

24APR2024: Nino3: 0.6, Nino3.4: 0.8, Nino4: 0.9 April ONI is +0.9.

Suspect the model differences relate to the progression of convection through the Pacific. Although I don't have the Euro chart, the GFS has weakened this a lot in recent days though it is still progressing.

WYorksWeather I'd be pretty dubious of that and suggest it's likely noise rather than signal. That is to say that years with a late final warming and stronger than average vortex may be followed by a +AO but the forner is not likely the cause. I don't really see much reason why slightly weaker net easterlies in the stratosphere would result in westerlies further down the troposphere. They are still trying to impinge net easterlies on the troposphere.

Addicks Fan 1981 Posted earlier in this thread but essentially the La Nina's that are not declared by JJA on ONI tend to be relatively blocked with the Azores High close to the UK. 2016 was in that group. La Nina's which go guns blazing tend to have a cyclonic July and August and end up stronger on average. Currently we are marginally on course to be in the slower group (dropping around 0.3 per month).

SqueakheartLW An above average season is very likely but shear profiles make or break ACE and that might not be extremely high this season. While we have the weak La Niña strengthening (likely) and warm SST’s, we also have a very negative PDO and for some reason this has in some seasons been correlated with an imperfect shear profile.

reef I suspect that the SSW impact is producing the blocking episodes given that the tropics have been fairly muted but SSW’s dont guarantee everlasting north blocking and cool weather here. In this case it’s just produced downwelling periods of weaker zonal winds that we’ve occasionally tapped into. With the tropics becoming active again in the west Pacific, I’d imagine we will lose any northern blocking into early to mid May.

12.4, 54mm. For the first time in some time, i see an anticyclonic pattern. Blocking over the UK and to the north and east. Shades of last May.

Something to watch but signs of a WWB progressing east into May which may generate mid-lattitude blocking closer to mid month.

17APR2024: Nino3: 0.5, Nino3.4: 0.7, Nino4: 0.8

B87 Strong trades around the dateline (easterlies) typically strengthen the mid-lattitude jet in response (stronger westerlies) and suppress AAM. It's why a lot of people tend to think that La Nina produces less favourable summers for the UK.

Anecdotal but for a lot of recent developing La Nina's, it's July that the trades in the Pacific suddenly pop up raging. Probably related to the timing of the monsoon season or something creating a downstream wavelength that can be amplified.

SqueakheartLW Current warmth is surface level and looks likely to be replaced.

Without defining what we consider dissapointing we can't really say. A lot of these type of questions are anecdotal and depend on subjective assessment. If we look at 2013, 2018 and 2022 as producing the 'proper summers' then actually spring 2013 was persistently poor, spring 2018 was essentially a flip and spring 2022 was mild and dry but i had to look it up which suggests the weather experienced was somewhat forgettable. What we know of March and April is that they will both come in fairly warm and wet so a more objective assessment would be to look at comparable years. March above 7.7C and April above 9C yields... 2022 2019 2017 2014 1997 1961 1948 1945 1779 1734 March and April above 100m yields.. 2001 1818 When we take out subjective anecdotal evidence, those are our best matches.

10APR2024: Nino3: 0.6, Nino3.4: 0.9, Nino4: 0.7

Is this hail or is this snow because it looks and feels like snow.

Sun Chaser Sadly I think its easier this time of year. April 09 was a cloudy and humid month here. March 17 and 24 were both unexceptionable. All have very warm CET's such that people probably won't question them in a few decades. July 22 is another example, for Yorkshire and Manchester barely more than a 2 day wonder.

In our hunt for an anticyclone it's worth saying that the Euro0z had 1020mb+ over the whole UK from days 7-10.

Before anybody gets overly excited it's worth remembering that the AO values are normally close to neutral in summer and that +/-1 months are rare. The polar vortex is net easterly regardless of what happens until late August.

Summer8906 I would hesitate to put 2022 on that list. The others produced nationwide summers, while by the time your as far north as even Leeds and Manchester, July 2022 was mediocre outside a handful of days. The two week spell was restricted to the south unlike the others. August 2022 was worthy of course but an individual month.

May 2020 was delightful and the trees here in full leaf.

03APR2024: Nino3: 1.0, Nino3.4: 1.2, Nino4: 0.9

raz.org.rain Sub-surface anomalies are pretty nuts currently so as soon as they surface we are going to see a stonking fall. We are likely go beyond -0.5 between July and September based on pacing from 1954, 2007 and 2010 which are good matches overall (a little ahead generally). 1959, 1966, 1984, 1993, 1998, 2003, 2016 and 2020 finished Q2 neutral after Nino events finished. 1998, 2016 and 2020 did move to La Nina by the end of Q3.

I think that any comparisons with 2007 thus far are likely to be coincidental (and not really true in weather type). In 2007 the Nino collapsed after January and SST's were already negative by April. In Feb-April the low -AAM suggested by the collapsing SST's (strong trades and possible atmospheric coupling) actually does tend to produce a somewhat anticyclonic response (for reasons beyond me). Our Nino is still hanging on with a WWB progressing over the next week or two likely to mean that our first collapse attempt won't occur until at least May (although sub-surface SST's are -5).

B87 A lot of synoptics from April 21 would result in a different temperature profile. April was still early enough that a slight inversion was present. The 1st-4th would likely feature a high durinal range and temperatures close to average. The 5th-12th would be quite cool but potentially damp with a stronger sun to spark showers. The 13th-19th would feature a west-east split but generally products temperatures close to or above average. The 20th-26th would draw mostly south easterlies and be warm. The 27th-30th would be cool and damp or even wet. So the first 12 days may be on the cool side but the 13th-26th would be warmer than average securing a warm month.