Final Summer Update:
Summer final forecast:
Welcome to the final summer forecast for 2020. Within this forecast will be seasonal model data along with the usual teleconnections and also our own forecast charts which we compile using historical data.
To start with and as many will know we are now in solar minimum and recently these have caused poor summers with low pressure becoming dominant through the summer. I’m sure we all remember the summers of 2007/08/09 very vividly.
Current thinking is we are not in a similar vein to those summers however that scenario certainly isn’t ruled out either at this moment in time.
Sea surface temperatures across the central pacific are set to be in a negative phase through our summer period so a cooler outlook across this area but a La Nina event isn’t thought to be a key factor in this forecast. It may have impacts for winter though which we will update on later in the year.
Sea surface temperatures across the N Atlantic are of more interest however with a cold pooling quite visible south of Greenland and stretching across from eastern USA to the UK.
This feature is thought to promote high pressure development in this area (west of the UK) with low pressure developing further south. This may be one serious driver of our weather through the summer period and will need monitoring frequently.
The QBO (Quasi-Biennial Oscillation) are stratospheric winds above the Equator with run in an easterly and westerly direction. A westerly phase can enhance our westerly flow across the Atlantic while an easterly flow can weaken or lessen the westerly flow.
Currently the QBO is in a weak easterly phase with a view to some strengthening through summer which may help in the amplifying of the jet stream which will already be on notice as low solar activity is also another factor of an amplified jet.
Seasonal models combined on the latest update are very firm on higher than normal heights across much of western Europe running into central Europe with lower than normal heights across south eastern parts of Europe. This would indicate a drier than normal summer across the UK and much of Europe with temperatures above normal as a result.
Our historical data uses a range of variables that we research intensively and recently our data has now included very dry periods of weather between April and May and we’ve included this alongside our usual forecasting system.
Below you see the 3 monthly pattern we are expecting and while this won’t tell the whole story it will give you a general idea of the pattern but don’t worry I will break down the 3 months.
Our data suggests that high pressure will be higher than normal across the north Atlantic than is normally the case. This will be due to an amplified (wavy like) jet stream and at times areas of high pressure will drift over to Scandinavia.
This will bring its own problems across the south or central and southern parts of the UK as cut off lows may bring the risk of heavy downpours from time to time.
The pattern in June is expected to be mostly drier than normal for most but perhaps on the cooler side from time to time as high pressure tends to linger to the west of the UK. This will open the door for northerly shots or even easterly shots and while this pattern may bring some rain at times, it’s not what you’d normally get from the west, thus, a drier than normal outlook is expected.
July is the month that may bring the thunder so to speak. Our data suggest a dominant trough over the UK which may bring thundery downpours to some areas with developing waves and lows more likely through this month than June according to the data. So with this in mind we may see a wetter than normal period of weather although it’s entirely possible some areas may not with local variations in rainfall through summer not uncommon.
Our data suggest August could well be the driest month of the three but still looks very blocked so again N/NE/E’ly flows look more likely here with low pressure development further south across France and Spain. This will open the door again for the south to see the potential for downpours from time to time but overall the majority of the UK may well be dry, in particular across the west.
So in summary using all the variables and forecasts mentioned the overriding signal coming through is for a rather amplified flow across the N Atlantic. What side we fall on will be important as to what weather we see.
Our historical data is suggestive of high pressure west or north/north east of the UK while the seasonal models disagree. However without going into too much detail the seasonal models are not in agreement on the overall pattern, some with varying solutions and as such can’t be used heavily.
There are some caveats to the forecast though, as there always is. Having such a dry spring normally doesn’t bode well for a “good summer” as periods of 4 to 6 months of dry weather across the UK don’t come around very often. This would favour our outlook as opposed to the seasonal models.
Furthermore NOAA (National Oceanic and Atmospheric Administration) in America along with a few private weather companies have issued a very active hurricane season.
Although we are not directly impacted by these hurricanes they can and do alter weather pattern, especially major hurricanes. So for all the above information and forecasts given, it could be totally scuppered by the development of these hurricanes. That being said we only expect impacts from these during late summer and to be honest could favour both dry and wet weather depending on where they develop and head to.
So in essence a think a mixed summer overall is the call but northern blocking will be a big feature in my eyes which should block any poor weather via westerly patterns but I’m not saying the summer will be very dry either, I’m sure we will get our fair share of rain too, most likely in July and most likely from thundery developments than sweeping low pressure systems from the west.
With blocking you can get warm and cool weather as the wavy jet passes through but overall given the warmer climate at the moment, warmer than average temperatures will be more likely than not I’d think.
Second Summer 2020 Update:
Here is our second Summer update of the week and today we are looking at ENSO which are temperatures in the tropical Pacific which do influence global weather patterns.
This region is where El Nino and La Nina develop and a strong event of either of these can change weather patterns quite severely. For example a strong El Nino has links to a stormy pattern here in the UK during late Autumn into early Winter.
Looking at the latest data and we are currently neutral positive (below the 0.5 threshold for El Nino) and the trend going through summer is to remain neutral but a slight shift to negative values is the trend, with a possible La Nina later in the year although that is far from certain as yet.
So again using historical data I have collated all the years with similar set ups and the results can be found below. Incredibly the results are very similar to the chart from the QBO data yesterday. Like that chart this one hints a low pressure to our north/north-east and this charts hints further at ridging in the Atlantic both of which mean a likely north-west flow across the country.
This by no means is suggestive of a washout, north-west flow can be dry patterns, especially for the east/south-east but the general feel will be cooler. So 2 lots of data which practically hint at the same flow across the UK through Summer. This brings a touch of confidence in the forecast but this is just 2 pieces of a very large jigsaw. Tomorrows update looks a solar output which will be surprising, make sure not miss that!!!
First Summer 2020 Update:
First update looks at the QBO (Quasi-Biennial Oscillation) which are stratospheric winds around the equator. There are 2 phases, a positive phase and a negative phase.
In a strong positive phase this can enhance the westerly flow across the North Atlantic. Equally a strong negative can lessen the westerly flow and allow more blocking to develop. Currently we have just flipped to an easterly QBO so by summer we can expect a weak to moderate E’ly QBO.
What will this mean for summer? Well obviously there are other factors to consider so please bear that in mind and we will be looking at these through the week but using the QBO alone looking back to 1948, then the odds favour low pressure our N/NE with some form of NW’ly flow across the UK.The anomaly chart below at 500mb also hints although not strongly of some form of ridging (high pressure) across the N Atlantic which is what we are seeing at the moment.
A cool and changeable summer would be the call on that pattern but of course there are other factors at play. Make sure you check in tomorrow where will be looking at ENSO which are sea surface temperatures across the tropical Pacific.