A mostly quiet and dry autumn on the way?

I don’t usually bother trying to forecast autumn or spring given that there is far less interest in them than winter and summer. However, given the heightened interest in this year’s hurricane season and emboldened, perhaps foolishly, by my reasonably correct summer forecast I decided to have a look at the stats and see if I can find any signs where autumn in east London may be headed.

Using the methsummer simsod for my seasonal forecasts resulted in a shortlist of 26 summers that were similar to 2016.

Because the NOAA ENSO index only goes back to the 1950 I decided to disregard all years prior to this date to try to make any results more reliable. This narrowed down the list to 11 years.

With these considered I then searched for years that had a similar ENSO index to June (0.1 – neutral) with a tendency to turn negative (La Nina). This narrowed the field further to three years: 1999, 1992 and 1964. However, the only year that is showing signs of being similar with regard to where the ENSO index is forecast to be heading is 1964.

Although, so far, there has been an uptick in hurricane activity similar to 1964 there is, of course, the added consideration that Saharan dust is playing a part in impeding the formation of these tropical storms in the Gulf of Mexico – something the weather models seem to struggle to get a grip on.

With this in mind perhaps there will also be lower than usual instances of these storms crossing the Atlantic to affect the UK: hence a quiet autumn though, on a national scale, interpersed with the odd interest from the Atlantic. weather notes 1964In London, perhaps we can expect something very similar to what is listed on the excellent website: http://www.london-weather.eu/article.103.html

autumn 1964

 

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Summer 2016 review

Summer 2016 turned out to be a very decent season overall, the mean temperature of 18.7C (1.1C above average) made it the sixth warmest summer since 1797.summertop20

While it wasn’t quite up there with the hot summers of 1976 and 2003 it still produced some notable records. The stormy beginning to June effectively ended with the Brexit vote, a period of 24 hours that coincided with the highest daily rainfall this area has seen since at least 1959.

The multi-cell thunderstorm in the early hours of June 23rd produced 60.8mm of rainfall, nearly half of the month’s total which became the third wettest June in a record going back to 1797. The high rainfall was in complete contrast to July and August and helped skew the overall figure: 168.6mm is 114 per cent over average summer rainfall.

sunWith so much rainfall overall sunshine was affected with only 451 hours recorded, just 80 per cent of what can be expected in an average summer.

July produced another record, this time the highest overnight minimum recorded since 1959. The minimum of 21.1C was recorded during the early hours of the 20th – coming hours after the hottest day of the year: 33.5C – the 14th hottest day on record.

The warm and very dry theme continued into the final month of summer with the warmest August for 12 years, the 10th warmest and 12th driest since 1797.

My summer forecast, when the monthly probabilities are considered, was broadly correct though I didn’t estimate correctly just how warm it would be.

Mean forecast: 16.7C (outcome 18.7C)
Rainfall forecast: 166mm (outcome 168.6mm)
Sunshine forecast: 546hrs (451.4hrs)

summer2016mean

summer 2016 rain

summer 2016 sun

 

 

August 2016: warm and very dry

Though there were no records broken August 2016 goes down as a mighty fine summer month, the warmest for 12 years. The mean of 19.5C was 1.3C warmer than average and only 0.1C cooler than 2004.

wanstead park
Grasslands around Wanstead Park have gradually turned brown because of the lack of rainfall

The month ended a three-year run of poor or so-so Augusts: in terms of mean temperature the month was the 10th warmest in a local series going back to 1797.

It was another very dry month: just 11.9mm fell, 24 per cent of average, the driest August since 2003 and the 12th driest in the local record.

The month only falls down in terms of impressiveness when sunshine hours are considered. Some 192 hours were recorded, the 59th sunniest since 1797 – 1995 had 80hrs more sun.

Air frosts: 0, Ground frosts: 0

So what has September got in store weatherwise? The models on the 1st suggest the month will start mixed, though any precipitation will be below average. Temperatures remaining on the warm side.

warmest augustsBeyond the grasp of the models my long range outlook method is again hampered by a very dry August. However, the data I do have suggests an average month at 100 per cent probability.

A wetter than average month looks most likely at 75% probability.

The rainfall probability makes me wonder whether we are in for a very unsettled second half of September, the Atlantic cranking into life with the remnants of tropical storms and hurricanes having an ever-increasing influence as the month progresses.

So to sum up: mean 15.3C (average), rainfall 162mm (300%), sunshine 140 hours (100%).

driest augustMy August outlook for temperature was good. I predicted a mean of 19C (outcome: 19.5C). It was drier than I thought: 30.3mm (outcome: 11.9mm). Sunshine was poor: 239 hours (outcome: 192 hours).

Here follows the full weather diary for August…Full stats for the month here:http://1drv.ms/1rSfT7Y

1st: Cloudy start to 1pm. Rain started at 5pm through to 10pm. A brief interlude before more light to moderate rain through the night 4.30am, then drizzle
2nd: Damp, miserable start – the rain became light to moderate in the early afternoon before drying up – very high dew points through the day.
3rd: Bright and breezy with variable cloud.
4th: Bright start with variable cloud and sunny spells.
5th: Good sunny spells all day – perfect summer’s day, not too much humidity – though an isolated shower passed over at 8pm.
6th: Sunny, clear start. Lots of sunny spells during the day.
7th: Bright start though very breezy. Cloud decreased through the day to leave a gorgeous late afternoon and evening.
8th: Sunny, clear start with lots of fair weather cumulus throughout the day. Cloudier spells mid afternoon.
9th: Sunny with fair weather cumulus up until noon then cloudy afternoon.
10th: Sunny with fair weather cumulus, variable throughout the day. Breezy.
11th: Cloudy start with very brief light rain, barely enough to damp ground. Some sunny intervals later and bright and warm.
12th: Sunny start with a few clouds. Turned gin clear at 11am and stayed clear all day. Feeling hot.
13th: Bright start but turning cloudier. Sunny intervals PM.
14th: Cloudy start breaking to some long sunny spells. Feeling very warm in the sun.
15th: Bright start soon turned sunny with a clearance at 1pm.
16th: Bright start though a lot of haze around. Sunnier later though still hazy.
17th: Sunny with patchy cloud to start, this clearing late morning to leave a clear if rather hazy afternoon.
18th: Sunny if a bit hazy to start, this tending to decrease to leave warm sunshine.
19th: Cloudy with rain threatening. Low cloud at Stansted. Brief rain in afternoon then cloudy.
20th: Dull and overcast at 9am. Burst of heavy rain at 10.15am clearing to sunny spells at noon 30. Rain between 7pm and 8pm and 3am and 4am.
21st: Bright start. Sunny intervals till 3pm then sunny spells.
22nd: Bright after earlier rain at 0719 then sunny spells.
23rd: Clear and sunny start with a few cirrus clouds through the day. Hot.
24th: Sunny, gin clear start. Patchy cirrus through the day. Hot.
25th: Lots of altocumulus and sunny spells but felt sultry due to high dew points.
26th: Cloudy start but gradually decreased to leave clear pm.
27th: Overcast but bright start. Brightness through the day but hazy. Some heavy storms further north.
28th: Overcast until early afternoon, 5 minute shower at 2pm then sunny intervals..
29th: Bright start then sunny spells and cirro cumulus gradually clearing to leave a sunny evening and clear night.
30th: Clear and sunny start.
31st: Bright start though cloud filling in by 3pm, clearing again at 8.30pm