Category Archives: Weather

Forecast, month ahead forecast, Monthly Review, monthly summary, Weather

May 2016: rather mild with average rain

June 2, 2016 wansteadmeteo 1 Comment

A stunning first week of weather in May 2016 probably led a few people into believing that we were in for a glorious start to the summer. But the second Sunday in the month when temperatures reached 27.1C under 13 hours of sunshine was about as good as it got.

view — May 10th 2016 looking toward Crown Hill from Dunton in Essex

The warm first week helped maintain the mean temperature to finish above average: 14.3 which is 1.2C warmer than average, the warmest May for five years.

Though on paper rainfall looked a little under average 44 per cent of the monthly total fell on the last day. Some 43.4mm fell during the course of the month, that’s 85% of what we can expect during a normal May.

Sunshine was about average. Some 184.5 hours were were recorded, 101% of what we can expect to see during an average May.

The wettest day occurred during the meteorological 24hrs of the 30th (09-09 31st) with 14.7mm, rain associated with a depression in the North Sea. Incessant cloud held temperatures down to 12.6C, the coldest May 31st for 36 years!

A conveyor belt of rain brought the coldest May 31st for 36 years

Air frosts: 0, Ground frosts: 5

So what has June got in store weatherwise? The models on the 1st suggest only slow changes in the next 3-4 days. These changes revolve around the release of low pressure from Europe towards high pressure later next week. This process begins as high pressure also begins to build down from the north at the weekend with several days of fine and increasingly warm conditions as the cool NE’ly flow is lost to warmer winds from the SE or south. Then next week with higher pressure over Europe and low pressure drifting slowly north or NE towards the west of the UK it could become very warm and humid in places and as that low to the west pushes troughs towards us from the SW it could feed some thundery rain and storms up from the SW at some stage by midweek. The pattern thereafter appears quite mixed. GFS suggests a more traditional pattern of low pressure to the NW and higher pressure to the SE with SW bringing rain at times to the north and west while the south and east see the best of prolonged dry and warm periods between intermittent rain.

Beyond the grasp of the models my long range outlook method suggests an average to rather mild month. The highest probability is 29% for something a little above average and rather mild. A little below average and mild both come in at 14% probability. Something cool or very cool comes in at 7%. If you combine the first two probabilities together something just over average would come in at 58%

A dryer than average month looks most likely at 57% probability. Sunshine probably about average.

So to sum up: mean 16.9C (0.8C above average), rainfall 38mm, sunshine 178 hours.

My May outlook for temperature was poor. I predicted a mean of 12.8C (outcome: 14.3C). Rainfall was also poor: 58mm (outcome: 43mm). Sunshine was good: 184.5 hours (outcome: 179 hours).

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

1st: Sunny start though with cirro cumulus around. Cloud tended to thicken up through the day to leave overcast late afternoon. A warm night followed.
2nd: Cloudy with spits and spots of rain to start. Some bright spells late morning but then overcast and some rain at 6.40pm – a decaying front gave little rain. Clearing overnight and cold.
3rd: Sunny with fair weather cumulus developing.
4th: Sunny, gin clear start with just a few fair weather cumulus developing. Clear and cold overnight.
5th: Sunny and warm, some hazy cloud in the afternoon.
6th: Sunny start though turned much more hazy than yesterday. Feeling humid.
7th: Hazy sunshine to start with high level strato-cumulus bringing cloudier periods.
8th Sunny start with just a few clouds. Air much clearer than yesterday and hot by mid afternoon on Canary Wharf.
9th: Cloudy start but became sunny late morning. Rain arrived 5pm, turning moderate 7.30pm and outbreaks through the night.
10th: Light rain to start, this turning moderate at times throughout the day, though petering out at 2.30pm.
11th: Dull, damp start that went into 11am. Heavy showers developing that lasted until late afternoon.
12th: Sunny start though with a fair bit of cirro cumulus floating around. Feeling very warm.
13th: Sunny start with spotted cirro cumulus. A pleasant day.
14th: Bright start with sunny spells into the morning. Cold wind took edge off sunshine.
15th: Sunny and cool with a cool breeze.
16th: Sunny start but quickly clouded over. Bright spells into the afternoon.
17th: Sunny start but cloud soon filled in. Sunny periods around lunchtime before more cloud arrived.
18th: Cloudy start after recent light rain. Bursts of rain at 11.20am, turning heavy at 12.30pm. Some more rain at midnight.
19th: Cloudy with brief sunny intervals before noon. Then cloudy.
20th: A Cloudy and breezy day. Feeling humid.
21st: Cloudy and breezy through the day though mild. Brief shower at 6pm while driving back from Broadstairs.
22nd: Sunny start though cloud increased during the day to fill in by 2.30pm. Showers, one moderate, from 6pm.
23rd: Sunny start but lots of cloud bubbled up. A lot of threatening cloud to west and east with funnel cloud spotted over Leighton Buzzard. https://twitter.com/Chxrlie_Mxrch/status/734818236211068930 Cleared overnight to leave cold night.
24th: Sunny start quickly clouded over by 11am, then just sunny intervals
25th: Cloudy and cool all day thanks to HP bringing drift off North Sea.
26th: Sunny start with sunny spells though the day
27th: Cloudy start though with sunny spells developing at lunchtime and a clearance around 1pm – 2pm. More convective cloud bubbled up however, to leave a humid evening. Rain developing at 7am.
28th: Cloudy, damp start though with a little brightness at 11am. Some sunny intervals in the afternoon though much cloud.
29th: Cloudy and cool start. Hazy sunny spells in early afternoon, though still much cloud around.
30th: Cloudy with just two sunny intervals that momentarily lifted the temperature. Rain started at 7.30am and was heavy at times up to obs time. Elderly man killed on crossing, possibly due to the bad weather
31st: Rain to start. Outbreaks lasted up until 1315z then stayed cloudy, damp and chilly into the evening and night.

Forecast, month ahead forecast, Monthly Review, Weather

April 2016: rather cold and thundery

May 1, 2016 wansteadmeteo 3 Comments

April 2016 has seen more occurrences of thunder than we can expect during a typical July.

radar hail — About an inch of hail collected on borders in gardens in Plaistow during a thunderstorm on 29th. This stuck around for over an hour thanks to the low humidity

A persistent flow of unstable Polar maritime air, coupled together with strong sunshine, provided the perfect ingredients for some really beefy showers.

The mean temperature of 9C was 0.8C cooler than average, the coldest April for three years and in stark contrast to the previous two Aprils that were mild and very dry. Air frost, notable for its absence in the previous two Aprils, returned with four incidences where the temperature dipped below freezing

Apart from a dry slot in the third week rainfall was fairly steady: 52.5mm is 124% of average for this area. It was the wettest April for four years.

bracka20160415 — A depression on 15th led to the wettest 24hrs of April

Sunshine was just below average. Over 153 hours were recorded, 96% of what we can expect to see during an average April.

The wettest day occurred on the 15th with 15.9mm, rain associated with a depression that ran along the Channel coast out into the North Sea, a system that heralded the colder pattern that defined the rest of the month.

Air frosts: 4, Ground frosts: 12

So what has May got in store weatherwise? The models on the 1st suggest that rather warmer weather will develop as we finally lose the northerly-sourced airflow and low pressure across the UK.

hail radar — The radar on 29th shows a thunderstorm right over Plaistow to the south of Wanstead

Low pressure to the NW will become influential with strong and milder WSW winds driving wind and rain bearing fronts east and SE across the UK late on Sunday and Monday. A bright and brisk NWly flow with sunshine and showers then looks likely to be replaced by a ridge of high pressure and drier weather. It will begin to feel quite warm in any sunshine across the south from midweek.

Beyond that the outlook is uncertain though it appears warmer, if changeable, conditions will prevail.

Beyond the grasp of the models my long range outlook method has conflicting signals. The highest probability is 32% for something rather cool. Average is 28% while rather mild comes in at 20% probability. Something cool comes in at 12%, while mild is 8% probability. Both cool and very mild have a probability of just 4%.

A wetter than average month looks most likely at 48% probability. Sunshine probably about average.

So to sum up: Mean: 12.8C (0.2C below average), rainfall 58mm, sunshine 179 hours.

My April outlook for temperature was good. I predicted a mean of 9.2C (outcome: 9C). Rainfall was also good: 57mm (outcome: 52.5mm). Sunshine also good: 149 hours (outcome: 153.9 hours).

Here follows the full weather diary for April. To view full stats follow this link:http://1drv.ms/1kiTuzv

1st: Sunny start though lots of haze around from late morning.
2nd: Sunny until 2pm before cloud then light rain spread in – this lasting into the evening.
3rd: Sunny start with hazy cumulus building through the day.
4th: Bright start though lots of cloud around. Some gin clear spells of sunshine.
5th: Sunny start though with variable cloud through the morning.
6th: Drizzly start, giving way to sunny spells and showers.
7th: Cloudy after recent light rain. Windy and cold. Some heavy showers mid to late afternooon with flash of lightning and thunder at 4pm and hail >5mm.
8th: Bright start though with much cloud around. Some brief sunny spells and v light showers.
9th: Cloudy, damp start after morning rain. This broke to sunny spells at 1pm ish. Cloudy again later but clearing at dusk to allow a frosty night.
10th: Sunny start but soon turned hazy with keen, cold SE wind building through the day.
11th: Cloudy start but brief brightness early afternoon. Rain at 2.15pm – this lasted until 5pm. More rain in the early hours, heaviest just before 5am.
12th: Bright start though hazy with lots of cirruo stratus. Clear and cold overnight.
13th Glorious sunny start and warm in the sunshine. Some patchy cloud at times. More cloud bubbled up late afternoon with a shower at 8pm and midnight. Clear and cold overnight.
14th: Sunny start though with much more cloud at times to 2pm. Showery rain in the evening lasted through the night.
15th: Cloudy with rain at 9.45am until 10.15 then turned a bit brighter before cloudy again at 11.45am. Rain set in at 12.30pm with thunder at 1.07pm then rain on and off into the evening. Clearing overnight and cold.
16th: Cloudy and cold start. Stayed cloudy all day with brief light rain shower. Cold and frosty overnight.
17th: Sunny, gin clear start with cloud gradually bubbling up. Sunny periods throughout the day.
18th: Sunny start with cumulus bubbling up.
19th: Mostly sunny start but then turned very cloudy. This cloud cleared just before noon.
20th: Sunny, clear start with just a few cirrocumulus drifting around during the day. Cold wind.
21st: Bright start but much cloud around. Some spells of hazy sun through the afternoon.
22nd: Cloudy, cold feeling start. Rain by 5pm, this heavier than expected. Next day dawned clear but cloud soon bubbled up.
23rd: Sunny start, cloud bubbled up with a shower at 12.25pm, clearing by 1pm. Early rain on 24th before obs time.
24th: Bright start, cloud bubbled up with light shower at midnight.
25th: Cloudy, cold start with lots of Arctic cumulus. Showers soon arrived that were mostly sharp but brief and heavier in the east. These cleared to leave a cold, breezy night.
26th: Sunny start but cloud quickly bubbled up. Some heavy showers of soft hail with odd snow flake. Thunder at 2.45pm.
27th: Sunny start though cloud quickly started building with snow and soft hail at 12.30pm. Further showers at 1712 and 2330. Clear, cold and frosty overnight.
28th: Sunny and mostly clear up until 12 noon.
29th: Sunny start though cloud quickly bubbled up. Some very heavy hail in Plaistow with an accumulation of one inch – this hung around for a while due to the low dew point and low humidity – less in Wanstead. Thunder and lightning too.
30th: Sunny, clear start though cloud began to bubble up. Felt cold in the wind as it became overcast last afternoon. Cleared overnight to give frost.

Another superb display of bluebells burst into life in Chalet Wood, Wanstead Park, this month

Forecast, month ahead forecast, Monthly Review, Weather

March 2016: cool and wet

April 3, 2016 wansteadmeteo 3 Comments

With the meteorological winter over the first month of spring saw the weather return to its modern type: cooler than average just when most people are looking for warmth.

squalllengthofuk — The squall of March 26th ran the length of England

The mean temperature of 6.7C was 1C cooler than average, the coldest March for three years and the first month more than 1C below average since last September.

The wet end to the month tipped the rainfall statistic well above average: 60.3mm is 148% of average for this area. It was the wettest March for eight years, notable because of a 14-day dry spell during the middle part of the month.

Sunshine was just above average. Over 116 hours were recorded, 107% of what we can expect to see during an average March.

The wettest day occurred on the 27th with 14.4mm, rain associated with blustery weather fronts from Storm Katie.

Air frosts: 7, Ground frosts: 14

So what has April got in store weatherwise? April is often a month when we can see huge swings in the weather from day to day as the natural warming of the atmosphere competes with the decaying coldness of northern latitudes.

squallonsynop — The squall of March 26th ran the length of England

This often results in big showers and vast temperature differences not only day to day but between night and day too. All of the above is going to be on offer over the coming few weeks if the model output on the 1st is correct. A warmer phase will begin the month as winds switch southerly, drawing warmth from Spain. However, with low pressure close big showers and outbreaks of rain should be expected. Then as the low switches to the NE of the UK the door opens next week for colder NW winds with further rain or showers and chillier air. A lot of output strengthens this northern sourced air through the second week and with low pressure never looking likely to be far from the UK we will be looking at lots of showers and spells of rain.

Beyond the grasp of the models my long range outlook method suggests the April mean will be average or just below at 60% probability. Rather cold comes in at 20% while cold has a probability of 20%. There appears no chance of something mild.

squall26032016 — The squall of March 26th ran the length of England

A wetter than average month looks most likely at 40% probability. Sunshine probably about average.

So to sum up: Mean: 9.2C, rainfall 57mm, sunshine 149 hours.

My March outlook for temperature was good. I predicted a mean of 5.9C (outcome: 6.7C). Rainfall was way off: 31.6mm (outcome: 60.3mm). Sunshine also out: 68 hours(outcome: 116 hours).

Here follows the full weather diary for March. To view full stats follow this link:http://1drv.ms/1kiTuzv

1st: Drizzly start turned to steady rain at 10am – this lasting past lunchtime but drying up to leave a cloudy afternoon. Very sharp squall blew threw at 2am with brief intense rainfall.
2nd: Bright start but soon turned very blustery and showery. Brighter after 3pm but cold as dew point fell away.
3rd: Sunny, cold start. Cloud bubbling up late morning.
4th: Sunny, gin clear start. Cloud bubbled up through the day. Clearing in the evening to leave a very cold early hours. Light rain moving in at obs time.
5th: Cloudy start with small area of rain around 10pm. Brief brightness at noon before more light rain moved in. Clearance again at 3.30pm. Small hail <5mm at 5pm. Clear spells overnight.

squallfall6c — The squall of March 26th ran the length of England

6th: Sunny, cold start. Coud bubbling up late morning.
7th: Sunny, cold start with light winds. Variable cloud but feeling cold, especially so overnight.
8th: Cloudy, calm and cold start.
9th: Very light drizzle am before briefly brightening up. Heavier rain pushed in between noon and 2pm. More rain at intermittent periods into the evening.
10th: Cloudy until 2pm. Cleared at dusk to leave a frosty, cold night with thick fog patches on Centre Road.
11th: Sunny start with early mist clearing. Variable cloud through the day. Clear spells up to midnight but then tending to cloud over.
12th: Cloudy start tending to brighten up though sunshine remained mostly wintry.
13th: Cloudy start quickly cleared to leave sunny morning. Pleasant until a keen N’ly wind set in.
14th: Bright start with cloud quickly breaking, cold wind.
15th: Cloudy and dull start. Mostly cloudy through the day.
16th: Bright start but cloud filling in by 10am. Mostly cloudy all day
17th: Sunny and clear until 11am – patchy cirrus thereafter.
18th: Cloudy, cool start – the cloud lasting past 12 noon.
19th: Cloudy start – very brief drizzle. Brief brightness just before 10am then cloudy.
20th: Cloudy start brief sunshine at 10am-ish before cloud spilled across. Another clearance at 11am before cloud returned for afternoon.
21st: Cloudy until brief sunny spells at 10.30am. Much milder for a time before a mostly cloudy afternoon.
22nd: Mostly sunny all day with just a few cumulus.
23rd: Cloudy all day
24th: Cloudy, chilly start. Rain spread in by 1pm and turned heavier in the evening, clearing around 3am to showers. Sunny dawn.
25th: Sunny start with just patchy cumulus
26th: Cloudy with intermittent light drizzle. Very heavy squall at 6pm brought 5C fall in temperature.
27th: Sunny start but with some very dark clouds around. Squally winds and showers thereafter at 11.30 and 2.30pm.
28th: Cloud and rain to start and very windy due to Storm Katie, becoming fine by mid afternoon though heavy showers moved in.
29th: Bright start with cumulus dotting the sky. Cloud thickened up during the day with heavy showers in the evening.
30th: Sunny start with fair weather cumulus doting sky – this lasting all day.
31st Sunny, misty start

Forecast, Seasonal summary, Weather

Winter 2015/16: Very mild with average rain

March 3, 2016 wansteadmeteo Leave a comment

The winter of 2015/16 was skewed by a ridiculously mild December which brought the natural calendar forward three months.

sahara — A persistent flow of air from the Azores caused the unseasonable warmth in December, skewing the overall temperature for the season

Daffodils and other spring bulbs which normally come out in early March in this part of the UK were in full bloom at the end of December. Spring blossom was also very early with many may trees out in early February.

The mean temperature for the season finished 7.38C, that’s 1.9C above average. It was the third warmest winter in my series going back to 1797, behind 1989 / 90 and 1974 / 75.

Rainfall was almost precisely average: 144.8mm fell, within half a millimetre of what normally falls. Sunshine was just under average: 162.8 hrs is just over 5 hours short of what we’d normally expect during December, January and February.

The warmest day of the winter occurred on December 19th with 16.3C recorded, the second warmest December day in my daily record going back to 1959 – the record fell short by just 0.1C.

new street — Snowfall, like the previous two winters, was very scarce

The coldest night of the winter coincided with the coldest mean temperature on January 19th. A low of -5.7C was the lowest value recorded in Wanstead for three years.

The wettest day of the winter occurred on January 10th when 11.6mm, a very unremarkable amount for winter and in complete contrast to the deluge that affected NW England and NE Scotland. There were 51 rain days (where 0.2mm or less fell) and 37 wet days (where 1mm of rain falls over a 24hr period).

Although sunshine was around average there were 24 sunless days.

Snow, like the previous two winters, was very scarce: just one day of snow falling and lying occurred on January 17th, though you had to be up early to see it.

A full weather diary is available for the months of December, January and February. To view full stats for each month follow this link:http://1drv.ms/1kiTuzv

Winter forecast review

At the beginning of December the opening par for my forecast for winter read:

Winter in the London area this year is likely to be average overall, following the pattern of the past two winters that saw little snow.

It was broadly correct though I won’t pretend that I knew just how mild December would be when I prepared the figures at the end of November.

January, as predicted, produced the coldest weather and best chance of snow while February was, as thought, about as average as you can get.

The stats overall:
Predicted – Mean: 5.4C, Rainfall: 153.5mm
Results – Mean: 7.3C, Rainfall: 144.8mm

So, all in all, not bad. The Daily Express and others should take note. This is what they printed last November… I’ll leave it up to the reader which forecast was more useful…

Forecast, month ahead forecast, Monthly Review, Weather

February 2016: average contrast

March 1, 2016 wansteadmeteo 4 Comments

Though it was devoid of snowfall February 2016 was average for temperature and sunshine and on the dry side.

broadstairs — On the 15th cold northerly winds brought sharp showers to the coast. A big swell was seen at Broadstairs allowing for some good surfing conditions

Some sharp frosts made for a couple of stunningly sunny days, “ski resort weather” the kind of days that were absent during the first half of winter after the super mild December.

Rainfall of 35.1mm was 90% of average – the driest February for three years. Mean temperature for the month was 5.4C, 0.1C above the 1981-2010 mean.

Sunshine was just above average. Over 79 hours were recorded, 108% of what we can expect to see during an average February.

The wettest day occurred on the 7th with 11.6mm.

Air frosts: 10

Ground frosts: 16

A rare Channel low but conditions weren’t cold enough for snow

So what has March got in store weatherwise? The late winter synoptic pattern could see the first snowfall above 1cm over the coming days and next week though amounts are likely to be small and temporary and restricted to night hours.

The pattern bringing this messy wintry mix is low pressure moving SE across the UK between now and the weekend each band bringing progressively colder air across the UK. Much of the precipitation will be showery although Friday looks more interesting as a secondary moving south brings cold N or NE winds. Models suggest next week will see high pressure from the west displacing this cold N. The timescale is very uncertain and it may be toward the second half of next week before the general theme of dry and settled conditions prevail. Frosts at night remain likely and daytime temperatures remain close to or a little below normal.

Overall the first half of March does not look like it will offer much in the way of spring weather.

My long range forecasting method suggests the most likely scenarios to be rather cold or cold, though both are only at 33% probability. Something average or below works out at 83% probability. The only mild indicator is for something rather mild at 16% probability.

squall — On the 15th cold northerly winds brought sharp showers to the coast. A big swell was seen at Broadstairs allowing for some good surfing conditions

A dryer than average month looks most likely at 66% probability. Something wetter than average works out at 34% probability.

Very dull conditions look most likely at 83% probability.

So to sum up: Mean: 5.9C, rainfall 31.6mm, sunshine 68 hours.

Taking all of the above into account perhaps the most likely scenario will be that the month will be predominantly anticyclonic with lots of gloom during the day and night frosts, varying in intensity.

So to sum up: Mean: 5.9C, rainfall 32mm, sunshine 67 hours.

My February outlook for temperature was good. I predicted a mean of 5.9C (outcome: 5.4C) with 31.6mm of rain (outcome: 35.1mm). Sunshine 68 hours (outcome: 79.5hrs)

Here follows the full weather diary for February. To view full stats follow this link:http://1drv.ms/1kiTuzv

1st: Cloudy, breezy start. Sunshine PM with nacreous clouds reported on east coast. Cold in a brisk wind.
2nd Cloud gave way to sunny spells around 11am – then feeling cold in a brisk wind.
3rd Cloudy and cold start then mostly cloudy with a cold wind.
4th Bright though mostly cloudy start. Cloudy through the day with odd spot of drizzle through the night. Area of very light rain gave about 0.1mm before 9am.
5th Cloudy with light drizzle up to 11am then briefly bright before more drizzle arrived.
6th Cloudy to start with odd burst of drizzle. Very windy and feeling chilly in wind. Rain arriving after 8pm.
7th Sunny start though cloud bubbling up after 11am and feeling cold in wind as dew point fell away. A very heavy, violent squall swept through at 2245z then blustery through the night.
8th Sunny start quickly gave way to squally showers which were mostly light. Strong winds into the afternoon with squally but light showers. Chilly overnight.
9th Cloudy and cold start, briefly clearing before noon before clouding over again.
10th Cloudy start though with some weak brightness lunchtime.
11th Mostly sunny all day and calm – warmth of the sun can now be felt. Just a few cirrocumulus. Stunning.
12th Bright start but cloud thickening. Day felt cold though as DP fell away.
13th Cloudy start with drizzle at obs time. Cold wind through to lunchtime and intermittent drizzle.
14th Bright, cold start with cloud increasing through the morning.
15th Bright, cold start with lots of wispy cirro-cumulus around. .
16th Stunningly sunny and frosty start. Just patchy cirrus through the day.
17th Cloudy through the day until 5.30pm when drizzle then rain set in.
18th Initially cloudy but then quickly brightened up. Sunny spells through the afternoon.
19th Sunny, clear and frosty start. Cloud began to build mid morning becoming overcast by noon. Light rain spread in about 4pm. Milder.
20th Bright start but cloud and wind quickly built. Light at times moderate rain fell through the afternoon – a thoroughly miserable day.
21st Dull, dry day up to 1pm. Very mild. Staying cloudy overnight with rain arriving at 5am, most falling until 7.30am.
22rd Drizzly start turned to a dull, overcast day
23th Cloudy with clearance at 11.30am. More cloud appeared to leave sunny spells. Much advection but cleared to leave frosty night.
24th Sunny, clear and frosty start. Lots of sunshine but quickly turned cold after dark with early frost. Cloud then wind lifted temperature though.
25th Bright start but quickly clouded over to become cold. Clearance in evening allowed temperature to fall quickly but cloud moved in and breeze picked up to prevent a sharp fall.
26th Cloudy, cold start. Brightening up to sunny spells by 1pm. Too much cloud overnight for a frost.
27th Bright start but became cloudy through the day with a cold easterly wind.
28th Cloudy start but some brightness around noon
29th Cloudy start but soon brightened up with long sunny spells before clouding in again early afternoon.

cold spell, Weather, weather pattern

‘SSW’ rumours and what it means for UK

February 4, 2016 wansteadmeteo Leave a comment

Over the past few days there has been a lot of speculation on the possibility of a sudden stratospheric warming event happening. These events can contribute to unseasonably cold snaps in winter though exactly where their effects happen on the globe is impossible to forecast at small scale resolution.

In short it looks like the eastern US is most likely to see any severe cold weather from this episode – what seems to happen a lot in recent winters in the UK.

Far from being an expert on this there was a very good posting on the usenet forum uk.sci.weather by Stephen Davenport.

“As far as the stratospheric warming is concerned, we’ve been keeping track of this for the last 1-2 weeks. Models have recently been consistent on this being a strong warming (10hPa 60-90 deg N zonal temperatures rising above 240K – see http://acdb-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/merra/t60_90n_10_2015_merra.pdf).

“A temporary wind reversal is likely in the upper stratosphere; for example, see ECMWF at http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/, and have a look at the off-the-chart EPV (although not so much poleward). However, I do not see this as a major SSW (by definition) and everything points to a recovering but weaker circumpolar vortex mid-month onwards.

“Meanwhile, though, the vortex is being shunted off the pole by warming and big height rises firstly over Siberia then the Bering Sea, with exaggerated deformation which will see it extend far south across eastern North America and introduce cross-polar flow (which you can see here: http://www.tropicaltidbits.com/analysis/models/?model=gfs&region=nhem&pkg=Tz10&runtime=2016020412&fh=132&xpos=0&ypos=255).

“At 500hPa a very deep trough digs southwards east of the Mississippi as far as the Gulf of Mexico. GFS shows a -3 to -4 sigma anomaly over the Southeast with ECMWF similar but a little less deep: http://www.tropicaltidbits.com/analysis/models/?model=gfs&region=eus&pkg=z500a_sd&runtime=2016020412&fh=120&xpos=0&ypos=155

“That opens the door to Arctic air pouring far southwards, and there’ll be snow chances at least as far south as the Tennessee Valley. Incidentally there is a risk of another Nor’easter around Feb 9th-10th.

“Downstream a mid-Atlantic ridge could build rather strongly from the subtropical high towards Greenland with slowed zonal flow but most likely surface low pressure developments eastern Atlantic / near the British Isles.

“If the long wave pattern shifts a little eastwards then the increased meridionality *could* see LP progression pull in temporary subsequent N-NW flows for the UK – a more likely route to short-lived cold shots than via any high latitude blocking in the medium range.

“I think that elsewhere people have got hung up on the stratospheric warming and, as so often, drawn excitable conclusions. Cold impacts are more likely for the eastern U.S. than Europe with a displaced rather than a split vortex; and the circumpolar vortex was so strong first half of winter it was always going to take a lot to break it down fully. And sure enough, as noted there should be a recovery after this “attack”. You can see the vortex distortion and latterly the beginnings of recovery in this rather nice animation of 10hPa potential vorticity:

https://www.youtube.com/watch?v=a3Ddld-JL58&feature=youtu.be

“And here are some 3D representations:

https://www.youtube.com/watch?v=eumaRb-bH5k

“GFS has occasionally pulled out a split vortex at various levels during the past week but doesn’t now.

“That’s not to say that a possible further warming (early final warming?) wouldn’t bring colder chances from the end of February into March.

“I was surprised to read recently that a well-known online forecaster had predicted significantly cold/blocked conditions for Europe in January via a major SSW. A bit premature, that.”

Forecast, Monthly Review, monthly summary, Weather

January 2016: average and wet

February 1, 2016 wansteadmeteo 2 Comments

The coldest night in three years was recorded last month together with the first lying snow in January since 2013 – though you had to be up early on Sunday 17th to see it.

epping snow — Snowfall on the 17th was just over 1cm deep at High Beech. In Wanstead it was just a thin covering that was gone by midday

For anyone looking for ‘traditional’ winter weather it was pretty desperate stuff and seems a continuation of the mild winters of the past three years.

Apart from a mild final week much of the month was rather cold with a couple of sharp night frosts that affected many early daffodils that bloomed during the super mild December.

Rainfall of 65.8mm was 124% of average – very similar to last January’s total. Mean temperature for the month was 5.8C, 0.6C above the 1981-2010 mean. It felt far cooler, however, because the December mean was 5C above average.

Sunshine was just above average. Over 54 hours were recorded, 108% of what we can expect to see during an average January.

The wettest day occurred on the 10th with 11.6mm.

Air frosts: 6

Ground frosts: 18

So what has February got in store weatherwise? There is no sign of any longer term changes in the pattern of synoptics across the UK. All models continue to suggest a very volatile jet stream with resultant low pressure close to or across the UK for much of the first half of February.

This week westerly winds will remain strong with severe gales in the north in association with Storm Henry over the next 36 hours. The current mild and damp conditions in the south should be replaced with colder, showery air moving south later on Monday, lasting into Wednesday. On Thursday another large warm sector will move up across the UK from the SW returning mild and damp conditions.

At the weekend all models show low pressure areas taking a much more southerly route across the UK with gales and wet weather. While no cold weather looks likely there may be incidences of very heavy and thundery showers. Only GFS on Monday is showing any hint of more settled, colder weather at the end of the period.

Using my long range method February is looking average, very dry and dull.

A mean of about 5.9C, just over average, is the highest probability at 71%. Something ‘rather mild’ comes in at 29% probability.

Rainfall is looking low: 15mm represents something 38% of average.

Sunshine totals will be low and it could be a dull month, around 60 hours of sunshine, that’s just 82% of average.

My January outlook for temperature good. I predicted a mean of 5.2C (outcome: 5.8C) with 59mm of rain (outcome: 65.8mm).

Here follows the full weather diary for December. To view full stats follow this link:http://1drv.ms/1kiTuzv

1st: Bright after sunny, clear dawn before clouding over with light rain. Rain at midnight.
2nd: Cloudy start after early overnight rain. Rainy spells and blustery throughout the day.
3rd: Drizzle to start then damp before more rain moved in at 11.30am – this fell intermittently through the day and evening and was often heavy.
4th: Bright, damp start after overnight rain. Some light outbreaks up to 2pm.
5th: Sunny, clear and cold start with contrails dotting the sky. Clouding over later with rain after 6pm. Misty around midnight.
6th: Bright, very damp start. Mostly cloudy with rain in the evening and overnight.
7th: Dull start with outbreaks of rain spreading in, some heavy and very blustery. Drying up after lunchtime though feeling cold. Cool overnight with frost on cars with a very brief shower on school run.
8th: Bright start though light showers around. Gradually clouding over. Clearer spells overnight and cool.
9th: Bright start though with plenty of cloud around. Showers, some heavy with small hail at 8.30pm. Clear spells overnight.
10th: Bright start after overnight rain. Cloud gradually decreasing to leave it clear at noon. Cloud returned after dusk and thickened up around 9pm. Heavy rain from midnight.
11th: Cloudy, damp and cold start. Some breaks after noon then clear spells overnight and cold.
12th: Sunny, cold start. Clouding over at midday to leave cold-feeling afternoon and overnight – too much wind for a frost.
13th: Bright, cold start but turning mostly cloudy. Rain in the evening and on ride home.
14th: Rainy. cold start, then cloudy with sunny intervals. Cold air digging in from midday.
15th: Sunny all day with just a few cirrus. Took a while for frost to form properly.
16th: Sunny, frosty start with just a few cirrus. Variable cloud and evening in London felt freezing. Some drizzle, this turned heavier and by 4am thick flakes were falling to give a thin covering. Some 1cm at High Beach during a bike ride.
17th: Cloudy start. Thin covering of snow (<1cm) thawed by lunchtime. Cloud built into afternoon to leave chilly evening.
18th: Bright start but sunshine was weak so felt cold. Mostly clear into the evening allowed for an early frost. A classic radiative cooling night until the early hours, assisted by a very gentle low-level flow off the continent where there were some very low dew points. Between 2am and 6am there was some thin, high-level cloud that drifted across, which stopped the radiative cooling. Warmth from the ground then briefly lifted the temperature until, once more the cloud cleared after 6am and allowed the temperature to fall again to its minimum of -5C at 0809z. There was also a little mixing of the layers of air between 2 and 6 which would also have had a cooling effect. Had it not been for the cloud I’d suggest that the low could have fallen to -6.2C, which would have been the coldest since February 2012 when it fell to -9.2C over full snow cover.
19th: Sunny all day with occasional alto-cumulus drifting across. Another cold night, the coldest in 3 years.
20th: Bright start with lots of scattered cumulus. Sunnier early afternoon and less cold. Another frost quickly forming after dark.
21st: Frost lifting quickly then cloudy with limited brightness throughout the day.
22nd: Cloudy start with rain arriving at 9.05am. Bursts through the day until early afternoon. Some brief brightness in the late afternoon.
23rd: Sunny, cool start. Clouding over with rain in the evening. Very mild.
24th: Cloudy start after overnight rain. Mostly cloudy with odd spot of drizzle though bright.
25th: Sunny, clear start though cloud bubbled up at 11am to leave mostly cloudy afternoon. Clear spells overnight and chilly.
26th: Cloudy and increasingly gusty up to midday. Some rain in the evening.
27th: Cloudy, blustery start.
28th: Sunny all day with just a few clouds around noon.
29th: Cloudy and breezy with some drizzle in the wind early afternoon. Report of 101mph gust on Shetland from Storm Gertrude. Wind seemed to strengthen at midnight before rain arrived.
30th: Cloudy and damp start after overnight rain. Sky soon cleared to leave mostly sunny afternoon.
31st: Drizzle in morning as warm front moved in.

1816: The Year Without a Summer, cold spell, History, UK climatology, Weather

The night temps fell to -20C in east London

January 6, 2016 wansteadmeteo 1 Comment

The ‘Year Without a Summer’ of 1816 brought many extremes of weather as well as a cold, wet and depressing summer.

Stats taken by Luke Howard during the February 1816 cold snap — Stats taken by Luke Howard during Feb cold snap

During the opening months frequent cold blasts brought much wintry weather. Cold weather at the end of January turned severe during the second week of February.

In the early hours of the 7th heavy snow, driven by gale-force north-easterly winds, brought some of the worst winter weather this area has ever seen. Some 35mm of precipitation is recorded on the 8th – this would normally give at least one foot of level snow that could obviously be whipped up into huge drifts.

Luke Howard described the scene in his diary entry saying the abundance of snow “loaded the trees to their tops and weighed down the smaller shrubs to the ground.”

The snow and polar continental air also produced perfect conditions for a textbook radiative cooling night within two days of the snowfall. The minimum recorded on the morning of the 10th: -20.6C has not, as far as I can tell, been repeated since.

To put that into perspective the lowest minimum of the severe winter of 1963 for this area was -12.2C recorded at Greenwich on January 21st. The coldest night I have personally recorded was -10.3C on January 12th 1987.

Howard, who would have taken readings at his laboratory in Stratford and home in Tottenham, remarked on the rare occurrence of the cold and said that the thermometer had remained below 0F (-17.8C) for a number of hours: “an occasion that happened less than five times within a century – the last appearing to be 19 years previous.”

Howard’s theory of the day was that such extremes didn’t occur during long continued frosts but rather at an interval of one winter after such a season. He mentions the frost of 1794-95, which lasted 44 days, immediately before which the thermometer fell to -2F. The following year a low temperature of -6.5F was recorded. The year 1816 followed the cold winter of 1813/14 – the same pattern, so Howard was prepared for the night of February 9th 1816.

Modern climatologists tend to discount these old records by arguing that standard conditions set by the World Meteorological Organisation were not met. However, Howard backs up his findings with a very thorough explanation of how he went about measuring the record low temperature that followed a freezing day where the maximum thermometer didn’t rise above -6.7C.

“Early in the evening on trying the experiment of placing a wet finger on the iron railing it was found to adhere immediately and strongly to the iron. I exposed several thermometers in different situations.

“At 8 pm, a quicksilver thermometer with the bulb supported a little above the snow stood at 0F. At 11pm a spirit thermometer in the same position indicated -4F, the former which had a pretty large bulb had not sunk below -3F. At 7.30am the 10th a quicksilver and a spirit thermometer hung overnight about 8ft above the ground indicated respectively -3F and were evidently rising.

“The thermometer near the surface of the snow had fallen to 5F and probably lower, but at the usual height from the ground of my standard thermometer the temperature was at no time below -5F. The exposure is north and very open.”

Howard goes on to describe the following day:

“From 8am the thermometer continued to rise steadily at noon a temperature of 25F was pleasant by contrast to the feeling and it was easy to keep warm in walking without an upper coat. Even at 0F, however, the first impression of the air on the skin was not disagreeable; the dryness and stillness greatly tending to prevent that sudden abstraction of heat which is felt in moist and quickly flowing air.

“Early in the afternoon the wind changed all at once to SW some large cirri which had appeared all day passed to cirrocumulus and cirrostratus with obscurity to the south. I now confidently expected rain as had happened in former instances but was deceived and the thaw took place with a dry air for the most part and with several interruptions by night.

As often happens with severe cold snaps Howard reported on the 17th that the snow “was mostly gone but very thick ice remains on ponds”; a period of just over a week.

The cold snap saw the mean temperature for February 1816 over three degrees colder than average at 0.8C.

Such extreme temperatures are rare in the capital though not unheard of. I know that there have been cases of sub -20C readings in, for example, the Rickmansworth frost hollow and Ian Currie’s Chipstead Valley, but I have never seen anything so low in east London. Could it be repeated again? Possibly, but like 1816, the synoptics would have to be absolutely perfect for it to happen.

Annual review of weather, Weather

Wanstead weather: 2015 review

January 3, 2016 wansteadmeteo 2 Comments

This year finished as the ninth warmest year on record – some 0.5C cooler than 2014.

Every month of 2015, apart from September, November and December, was roughly average – the means being within +/-0.7 every month, bringing the mean temperature to 11.9C, 0.7C above the 1981-2010 average.

Rainfall was less remarkable with the year being dryer than average. The total of 553mm puts it as the 162nd wettest since 1797.

It was also a very slightly duller than average year with 1,433 hours of sunshine recorded. That’s 97 per cent of average, the 77th dullest since 1881 – the least amount of sunshine for 11 years.

For a review of each month, click January, February, March, April, May, June, July, August, September, October, November, December.

To view full stats follow this link:http://1drv.ms/1kiTuzv

Events, Forecast, month ahead forecast, Monthly Review, monthly summary, Rainfall, Weather

December 2015: Exceptionally mild

January 1, 2016 wansteadmeteo 13 Comments

December 2015 was a ridiculously warm month, the mildest on record in my local series going back to 1797.

The mean temperature of 10.9C is 5.3C above the average for the first winter month and breaks the previous record set in 1974 by an increadible 2.2C.

Indeed the month was warmer than what was a very mild November and was air frost free.

Sunshine was below average: 34.6hrs (86% of average) was the lowest total recorded since 2010, another December that was as exceptionally cold as this month was mild.

Rainfall was more run-of-the-mill: 44mm fell during the month: that’s 83% of average.

The warmest day occurred on the 19th with 16.3C recorded, the second warmest December day in my daily record going back to 1959 – the record fell short by just 0.1C.

Other daily records were broken including for daily mean temperature: 14.3C on Boxing Day smashed the previous record set on December 4th 1985 by 0.4C. This day also saw the highest daily minimum for December recorded: 13.5C. It was also the warmest Christmas Day on record in a series going back beyond 1852.

The lowest temperature occurred on the 8th when the mercury fell to 2.4C.

The wettest day was on the 3oth when 5.9mm of rain fell. There were only three completely dry days during the month. Thanks to the synoptic situation this area thankfully escaped the awful flooding which affected the north of England and Scotland.

december mean 1797-2015 — There is quite a marked upward trend in the December mean since 1797

What has January got in store weatherwise? The models today (January 1st) suggest that low pressure will continue to pile into the UK from the west on quite southerly latitudes over the next week with some colder air infiltrating into the east and north of the UK from Europe with rain at times for our area. From that point on most output suggests largely unsettled weather continuing until the end of the two week period though there is a hint that high pressure may try to edge up from the SW or west later with less wind and rain but still mild.

Because of the exceptionally mild December there are virtually no figures I can work with to try to estimate January – but I’ll have a crack anyway, using figures that were at least 1C above the 1981-2010 December average.

A mean of about 5.2C with 59mm of rain, both around average. The highest probability is for average temps at 33% probability. Interestingly something ‘very cold’ comes in at the same probability. Rather mild and rather cold come in at 16% probability. I emphasise that even at such low probability my confidence is even lower.

My December outlook for temperature was way off – there was no chance shown of anything ‘very mild’.

Here follows the full weather diary for November. To view full stats follow this link:http://1drv.ms/1kiTuzv

1st: A few spots of rain after deluge overnight then cloudy.
2nd: Cloudy to start, some sun mid morning before it clouded over with two spots of rain. Mild overnight.
3rd: Cloudy start with little brightness all day. Rain moving in at 7.15pm and intermittent into the evening, clearing later with temp falling from midnight.
4th: Sunny, clear start, tending to cloud over at 11am with limited brightness.
5th Cloudy and windy all day – the wind peaking at 9pm but remaining fresh through the night.
6th: Cloudy and dull most of the day.
7th: Cloudy start with some light drizzle mid morning.
8th: Dull, drizzly start with steadier bursts. Heavy rain as front cleared through at 2pm. Evening and overnight much colder than of late.
9th: Sunny start, clouded over afternoon.
10th Cloudy start and through the day. Rain spreading in in the evening, clearing by midnight.
11th: Cloudy through the day until 2pm when a narrow band of rain passed through then dry and feeling cooler.
12th: Cloudy start with some drizzle around 10am.
13th: Cloudy and drizzly to start then just cloudy.
14th: Cloudy start with some brightness at noon. Cloudy into the afternoon with some drizzle overnight.
15th: Cloudy and dull. Rain later in the evening.
16th: Cloudy with two sunny intervals then cloudy with odd drizzle.
17th: Cloudy with odd brightness then rain at 5pm.
18th: Cloudy all day.
19th: Bright and breezy start.
20th: Dull start with heavy rain at 3.40pm. Then cloudy but clear by morning.
21st: Sunny start but quickly clouded over with rain.
22nd: Dull start with patchy drizzle up to 11.30am. More rain later with squall at 8pm.
23rd: Sunny start with cloud moving in then sunny spells.
24th: Sunny start quickly turned cloudy with heavy rain around noon, clearing to sunny spells.
25th: Cloudy start with light rain spreading in at 10.10am. Cloudy rest of afternoon with temperature climbing through the day for record warm Christmas day. Temp didn’t fall below 14C all night.
26th: Cloudy and warm all day. Temp fell to just 13.9C though the day then rose again to give the warmest December night on record, and also warmest December mean.
27th: Dull with brief burst of drizzle early then breezy and very mild. Clearer overnight and cooler than of late. Sunny start with pink clouds am.
28th: Sunny start with just a few cirrus. Mostly sunny through the day.
29th: Sunny start with brief heavy shower at 10.05am. Then sunny intervals.
30th Cloudy and breezy to start. Rain spreading in in the evening, stopping around midnight
31st: Sunny and clear to start but with cloud bubbling up from late morning. Brief rain after dark then dry and turning colder. Frost in early hours of 1st