Is it warm, cold or just normal?

Saying how warm or cold a day feels is subjective; one person’s hot day in spring is another’s ‘on the warm side’. Similarly when someone says the temperature on any given day is ‘normal for the time of year’ others will be exclaiming how cold they’re feeling.

The ‘heatwave’ in February was a case in point. Though many places recorded their warmest February maxima on record many were saying it was just a nice, warmer than normal spell of weather.

Some years ago the Met Office issued guidance on how warm or cold a day was relative to the anomaly. Earlier this month the table was posted on Twitter and I have plotted a graph for the spring period.

Today’s (March 22nd) maximum of 11.1C is therefore described as ‘normal’.

temp feel

cold hot warm

 

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Data reveal windiest March for 4 years

March 2019 has been a windy month so far. With 11 days to go it is already the windiest March for 4 years and the windiest month for over a year.

The windiest month recorded since 2013 was December 2015.

Looking at the data in general there seems to be a pattern of a windy month that is followed by a decline of between 10 and 13 months.

monthly wind run

 

Spring or still winter? Plants reveal all.

With the record warm spell last month and high sunshine totals you would think that the growing season is well under way. Spring bulbs have been out for weeks, trees are blossoming and many shrubs are on the verge of flushing.

But a look at the local temperature records over the last six years shows that things aren’t as advanced as previous seasons.

Considering the period from December 1st – in recent years a date when it is common to see bulb shoots beginning to emerge – to March 10th reveals the following table in terms of growing degree days.

growing degree days

The warm days of last month were cancelled out by cold, frosty nights, leading to little net warmth. And the last ‘growing degree-day’ was on March 2nd. Nevertheless growth is further on than last year that saw record cold in March. 

The season is a long way behind 2015-16, however, which saw a record-breaking mild December.

Looking at the list below, and the at best average outlook, we’ve still got a way to go before we’ll see most trees in full leaf…

plant development
This list courtesy of Wikipedia

 

 

February’s record diurnal temperature ranges

Last week’s warm spell not only saw national maxima records tumble but, locally, saw the February diurnal temperature range record shattered too.

Four days of near cloudless skies produced classic conditions whereby the maximum amount of solar heating by day was followed by clear nights allowing all that heat to escape with air frosts forming.

The spell saw five new entries in the ‘top 10’ of February diurnal temperatures since 1959, with both the 25th and 26th surpassing the record set in 1976 by at least 0.3C.

feb diurnal new
Top 10 February diurnal temp ranges

The diurnal ranges were not enough to make the annual list, however

top 10 diunrals
Top 10 diurnal temperature ranges since 1959

 

 

Winter 2018/19: average with extremes

The winter of 2018/19 will probably be remembered most for the remarkable warmth in the last week of February. And for its lack of snowfall.

The mean temperature finished 6.1C, that’s 0.7C above average, the mildest for 3 years.

Rainfall was below average: 127mm fell, that’s 87 per cent of average and the driest for two years.

Sunshine was well above average: 211.6 hrs is 126 per cent over average, the sunniest for seven years.

The warmest day of the winter occurred on December 30th with 14.2C recorded. The warmest night was on January 28th when the temperature fell to just 10.8C.
The wettest day of the winter occurred on January 2nd when 15.3mm was recorded.

Snow first fell on 5 days between January 22 and February 1st: five days of snow falling and two days of snow lying over the three months is below average.

There were 29 air frosts during the three months, seven above the 1981-2010 average.

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

TMax winter

Summary for period 01/12/2018 to 28/02/2019

Temperature (°C):
Mean (min+max)   6.1
Mean Minimum     2.6
Mean Maximum     9.7
Minimum          -6.5 on 30/01/2019
Maximum          18.7 on 26/02/2019
Highest Minimum  11.5 on 06/12/2018
Lowest Maximum   1.3 on 23/01/2019
Air frosts       29
Rainfall (mm):
Total for period 127.0
Wettest day      11.4 on 20/12/2018
High rain rate   28.1 day 26/01/2019
Rain days        31
Dry days         59
Wind (mph):
Highest Gust     31.1 on 09/02/2019
Average Speed    2.8
Wind Run         6152.3 miles
Gale days        0
Pressure (mb):
Maximum          1043.8 on 02/01/2019
Minimum          980.4 on 01/12/2018
Days with snow falling         5
Days with snow lying at 0900   2
Total hours of sunshine        0.0

February 2019: very mild and sunny

February was most notable for how mild daytime temperatures were in comparison with night-time.

The 27th and 26th saw diurnal ranges of 19.4C and 19.3C respectively, the highest range recorded in any February since 1959, helped by huge temperature anomalies brought by the synoptic conditions. Although the UK maximun temperature record for February was broken with Kew Gardens reaching 21.2C the February TMax record in Wanstead, 19.7C set in 1998 remained intact.

The mean temperature finished 7C, 1.7C above average, the mildest February for 5 years.

Some 33.7mm of precipitation was recorded, 86 per cent of the 1981-2010 average, about the same as last year.

Some 124.6 hours of sunshine were recorded, that’s 170 per cent of average, the sunniest February for 11 years.

Ten air frosts were recorded.

There was one day where snow fell and one day of snow lying, 1cm on 1st.

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

feb max 2019
Summary for February 2019

Temperature (°C):
Mean (1 minute)  7.0
Mean (min+max)   7.2
Mean Minimum     2.5
Mean Maximum     11.8
Minimum          -3.9 day 02
Maximum          18.7 day 26
Highest Minimum  7.6 day 28
Lowest Maximum   2.2 day 01
Air frosts       10
Rainfall (mm):
Total for month  33.7
Wettest day      6.7 day 03
High rain rate   8.1 day 03
Rain days        10
Dry days         18
Wind (mph):
Highest Gust     31.1 day 09
Average Speed    2.7
Wind Run         1793.2 miles
Gale days        0
Pressure (mb):
Maximum          1038.4 day 25
Minimum          986.4 day 01
Days with snow falling         1
Days with snow lying at 0900   1

Longest winter ‘heatwave’ since 1959

With the return of more seasonal temperatures February 2019’s heatwave already seems like a distant memory.

Looking back at the stats for this area the past eight days have seen an average anomaly of 7.7C, beating the previous eight-day long warm spell of December 2015, which returned a mean anomaly of 7C. That spell was quickly followed six-day long warm spell that had a mean anomaly of 6.6C. There appears no chance of the heat returning any time soon.top 5 winter heatwaves

Wanstead missed out on breaking the February high temperature record. While Kew Gardens recorded a high of 21.2C, the local area reached just 18.7C, falling short of the record of 19.7C set in 1998.

St James’s Park, our closest official climate station, set a new top 3 of TMax values. , as did Heathrow.

 

Diurnal temps present a clothing challenge

The erratic onset of spring in some years often presents that problem of what to wear every morning. During the current warm spell I’ve seen all manner of attire on the school run; everything from T-shirt and shorts to full winter regalia topped off with hat and gloves.

The position of the sun is now bringing in to range the season when the gap in temperature between day and night can be at its greatest.

On Saturday (23/2), virtually unbroken sunshine and ‘thick’ air saw the temperature in Wanstead peak at 16.1C before clear conditions overnight saw the minimum plunge to just 0.2C. The gap of 15.9C represents the fourth highest diurnal temperature range for February in this area back to 1959.

feb diurnal
Top 10 February diurnal temp ranges

 

Looking at the year as a whole the greatest range is 20.8C with the months of May and June the most likely to see the condition.

top 10 diunrals
Top 10 diurnal temperature ranges since 1959

 

Gertrude, Fionn and Erik were all bluster

Since the Met Office introduced its system of naming storms at the beginning of the autumn season in 2015 the effects felt in the capital have been fairly limited.

Introduced partly in response to the devastation caused by the St Jude Storm in October 2013 every wind storm since has failed to live up to the hype, at least at a local scale.

Woodford Green tree
This tree at the side of the road in Woodford Green was a victim of the St Jude Storm in 2013

Of course many storms have caused major disruption elsewhere, not least Storm Desmond, floods from which devastated Glenridding in the Lake District.

But closer to home many of these storms have been marked simply by a higher than average ‘wind run’, the number of revolutions of this weather station’s anemometer.

The windiest days in this locality coincided with Storms Gertrude, Fionn and Erik but these were minnows compared with St Jude and the most recent devastating storm in living memory, the Great Storm of 1987.

The graphs below also highlight the ongoing problem of naming storms in that some of the windiest days in this area occurred when there was no named storm.

The windiest day in the dataset was June 6th 2017 when a low pressure system saw Force 9 winds recorded in the Channel. Locally the day was very blustery and trees that were in full leaf were blown down.

met office storms

storm season 2015-16

storm season 2016-17

storm season 2017-18

storm season 2018-19

 

An erratic season for snow in the Alps

Earlier this winter there were many reports on how good snowfall had been in Austria. But on closer inspection it was clear that the weather pattern at that time only favoured certain resorts.

In contrast with last year the totals I’ve used in my cross section of the range don’t look that exciting; Bourg-St-Maurice, the jumping off point for Savoie resorts including Les Arcs and Val d’Isere, has recorded 96mm of precipitation this season, in stark contrast to the 433mm it recorded last season between Christmas Day and February 5th.

In Switzerland Arosa, a resort well placed to pick up snow from any direction, has recorded the same this season as last. Totals in Davos are well down on last season. Similarly San Bernardino has recorded about half the amount of precipitation than it did last season. Its location toward the southern side of the range has been sheltered from the prevailing winds this year. That said it did enjoy a big dump last week.

Going further south and east St Vallentin in Italy has recorded about a third what it did at this stage last season.

Mean temperatures overall are about 2C to 3C lower than they were last season.

snowmap update
30-day precipitation totals reveal that Bourg St Maurice recorded just 96mm, compared with last year’s 433mm while Obertauern in the east recorded 77mm, compared with 106mm the same period last year

 

Meteorology-based musings about east London and beyond

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