Rainfall constrasts from exceptionally wet to exceptionally dry

[damianslaw]

February 2020 was the wettest on record in many places, here it was exceptionally wet, easily over 300 mm. Since mid March though we've had barely about 50mm, probably about 20% long term average. That is an impressive contrast.

Any stats to show similiar marked changes in rainfall totals over such a short space of time. I remember the contrast between March 2012 and April 2012 that was a marked change. Feb 97 contrasted with March and April 97. August 95 vs Sept 95.

I only want to know sudden changes in the space of a week or two from exceptional wet to exceptional dry and vice versa, the length of dryness and wetness should be relatively balanced, a month, or two months.

[MP-R]

We're not a particularly wet area of the country so the figures aren't quite as impressive as the Lake District, but by calendar month, some notable contrasts here are as follows:

April 2017 - 06.8mm > May 2017 - 102.6mm

March 2012 - 36.9mm > April 2012 - 143.7mm

April 2007 - 16.0mm > May 2007 - 159.7mm

July 2007 - 193.7mm > August 2007 - 24.3mm

Not by calendar month, but by same intervals back to back:

2001: August 10th - September 20th - 26.7mm / September 21st - October 31st - 172.6mm

2001/02: December 10th - January 10th - 05.4mm / January 11th - February 11th - 143.6mm

2002: August 10th - October 10th - 54.5mm / October 11th - December 11th - 359.4mm

2003: March 24th - April 24th - 04.4mm / April 25th - May 25th - 138.0mm

2009: September 01st - October 15th - 51.1mm / October 16th - November 30th - 332.3mm

(although not consecutive months, September 2009 had 28.5mm and November 2009 had 275.8mm)

2019: May 17th - June 17th - 121.7mm / June 18th - July 18th - 10.8mm  

[damianslaw]

1 hour ago, MP-R said:

We're not a particularly wet area of the country so the figures aren't quite as impressive as the Lake District, but by calendar month, some notable contrasts here are as follows:

April 2017 - 06.8mm > May 2017 - 102.6mm

March 2012 - 36.9mm > April 2012 - 143.7mm

April 2007 - 16.0mm > May 2007 - 159.7mm

July 2007 - 193.7mm > August 2007 - 24.3mm

Not by calendar month, but by same intervals back to back:

2001: August 10th - September 20th - 26.7mm / September 21st - October 31st - 172.6mm

2001/02: December 10th - January 10th - 05.4mm / January 11th - February 11th - 143.6mm

2002: August 10th - October 10th - 54.5mm / October 11th - December 11th - 359.4mm

2003: March 24th - April 24th - 04.4mm / April 25th - May 25th - 138.0mm

2009: September 01st - October 15th - 51.1mm / October 16th - November 30th - 332.3mm

(although not consecutive months, September 2009 had 28.5mm and November 2009 had 275.8mm)

2019: May 17th - June 17th - 121.7mm / June 18th - July 18th - 10.8mm  

Many thanks for these stats, as I thought some impressive contrasts, and backs up my statement that very wet spells can often be followed by abrupt very dry spells and vice versa, and throughout the year. I thought March-April 2012 would feature. Most impressive contrast the 2002 figures. The dryness of Dec 01- Jan 02 also very startling. April - May 07 and 17 almost a carbon copy. 

Oct-Nov 09 was exceptionally wet here as well, however, the period preceding it wasn't especially dry here.

[hillbilly]

Some met office data for my area.These are calendar month and surprising how so few times it changes dry to wet or vice versa.

1921 Jan 148   feb3.3

1969 oct 12   nov 158

1976 aug 17   sep 177

1980 may 19   jun 145   jul 26

1982 jun 195   jul 8

1986 jan 148   feb 22

 

[B87]

It hasn't been exceptionally dry here, but we did have almost 6 months of constantly above average rainfall before March.

Sep: 63.0mm

Oct: 92.8mm

Nov: 74.8mm

Dec: 89.6mm

Jan: 47.6mm

Feb: 99.8mm

Mar: 42.8mm

Apr: 38.2mm

 

Aug 1995: 0.3mm, Sep 1995: 95.0mm

Edited May 10, 2020 by B87

[damianslaw]

5 hours ago, hillbilly said:

Some met office data for my area.These are calendar month and surprising how so few times it changes dry to wet or vice versa.

1921 Jan 148   feb3.3

1969 oct 12   nov 158

1976 aug 17   sep 177

1980 may 19   jun 145   jul 26

1982 jun 195   jul 8

1986 jan 148   feb 22

 

Calandar month wise perhaps less so than bookended periods over 2 or 3 months as shown by MP-R. I suspect deviations are more pronounced in the wetter west, especially further NW you go, lengthy atlantic spells followed by blocked scenarios with easterlies, northerlies developing. The drier east will see less variation in this respect being drier under westerly interludes and wetter than the west in northerly and easterly scenarios, but these are not 'wet' airstreams in the main, unless cyclonic - such conditions rarely last.

[Weather-history]

20 hours ago, damianslaw said:

February 2020 was the wettest on record in many places, here it was exceptionally wet, easily over 300 mm. Since mid March though we've had barely about 50mm, probably about 20% long term average. That is an impressive contrast.

Any stats to show similiar marked changes in rainfall totals over such a short space of time. I remember the contrast between March 2012 and April 2012 that was a marked change. Feb 97 contrasted with March and April 97. August 95 vs Sept 95.

I only want to know sudden changes in the space of a week or two from exceptional wet to exceptional dry and vice versa, the length of dryness and wetness should be relatively balanced, a month, or two months.

Look at  July last year for our region

1st-16th July: about 7mm

17th-31st July: about 100mm

 

Back in 1940 for England and Wales

June: 20.9

July: 112.5

August: 15.0

 

1829

Mar: 25.7

Apr: 123.4

May: 16.6

 

1865

August: 126.0

September: 9.5

October: 168.4

 

1950

Jan: 38.9

Feb: 143.6

Mar: 39.3

 

------------------------------------------------

Here's a strange oscillation pattern

Dec 1934: 183.5

Jan 1935: 42.3

Feb 1935: 102.5

Mar 1935: 25.4

Apr 1935: 101.6

May 1935: 37.2

Jun 1935: 96.2

Jul 1935: 27.2

 

 

 

 

 

Edited May 11, 2020 by Weather-history

[cheeky_monkey]

what about the flip from a long wet period beginning Oct 1994 - end of March 1995 followed by a long dry period Beginning of April 1995 - Beginning Sept 1995

[damianslaw]

6 hours ago, cheeky_monkey said:

what about the flip from a long wet period beginning Oct 1994 - end of March 1995 followed by a long dry period Beginning of April 1995 - Beginning Sept 1995

Yes possibly the most extreme flip, an exceptionally wet period followed by an exceptionally dry period. 

[A Face like Thunder]

12 hours ago, damianslaw said:

Yes possibly the most extreme flip, an exceptionally wet period followed by an exceptionally dry period. 

.... until 2020 by any chance?

[AderynCoch]

Bidston Observatory near Liverpool:

August 1976 - 2.6mm

September 1976 - 204.3mm

[B87]

A few examples from London in recent years.