Heavy Rainfall how rare is it?

[The PIT]

After the floods on June 25th 2007 in Sheffield the press was alive with people saying it's a one a hundred year event and other nonsense including a certain local weather man. I sat listening thinking piffle I've known rain like it and eleven days earlier we had a lot worse. I then went back through our records to 1989 finding large rainfall events in Sheffield. They are in fact quite frequent, a lot more so than one would think.

I made a pdf looking at 24 hr period rainfall then 48 hr period then 72 hr period. You can see the results here. http://www.sheffieldweather.co.uk/Heaviest...l_From_1989.pdf

As you can see it's far from rare and the results will probably be the same across the country as the whole. I can also add yesterdays rainfall to the list which comes in at 50.1mm for the 24hr period coming in at no.4. So that's 13 events since 1989 hardly a once in 100 year occurrence.

What we have seen though is increased flooding which for many is due to building on floodplains, poor river management and certainly in Sheffield poor drainage management which still isn't being dealt with. The Sheffield Floods were also made worse by a large rain event 11 days earlier meaning the ground was totally saturated and smaller falls rain in between prevented any drying of the catchment areas..

We do now have a Met office warning system which does leave a little to be desired at the present time but as technology advances it will get better. At the moment for Sheffield it's got a 40.6% success rate and mostly over predicts the rainfall by a large margin. Better safe than sorry but beware the Cry Wolf syndrome which already effects many people. However that's another discussion.

[peterf]

my location is as elevated as it goes.and i must say this is the wettest 28hrs i can remember.

no flood plains here, it all shoots off into the river derwent at a rapid rate of knots.

fish in the pond are growing legs .

[The PIT]

Well the wettest one I can remember is Aug 9th 2004 roads flooded and it took me ages to get to work driving round all over the place. Most of that rain fell in a few hours then showers afterwards. Although the council couldn't manage the roads properly Sheffield United managed the football pitch and the evening game went ahead without any trouble. I always thought the groundsman should get a job a street force and show them how it's done.

I also remember plenty of heavy rain the seventies and despite better drainage maintenance the road outside our house was like a river. So it happens on a regular basis.

[peterf]

Well the wettest one I can remember is Aug 9th 2004 roads flooded and it took me ages to get to work driving round all over the place. Most of that rain fell in a few hours then showers afterwards. Although the council couldn't manage the roads properly Sheffield United managed the football pitch and the evening game went ahead without any trouble. I always thought the groundsman should get a job a street force and show them how it's done.

I also remember plenty of heavy rain the seventies and despite better drainage maintenance the road outside our house was like a river. So it happens on a regular basis.

looking like it may become even more regular

[The PIT]

looking like it may become even more regular

As we continue to build on flood plains then put flood defences up on the former plains it will but I don't think they'll be much change in the overall pattern it may even become dryer as they were once quite sure about or it may become wetter. Remember not very long ago they were on about the rivers drying up for good. Country file once even had a good program on it. John C standing in a dry river bed saying it's the shapes of things to come. A few years later he returned to same spot and said err no it wasn't sorry.

[peterf]

As we continue to build on flood plains then put flood defences up on the former plains it will but I don't think they'll be much change in the overall pattern it may even become dryer as they were once quite sure about or it may become wetter. Remember not very long ago they were on about the rivers drying up for good. Country file once even had a good program on it. John C standing in a dry river bed saying it's the shapes of things to come. A few years later he returned to same spot and said err no it wasn't sorry.

thats countryfile for ya .

stopped watching it over 2 years ago.

[Snowyowl9]

After the floods on June 25th 2007 in Sheffield the press was alive with people saying it's a one a hundred year event and other nonsense including a certain local weather man. I sat listening thinking piffle I've known rain like it and eleven days earlier we had a lot worse. I then went back through our records to 1989 finding large rainfall events in Sheffield. They are in fact quite frequent, a lot more so than one would think.

It was a 1 in 100 with last summers floods across the country, as for this in sept is getting on for a 1 in 50 year event for it so being early in autumn the severn starts flooding in november normally.

My 90 year old Uncle hasn`t seen a summer like last year before.

For spring autumn/winter we can expect it as the ground is soft but not now,it should be hard.

[The PIT]

It was a 1 in 100 with last summers floods across the country, as for this in sept is getting on for a 1 in 50 year event for it so being early in autumn the severn starts flooding in november normally.

My 90 year old Uncle hasn`t seen a summer like last year before.

For spring autumn/winter we can expect it as the ground is soft but not now,it should be hard.

No it wasn't. If you look at rainfall figures you can see it isn't at least not for Sheffield. I don't know if you keep rainfall records if you do go through them you'll be surprised.

[Snowyowl9]

I can`t access the file, but as far as rainfall being rare on a 24 hour event then no it`s not thats frequent, but continues rainfall over the period as last summer being the wettest on record was it not with the severn flooded for the first time in summer July, then this long wet spell for early sept then yes it is a rare event seen the archives charts and theres proof out on the rivers it hasn`t flooded this early before as I`ve seen.

Edited September 6, 2008 by Snowyowl9

[The PIT]

I can`t access the file, but as far as rainfall being rare on a 24 hour event then no it`s not thats frequent, but continues rainfall over the period as last summer being the wettest on record was it not with the severn flooded for the first time in summer July, then this long wet spell for early sept then yes it is a rare event seen the archives charts and theres proof out on the rivers it hasn`t flooded this early before as I`ve seen.

I'm pretty sure I didn't look for events in September and if I did they would have occurred before and made the list longer. Perhaps I didn't make myself clear they were talking about daily rainfall. Even so 228mm of rain fell in June 82 24 years earlier. If our records went back longer we'd probably find a few more. Rainfall in September we've had 7 months since 1955 with over 120 mm of rain so is it really that rare????

Looking at the summer months we've had 11 years well above average since 1955. By well above I mean +50mm.

By the way the file opens but you will need acrobat reader installed.

[Snowyowl9]

I`ve recorded wetter septembers but this month is only 6 days young!!!! 1999 was the wettest with 6.1"

Nearly had half that already with 2.75" as sept 2000 was the 2nd wettest I`ve recorded which was the wettest since 1981 my rainfall records go back to 1992 had 1.3inches for the first half summer 2000 was quite wet/unsettled.

Unless we have a dry 2nd half.

Every location differs of course. :lol:

Yes daily/24 hour rainfall in summer that goes to last june and July here for the highest I`ve recorded 3.1" in june with 2.6" in July with torrental thunderstorms/heavy rain, pity I always say this that I didn`t record weather in the 80`s too young I suppose.

Edited September 6, 2008 by Snowyowl9

[The PIT]

I`ve recorded wetter septembers but this month is only 6 days young!!!! 1999 was the wettest with 6.1"

Neither does it mean the rest of the month is going to be the same. This where I went wrong predicting last year to be the wettest for us on record. Three dry months on the bounce followed by two average months and it was goodbye record year chance.

[Snowyowl9]

Neither does it mean the rest of the month is going to be the same. This where I went wrong predicting last year to be the wettest for us on record. Three dry months on the bounce followed by two average months and it was goodbye record year chance.

That true as last may/June and July were the wettest on record then august was mainly dry with the autumn the driest on record what a strange year and even december was dry. although last sept wasn`t so dry here with 1.6 inches.

[Northernlights]

Not that rare but thunderstorms and torrential rain are more frequent up here than 40 years ago when thunder was restricted to July and August along with occasional downpours and not from the end of April to the middle of September as happens today. The evidence is in arable fields around me where you can see gully erosion in most years something which was pretty rare 40 years ago. Steady rainfall seems a thing of the past.

[Typhoon John]

Not that rare but thunderstorms and torrential rain are more frequent up here than 40 years ago when thunder was restricted to July and August along with occasional downpours and not from the end of April to the middle of September as happens today. The evidence is in arable fields around me where you can see gully erosion in most years something which was pretty rare 40 years ago. Steady rainfall seems a thing of the past.

Are you sure?

I cannot believe that until 40 years ago there was never thunder or downpours outside of July and August.

It seems to me the general weather patterns this year are more like those of 40+ years ago rather than the recent past. I think the fact that we see more devastation today is due to a number of factors:

1. Larger cities and towns with more water draining into rivers.

2. Development on flood plains where for some reason people expect to be protected (well it is a FLOOD plain).

3. More news coverage of flooding when it occurs making it seem more severe and exceptional than it really is.

Edited September 7, 2008 by fozi999

[Northernlights]

Would I be right in thinking that the increase in thunderstorms up here( NE Scotland) outwith the normal summer months of July and August particularly at the end of April is down to a warming climate, more energy in the atmosphere and therefore more evaporation and more rainfall? This and lots of concrete and hard surfaces everywhere is leading to faster rainfall runoff into rivers and drainage systems that do not have the capacity to cope. The Moray Firth area was once reknowned for its dry climate ( never sowed grass on the farm without including cocksfoot due to its ability to withstand drought conditions which usually occured in late May and June nearly every year but rarely now) as it was in the rainshadow of mountains in the path of the prevailing SW winds. What seems to be happening today is more depressions passing over us on a path which gives us more northerly based winds from the sea and therfore no rainshadow effect. Also the old saying of rain before 7, fair before 11 seems out of date now as lots of rain areas seem to slow up or stall over us and do not get blown through quickly on SW winds but linger with winds from the north.

[The PIT]

Has there been an increase in Thunderstorms ???

[ribster]

As we continue to build on flood plains then put flood defences up on the former plains it will but I don't think they'll be much change in the overall pattern it may even become dryer as they were once quite sure about or it may become wetter. Remember not very long ago they were on about the rivers drying up for good. Country file once even had a good program on it. John C standing in a dry river bed saying it's the shapes of things to come. A few years later he returned to same spot and said err no it wasn't sorry.

What like the ice caps melting, and us all disappearing under the sea?!

[Snowyowl9]

Looks like thunder has increased outside of summer in september for Wales and Scotland.

Something I`ve noticed outside of summer,but less thunder in the summer to the 80`s.

[If Wishes made Weather]

Interesting mail 'The Pit'. You seem to pick up on two points that I (and others) have previously noted:

a) - for whatever reason, the Met O' seem to use vague phrases (severe, heavy, torrential ...) rather than simply expressing the expected weather in empirical terms. I'm slightly bemused by this - the dumbing down thing may have something to do with it - but the problem that they lead themselves into when using subjective language is that it awakes and links to people's own subjective expectations.

- here I could give chapter and verse ... measurably, in the UK we build infrastructure projects to lower tolerances than many other comparable countries. Coupled to that, our rescue services - and this is not aimed at the individuals who work hard in the rescue services for little grace - are similarly inadequate, when not in equipment, then certainly in numbers. Again, the point is measurable, rather than my opinion.

Tim

[johnholmes]

if you send an e mail to the Met O Tim, I'm sure they would be happy to quote what the exact terminology they use in each aspect, be it temperatures, wind, or weather.

there are, or were strict guidelines on what words may and may not be used.

[noggin]

We've had two really wet Summers in a row, with much terrible flooding.

In 1975 and 1976 we had two really dry Summers in a row.

The Summers of my childhood (late50's and early 60's), IIRC, were wet.

Some of the Summers more recently (2004? 2007) have been hot.

Is it not just the vagaries of the weather for an island on the western side of the North Atlantic?

Edited September 7, 2008 by noggin

[If Wishes made Weather]

if you send an e mail to the Met O Tim, I'm sure they would be happy to quote what the exact terminology they use in each aspect, be it temperatures, wind, or weather.

there are, or were strict guidelines on what words may and may not be used.

Many thanks John - I had somewhere in what passes for my memory some info as you are suggesting, I'll mail the Met O as to the current and report back.

T

[johnholmes]

I did have the old Media file I used but its long since got thrown away.

[Gray-Wolf]

God only knows what some on here will make of it when we cop for our share of 'displaced arctic air' in the way that Japan, eastern Europe, U.S., Greece,Turkey have over the last few years!!!! Will it be a signal that we are bound for an ice age????. (BTW, I think we will see our 'share' this Jan/Feb with cold 'lobes' descending and stalling over western Europe.......what fun! 60% of drivers haven't 'enjoyed' driving in proper snow over the past 30yrs......Gridlock anyone???)

Edited September 7, 2008 by Gray-Wolf