Weather

Widespread heavy rain on its way

The UK will be affected by some very disturbed weather in the next few days, as two separate weather systems threaten appreciable rainfall to many areas.

The first system will bring heavy rain northwards to Yorkshire and Lincolnshire through this evening.

15-20 mm is expected quite widely across the area in the next 24 hours, with higher totals locally, especially over the Pennines.

Even snow is possible over the higher Pennines later tonight, due to the intensity of rain lowering the air temperature, in a process known as evaporative cooling.

The heavy rain will slowly clear northwards tomorrow, with a return to sunshine and showers on Thursday and Friday.

The next system looks set to move across much of the UK this weekend.

The timing and positioning of this next area of heavy rain is uncertain at this stage, with current projections bringing it into Yorkshire and Lincolnshire later on Saturday.

The heaviest rain may occur to the south of our area – with some parts of the UK in the next 5 days recording a month’s worth of rain.

Farmers and gardeners will welcome the rain following a very dry April, which saw a significant rainfall deficit.

But it’s all rather far removed from a front page article in the Daily Express written just two weeks ago, which you can read by clicking here.

Follow me on twitter @Hudsonweather

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  • Comment number 89. Posted by ukpahonta

    on 21 May 2013 18:59

    #88 QV

    I read something a while back that indicated geothermal activity was converted more into forming deep currents than raising heat content. Can't remember the source but a quick search reveals a paper from Southampton uni archives along the same lines:
    http://eprints.soton.ac.uk/259/1/ASM_GRL_2001.pdf

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  • Comment number 88. Posted by QuaesoVeritas

    on 21 May 2013 17:01

    #86.ukpahonta
    "What else could affect the amount of heat that the oceans absorb? Hhmm."

    I think I have raised this before, but how do we know that the oceans are not being heated by geothermal activity?

    It seems perfectly logical to me, but presumably someone has thought of it before.

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  • Comment number 87. Posted by ukpahonta

    on 21 May 2013 15:45

    #85 greensand

    Nice to know.

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  • Comment number 86. Posted by ukpahonta

    on 21 May 2013 15:29

    #84 newdwr54

    What a conundrum?

    Don't agree with the use of negative by the way, implies that the earth is heating the sun.

    What else could affect the amount of heat that the oceans absorb? Hhmm.

    Clouds reflect solar radiation and stop it entering the oceans. So if there were less cloud cover that would mean more solar radiation entering the oceans.

    'Variations in solar irradiance are recognized as a fundamental forcing factor in the climate system and may directly or indirectly influence the amount of clouds. For instance it is generally believed that the main cause of the cold intervals during the Little Ice Age 1300-1900 was reduced solar irradiance (Lean and Rind 1998; Shindell et al. 2001).

    The solar irradiance varies by about 0.1 percent over the approximate 11-year solar cycle, which would appear to be too small to have an impact on climate. Nevertheless, many observations suggest the presence of 11-year signals in various meteorological time series, e.g., sea surface temperature (White et al. 1997) and cloudiness over North America (Udelhofen and Cess 2001).

    The flux of galactic cosmic rays (GCR) varies inversely with the solar cycle. Svensmark and Friis-Christensen (1997) suggested that GCR enhance low cloud formation, explaining variations on the order of 3 percent global total cloud cover over a solar cycle. A 3 percent cloud cover change corresponds to a radiative net change of about 0.5 W/m2 (see above), which may be compared with the IPCC 2007 estimate of 1.6 W/m2 for the total effect of all recognized climatic drivers 1750-2006, including release of greenhouse gasses from the burning of fossil fuels.

    Since clouds have a net cooling effect on climate, the above would imply (Svensmark 1998) that the estimated reduction of cosmic ray flux during the 20th century (Marsh and Svensmark 2000) might have been responsible for a significant part of the observed warming. Since 1983, the cooling cover of low clouds have decreased from 29% to about 25% (see below). During the same period the net change of warming high clouds have been small (see below).

    The new hypothesis on cloud formation being influenced by the intensity of galactic cosmic rays has been exposed to critique (Kristjánsson et al. 2002; Kristjánsson et al. 2004). Later, however, new experiments demonstrated that cosmic rays may indeed produce cloud condensation nuclei (CCN's). By way of the SKY experiment in Copenhagen was demonstrated how electrons set free in the air by passing cosmic rays help to assemble building blocks for CCN's (Svensmark et al. 2006, Svensmark 2007).'
    http://www.climate4you.com/ClimateAndClouds.htm#DiagramCloud%20cover%20change%20observed
    There is also a graph there showing cloud cover change since 1983

    I am led to believe that there will be some papers issued shortly from the CERN CLOUD work.

    I wonder if that would also tie in with jet streams being more polar during active solar cycles and less polar during inactive cycles. Worth thinking about.

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  • Comment number 85. Posted by greensand

    on 21 May 2013 14:51

    #82. ukpahonta

    Bob Tisdale has kindly replied:-

    "Green Sand: The differences between the BOM and NOAA classifications of El Nino and La Nina conditions have existed for as long as I’ve known."

    So there you go we have at least 2 threshold levels, I have no doubt there will be some others out there!

    I am even more resolved to just observe the actual SSTs and their associated trends. Many thanks for raising the question.

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  • Comment number 84. Posted by newdwr54

    on 21 May 2013 13:50

    77. ukpahonta

    Re ' Energy has to pass into the oceans from the atmosphere first. You have previously agreed with this.'

    "Nope, the sun heats the oceans. The atmosphere can restrict or block the sun heating the oceans and even restrict the ocean from releasing heat but it's the sun what did it."

    But the only change in solar radiation energy over the recent observed period of both ocean and atmospheric warming has been negative. So the 'increased' heating of the both cannot be attributable to the sun.

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  • Comment number 83. Posted by greensand

    on 21 May 2013 12:13

    #82. ukpahonta

    Ah, now I see, sorry I hadn't picked up that it was in the "Climate Model" section, should have done so with you mentioning "in the new layout". I don't go there very often as the model predictions seem to be reactive not proactive.

    As you will have gathered by now I don't know the answer, I have left a note at Bob Tisdale's asking if he can shed any light on it.

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  • Comment number 82. Posted by ukpahonta

    on 21 May 2013 11:48

    #80 greensand

    Climate Model Summary
    http://www.bom.gov.au/climate/ahead/model-summary.shtml#tabs=Pacific-Ocean

    'The following graph shows the average forecast value of NINO3.4 for each international model surveyed for the selected calendar month. If the bars on the graph are approaching or exceeding the blue dashed line, there is an increased risk of La Niña. Similarly, if the bars on the graph are approaching or exceeding the red dashed line, there is an increased chance of El Niño.'

    Lines set at +/-0.8C

    'NINO3.4 and other indices

    The National Climate Centre (NCC) uses the "NINO3.4 index" to classify ENSO conditions (see "Note:" below). The NINO3.4 index is defined as the average of SST anomalies over the region 5°N - 5°S and 170° - 120°W. NCC classifies the NINO3.4 temperature anomaly as "warm" if it exceeds 0.8°C, which is about one standard deviation above average. Similarly, anomaly predictions below –0.8°C are tabled as "cool", with those in between classed "neutral". There are also other "NINO" indices that refer to SST anomalies over different areas of the Pacific Ocean. The regions covered by the NINO indices are shown in this map of the tropical Pacific Ocean. '
    http://www.bom.gov.au/climate/ahead/about-ENSO-outlooks.shtml

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  • Comment number 81. Posted by greensand

    on 21 May 2013 10:09

    Sorry forgot the link to BT:-

    http://bobtisdale.wordpress.com/2013/05/20/mid-may-2013-sea-surface-temperature-anomaly-update/

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  • Comment number 80. Posted by greensand

    on 21 May 2013 10:06

    #79. ukpahonta

    "Have BOM changed their ranges..."

    Don't thinks so uk, are you referring to their Southern Oscillation Index (SOI)?

    "Sustained positive values of the SOI above +8 may indicate a La Niña event, while sustained negative values below −8 may indicate an El Niño event. Values of between about +8 and −8 generally indicate neutral conditions."

    http://www.bom.gov.au/climate/glossary/soi.shtml

    "The SOI is calculated using the pressure differences between Tahiti and Darwin........."

    I have never really got a clear understanding of the ENSO Indexes, SOI, ONI, etc, probably because |I have never really tried and each time I do have a look they seem to change something. So now I limit myself to the actual SSTs in the area using 2 sources BOM and Reynolds:-

    http://www.bom.gov.au/climate/enso/indices.shtml?bookmark=nino3.4

    Even then care is needed the chart shows "Latest Weekly Value = +0.07" but if you go to "Data sorted by date" to the top right of the chart you will find that actual latest weekly value is -0.14. No big deal just confusing, I think they post the data weekly and change the chart every 2 weeks.

    I also check out Reynolds and keep a watch on Bob Tisdale and his use of Reynolds for ENSO and Global, they compare very well with the data produced by the BOM so it is good to have confirmation.

    Bob uses actual SSTs of +/-0.5c for the La Nina/El Nino thresholds, lot easier to comprehend than the indexes.

    The latest BOM numbers have all ENSO areas 1 - 4 in negative territory and at present trending lower, ENSO 1 & 2 at approx -0.60c, will have to wait and see if this transposes into the 3.4 region.

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