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Weather reports on Met Eireann?

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  • 13-08-2008 1:02pm
    #1
    RoisinD
    Registered Users Posts: 408 ✭✭


    I have been looking at the latest weather reports on and off all morning, particularly for Shannon airport which is the one closest to me. As I read it the rainfall for there is being measured at 0.5mm per hour. Our rainfall since approx 8.00am is over 50mm to now as it has been lashing down without stopping.

    How can there be such a big difference between us given that we are only about 45mins from Shannon and sitting under the same rain band or am I reading the Shannon info wrong? I understand differences with the winds etc as we are on coast and Shannon is inland but this has me and others stumped.

    Any help would be appreciated.


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    #2
    Deep Easterly
    Closed Accounts Posts: 5,150 ✭✭✭Deep Easterly


    RoisinD wrote: »
    I have been looking at the latest weather reports on and off all morning, particularly for Shannon airport which is the one closest to me. As I read it the rainfall for there is being measured at 0.5mm per hour. Our rainfall since approx 8.00am is over 50mm to now as it has been lashing down without stopping.

    How can there be such a big difference between us given that we are only about 45mins from Shannon and sitting under the same rain band or am I reading the Shannon info wrong? I understand differences with the winds etc as we are on coast and Shannon is inland but this has me and others stumped.

    Any help would be appreciated.

    As far as I am aware, you are on the North Clare coast right? Having looked at the radar sequence for last night, it is pretty obvious you had much more rain than our cousins down in Shannon, and without doubt, much more than us here on the other side of the bay! The hills on the north coast of Clare would have caused an awful lot of uplift thus bringing you a healthy amount of rain!:) Plus many of the rain showers this summer have been very localised, so just a few miles down the road could have been dry while you were soaked.

    I think this calls into question though the abnormal sparsity of synoptic stations around the county, because none of the ones shown on the "latest reports" page represent the bulk of the county at all. This is not Met Eireanns fault at all, but the lack of funding they are given by this tosspot of a government is to blame. :mad:

    Pissing rain here for the last 3 hours by the way. :)


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    #3
    Danno
    Registered Users Posts: 8,913 ✭✭✭Danno


    In last weeks event I got 34mm whilst Carlow, 20-25 miles due east got about 33% less.


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    #4
    RoisinD
    Registered Users Posts: 408 ✭✭RoisinD


    Thank you DE for your explanation. You are right I am on the North Clare coast. Will be interested to see the cumulative totals for Shannon today and do a comparison.:)

    Agree re the lack of stations around the country. There are none on the coast between Valentia and Bellmullet which can be frustrating and can give a false impression of the weather around the country especially on the coasts.


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    #5
    Mothman
    Closed Accounts Posts: 6,498 ✭✭✭Mothman


    9th August
    Dublin 40-70mm
    Wicklow 8mm

    These rains hit some parts and not others.

    About stations, there are about 100 climatological stations and hundreds more rain gauges. Still huge gaps, but no way can one have enough rain gauges to be able to measure every "cloudburst"
    See map of climatological stations Somewhat outdated.

    Cloudburst becasue ME used term recently in a forecast


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    #6
    Snowbie
    Registered Users Posts: 5,033 ✭✭✭Snowbie


    But the difference MM is that N Dublin 9th Aug event was convective precip and did not cover a wide area while today the frontal stuff was covering where Roisin is and Shannon AP simultaneously at her time of posting and did not budge from either area both before and after her OP.

    Obviously rain does not fall uniformly and in intensity across any area so I'm therefore interested myself to see Shannon's rainfall today compared with rainfall Roisin got after her OP.

    Below is the attach of Clare radar at 1300


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    #7
    Danno
    Registered Users Posts: 8,913 ✭✭✭Danno


    You should see the differences around here that local hills under 350m make to showers! I often travel the N8 between Abbeyleix and Urlingford and it is "the usual suspects" areas where the roads are wet, whilst a few hundred metres up the road it is bone dry. Hills affect the airflow which showers follow.
    Interestingly, frontal rain sometimes behaves in the similar fashion with far heavier rain fall in these areas too, but alot of the time, differences in wind direction can shift heavier rainfall in over areas that usually don't get it as heavy.

    Oh, here is the greatest example of them all: http://www.boards.ie/vbulletin/showpost.php?p=56813508&postcount=132


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    #8
    Deep Easterly
    Closed Accounts Posts: 5,150 ✭✭✭Deep Easterly


    Close proximity to hills do play a huge part in rainfall alright. It is not unusual for Maam Valley in West Galway to recieve daily falls of 50mm+ during frontal rain passages despite no astounding reflections on the rainfall radar.

    I argue that Lenann on the west coast is even wetter; in fact I argue that it is the wettest place in Ireland. Not statistical based, but from personal experience. A true piss pot of a place. :D


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    #9
    Mothman
    Closed Accounts Posts: 6,498 ✭✭✭Mothman


    RoisinD wrote: »
    Thank you DE for your explanation. You are right I am on the North Clare coast. Will be interested to see the cumulative totals for Shannon today and do a comparison.:)

    Shannon AP 8.9mm
    Knock, Clarmorris, Belmullet all c40mm

    Fair point Snowbie and it wasn't good example to use.


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    #10
    StratoQ
    Registered Users Posts: 41 ✭StratoQ


    Re: Lack of Met Stations

    Met Eireann have been commisioning several other auto stations over the past few years. e.g. one at Mace Head Co. Galway (wouldnt it be great for storm reports!) and I believe another nearby Markree Castle Co. Sligo (which incidently holds many low monthly temp records in Ireland).

    Now I havent seen any met data (available to public) yet from these stations. Maybe there have been some teething problems. I dont know. If they are ready to go and up and running it would be a shame that we the public have no access as yet to them.

    Re: Diverse rain totals

    Topography has a huge effect. Even over short distances. Another recent example. I happened to be in west clare the day Shannon Airport rec'd 38mm in one hour from intense convective showers. The showers were pretty widespread and were moving to the NW. However Sliabh Callan and a light sea breeze managed to keep the Spanish Point area almost completely dry that day. I moved 10 km up the road later in the afternoon to Lahinch and saw some of the heavy showers that deluged Shannon. It's another "convective" example but shows the diversity that can exist even over 10km.


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    #11
    Snowbie
    Registered Users Posts: 5,033 ✭✭✭Snowbie


    The theory about topography for it's affect on rainfall is somewhat true.

    But one thing i will add is that the Shannon doppler radar image is on the blink for a couple of years now, dropping it's singnal(or maybe the data feed) to the main site and other sites we use.
    In particular the 5 min radar i use. In every half hour the Shannon radar is blank for 15 sometimes for 20 mins peroids.

    Dublin AP is out of range for the majority of the SW so Shannon is relyed to give data down that way and even when it does transmit certain areas seem to be lost and blank.
    This can also have the affect of intensifying the rainfall return image falsely which seems to be the case around Shannon?

    I thnk someone only last week on this forum commented on this already from the SW. Very little was falling but radar suggested a higher rate?


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    #12
    Deep Easterly
    Closed Accounts Posts: 5,150 ✭✭✭Deep Easterly


    Snowbie wrote: »
    The theory about topography for it's affect on rainfall is somewhat true.

    But one thing i will add is that the Shannon doppler radar image is on the blink for a couple of years now, dropping it's singnal(or maybe the data feed) to the main site and other sites we use.
    In particular the 5 min radar i use. In every half hour the Shannon radar is blank for 15 sometimes for 20 mins peroids.

    Dublin AP is out of range for the majority of the SW so Shannon is relyed to give data down that way and even when it does transmit certain areas seem to be lost and blank.
    This can also have the affect of intensifying the rainfall return image falsely which seems to be the case around Shannon?

    I thnk someone only last week on this forum commented on this already from the SW. Very little was falling but radar suggested a higher rate?

    I think that is a countywide problem Snow. I have noted myself that for my own area, (and generally speaking), that shower intensity on the radar is often underestimated, while frontal rain intensity is sometimes (but not always) overestimated. I have noted this for the Dublin area as well. Even during the big event down in Shannon and Limerick a couple of weeks back, the rainfall radar was showing an intensity that was much less than the actual.

    Secondly, I think there is an appalling coverage of the Northwest and North of the country on the Met radar. From mid Mayo to Louth northwards is almost viod. I am surprised that ME don't commission the Radar in Belfast to give a better coverage of our nation?


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    #13
    Snowbie
    Registered Users Posts: 5,033 ✭✭✭Snowbie


    Oh yeah Paddy its defo countrywide. One doppler needs the other as signal bounces off the precip to give the complete picture. The same idea as pro strom chasing in the states when you triangulate doppler images from 3 seperate sites around a cell.

    Also doppler does not work too well through hills or mountainous area.
    So when the Shannon radar goes down so does the intensity of rainfall from the Shannon side of the echo and vica versa.


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