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Gavin P

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Posts posted by Gavin P

    Model Output Discussion 01/06/2012

    in Forecast Model Discussion

    Posted

    Interesting discrepency between GFS and NAE for late tonight and tomorrow morning

    NAE wants to take an area of pretty heavy rain from Bristol to The Humber in the morning;

    http://www.weatheronline...ES=0&WMO=&PERIOD=

    http://www.weatheronline...ES=0&WMO=&PERIOD=

    GFS doesn't really show much at all. Maybe some showers over East Anglia by lunchtime, but certainly nothing that significant;

    http://www.wetterzentrale.de/pics/Rtavn124.png

    http://www.wetterzentrale.de/pics/Rtavn184.png

    Unusual to have a differance like that at such a short time out.

    Model Output Discussion 01/06/2012

    in Forecast Model Discussion

    Posted · Edited by Gavin P

    GFS and UKMO 12z have that look of big thundery showers and storms from the cut off;

    http://www.wetterzen...s/Rtavn1444.png

    http://www.wetterzen...cs/Rukm1441.gif

    Now, when cut off's get invoved the models have all sorts of problems, so this might not be a done deal yet, BUT as it stands this evening (still waiting for ECM of course) expect some VERY big showers, thunderstorms, lightning, hail, tornado's and flooding in the south next week

    Nao Forecast For Winter 2012/2013

    in Spring Weather Discussion

    Posted

    The question I ask is why May? What is so special about May? Why not November? I don't see how a month that is 6 months away can be used.

    I believe the sea surface temperature anomalies that occur in May have a tendency to re-occur in the subsequent winter.

    How that happens and what the mechanism is that cause's it, I don't know I'm afraid. :)

    Nao Forecast For Winter 2012/2013

    in Spring Weather Discussion

    Posted · Edited by Gavin P

    I suspect that if using the SST idea gave a better than 50/50 probability using past winters as an example then it would have been used by professional sites.

    Well it was used by the UK Met Office for years (still is as far as I know, just they don't make their findings public anymore after the media bullied them into silence sad.png ) in conjunction with the long range dynamic model.

    I agree though, I certainly don't see NAO forecast as the be all and end all. I definately wouldn't want to resolve an entire winter forecast around this one prediction.

    Nao Forecast For Winter 2012/2013

    in Spring Weather Discussion

    Posted · Edited by Gavin P

    Hi Gavin,

    Without calling your methods into question, I found the opposite to be the case for May this year. I had a look at the stats for my local weather station (Royston,Herts) and I noticed that the winds were very much coming from a northerly or easterly quarter for most of the month so I checked out the synoptics for May and saw for around 2/3rds of the month, there was high pressure over greenland or the mid atlantic causing the jet-stream to head further south forcing the storm track over the channel, thus giving us the appauling month we had. Wouldn't that suggest we had a neutral or negative phase of the NAO for the month? I could be reading this completely wrong so bear with me smile.png

    Alex

    P.S May 2012 looked incredibly similiar to 2008,9 and 10

    We look at the SST's in May with a view to how the Atlantic *MAY* force the atmosphere in winter. The things that dictate the NAO in winter are not the same as the things that dictate the NAO in May - Remember April and May will usually have more northerly and easterly winds than any other time of year due to the decline of the westerlies which is a common occurance in spring, primarily because the arctic is warming and the PV is breaking down.

    Good work gavin. How ever going by last winter i think the stratosphere has a big part to play.

    Indeed. Its just one part (small, big?) of the puzzle. No more, no less.

    I personally feel that there is little merrit in this and its basically a no-brainer to call +NAO from this far out. At very worst its no better than flipping a coin.

    Heads positive NAO and tails negative NAO. Who goes first ?

    Lets not forget that the default lends itself to a positive NAO, particularly when its been so long since the last that on a balance of probabilities a +NAO is long overdue.

    Thanks.

    Just one point I'd like to make.

    If the sea surface temperature anomaly had indicated a negative NAO for the subsequent winter (in other words if there had been the warm, cold, warm tripole) I'd have called it that way. So this isn't a "balance of probability" or "no brainer" call but a genuine attempt to use May's SST's anomalies to predict the NAO next winter.

    Whether you think theres any merrit in this particular methodology or not is of course up to you. smile.png

    First Autumn 2012 Forecast

    in Spring Weather Discussion

    Posted · Edited by Gavin P

    Cheers Gav.....watched from start to finish. Wow, what an impressive winter anomaly that is.....I can but dream!

    It certainly is isn't it? You'd need some lagging round pipes if that came off.rofl.gif

    But remember, its JFF right now. If its still showing a similar anomaly in September we can start getting interested.

    First Autumn 2012 Forecast

    in Spring Weather Discussion

    Posted · Edited by Gavin P

    Hey folks,

    Here's my first forecast video for autumn 2012:

    http://gavsweathervids.com/seasonal.html

    Long range models generally painting a picture for a rather cool autumn at the moment, though its very early days.

    BTW, if you stick around to the end theres a little sneak peak at winter 12/13 - JFF

    Next months autumn 2012 update should have a better handle on where things might be going.

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