On Apr 13, 9:14*am, Dawlish wrote:
On Apr 11, 9:28*am, Dawlish wrote:





On Apr 10, 9:39*am, Dawlish wrote:

On Apr 9, 12:27*pm, Dawlish wrote:

On Apr 9, 11:55*am, Bridge of Sighs wrote:

On Apr 9, 9:40*am, Dawlish wrote:

On Apr 9, 9:31*am, Dawlish wrote:

On Apr 8, 1:14*pm, Dawlish wrote:

Well, there you go.The possible warmth has continued for 5 runs, I can
now be 75-80% certain of this:

By 18th April at T240, the effects of the first warm plume of the year
will be being felt in Southern England. Temperatures on the 17th and
18th of April will peak above 18C and may well be higher. Winds around
this time will be from a Southerly quadrant and the air will have had
its source in North Africa. This air could well be unstable enough to
bring the possibility of heavy, perhaps thundery showers. If the
showers stay away, Southern England, at least, will have some
pleasant, warm conditions for April.

It can never be a higher confidence forecast than 75-80%, as my
success from the past is about 78%. It's not a certain forecast, as
certainty doesn't come in to forecasting. See how it goes.

Paul

The gfs develops the North African plume further this morning, with
some pretty scorching spring weather over Spain (El Horno could be
fired up early!) on the 18th but this run terminates the Northerly
extent of its influence in the Gironde and leaves us in cool North-
Westerlies. That could change over the next couple of days, but if
this forecast joins the 20-25% of complete and utter faliiures - oh
well! So be it! It happens. It's still a lot of fun trying. My
forecast of a Northerly plunge and a cold Easter in 2007 wasn't the
best *)) , but there have been 42 successes over the last couple of
years! Plumes seem to be very hard to correctly forecast at 10 days.
They require such specific synoptics to reach the UK. The gfs is still
wrestling with the position of that Atlantic Low sitting off Iberia on
the 00z.

http://www.wetterzentrale.de/pics/Rtavn2282.png

This run puts it further South than it was when I made the forecast
yesterday. For the plume to reach the UK, it needs to be several
hundred miles further North. It'll be interesting watching it.

Paul- Hide quoted text -

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Further out, another thing I'm watching is a possible cooler plunge,
with High pressure to our west and low pressure to the East, which
would lead to .......you guessed it! Another bout of cool, showery
Northerlies to end April. Just what we need to cheer us up in mid-
spring! If the plume doesn't get to us, April may is likely to end up
with a colder CET than average.

Presently: * CET: (Apr 1- 8): 7.4°C (-0.1 degC)
(C/O climate-uk.com Thanks Philip)

Paul- Hide quoted text -

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Seems reasonable. I've gone for a cooler than average April to follow
the "technically" correct wet,windy and cool March although in many
ways it wasn't that far from average. Theres little zonal movement
currently and unfortunately we are not yet able to tap into the very
warm air that keeps drifting into S Europe. This will be more likely
in May.- Hide quoted text -

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Hi,

I've not a believer that anything is forecastable a month in advance,
but I would accept that unless this plume reaches our shores, it is
more likely that May will see warmer weather, than will late April;
though the far reaches of the run show warmer than of late!

The gfs is still playing with that warm, North African air on the 06z.

Paul- Hide quoted text -

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Not looking one of the best forecasts I've ever produced, this
morning, but judge it at outcome, as we should all forecasts. I will!

Paul- Hide quoted text -

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Back to my forecast for the 18th being largely correct. The gfs is
again showing Southerlies on the 18th, but perhaps not quite as warm
as I've forecast.

http://www.wetterzentrale.de/pics/Rtavn1682.png

It's that model development of a particular event, seeming
abandonment, then reappearance of that event which first interested me
in the possibilities of forecasting at 10 days+. Time delayed
coincidence. What are the chances of that happening, through simple
inputs of changing data? These are simply numbers remember. 5
consecutive runs showing a particular synoptic situation, then a
fairly radical change away from it, for several runs, then a
reappearance of the same phenomenen that then (hopefully) sticks.

If Southern England gets Southerly winds on the 18th, somewhere is
likely to achieve the 18C that I predicted. However, there's still a
week for this to go down the pan.........! It really does depend on
the exact position of that Atlantic low and it's counterpart, the old
"Scandi high" (so often quoted as a friendly chappie, with its cold
winter buddy, the Greenie high!) . With the low a little further South
than present and more warmer air being dragged Northwards, 18C could
be widespread at the start of next week. Then again, if the high
declines and that low makes progress Eastwards, Atlantic mP air
spreads across the UK and the forecast is down. If the high spreads
its influence Westwards, we end up in Easterlies, the holy grail of
winter, and again, the forecast is down.

After the reappearance of those Southerlies, I'm reasonably confident
they'll be there in a week's time, but "reasonably confident" marks
that as about 80%. As the Alcoholic always knows, it's just the last
fifth that kills you - the rest of the bottles were no problem!

Paul

Paul- Hide quoted text -

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Not looking good for this forecast now. It is more likely that the
winds will swing SE, then East towards the end of this week, with a
low over Northern France cutting off any hopes of warmth from the
South approaching us.

There's always something to look at T240+ though. The cold Northerly
plunge, that I remarked on a few days ago never developed and never
stayed long enough for a forecast, but the gfs is keen to sink that
low SE and allow high pressure to build SE over us and that may be
worth a T240 forecast, should that development stay on the charts
until tomorrow morning. It would bring much more settled conditions,
but, should it develop, we are not looking at warmth. This would be a
far cry from a warm Azores high. This high would have developed over
the cold North Atlantic and it could lead to some pretty cool and
cloudy weather if moisture became trapped in a temperature inversion
as it tracked SE. My confidence is not high enough for an actual
forecast yet.

Paul- Hide quoted text -

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No UK hIgh pressure forecast at 10 days from this changing output. The
blocking stays firmly to our North, out to T240 and is not now being
shown to settle over us. Something perhaps interesting at T300. Some
late April warmth has been there for two runs and has caught my
attention, but no more.

Paul