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

I always return to any forecast I make, be it good, or bad!

OK a hopeless forecast. This one fell into the 20-25% of faliures and
it ranks as a stinker amongst those (Euro stinker? No muck on the
ground in the rain though in Devon!) . It's not even a near miss and
it ranks on the abysmal level of the Cold Northerly I forecast at
Easter 2007 (remember that glorious, warm sunny weather at an Easter
which now sits in the warmest April for 350+ years?)

The reason was a combination of a Southerly diving jet, producing cold
uppers and an associated lee depression which is likely to track W to
E along the channel and across Northern France. It has stymied any
development of that warm plume that was shown on the gfs for a few
days, in one form or another, 10 days ago. This was compounded by*
the Northern blocking of Early April continuing and sitting there over
Iceland, like a giant high pressure toad, squatting with its heavy
haunches and putting up an impenetrable wall of toady atmosphere
against the release of my predicted North African plume. OK,
stretching a metaphor, but I hope you get the picture.

Maybe I've got the first plume right, at 10 days, on the max temp
record thread!

Paul

* Does high pressure at our latitudes result from the track of the
jet, or does it alter the jet's path. Has this jet been forced South
by an anticyclone which stretches from ground level to the 200mb hpa
level, or did it form as a result of the jet tracking south? It's a
chicken and egg scenario that I've always found hard to interpret. In
this case, I'd go with the high developing and the jet being forced
around it, but I could be wrong! Any clues, anyone?