On Tuesday, August 18, 2015 at 9:59:08 AM UTC+1, Dawlish wrote:
On Saturday, August 15, 2015 at 7:05:29 PM UTC+1, Dawlish wrote:
If only t'were January!

**At T240, on 25th August, a large and persistent high pressure system will be located over Scandinavia/Baltic sea. It will lead to one of several types of weather for the UK, depending upon its exact location and orientation, but low pressures will be stalled in their passage across the UK from the west. If the stall occurs with the low centre over the UK, some areas may be experiencing heavy rain and flooding may well result in some areas. If the high is a little further north, dry easterlies will be affecting the UK and if the lows stall further to the west, with the high pressure itself a little further west, warm air from the south will be drawn across the UK.**

Thus, very difficult to predict the UK's exact weather, as a small change in location of the centre of the high could lead to a large change in our weather type, but high pressure will have become firmly established to our NE by the 25th.

Persistent swine, this blocking high, isn't it? All models, including GEM, which has shown a more progressive situation over the last few days, are showing a Scandinavian high still present on the 28th. If this agreement is still there tonight, I'll be forecasting an extension to my forecast for the 25th. (I've always given a gap of three days between forecasts of a similar set-up).

And tonight's output rather scuppers an extension to that forecast. Perhaps a change from the blocked situation is afoot!

"Dawlish" wrote in message
...

Your problem with that is exactly where?

I can't really speak for Col, but I suspect that he's more sympathetic to
your forecasting attempts than you might think, as indeed I am. But rather
than trying to answer his question by misplaced obfuscation or bluster,
wouldn't it have been simpler and more honest just to say:

'All my forecasts can really do is to try to predict the broad pressure
pattern across NW Europe. Sometimes this allows some specifics of the UK
weather type to be forecast, but at other times, as now, there is too much
uncertainty in the detail to permit much more than the broad pressure
preview.'

On Wednesday, August 19, 2015 at 9:22:51 AM UTC+1, JohnD wrote:
"Dawlish" wrote in message
...

Your problem with that is exactly where?

I can't really speak for Col, but I suspect that he's more sympathetic to
your forecasting attempts than you might think, as indeed I am. But rather
than trying to answer his question by misplaced obfuscation or bluster,
wouldn't it have been simpler and more honest just to say:

'All my forecasts can really do is to try to predict the broad pressure
pattern across NW Europe. Sometimes this allows some specifics of the UK
weather type to be forecast, but at other times, as now, there is too much
uncertainty in the detail to permit much more than the broad pressure
preview.'

Col just got the wrong end of the stick! The clue to this forecast is in the title: ** Forecast: Scandinavian high on 25 Aug** *))

I have no idea how many times I've said something similar to your summary, John. It's what the models show at 10 days, when I determine there is sufficient agreement and consistency and the detail is always going to be difficult, though I usually try to add some.

On Saturday, August 15, 2015 at 7:05:29 PM UTC+1, Dawlish wrote:
If only t'were January!

**At T240, on 25th August, a large and persistent high pressure system will be located over Scandinavia/Baltic sea. It will lead to one of several types of weather for the UK, depending upon its exact location and orientation, but low pressures will be stalled in their passage across the UK from the west. If the stall occurs with the low centre over the UK, some areas may be experiencing heavy rain and flooding may well result in some areas. If the high is a little further north, dry easterlies will be affecting the UK and if the lows stall further to the west, with the high pressure itself a little further west, warm air from the south will be drawn across the UK.**

Thus, very difficult to predict the UK's exact weather, as a small change in location of the centre of the high could lead to a large change in our weather type, but high pressure will have become firmly established to our NE by the 25th.

Too progressive really. The lows have made more progress eastwards than the models showed back on the 15th. The high has retreated eastwards and is not now located over Scandinavia and the Baltic.

On Tuesday, 25 August 2015 19:51:09 UTC+1, Dawlish wrote:
On Saturday, August 15, 2015 at 7:05:29 PM UTC+1, Dawlish wrote:
If only t'were January!

**At T240, on 25th August, a large and persistent high pressure system will be located over Scandinavia/Baltic sea. It will lead to one of several types of weather for the UK, depending upon its exact location and orientation, but low pressures will be stalled in their passage across the UK from the west. If the stall occurs with the low centre over the UK, some areas may be experiencing heavy rain and flooding may well result in some areas. If the high is a little further north, dry easterlies will be affecting the UK and if the lows stall further to the west, with the high pressure itself a little further west, warm air from the south will be drawn across the UK.**

Thus, very difficult to predict the UK's exact weather, as a small change in location of the centre of the high could lead to a large change in our weather type, but high pressure will have become firmly established to our NE by the 25th.

Too progressive really. The lows have made more progress eastwards than the models showed back on the 15th. The high has retreated eastwards and is not now located over Scandinavia and the Baltic.

Yes, high pressure was persistent from the 13th to the 24th.

What about the chances of an anticyclonic (N) from the 3-10th September?

The latest GFS has very little in the way of cyclonicity in its later frames.

Gem was the first of the models to begin to push the high eastwards by the 25th. I might have expected it to be the gfs, but this time the gfs and ECM fell into line with their Canadian counterpart.