Model Output Discussion

[Glacier Point]

Your fears are well founded Rob.

Model guidance tools are beginning to come round to the idea of a pleasant spell early May with operational ECM and GFS ensemble means converging on a ridge developing just to the west of the UK pushing across temporarily.

Thereafter, confidence is increasing in the ridge becoming centred in the mid Atlantic allowing a coolish NW'ly flow to become established. Into June and it looks unsettled.

[The PIT]

GFS 00 oz showing another Northerly outbreak just outside the reliable time frame. ECM shows the same but a much shorter duration. Before that warm with showers at times.

[TonyH]

im concerned.... on a personal basis i need some rain, not too much, i dont want a drought... i fear though that summer will follow the past three with a dry spring breaking and a summer washout taking over.

Our only hope could be that the Ash is edging the Oak this Spring.

Recent years (poor Summers) have all seen Oak before Ash by a clear margin.

If theres something in this a good Summer could well be in the offing.

(Sorry OT, nature ramblings again!).

[reef]

The GFS seems pretty bullish at the moment about a cold start to May with a northerly airflow and temperatures around 7-14C by day and with some frosts at night. FI is rather extreme with a northerly flow from almost start to finish and would give a very cold first half of the month.

I suspect with a jet flow like this in mid-May the alarm bells might start to ring for summer:

http://www.wetterzentrale.de/pics/Rtavn36014.png

Lots of northern blocking and a very southerly track with depressions moving to the south of the UK. Buckets of salt required at the moment due to the timerange but it seems to be a recurring theme.

[Frosty.]

Both the GFS 00z & 6z are showing an Arctic N'ly flow across the uk for next weekend, cold enough for snow in north and on hills in the south. the ecm 00z is not buying the N'ly and quickly throws a ridge in from the west which would reduce the risk of any showers. The further outlook suggests high pressure close to the uk but a lot depends on what happens next weekend. As for this week, wednesday looks the warmest in the southeast at 23c 73f but it's downhill from then on.

Edited April 26, 2010 by Frosty039

[johnholmes]

the models are already diverging by BH Monday, 2 with a coldish NW-N flow and 1 with a more anticyclonic weather pattern but still giving cold nights.

The NOAA site running checks on the 500 hemisphere performance for 5 and 6 days shows at 5 days EC and UK better than GFS but all 3 tending to fall. By day 6 and GFS just shaves it from the other 2, both of which has shown a marked fall over the last few days with GFS rather less of a fall.

Its probably without any doubt that the weekend is going to turn noticeably cooler with night frosts a possibility for many inland areas by Sunday morning.

As to precip, then showery type rain as the colder air moves in and showers dotted around, probably around the coasts but also inland in places as the sun is high enough to trigger showers in P/Am type air masses. Snow really restricted to the northen hills I fancy but wintry hail type showers are possible to low levels in heavier showers.

Further out at T+240 and the 2 models have some differences but both suggest blocking at 500mb to the west or NW of the UK, so a coldish rather than a warmish outlook seems probable.

The teleconnections are somewhat at variance with one another. AO, NAO and PNA suggest less blocking likely but both the 500mb anomaly centres show blocking so we have to wait and see what transpires.

Little sign, after a couple of pleasantly warm days for many parts this week, of any marked warmth.

Edited April 26, 2010 by johnholmes

[mushymanrob]

Our only hope could be that the Ash is edging the Oak this Spring.

Recent years (poor Summers) have all seen Oak before Ash by a clear margin.

If theres something in this a good Summer could well be in the offing.

(Sorry OT, nature ramblings again!).

but that neans nothing for the summer

oak trees depend upon light to bring them into leaf whilst ash rely on temperature.... so oak this year will be out long before the ash, remember, nature is responsive, not predictive.

the 06z suggests a coold pattern emerging with slack winds from the northeast after this weekend (into fi)... yet again ill call that 'normal'

Your fears are well founded Rob.

Model guidance tools are beginning to come round to the idea of a pleasant spell early May with operational ECM and GFS ensemble means converging on a ridge developing just to the west of the UK pushing across temporarily.

Thereafter, confidence is increasing in the ridge becoming centred in the mid Atlantic allowing a coolish NW'ly flow to become established. Into June and it looks unsettled.

oh ek! .... i was hoping my concerns are misplaced but tbh i have a nasty feeling about this summer now we are dry for so long.

[phil nw.]

Not a warm outlook after the next few days for sure.

However some difference in the alingement of the Heights to our West going towards the outlook.

Mean Ht. Comparsons show that GFS is more bullish with the colder flow,

http://www.meteo.psu.edu/~gadomski/ECMWF_0z/test8.gif

A meridonal jet throwing a more pronounced ridging to our West.

ECM a better(warmer?)outlook for the BH weekend wanting to topple any ridging turning the flow more Westerly later.

http://www.wetterzentrale.de/pics/Recm1441.gif

UKMO trending that way too.

http://www.wetterzentrale.de/pics/Rukm1441.gif

Early doors yet but a decent BH weekend is still possible,particularly further South and East where more shelter is had from any North Westerly flow.

[TonyH]

but that neans nothing for the summer

oak trees depend upon light to bring them into leaf whilst ash rely on temperature.... so oak this year will be out long before the ash, remember, nature is responsive, not predictive.

Your wrong the Ash around here are just starting to open into leaf while the Oak are not! Oak is actually more responsive to a mild spring compared with Ash:

Nature's Calender

If the oak before the ash,

Then we'll only have a splash.

If the ash before the oak,

Then we'll surely have a soak!

This has been wrong in recent years and as we have had wet Summers, while Oak came into leaf ahead of Ash.

However the cold Winter and frequent Spring frosts this year has resulted in Ash coming out first:

Ash before Oak

Fascinating stuff to ponder while the model- watching is rather slack...

oh ek! .... i was hoping my concerns are misplaced but tbh i have a nasty feeling about this summer now we are dry for so long.

Not sure that there is much of a correlation that a wet Summer is bound to follow a dry Spring, other than that nature is likely to even itself out and become wet eventually. Perhaps that could be delayed to the Autumn.

Edited April 26, 2010 by Tonyh

[conor123]

GFS has the high moving into a very favourable position after a brief very chilly blast, would give clear blue skies for most and any sunshine this time of year always feels lovely.

[Nick F]

Looking at all the NWP output today, it looks to me that the Azores ridge will make another return into the medium range, once the trough moving SE across the UK later this week, introducing colder air, moves away. The Azores ridge has made several passes at the UK this last month, ensuring it has been a rather dry month, though the Atlantic is trying its darn hardest now to take approaches over the top of the Azores ridge from the west and looks to succeed during the second half of this week as the ridge building in from the SW tomorrow breaks down from the west by Thursday.

[The PIT]

Yup another possible cool snap moving into the reliable time frame. This seems to hang around a bit with the winds swinging to the north east so cloud on the eastern side could be a problem again. However that's well into FI so the high may end up elsewhere. Interestingly this was scene that ECM was showing several days ago.

[Duane S.]

A cold showery spell coming up, likely only to be quite short-lived as a ridge pushes eastwards and settles things down once more but certainly no sign of anything too warm in the offing. Relatively dry but not that warm. A chance that we could draw in a warmer continental feed for a while but NW,N and NE winds will prevail from the end of the week, for most, by the looks of things.

What has become very noticable of late, in fact over the past 2-3 years, is that every time a sustained northerly based jetstream looks like getting its feet under the table, before you can blink it is getting forced back down south, thus decreasing the opportunites of any sort of sustained mild/warm/hot spell, depending on the season. I'm sure there are plenty of exceptions but they seem to be just that...

[Bottesford]

Looks a bit disappointing for the bank holiday weekend (as ever!). Lots of sunshine and temps into the low 20s during the working week then I note BBC 5 day (often wrong of course) saying 9c with heavy rain for Sat.

Lets hope it isn't quite that bad as single figure maxima and rain seems about the worst option possible for the weekend.

[skifreak]

LOL at the Pub Run!! *If* the 18z GFS run were to come to pass, then we'd be skiing on CairnGorm Mountain on May 15th/16th on no less snow than is on the hill at the end of this week!!

Endless winter has a better ring to it than the usual scenario of perpetual autumn!

[Eugene]

Cold northerly at the weekend then HP sitting just to our west(a cool high) but drying up, great if you ask me lovely cold mornings and pleasant days, perfect for walking, bring it on

[mushymanrob]

Your wrong the Ash around here are just starting to open into leaf while the Oak are not! Oak is actually more responsive to a mild spring compared with Ash:

i can assure you that here theres no sign of any ash opening, they are always late whilst oak are opening now and their timing varies more then the ash. are you sure its not the asho flowers that arnt opening? they tend to be earlier then the leaf.

that research though took no notice of light and concentrated on temperature only. i dare say another set of statistics will take moisture into account..

[picog]

i can assure you that here theres no sign of any ash opening, they are always late whilst oak are opening now and their timing varies more then the ash. are you sure its not the asho flowers that arnt opening? they tend to be earlier then the leaf.

that research though took no notice of light and concentrated on temperature only. i dare say another set of statistics will take moisture into account..

Oak definitely ahead of the ash here, and it's happened in a few days! Looks like we might be at risk of a late frost or two — the type that catch out the potato plants! Despite predictions of a mild night last night, we got down to a surprisingly low 2.1C, which is close enough if you're a gardener!

[Coast]

New thread here folks!! http://forum.netweather.tv/topic/62384-model-output-discussion/