Models, teleconnections and nowcasting

[knocker]

The North Atlantic 500mb and surface analysis for midnight

still cloud around  the vicinity of the front in the north with perhaps some patchy rain, otherwise today will be sunny and quite warm. But not quite so warm in the areas under the cloud and in particular NE coastal areas where there is an onshore drift

Still some rain around in the far NW otherwise a dry night but quite cloudy in the north

Friday a sunny and warm day, including the NE, with perhaps the odd shower in the NW

For most places another warm and sunny day on Saturday but fronts associated with the shallow low tracking south east will bring cloud and some rain to NW regions

As discussed in previous posts the low has now briefly phased with a lobe of the tpv to the north as the the subtropical high amplifies to the west of Ireland. Another warm day for England and Wales albeit some showery rain in western regions courtesy of a weakening occlusion, but much cooler in N./ Ireland and Scotland

By Monday the high has ridged NE over the UK with the low becoming a cut off feature west of Iberia resulting in a much cooler day for all with maybe the odd shower

Edited April 9, 2020 by knocker

[knocker]

Moving on with the gfs and a brief summation of midweek

Another trough in the NW tracks east and phases with the cut off low near Iberia which briefly interrupts the subtropical high dominance Still remaining generally dry but with some more unsettled weather encroaching from the west

 

Edited April 9, 2020 by knocker

[knocker]

In previous posts back in the day the reasons why using 850mb temps to estimate surface temps in fraught with danger has been discussed. Without going through it all again essentially the reason is you have to have a fair idea of the airmass characteristic from the surface to 850mb and thus calculate the average lapse rate. Quite tricky but there are occasions when you can take a good punt at this and now is one. The air is quite dry in many regions, the south east in particular, so assuming a lapse rate near the DALR (dry adiabatic lapse rate 9.8C/km) is a fair bet

Using yesterday's Hurstmonceux midday sounding as an example

The 850mb height is 1574 metres and temp +7C

Surface temp 22C

So difference 15C and average lapse rate surface > 850mb 9.5C/km

Which is very close to the DALR of 9.8C which is no big surprise as the sounding shows the temp profile very close to the DALR line

But the added complication at this time of year, and particularly in the summer, is that you have to take into account surface heating and a supper adiabatic lapse rate in the lower boundary layer which can also be seen on the sounding.

Ergo using a lapse rate close to the DALR and adding whatever you think the surface heating may be might get you pretty close

 

Edited April 9, 2020 by knocker

[knocker]

There are still some significant differences between the ext anomalies this morning. Mainly involving the structure and orientation of the tpv and over the eastern Atlantic/Europe the relationship between amplification of the subtropical high and the trough in the Iberia/North west Africa region. The same trough which starts to become a feature over the next few days

[knocker]

The ecm 06 Frid > Sun

[knocker]

Merely a watching brief at the moment but the next 'interlude' in the high pressure dominance after this weekend could be when another trough tracks east and attempts to link with the cut off low to the south

[knocker]

Some interest by the ext anomalies this evening in moving the centre of the tpv to northern Canada but no agreement on any associated trough into the NW Atlantic.The EPS is even  suggesting a possible link to the low pressure in the western Med.Whilst at the same time indicating strong positive anomalies over Europe

The lower strat no dissimilar

Edited April 9, 2020 by knocker

[knocker]

The North Atlantic 500mb and surface analysis for midnight and the sat image

Much of the cloud on the above image should clear, perhaps cirrus around in places and some showers popping up, otherwise another warm and sunny day. But some rain will encroach the NW late on

Some rain still in the NW overnight otherwise clear with the odd mist patch by morning

Fronts associated with the low in the Atlantic edge east on Saturday so although it will generally be another sunny and warm day there could well be some heavy showers in places in England and wales Much cooler in the NW

Over Saturday night there is a brief phasing of the troughs (previously discussed) as the subtropical high amplifies to the west resulting in a complex picture over the UK of sunny periods, heavy showers and some longer periods of rain

By Monday the merging of the troughs is brought to an abrupt end as a high cell develops over the UK and once any frontal rain has cleared to the south it should be quite sunny, albeit a lot cooler

The high cell is still at the helm on Tuesday but a weak Atlantic trough is edging east

 

Edited April 10, 2020 by knocker

[knocker]

According to the gfs the aforementioned trough does briefly phase with the trough to the south and by so doing activates the latter resulting in a brief interruption of high pressure dominance over the UK. So perhaps a tad more unsettled, particularly in the south

[knocker]

The ecm differs with the phssing of the troughs and the development of the surface low next week which pretty much leaves HP in charge

[knocker]

Today's EC weeklies update for the first couple of weeks of May

01 > 08

A weak tpv aligned N. Russia/N, Canada with minimal trough influence in the Atlantic facilitates some positive amplification of the subtropical high in the east which suggests  a relative quiet and dry period with temps around average

08 > 15

Slightly less amplification in the east so perhaps a tad more unsettled, more particularly in the north

Edited April 10, 2020 by knocker

[knocker]

The varied weather over the weekend with the 06 ecm

[knocker]

Quite interesting to note the key role that the cut off upper lows, the formation of which gets underway on Sunday, play in the forthcoming evolution

[knocker]

Synop max temps today

http://www.met.reading.ac.uk/~brugge/18.html

[knocker]

The North Atlantic 500mb and surface analysis for midnight and the sat image

Some showery rain in the north today, courtesy of fronts associated with the trough to the west, otherwise another sunny and warm day for England and Wales with perhaps the odd shower developing in some areas

Remaining cloudy with the odd spot of rain in the north and perhaps the odd shower in the Midlands area as the weak cold front moves south

By Sunday the aforementioned trough has briefly phased with the tpv lobe and is over the UK,  as the subtropical high amplifies in the west. Thus a day of sunny intervals and showers, coalescing on occasion to longer periods of rain, and regional temp variations

The high continues to amplify NE over Sunday night through Monday, splitting the trough and creating a cut off low to the SW. Resulting, once any rain has cleared the south coast, in a dry but much cooler day than of late.

Over Tuesday and Wednesday high pressure remains pretty much in charge but movement of a trough to the north west does push a cold front east thus complicating the structure and orientation. Ergo a tad more cloud in some areas, cooler down eastern coastal regions and perhaps some rain into the NW on Weds

 

Edited April 11, 2020 by knocker

[knocker]

The movement of the weak trough east briefly boosts the low pressure to the SW which moves north giving a more unsettled day on Thursday before the ridge amplifying north east takes over again for the rest of the week (further troughs moving east across the Atlantic cannot be ruled out) and temps once more rise above average

According to the gfs

Edited April 11, 2020 by knocker

[knocker]

The evolution of the ecm is along similar lines with the natural detail differences

[knocker]

[knocker]

If your web site is still down @johnholmes

 

Edited April 11, 2020 by knocker

[johnholmes]

Thanks k but it seems to be back up

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

At least they are not a million miles apart and NOAA also similar so no wild Atlantic and prospects for some warmth at times?

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

Even its 8-14 similar

 

Edited April 11, 2020 by johnholmes

[knocker]

The gfs continues to differ with the ecm as early as Wednesday. Apparently all to do with the interaction, or not, of the weak trough crossing the Atlantic and the cut off low to the south west of the UK. The former makes much more of it

[knocker]

The 06 ecm Sunday > Tuesday

With some rain/showers mainly on Sunday

[knocker]

A cracking day here with a lot of thin Ci that looks very high and is probably around 30, 000 ft

Edited April 11, 2020 by knocker

[knocker]

The gfs still indicating at some interaction between the Atlantic trough and the cut off upper low west of Iberia which has some impact on the UK mid week

 

Edited April 11, 2020 by knocker

[knocker]

Albeit with entirely different detail the ecm also brings the low tp the south west into play next week