Models, teleconnections and nowcasting

[knocker]

The medium term anomalies all agree on the jet tracking troughs south east around the Atlantic high pressure in the medium range but the detail will need to be sorted by the upcoming det runs

[knocker]

Given the advent of a couple of TS in the Atlantic Basin recently perhaps the paper by Bentley, et al may be of interest

Upper-Tropospheric Precursors to the Formation of Subtropical Cyclones thatUndergo Tropical Transition in the North Atlantic Basin

Quote

The opportunity to examine the structure and evolution of the various upper-tropospheric precursors to the formation of North Atlantic (NATL) subtropical cyclones (STCs) that undergo tropical transition (TT)motivates this study. Intraseasonal variability associated with the location and frequency of NATL STCs forming in the presence of similar upper-tropospheric features, as well as similarities and differences in thevarious upper-tropospheric precursors to the formation of NATL STCs that undergo TT, are examined.NATL STCs that undergo TT are categorized according to the upper-tropospheric features associated withtheir formation during 1979–2010 using the 0.58NCEP Climate Forecast System Reanalysis dataset. Thiscategorization allows for the documentation of the location and frequency of STCs forming in the presence ofsimilar upper-tropospheric features and for the construction of cyclone-relative composites during the fivedays prior to STC formation.NATL STCs that undergo TT are separated into one of three categories based on the upper-tropospheric features associated with their formation: 1) cutoff lows, 2) meridional troughs, and 3) zonal troughs. STCs included in the cutoff low and meridional trough categories typically develop poleward of;258N over the western, central, and eastern NATL during September–November and August–November, respectively. In contrast, STCs included in the zonal trough category typically develop equatorward of;308N over thewestern NATL during June–September. Cyclone-relative composites reveal that;61% of the categorized NATL STCs that undergo TT form in association with an upper-tropospheric feature whose structure and evolution are linked to anticyclonic wave breaking

https://journals.ametsoc.org/doi/pdf/10.1175/MWR-D-16-0263.1

[knocker]

I don't normally look at the 0600 gfs with good reason

The difference, in the  reliable time frame in just six hours, in the handling of the trough to the NW

Edited May 28, 2020 by knocker

[knocker]

Friday > Sunday with the 06 ecm

[knocker]

The gfs is now considering some phasing with the upper trough to the south/south east and developing a surface low

Edited May 28, 2020 by knocker

[knocker]

The ecm not keen on the gfs take around t120 but then has the jet tracking around the mid Atlantic high pressure resulting in a trough dropping south in the vicinity of the UK

[johnholmes]

1 minute ago, knocker said:

The ecm not keen on the gfs take around t120 but then has the jet tracking around the mid Atlantic high pressure resulting in a trough dropping south in the vicinity of the UK

yuk, hopefully it is not correct!

[knocker]

36 minutes ago, johnholmes said:

yuk, hopefully it is not correct!

Yes indeed John and as you know it would only take a little  shift of the jet to improve the outlook. Needs watching though

[knocker]

The ext mean anomalies this evening are indicating a fairly amplified NH pattern with troughs associated with the tpv, centred NW Greenland, interspersed by the subtropical high zones central North America, mid Atlantic and eastern Europe  They are all on the same page but the precise alignment and intensity of the features in the Atlantic/European arena will dictate the surface analysis in the vicinity of the UK and that is yet to be decided. Suffice it to say at the moment the percentage play is for it to get cooler with temps average or a bit below but there are no indication as yet of any significant precipitation

[knocker]

The North Atlantic 300mb wind field and surface analysis for midnight

Today will be warm and sunny with the highest temps in the west and, particularly, Scotland where a stray storm is possible (usual caveats vis model temps),

A clear night to follow but perhaps some Stratus creeping in off the North Sea

Another warm and sunny day Saturday with highest temps likely over northern Scotland and lowest eastern coastal regions

No significant change overnight and through Sunday

Not a lot of change over Monday/Tuesday, perhaps some patchy rain in the far NW on Tuesday courtesy of the weak cold front. But the overall NH pattern is slowly evolving

 

Edited May 29, 2020 by knocker

[knocker]

The question is how will this evolve over the next few days

The answer rather depends on the precise configuration of the Atlantic high pressure and the energy flow around it with troughs dropping south east and attempting to phase with the trough west of Iberia and thus introducing much colder air and more unsettled weather/ And the gfs this morning has the colder air arriving through Thursday

Edited May 29, 2020 by knocker

[knocker]

The overall comment equally applies to the ecm but the charts illustrate a different interpretative of the structure vis the alignment of the ridge and energy flows. The colder (relatively)air  moving south early Friday

Edited May 29, 2020 by knocker

[johnholmes]

59 minutes ago, knocker said:

The overall comment equally applies to the ecm but the charts illustrate a different interpretative of the structure vis the alignment of the ridge and energy flows. The colder (relatively)air  moving south early Friday

Unfortunately these charts fit the latest 500 mb anomaly charts. All 3 now suggest a colder pattern developing in the 6-10 day period, see man model thread

[knocker]

Interesting to note that the EC weeklies update for the third week in June is better than ti was a couple of runs ago with a pattern that is hinted at by the end of the ext this morning

So perhaps temps returning above average and still little rain

 

S

[knocker]

Saturday > Monday with the 0600 ecm  And for what i's worth a spot cloud cover

 

Edited May 29, 2020 by knocker