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Glastonbury Forecast 8 - 14th June



Since the last full blog on Wednesday, it has come to my attention that this blog or extracts from it have made the national press.


Don't know whether to take the nerd comment as a compliment, but fame at last, and a bit pressure in getting the forecast right.

Again we start off with the [b]GFS Operational Charts [/b][based on 12Hz 14th June run]

I'll bring the days forward to be consistent with the op runs of Wednesday,

Charts shown in order (192 Sat 22nd June, 312 Tue 25 June, 336 Wed 26 June, 384 Fri 28 June)

The trend is for High Pressure to build from the Azores across the UK over the next few weeks,which has been the theme for a number of days.
[attachment=174301:GFS 14 1.JPG] [attachment=174300:GFS 14 2.JPG] [attachment=174299:GFS 14 3.JPG] [attachment=174298:GFS 14 4.JPG]

If this run is right the festival itself looks mostly settled with bright or sunnier than average, rainfall would be below average. Most would be happy with this. The remains uncertainty between the models, as an example the GFS 06Hz run had High Pressure more dominant by next weekend, reducing the risk of Low Pressure shown in the first image above for Next Saturday. I would suspect that the Pressure is below the ensembles average for Next Saturday, but above the ensembles average thereafter.

In the last blog update, I mentioned the potential of the festival itself being dry, but the changeable weather beforehand making the camp-site susceptible to mud due to rain over the next 12 days. The next charts is the GFS total rainfall predictor over the next 6 days.

[attachment=174302:Rmgfs144sum 14.gif]

This suggests about an inch of rain over the next 6 days, and by looking at the daily progression not shown by charts, it suggests the heaviest of the rain, on the feature Monday into Tuesday. This would considerably wet the ground, but there is still time for the ground to dry, providing the weather remains dry until the festival.
[b]GFS Ensembles[/b] [based on 06Hz 14th June run]

[attachment=174306:GEFS 14 06 1.png] [attachment=174305:GEFS 14 06 2.png]

[attachment=174308:GEFS 14 1.png] [attachment=174307:GEFS 14 2.png]

These ensembles show a steady increase in pressure from the South West along with a reduction in rainfall possibility, but the key word here is slow.

[b]GFS Ensembles[/b] [based on 06Hz 14th June run]

[attachment=174320:GEFS 14 12 4.png] [attachment=174321:GEFS 14 12 3.png] [attachment=174322:GEFS 14 12 2.png] [attachment=174323:GEFS 14 12 1.png]

These ensembles confirm the op run was indeed lower than the average in terms of pressure next Saturday, although there is a spike in rainfall around here, and then above the average thereafter. As per the 06Hz run, there is a slow rise in pressure before the start of the festival.

[b]NOAA Upper Charts [/b][based on run published 13th June]

[attachment=174303:610day.03 13 2.gif] [attachment=174304:814day.03 13 2.gif]

[b]NOAA Upper Charts [/b][based on run published 14th June]

[attachment=174325:610day.03 14 1.gif] [attachment=174324:814day.03 14 2.gif]

The upper charts continue to show a trough over the UK, the 8-14 finally showing signs of this weakening over the UK.

[b]ECM[/b] [based on 12Hz 12th June run]

This shows unsettled weather this weekend, remaining rather changeable thereafter, with low pressure to the North West for the following weekend very similar to that portrayed in the GFS 192 above), pressure still is building slowly from the South West, but has less success in having an influence over the UK compared to the GFS.

Charts shown in order (120, Wed 19 June, 192 Sat 22 June, 240 Mon 24 June)
[note these are now in a better format, but makes them easier to download if required]
[attachment=174309:ECM 14 120.JPG] [attachment=174311:ECM 14 192.JPG] [attachment=174315:ECM 14 240.JPG]

[b]Summary [/b]
The charts are still a bit contradictory which is understandable this far out from the festival, there are tentative signs of things settling down once again, but there remains a period of unsettled weather to get through first. The big question is when things start to settle down, the GFS today has been pretty positive bridging the High Pressure in before the festival, the ECM tonight is a bit of a fly in the ointment, keeping low pressure close to the UK a few days before, I wouldn't have thought the end of the ECM run would be particularly wet, but they are not dry either.

[b]Starting the ratings :- [/b]

Festival Dryness (0=washout, 10 = dry) 6/10, it would have been higher if ECM was better
Ground Mudbath Rating (0=mudbath, 10 = dustbowl) 4/10, I am still concerned about rainfall before the festival.
Heatwave Rating (0= freezing, 10 = heatwave) 5/10, My guess is winds from the West,

[b]Newspaper Taglines [/b]

Bring your wellies and your sunglasses, the festival itself probably drier than average,but pre festival rain could make ground underfoot wet and cause some mud on site, but probably without actually mud bath conditions.

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In addition to these blogs, additional information and discussion will occur on the dedicated Glastonbury 2013 thread on the main forum.




Well worth a visit for the latest news and for other thoughts.


Below is my update based on the 00Hz runs, interesting, but not worthy of a full blog update.


Update based on 00Hz today, this week - risk of rain from and possible plume from east reduced. Next weekend GFS makes more of feature emphasised last night by ECM, ECM conversely makes less of it than last night, However they both have buckles in NW flow thereafter meaning Low Pressure cells are further south than they would otherwise be.




This shows a ridging Azores High giving a NW flow for SW areas, which should mean mostly dry conditions.



This shows the Azores High being edged or flattened down by the Jet to the North, so changeable over the UK, but probably not too bad conditions for SW areas.


This shows a real "buckle" in the flow, a LP to the south, which most likely would be a a direct hit for southern areas, not good news 1 day before the festival.





Despite ensembles continuing to go with the Azores High building theme, Today's op GFS run 06Hz very disappointing from T+240 onwards, the models continue to vary but if there exact models are published on the 12Hz, then the wetness ratings would be worsened.

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