This is the 7th forecast blog for Glastonbury 2015.

The 4th blog (Issued 10 June) was mostly positive.
The 5th blog (Issued 13 June) was positive and scored 3 out of 10 on the Dustbowl - Mudbath rating. Things were looking positive.
The 6th blog (Issued 15 June) was slightly positive and scored 4.5 out of 10 on the Dustbowl - Mudbath rating.

This forecast will contain charts for the past 2 days, and most of these charts were already posted in the main thread yesterday.

As we move closer to the festival, the operational charts become more important, and I will start with these, although the other forecast methods will still be shown.

[b]1. Operational Runs from GFS[/b] (06Hz and 12Hz) [b], ECM [/b][b](00Hz and 12Hz)[/b][b] and UKMO (12Hz) [/b]

[b][size=3][b]Monday 22nd June [/b][/size][/b]
[sharedmedia=core:attachments:253171] [sharedmedia=core:attachments:253187] [sharedmedia=core:attachments:253168] [attachment=253221:UKMO 17 June 17Hz + 120.gif] [attachment=253227:ECM 17th June 00Hz +120.png] [attachment=253233:ECM 17th June 12Hz +120.png]
The UKMO/ECM keeps things a bit drier than the GFS with the Low Pressure further North and East, in this sense it is a more progressive pattern.

[sharedmedia=core:attachments:253172] [sharedmedia=core:attachments:253177] [attachment=253219:GFS 17th June 06Hz + 120.JPG] [attachment=253220:GFS 17th June 12Hz + 120.JPG]
The last 4 GFS runs are consistent in having Low Pressure to the North East of the UK, with a Cool N to NE flow over the UK, this would mean a showery outcome for Glastonbury, with some moderate rain probable.

[size=3][b]Wednesday 24th June [/b][/size]
[sharedmedia=core:attachments:253170] [sharedmedia=core:attachments:253186] [attachment=253226:ECM 17th June 00Hz +168.png] [attachment=253234:ECM 17th June 12Hz +168.png]
ECM has a West to South flow, but the low pressure further south than the GFS, but this means that ti would be wetter for Glastonbury than the GFS option, and this would cover Wednesday and the Thursday.
[sharedmedia=core:attachments:253173] [sharedmedia=core:attachments:253176] [attachment=253218:GFS 17th June 06Hz + 168.JPG] [attachment=253217:GFS 17th June 12Hz + 168.JPG]
According to GFS the mostly likely outcome is a mild SW flow with Tropical Maritime air, keeping things rather damp for Glastonbury, although this mornings run is somewhat drier.

[size=3][b]Friday 26th June [/b][/size]

[sharedmedia=core:attachments:253169] [sharedmedia=core:attachments:253185] [attachment=253225:ECM 17th June 00Hz +216.png] [attachment=253235:ECM 17th June 12Hz +216.png]
ECM continues to be more progressive, and woulds have the wetter weather moving through quicker, and would lead probably to a more settled weekend than the GFS option.
[sharedmedia=core:attachments:253174] [sharedmedia=core:attachments:253175] [attachment=253215:GFS 17th June 06Hz + 216.JPG] [attachment=253216:GFS 17th June 12Hz + 216.JPG]
The GFS pattern is for a mild west to South west flow, with some damp weather possible for Glastonbury, however there is a real chance that the heaviest rain will be kept away further to the North.

[b]2. Ensemble Forecasts[/b]
[size=3][b]GFS Temperature Ensembles [/b][/size]
[sharedmedia=core:attachments:253182] [sharedmedia=core:attachments:253178] [attachment=253222:Ensemble Temp 17 June 06Hz.png] [attachment=253230:Ensemble Temp 17 June 12Hz.png]
Temps are looking cool to start, but as they switch round to more of a West to South Westerly flow, they are likely to improve steadily as the festival continues.
[size=3][b]GFS Rainfall Ensembles [/b][/size]
[sharedmedia=core:attachments:253181] [sharedmedia=core:attachments:253179] [attachment=253224:Ensemble Rain 17 June 06Hz.png] [attachment=253228:Ensemble Rain 17 June 12Hz.png]
These ensembles are a bit better than a few days ago with the bigger spikes disappearing, however there is still a trend for patchy rainfall for much of the festival.
[size=3][b]GFS Pressure Ensembles[/b][/size]
[sharedmedia=core:attachments:253183] [sharedmedia=core:attachments:253180] [attachment=253223:Ensemble Pressure 17 June 06Hz.png] [attachment=253229:Ensemble Pressure 17 June 12Hz.png]

Pressure is forecast to be around 1015mb for the duration of the festival, and slightly higher at the start. this continues the theme of slightly unsettled weather .

[b]3. Prognostic Charts at 6-10 day and 8-14 day [from NOAA][/b]

[attachment=253248:610day.03 from 16 June.gif] [attachment=253244:610day.03 from 17 June.gif]
The 6-10 forecast which is the most relevant for the festival shows neutral conditions over the UK.

[attachment=253247:814day.03 from 16 June.gif] [attachment=253243:814day.03 from 17 June.gif]


[b]Summary [/b]

The models have things rather unsettled for next week as things stand. GFS at least keep High Pressure closer to the south, which should minimize rainfall amounts, and mean a rather damp unsettled start to the festival and probably through much of the weekend. This would minimize mud levels to reasonable levels, and no mudbath would be likely. There is also decent support in the ensembles for this.

ECM is far more progressive, and this would mean the prospect of heavier rain for a time from Wednesday through to Friday, but probably would mean a drier weekend. However there seems less support in the ensembles for this.

Calling a rating today is tricky, GFS/Ensembles would be close to 5 or 5.5 while ECM would be closer to 6.5 or 7. So I'll go for middle ground and a gave a rating of 6. There is still enough uncertainty which could make a big difference to the Glastonbury conditions.

[attachment=253236:Glasto Rating 17th June.JPG]