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Glastonbury Forecast 12 - 18th June

Posted by J10, in Glastonbury 2013 18 June 2013 · 2,359 views

washout dustbowl heatwave glastonbury 2013
Time for the latest update,

Please get involved on the dedicated Glastonbury forecast thread on the main forum here

http://forum.netweat...-4#entry2714670

Starting off with the

GFS Operational Charts
As per yesterday, I'll start by trying to find the common ground between the runs. Remaining unsettled this week, with the risk of some heavy rain on Thursday. Low Pressure now on its established southern track pushing westwards across the UK during early hours of Saturday morning with showers to follow on Saturday. Pressure slowly increasing from the South West on Sunday and into next week and this is where the disagreement start.

[based on 06Hz 18th June run]
The 06Hz op run shows quite a quick pressure build up from the South West, (this reducing the shower risk on Sunday), so that a ridge of High Pressure is over South Western areas by early hours Monday. While the High Pressure is never in complete control, it keeps weather fronts away to the north and the start of the festival looks dry and mostly settled. There is an increased risk of fronts making more of an impression towards the weekend, but any rainfall not looking heavy at this stage.

Charts shown in order (96 Sat 22 June, 168 Tue 25 June, 216 Wed 27 June, 264 Fri 29 June)
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The 06Hz op run shows quite a quick pressure build up from the South West, (this reducing the shower risk on Sunday), so that a ridge of High Pressure is over South Western areas by early hours Monday. While the High Pressure is never in complete control, it keeps weather fronts away to the north and the start of the festival looks dry and mostly settled. There is an increased risk of fronts making more of an impression towards the weekend, but any rainfall not looking heavy at this stage.

The 06Hz run shows around 12-14mm of rain for the next 6 days.
Attached Image
[based on 12Hz 18th June run]
The 12Hz op run shows a slower pressure build up from the South West, with a ridge of High Pressure mid Monday, this ridge holds for the start of the festivals and looking dry until Thursday. Fronts a bit further south than the 06Hz run, and some rainfall is possible on both Thursday and Friday, but not looking that heavy at this stage. However a deep area of low pressure is forecast for the weekend, giving the potential of further heavy rain.

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The 06Hz run shows around 22-30mm of rain for the next 6 days. So despite largely similar synoptic pattern over the next few days, the 12Hz run is wetter, most of this relates to the expected rainfall this Thursday.
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GFS Ensembles

[based on 06Hz 18th June run]
Pressure remains steady this week and drops over the weekend, however despite rainfall totals not looking that massive generally, although the op run was drier than the ensemble mean. Next week sees a quick rise in pressure in line with the op run, and remaining mostly settled until the weekend when pressure drops back once again, most ensembles though go for a mostly dry festival.
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[based on 12Hz 18th June run]
Pressure remains steady this week and drops over the weekend and more than the 06Hz run suggests, rainfall totals are generally a bit higher than the 06Hz run , and the op run is in line with the mean. Next week sees a steady rise in pressure in line with the op run, and remaining mostly settled until the weekend when pressure drops back once again, and while the op run is a bit of an outlier in terms of pressure drop and weekend rain, generally more ensemble runs go for weekend rain.

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NOAA Upper Charts [based on run published 18th June]

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Continues yesterdays improvement.

ECM
Trying to find a consensus between runs, this week has fairly low pressure, with the risk of some rain from the east this week, although this risk is less than on the GFS. Low Presure set to push in across the UK over the weekend, giving moderate rainfall to all parts.
[based on 00Hz 18th June run]
The op 00Hz run starts next week with Low Pressure to the North East of the UK, with a tenuous ridge of High Pressure developing to the west of the UK, only by Wednesday does High Pressure properly build over the UK, whihc should mean a mostly dry start to the festival, although such a pattern is quite risky in terms of potential for rainfall.
Attached Image Attached Image Attached Image Attached Image
based on 12Hz 18th June run]
By Monday, we see a healthier build up of High Pressure for southern parts of the UK, which builds over the next days into a High Pressure block, more especially for western areas of the UK. Although within this High Pressure there is worrying T (identifying trough - mini area of low pressure) enclosed within it close to Southern areas for Tuesday. High Presure looks fairly steady over western areas until the end of the run, Friday 28th June.

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Summary
This week now looking generally unsettled however the risk of rain heavily concentrated heavily towards Thursday, other days not looking that troublesome. This weekend will see further rain as low pressure sweeps East/South Eastwards across the UK. For Glastonbury festival week itself, signs of pressure building from the south west, but disagreement between models as to this extent. ECM is more promising in this regard, and next week is looking drier than this week.
Sorry to repeat yesterdays comment pre festival rain, but this weeks rain could make ground conditions saturated, and hence increase the risk of a mud bath.

Ratings :-

Festival Dryness (0= washout, 10=dry) 6/10 More promising. Despite GFS 12Hz run most runs are positive for next week, and ECM today quite steady in this regard.
Ground Mudbath Rating (0=mudbath, 10 = dustbowl) 3.5/10 It seems very likely that there will be moderate rainfall between now and the festival commencing, quite possibly around an inch of rain, however the risk of more than that has receded, althoguh This Thursday still needs to be watched, perhaps some mud is expected but not a complete mudbath. .
Heatwave rating (0 = freezing, 10 = heatwave), 5.5/10 winds from SW much of the time, and ECM goes for 850HPa temps above average.

Newspaper Taglines

Bring your wellies and your sunglasses, the festival itself still possibly drier than average, but pre festival rain makes some mud on site a probability, with an increased risk at the moment of mudbath conditions.

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