A bit of a question mark

[xmetman]

I was just watching Ben Rich in the 12:57 PM BBC weather and he was saying that there was "a bit of a question mark" about whether the thundery showers that were forecast to develop over central southern England this afternoon would affect the London area at 4 PM

That made me wonder why there was still a question mark about forecasting the weather in just 3 hours time?

What happened to nowcasting, or has that be consigned to the dustbin along with asperatus undulatus?

Looking at the latest weather radar the showers have certainly starting to develop, but they look a little too far west, and they seem to have a curved trajectory that's taking them around the capital.

[xmetman]

Well the thunderstorms that have developed across central southern England are certainly heavy and have put down an inch or more of rainfall in places especially around Banbury by my estimated totals. London still getting away with it just a splash of rain on the 1400 UTC radar frame.

[vidcapper1]

We didn't get a full dose here in Cheltenham, but still some impressive rain intensities.

[xmetman]

I bet it's horrendous on the motorways especially as it's a Bank holiday.

[xmetman]

I estimate that places like Spalding and Cottesmore (shame that they removed the AWS) have had upwards of 35 mm of rain from these thunderstorms this afternoon. I notice that Coningsby are having a bit of a belter at the moment:-

AAXX 27164 03391 41620 81013 10160 20150 30153 40160 55014 79799 889// 333 88940=

2000 metres in a heavy thunderstorm at 1600 UTC.

[Dick Lovett]

At Brize Norton the visibility was only 800m in a heavy thunderstorm on a metar at 1359UTC. Rainfall in the following hour was 21mm.

Here, 10 miles to the NE, I measured 15mm. The light level during the storm was as low as I can ever remember for the middle of an August afternoon.

Charlbury (Oxfordshire Cotswolds)

[xmetman]

It will be interesting to see the rainfall totals in the 1800 UTC obs.

[xmetman]

Kirton in Lincolnshire is the wettest place today with 54.3 mm by my estimates (0900-1800).

[xmetman]

╔═════════════════════════════════════════════════════╗

║                 Highest Rainfall [mm]               ║

║         1800 UTC on Saturday, 27 August 2016        ║

║                    In WMO Block 03                  ║

╠═══╤═══════╤═════════════════════════╤═══════╤═══════╣

║ # │  WMO  │         Station         │   mm  │   Ins ║

╟───┼───────┼─────────────────────────┼───────┼───────╢

║ 01│ 03544 │Church Lawford           │  32.0 │  1.26 ║

║ 02│ 03391 │RAF Coningsby            │  28.0 │  1.10 ║

║ 03│ 03392 │Wainfleet                │  27.0 │  1.06 ║

║ 04│ 03649 │RAF Brize Norton         │  24.0 │  0.94 ║

║ 05│ 03469 │RAF Holbeach             │  19.0 │  0.74 ║

║ 06│ 03462 │RAF Wittering            │  15.0 │  0.59 ║

║ 07│ 03379 │RAF Cranwell             │  13.0 │  0.51 ║

║ 08│ 03373 │RAF Scampton             │  12.0 │  0.47 ║

║ 09│ 03330 │Leek Thorncliffe         │  11.0 │  0.43 ║

║ 10│ 03743 │Larkhill                 │   9.0 │  0.35 ║

║   │ 03377 │RAF Waddington           │   9.0 │  0.35 ║

║ 11│ 03560 │Thurleigh                │   8.0 │  0.31 ║

║ 12│ 03535 │Coleshill                │   7.0 │  0.27 ║

║   │ 03382 │Leconfield               │   7.0 │  0.27 ║

║ 13│ 03354 │Nottingham               │   6.0 │  0.23 ║

║ 14│ 03529 │Pershore                 │   5.0 │  0.19 ║

║   │ 03292 │Bridlington              │   5.0 │  0.19 ║

║   │ 03660 │High Wycombe             │   5.0 │  0.19 ║

║ 15│ 03522 │Hereford                 │   4.0 │  0.16 ║

║   │ 03520 │Shobdon                  │   4.0 │  0.16 ║

║   │ 03740 │RAF Lyneham              │   4.0 │  0.16 ║

║   │ 03746 │Boscombe Down            │   4.0 │  0.16 ║

║ 16│ 03346 │Leeds                    │   3.0 │  0.12 ║

║   │ 03257 │RAF Leeming              │   3.0 │  0.12 ║

║ 17│ 03266 │RAF Linton-On-Ouse       │   2.0 │  0.08 ║

║   │ 03482 │RAF Marham               │   2.0 │  0.08 ║

║ 18│ 03414 │RAF Shawbury             │   1.0 │  0.04 ║

║   │ 03281 │Fylingdales              │   1.0 │  0.94 ║

║   │ 03857 │Isle Of Portland         │   1.0 │  0.94 ║

║ 19│ 03628 │Filton                   │   0.8 │  0.31 ║

║   │ 03321 │Hawarden                 │   0.8 │  0.31 ║

║ 20│ 03275 │Loftus Samos             │   0.6 │  0.24 ║

║   │ 03951 │Sherkin Island           │   0.6 │  0.24 ║

╚═══╧═══════╧═════════════════════════╧═══════╧═══════╝

                 Data courtesy of OGIMET               

[Brian Wakem]

On Saturday, 27 August 2016 19:18:52 UTC+1, xmetman wrote:

Kirton in Lincolnshire is the wettest place today with 54.3 mm by my estimates (0900-1800).

60.7mm at the nearest PWS.

https://www.wunderground.com/personal-weather-station/dashboard?ID=IENGLAND1162

-- 

Brian Wakem

Lower Bourne, Farnham, Surrey

http://www.brianwakem.co.uk/weather

Live obs @ 21:25:17 : 19.3C, DP 17.3C, RH 88%, 0.0 mm

[xmetman]

I'm totally amazed by how closely my estimate made from 15 minute weather radar images compares with the total from the nearby AWS. Thanks for sending me the link. 

When I worked in the Nimbus visualisation team in the MO I tried hard to get the radar accumulations images disseminated to the outstations without success. I never thought that when I retired I would write some code that thanks to the speed and power of modern processors could download the individual tiles and build a composite picture, and then  take the whole thing apart pixel by pixel and add up the 15 minute totals to get an accumulation.

I can never understand why you don't see accumulation charts derived from weather radar used on TV forecasts.  That and temperature anomaly charts are sorely lacking from our forecasts in my opinion.

[Smartie]

Thanks for the plots and link.

NB there are several hydrostatic pressure jumps due to downdraughts  as well.

The system that gave this was a MCS with of a wave pattern parallel stratiform type.

[xmetman]

It's OK. 

London was never really at risk from this thundery activity after all, which prompted my oriiginal posting.