Storm Henk

[jack.h...@gmail.com]

Something of a forecast failure.  Although up here in the north I hadn't been especially interested in the southern England predictions, I'm sure I would have noticed a prediction of damaging winds.

Significant forecast failures are quite rare these days but developing lows that move along the English Channel often seem to catch them out.

Jack

[Freddie]

Why do you see it as a forecast failure?  There was an amber warning out for strong winds.

[jack.h...@gmail.com]

If this is what happens after an 'amber' what does a 'red' do?

https://www.bbc.co.uk/news/av/uk-67868616

Jack

[Freddie]

For a red it needs to satisfy the "very likely" and "high impacts" criteria on the impacts matrix.  As there was still some doubt about the depth of the low and consequent wind strengths even just ahead of the event then there probably wasn't enough confidence to say "very likely".  This is why red warnings are relatively rare.  I'm not saying it couldn't have been upgraded to red - just justifying what it wasn't initially a red.

[jack.h...@gmail.com]

Freddie: "I'm not saying it couldn't have been upgraded to red - just justifying what it wasn't initially a red."

That's exactly my point about a "forecast failure".  The potential impact of Henk had not been recognised until Henk had almost arrived.

Bearing how good three/four/five day ahead forecasts normally are these days, I would still call it a forecast failure.

https://www.bbc.co.uk/news/uk-67870028

Jack

[Ashley haworth-roberts]

I thought of it as a late change of forecast and a correct forecast issued with little advance notice - for reasons given here (the massive rainfall totals were known about on Monday but 81 mph at Exeter airport and 69 mph at Heathrow were seemingly not - and storm naming is usually on account of severe gales not flooding): https://www.bbc.co.uk/news/uk-67861206 Naming and upgrading to amber for wind only happened around 9 am on Tuesday - which can't have been much before extreme winds hit Devon, the Isle of Wight, Mumbles and the Bristol Channel. The severe winds happened in the late afternoon in the London area. Currently 265 flood warnings in Englnd with 6 in Wales.

[Len]

I can't understand why one anemometer at Exeter airport recorded peak gust of 81 mph and the other 53 mph.

This is from the Online weather website.

Len

Wembury

[Ashley haworth-roberts]

Worth asking the Met Office - especially as they are based at Exeter?

[Graham Easterling]

I found that gust surprising, especially given the maximum gusts at all the usual culprits (like Gwennap Head, Culdrose & The Needles) being lower.

It was not stormy here, just blustery, several windier days in the last couple of months. Unusually the windiest spots were to the east of us, as the storm continued to develop. In fact people were walking on the beach and along the prom. My maximum gust was 43mph, well down on a few days in the last couple of months.

What irritated me when they repeatedly said on Spotlight SW (including David) that 80mph was the strongest gust in the region this season. They soon forgot about Ciaran then, which brought down more trees in Penzance than I've ever known. Closed all road out of Penzance and there were no train in the whole of Cornwall. 92mph at Gwennap Head,  and >80mph along most west & north facing coasts cliff tops. In fact they seem to use so few stations these days (even Gwennap, Culdrose, Bude & Newquay seemed to have been dropped) leaving just Camborne & Cardinham in Cornwall. In the old days there was Penzance, Falmouth . .  The way things are going the sdame place will be the wettest, driest, coldest, warmest & windiest spot every day.

Still, the last storm always has to be the worst. I saw a recent Express headline which said a "383 mile wide wall of ice" was heading for the UK. Very precise I think you'll agree.

Graham

Penzance 

On Wednesday 3 January 2024 at 23:19:23 UTC Len wrote:

[Freddie]

A storm is named by the Met Office if it is going to result in impacts that would require an amber or higher warning to be issued.  So it could be named for heavy rain (and consequent flooding) or any other element - such as snow.  Obviously other organisations (such as Met Eireann) could name the storm independently and it affect the UK without a UK amber warning being required.

[Freddie]

On Wednesday 3 January 2024 at 18:42:49 UTC jack.h...@gmail.com wrote:

 Yes but you occasionally get systems where there is much doubt in the level of expected impacts due to the systems degree of development being finely balanced, as was the case here.  The prospect of heavy rain and strong winds were not in doubt - but their location and severity was.  Sure, the Met Office could've issued a warning covering all eventualities but there was a very real possibility that the system wasn't going to develop along the lines of the worst case scenario, and if you always put out the warning early in these scenarios then there will be many occasions where you "over warn" and the Met Office would then be accused of crying wolf.  Then there would be the potential for future warnings to be ignored or played down by recipients, to their detriment.

[Ashley haworth-roberts]

I thought the main criterion for Met Office naming at least was predicted severe wind, usually that they need to issue an amber warning for severe gales (especially if in populous areas and during the daytime). Torrential rain is falling in part of southern England right now - but were this to be upgraded to amber in part of the area I doubt they would also name the storm (though some brisk winds may occur for a short time). In fact parts of the French north coast might get severe gales so maybe they will name the storm 'Hipolito').

[Freddie]

From the horse's mouth: https://www.metoffice.gov.uk/weather/warnings-and-advice/uk-storm-centre/index explains it better than I do under the "When is a storm named?" section.

[Ashley haworth-roberts]

Thanks. I think the criteria have widened slightly during the past eight years:

https://www.metoffice.gov.uk/weather/warnings-and-advice/uk-storm-centre/uk-storm-season-2015-16

[jack.h...@gmail.com]

Surely the massive impact of today's rain/flooding (again inadequately forecast in my view) required a bit more than a last minute 'yellow'?

OK, it might not have met the strict criteria, but I doubt if the public in Nottinghamshire is too interested in the nuances.

Those criteria need rethinking.

Jack

[Ashley haworth-roberts]

The widespread flooding in Notts, especially near the Trent, is from rain late on Monday as well as Storm Henk, and any new flood warnings tonight in the south are because of those events and today's heavy downpour. Water accumulating from several rain 'events'. That said, presumably the Met Office consider whether what would have been a yellow rain warning should be amber if there's already flooding and/or saturated ground in the areas that will be affected. Looks like today's rain will miss Notts if that's any consolation.

[Freddie]

The criteria are not set by the Met Office.

Flooding is covered by flood alerts/warnings issued by the Environment Agency (England), Natural Resources Wales (Wales) and the Scottish Environment Protection Agency (Scotland).  Their catchment models are fed by rainfall data from the Met Office models.  See https://www.metoffice.gov.uk/weather/guides/flood-warnings

Nuances perhaps, but no need to point guns at the Met Office exclusively.

Forecast rainfall totals were correct but to correctly forecast flooding, antecedent conditions need to be considered, and that is the job of the Environment Agency or similar bodies and their river flow modelling.

[Julian Mayes]

River levels on the Thames this evening in places are higher than both the 2003 and 2014 floods, especially around Reading, though there's quite a bit of variation between gauging stations. 

https://check-for-flooding.service.gov.uk/station/7110

- though not as severe at nearby Caversham Lock.   

I'm surprised that the media had not latched on this situation.   There does seem to be inertia in the media coverage of weather events, maybe depending on where reporters have been sent.   Nevertheless, it is a bit touch and go in places (I have a personal interest in this - the Thames is at the end of my road in Molesey and I hope it stays there!).   I've tried to stir things up on twitter a bit 

Despite the subject line, the flooding in the south is really a culmination of recent weeks of rain plus the heaviest rain of all - which was 2 days ago of course.   (26mm / 24hrs here).   

Julian         

[Graham Easterling]

I'm surprised that the media had not latched on this situation.   There does seem to be inertia in the media coverage of weather events, maybe depending on where reporters have been sent.   

I think you're absolutely right. MInd you, there are now few reporters to be sent anywhere, the news often just relies on social media. In the old days, if there was a forecast of a gale in Cornwall, a reporter would be despatched to Porthleven. Other locations were available, but rarely visited.  They also associate the biggest seas, with the strongest winds, which is absolutely not the case. It's dependent on what's happening in mid Atlantic.

Newquay on a sunny autumn day. Offshore wind so some shelter allowing the wave to build on the reef to >25'.

Nowadays, it's forecasts of bad weather that are most newsworthy. So an unforecast event with no warning get's no coverage at all.

Graham

Penzance