The Met Office have issued a yellow ‘advisory’ warning today for storm Dietrich this coming Saturday. These ‘advisories’ seems to be the way they’ve started doing things these days, which I must say is a vast improvement on last year, when they almost seemed to wait until the last-minute to give the general public a clue about what they were thinking. They’ve chosen to use a brand new ploy in this strong wind warning, the 50-70 mph ploy, and lucky us they even managed to mention the wind direction in this one! Now all that we’ve got to get them to do is to include the maximum mean wind speed that they expect, and we’ll have a proper warning, just like those issued at RAF outstations for the last 70 years. I suspect a big part of the problem is that many Chief Forecasters have never spent any time on an RAF outstation, or ever issued a warning come to that.
The current warm spell of weather across Central England, and rather spookily ushered in by the start of the astronomical Autumn, seems to be running on and on, and there doesn’t seem to be any sign in the latest NWP forecast charts that it intends to stop! The above chart clearly shows the warmth of the last four weeks or so (fig 1). The maximum temperature on ‘Ophelia day’ (the 16th of October) of 19.5°C, broke a record that had stood since the great Autumn of 1959, no mean feat.
Autumn mild spell continues into start of November
The low pressure area that’s currently over the northeast of Russia; as forecast by the latest run of the GFS model; is set to be replaced by a large anticyclone with a central pressure of 1040 hPa or higher by this time next week. This will in effect stem the flow of cyclones from tracking from the Atlantic across Scandinavia and into Russia as they have been doing of late, as pressure rises over Scandinavia and a block forms. This in turn will back the flow across the eastern Atlantic as it becomes progressively more meridional. This in turn will ensure the continuation of the autumn warm spell, and if anything we could see even higher anomalies both by day and night as we move into Autumn.
There’s quite a bit of conjecture in that last paragraph, so take it with the pinch of salt it deserves, but remember that you read it here first.
The forecast for Saturday is starting to firm up now with the latest T+84 products from the UKMO and the GFS. The tightest gradient at 12 UTC on Saturday look to be across south Wales and the Southwest, all though truth be said, it looks a pretty stormy affair anywhere south of 54° north across the British Isles, as the low itself tracks across central Ireland and across the Irish Sea, exiting across the southeast coast of Scotland by midnight.
By the time Dietrich; as I think it will be called by the Berlin Meteorological Institute; reaches the British Isles on Saturday it’s already a well occluded low, because it peaks as early as Friday at 20° west in the central Atlantic, when its central pressure is much lower at 960 hPa. So I suppose if the cyclogenesis took place later than forecast it could arrive in an even more angry mood than this forecast. Don’t you just love the British weather?
And please rest assured as Darren Bett has just reminded us
This IS NOT a hurricane!
Ophelia was born on the 9th of October as a tropical depression at 09 UTC in the mid-Atlantic somewhere to the southeast of the Azores. Her early days were spent meandering around the place of her birth, at times it almost appeared that she was going around in circles. Then suddenly one day her life found a new direction, and she decided to head off and take a swipe at the British Isles, so off she went tracking ever more faster each day in a northeasterly direction. She made good progress, and before long she surprised every on by becoming a category 3 major hurricane! She had become the furthest east major hurricane in the satellite era! But then rather unexpectedly (to some people’s mind’s at least) and just as she was closing in on her intended target, someone called (Ice) Berg in America decided that her life as a hurricane was at an end, and he declared her a post-tropical cyclone! Not to be outdone she put on an extra spurt and deepened from 971 to 958 hPa to show them she was not finished quite yet. The rest as they say is history…
For the purists out there that say that hurricanes can only survive in oceans with a SST of around 79 °F (26 °C) or more, how did Ophelia manage to steadily intensify from a category 1 to a category 3 major hurricane in the Atlantic Ocean during on the 14th of October southeast of the Azores, with SST that were much colder (fig 2), between only 22°C and 24°C?
Please don’t bother replying with comments about how “the large temperature contrast between the abnormally warm seawater and the extremely cold temperatures in the upper atmosphere” providing instability for Ophelia’s thunderstorms “which allowed the storm to continue strengthening” because I simply won’t’ believe you!
If Ophelia can intensify over cooler waters like she did, then there is no reason not to accept that the NHC killed Ophelia off around 12 hours too soon, I think she survived till at least 09 UTC on the 16th of October and close to 51° north. She might have looked pretty crappy in the visible images as she approached Ireland early on Monday but her inner core winds that had driven her down to 951 hPa were still spinning.
FAAM and its relationship with the Met Office
Why wasn’t it possible for the Chief forecaster at the Met Office to call on the services of the Facility for Airborne Atmospheric Measurements [FAMM] and get them to fly their modified BAe 146-301 large Atmospheric Research Aircraft [ARA] to the Azores on Saturday afternoon and back again during Sunday, drop a couple of dropsondes into the eye of Ophelia, and run their fancy array of sensors over her?
All their findings could have been passed onto the NHC and fed directly into the NWP models around the world to get a better fix and track on Ophelia during the next 24 hours, all excellent meteorological research.
How come the Americans can afford to send a hurricane hunter out every six hours to investigate a tropical cyclone whenever an island in the Caribbean or the coastline of America is threatened, and yet when the tail end of a hurricane threatens our shores, we just curl up with a good book and issue a couple of warnings?
Of course it may have been that they did ask them, but maybe they were just too busy investigating stratocumulus, volcanic ash or contrails, and just couldn’t find the time for a jolly to the Azores.
When I was an assistant at Kinloss we had installed a boundary layer sonde [BLS] system from Vaisala, as did a number of other RAF stations across the UK. And when there was anything interesting going on meteorologically, we would fill up a balloon with helium, attach a small package of sensors to it, and throw it into the air. The rest was more or less automatic, a radio receiver attached to a PC processed the upper air data into a regular WMO TEMP message.
What I’m rather long-windedly trying to suggest, is that back then we realised the importance of good observational data, even when we had an excellent upper air network, something we don’t have these days. We don’t launch radiosondes from Weather Ships, we don’t even launch them from Stornoway, Shanwell or Hemsby these days, so why can’t we very occasionally just use something that we do have. I know the FAAM aircraft is primarily for research, but for exceptional hurricanes like Ophelia surely this could have been waived. As far as I know not a single aircraft from either Portugal, Spain, France, the UK or Ireland went out to take a look at Ophelia, surely the air force of one of these countries could have?
Just a ‘normal low pressure system’ says Chris Fawkes
I’m personally fed up to the back teeth of being told by weather presenter after weather presenter that Ophelia was now no longer a hurricane, and as Chris Fawkes so eloquently put it yesterday “is just a normal low pressure system”. Many of us don’t need this constantly rammed down our throats, or the 50 second video of Tomasz Schafernaker waving his arms about like some born again Magnus Pyke describing how a hurricane is formed and what powers them, because we already very well what the latest theories are.
The highest gust that occurred between 00 UTC on Monday and 07 UTC this morning from Ophelia was 96 mph at Roches Point on the south coast of Ireland, and occurred at 11 UTC (fig 1).
And just for completeness here are all the low-level stations that reported storm force gusts at anytime during that same period (fig 2).
On the face of it the warnings issued for the winds from ex-hurricane Ophelia look like they did there job, and that although three people died in Ireland, the warning saved many more, and that might well be true. But what about the accuracy of the warnings issued by both Met Eireann and the Met Office?
If you remember Met Eireann amended their status Red and Amber warnings at around 9 am on Monday morning. They jumped the highest gusts expected from 80 mph to 93 mph, and extended the status Red to cover the entire country. If we look at the maximum gusts across Ireland in more detail (fig 3) you will see that the first warning they issued on Saturday for maximum gusts to 80 mph would have sufficed for all stations bar Roches Point, even across the north of Ireland all the gusts from the observing network were within the range of 50 to 80 mph stipulated in the original warning. The one thing that was wrong with Saturdays warning is that it didn’t single out the south coast as particularly vulnerable to the storm force southerly winds from Ophelia, especially the county of Cork which saw the highest gusts in excess of 90 mph. I’m not going to say whether the status red for the entire country was not warranted because I would likely put my foot right in it.
Lets remind ourselves what the Met Office were warning us about as regards strong winds from Ophelia for the 16th in the UK.
Well as we’ve seen already the highest gust across Northern Ireland was 63 mph and did fall in the 55-65 mph range mentioned in the warning, but gusts in the range 65 to 75 mph or even 80 never occurred. And there lies the rub, because it’s never entirely clear from any warning issued by the Met Office what limits they use for yellow, amber or red warnings, and the reason why they don’t specify them is because it makes them impossible to verify. There is little doubt that the core of the strongest wind was along the south coast of Ireland, and up through the Irish Sea, in fact three stations in the northwest of Wales reported gusts of higher than 80 mph, and two of those, Aberdaron and Capel Curig reported gusts of 90 mph.
So using gusts of 70 mph or more as the basis for delineating the area of an amber warning, what should the area have looked like for the UK? Well on the basis of the wind speeds from the SYNOP stations it certainly wouldn’t have covered Northern Ireland, but instead stretched in an arc from Islay in the north down the Irish Sea possibly as far down as South Wales in the south (fig 6).
Looking back at the graphic from the NHC from Friday which shows the wind speed probabilities for Monday it shows look remarkably accurate. If the axis of the core of strongest winds had been aligned a little bit further east then it would have been spot on (fig 7). Perhaps we ought to leave it to the NHC to issue the warnings the next time a ex-hurricane heads our way.
The GFS maintains that this coming Saturday will be a very windy, maybe even a stormy day over the British Isles. As you can see from the last six model runs, which show the 12 UTC chart for Saturday from progressively later runs, the GFS model just can’t just decide where to plonk the vigorous low it develops (fig 1). The consensus seems to be that the low itself will run east-northeast from the southwest of Ireland (again), across the Irish Sea and the north of England, with a tight west or northwesterly gradient to follow along behind. At this range it’s still impossible to be precise, especially with so many diverse solutions so far. I’m not even going to say anything about this low being a named storm!
It’s such a beautiful start to the day down here in Devon; with the old moon towards the east high above Venus; it’s a shame that it’s going to rain!
Well that’s what the latest GFS model says (fig 2), it’s a strange finger like feature, that eventually extends northeast to spread a spell of rain across the entire southeast of the country.
As I mentioned a couple of times in my blogs on Monday, yesterday was indeed the warmest 16th of October in UK on record. The temperature reached 23.5°C at Manston in Kent before the dust from the Sahara and the smoke cloud from Portugal blocked out the sun during the afternoon (fig 1). The previous record of 23.2°C was recorded at Valley on Anglesey in 1977 (fig 2).
There’s still a number of stations reporting means of 50 knots or more (black triangles) across Wales, with gusts to 86 mph still occurring across the north of the country at 17 UTC (fig 1). It’s been quite a day, and I hope you’ve enjoyed these hourly reports on Ophelia’s progress. Apologies to those in Scotland where the winds are just starting to pick up, but I’m now packing it in for the day, I’ve been at it for nearly 12 hours! A full analysis on today’s gales and storm force winds from Ophelia tomorrow morning. I did manage to get to Tesco eventually so all in all a pretty good day.
Gusts to 90 mph at Capel Curig in the last hour, and another at Aberdaron to 84 mph (fig 1). The table of mean wind speeds make interesting reading, quite a number of inland stations running a full gale especially across Northern Ireland, but Mumbles Head tops the lot, with a 64 mph storm force 11 mean wind speed at 16 UTC (fig 2), why can’t the BBC send a weather presenter there? I’ve seen a very poor selection of on-the-spot-reports across Ireland and western parts of the UK for today.