Atlantic SST – Is this the end of the cold blob?

Figure 1 – 24 November 2015

Figure 2 – 27 November 2016

Figure 3 – 22 November 2017

You can tell just by looking at these sea surface temperature charts since 2015 (figs 1-3) that there’s been considerable warming going on in the last two years. The cold anomaly that was a feature for so long in the central Atlantic is now less intense and much smaller a feature than it once was. It’s shifted and has been squeezed further northeast towards the southeast coast of Greenland and the opening of the Labrador Sea.  The other notable difference that’s appeared in recent months is the area of warmer SST anomalies ~1500 km to the west of Portugal (42N 17W), a warm blob if you like.

The warm blob and this coming winter

To be honest I don’t have a clue if this warm blob will have the slightest effect on the weather in the British Isles this coming Winter. It would be nice to think that the area of warmer SST might weaken the Azores high in some way, and that might increase cyclonic development in the southeast Atlantic which will run northeastward towards Biscay – who knows. Looking at the actual MSLP anomalies (fig 3) for so far this month, it’s true that the Azores high is displaced further to the northeast, but all this has done has been to increase the strength of the zonal flow across the Atlantic. In fact everything seems to be enhanced in some way, if you look at the underlying anomalies (red dashed line) both highs and lows have been more intense in the first three weeks of November 2017 than usual.

Figure 3 – Data courtesy of NOAA/NCEP reanalysis

Guardian: Ophelia’s arrival hints at a new vulnerability for Europe

My first reaction to this article in the Weatherwatch section of the Guardian was to measure the distance in miles between the Isles of Scilly and the nearest 26°C SST isotherm and then divide by thirty!

Figure 2

And so if the North Atlantic did continue to warm at this rate (with the 26°C SST moving 30 miles every 10 years), you can expect the 26°C SST isotherm to be lapping on the beaches of the Cornish Riviera in a little over 692.7 years in the late summer of 2709!

I do think Paul Brown did manage to completely miss the point with this article about Ophelia though, and instead of repeating the “hurricanes only form over water of 26°C” mantra like we’ve never stopped hearing from the BBC weather presenters of late, the question that he should have been asking was “why did Ophelia intensify to a major category three hurricane over an Ocean with marginal SST of between just 22 and 24°C“?

Ophelia : The life and death of a hurricane

Figure 1 – Provisional track from NHC and Met Office

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…

Figure 2

 

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.

How openings in Antarctic sea ice affect worldwide climate

I noticed this interesting article about polynya on the Phys.org website (you might what to add this to your favourites because it looks a great site) that might interest some of you out there. I was thinking, it’s only because the upwelling of warm water occurs under an ice sheet that we realise that they’re happening at all. They must happen all the time in the worlds oceans, but we just don’t see them, apart I suppose from anomaly charts of very sensitive SST satellite sensor data.

The Guardian – It’s a fact: climate change made Hurricane Harvey more deadly

The Guardian must have known they were onto a winner with this article from the great Michael Mann about Hurricane Harvey, who states categorically in the article that Hurricane Harvey was made more deadly due to climate change (fig 1). I wonder just how many comments this article will attract?

Michael Mann states that one of the main factors why it was more deadly was due to higher than average SST in the Gulf of Mexico. So I thought that I’d have a quick look and see what the latest anomalies were across the North Atlantic, Caribbean and Gulf of Mexico to see if what he was saying was correct. Courtesy of NCOF, here are the SST (fig 2), on which I’ve drawn a very approximate track for the path of tropical cyclone Harvey, which as far as I can see from the NHC records, sprang into life as a cyclone at around 54° west on Thursday the 17th of August. Harvey has had a very fitful life, it ‘died’ as a tropical storm as it entered the Caribbean late on Saturday the 19th, before being reborn again as a tropical depression on Wednesday the 23rd as a tropical depression in the Bay of Campeche, the rest as they say is history.

Figure 2 – Courtesy of NCOF

All that you can say about the SST anomalies along the path of Harvey was that they were generally in the slightly warm category +0.5 to +1.0°C for much of its life. Interestingly these ‘higher’ than average SST in the Caribbean didn’t seem to stop it from dying for four days though, and it wasn’t till it entered the Bay of Campeche that it was reinvigorated. Because the SST anomalies in the above chart (fig 2) are in a bit of a turmoil after the passage of what was a category four hurricane, I have included an extra chart (fig 3) from the 23rd  and before the waters got churned up. The SST anomalies in that chart show anomalies between +0.5°C and 1.5°C, generally across coastal regions of Texas extending eastward to Florida, with negative anomalies of the coast of the Yucatan peninsula.

Figure 3 – Courtesy of NCOF

So what caused Harvey to reform and quickly turn nasty as she entered the Gulf of Mexico? I personally don’t think it was ‘more deadly’ because the waters of the Gulf of Mexico were slightly warmer than average, I think it was more to do with the atmospheric mechanics that were driving Hurricane Harvey, of which the SST, although important are just one factor. Anyway now that I have provided one piece of the evidence you can make your own minds up.

Latest Mediterranean SST

Figure 1

Not surprisingly, the sea surface temperatures in the Mediterranean, are generally well above the average for this time in August, no doubt helped by the recent hot and sunny weather of the last week or so, with anomalies of +3°C above average in parts of the Adriatic, and off the Costa Calida in Spain. There’s also a curious tongue of colder water that seems to project westward into the northern Aegean sea. The SST in the coastal waters around the UK, are above average in the west and the southeast, but cooler than average in the southwest, and along the east coast from Fraserburgh down to the Humber.

Figure 2

July 2017 – why so mobile?

Figure 1 – data courtesy of NCEP Reanalysis.

July continues it a mood of being mobile and often quite cyclonic at times, in fact that’s how it’s been since the end of May across the British Isles, as this graph of zonality shows (fig 2). The simple answer  of why has it been so mobile is that mean pressure in the first three weeks of July 2017, has been 8 hPa below average across Baffin Island, and there has been a band of lower than average mean pressure extending westward across Iceland, before arching around Scandinavia and into eastern Russia. South of that the mean pressure across much of the central Atlantic has been higher than average (+3 hPa), and between the two the W’SW gradient has been tightened.

Figure 2 –  data courtesy of NCEP Reanalysis.

It’s very likely that this is all driven by temperature of the atmosphere at all levels. The SST is well below average around Baffin Island (-4°C), and the central mid Atlantic remains generally cooler than average (-1.5°C), although there is now a band of warmer water (+1.5°C) extending westward from America at ~38° north. It’s interesting to see the SST down the east coast of Greenland being colder than average, probably from fresh water from the summer melt of the glaciers.

Figure 3

This may help explain the very intense lows for July’s that we are seeing. Here’s the forecast for this Wednesday (26 July) from the Met Office, which shows an intense low of 973 hPa low at 19° west, throwing a frontal system across the British Isles. This low in turn, will spawn a series of secondary lows that will dumbbell around it before the week is out maintaining the mobility.

Figure 3

Finally, I thought that I would look at a virtual barograph that I would sit at 57.5° north and 22.5° west (where hopefully it won’t get too wet). As you can see (fig 4) the anomalies there have been mainly negative there for  long periods, and this is in an area of low pressure anyway and generally close to where the Icelandic low is found on mean pressure charts.

Figure 4

 

 

 

Central Atlantic refuses to warm

Figure 1 – Courtesy of NCOF

No change in the SST in the central Atlantic this month (fig 1), any changes in SST would be very slow anyway, but when comparing it to last September’s chart (fig 2) there is little difference apart from the appearance of a massive negative anomalies at 43N 50W, and the almost complete disappearance of the intense warm clusters south of Nova Scotia in last years chart. If these charts from NCOF are accurate, then I wonder what’s responsible for producing that massive area of violet-coloured negative anomalies SW of Newfoundland? You can imagine that they are mostly responsible for fueling the cooling further that s occurring further east.

Figure 2 – Courtesy of NCOF

A cold wind from Europe…

Figure 1

Chilly down the east coast of England today with a moderate or fresh northeasterly straight of a relatively cold North Sea (fig 2) keeping temperature at around 9 or 10°C (fig 1).

Figure 2

Meanwhile in comparison, the west of Scotland has seen temperatures as high as 20°C in some places this afternoon, on what’s been another generally sunny day in the north, although with a bit of cirrus (fig 3) and a keen breeze at times.

Figure 3

Recent changes in North Atlantic SST

Figure 1

I thought that I would compare changes in the North Atlantic SST by using two charts, one from the 14th March 2017 (fig 2), and one from the 13th of March last year (fig 1). It looks to me that in the last year sea surface temperatures seem to have warmed by 1 or 2°C in many areas where the North Atlantic has influence. The cold pool that has been resident in the central Atlantic for so long, now seems to have shrunk and become less well organised as it once was. Waters around the British Isles and for much of the North and Norwegian Seas have predominantly positive SST anomalies. I have no idea what the current SST setup in the Atlantic might mean for the weather in our part of the world for the rest of this year.

Figure 2