NASA: Hurricanes and Aerosols Simulation

I was a bit late on this one, but here’s an interesting NASA video from the APOD site about aerosols and the formation of hurricanes in the North Atlantic and eastern Pacific this season.

BBC: Extreme flash flooding in Greece

Figure 1 – Courtesy of BBC weather

You can trace back the low that ended up being the root cause of the flash flooding in Greece in recent days as originating from the remains of what was tropical storm Rina that crossed the UK on Saturday. The Meteorological Institute of Berlin quickly renamed it Numa, but I did think that it would cause problems as it deepened over southern Germany on Sunday. I can’t add much to the fancy graphics and smart suit of Stav Danaos (fig 1), so this animation of 06 UTC MSLP charts for this week over that part of the world will suffice (fig 2). Hopefully the plotted values are the 24 hour rainfall totals might give you an idea of how wet it’s been over parts of Greece.

Figure 2

Ex-tropical storm Rina holds up cold front clearance on Saturday

Figure 1 – Data courtesy of the NHC (approximate GFS positions from the 00 UTC 10 November model run)

I wondered what was holding up the cold front clearance on Saturday across southwestern parts of England (fig 2), but then I noticed on the Berlin Meteorological Institutes website, that the second shallow low the follows behind the low that tracks WNW- ESE across Ireland, Wales and the southeast of England during Saturday morning, was labeled ex-tropical storm Rina (fig 1). The Met Office of course are having none of that because it wouldn’t be correct would it.

Figure 2

Will Rina be the finale of the Atlantic hurricane season?

The last advisory on Rina highlighted what had been yet another rather unusual tropical cyclone in 2017 (fig 3):

Figure 3 – Courtesy of the NHC

Rina lives on in Europe

Interestingly, that rather shallow low which was Rina was when it crosses the UK is forecast to develop into quite a deep low of 991 hPa by 12 UTC on Sunday, as it tracks southeast across the Alps into the northern Adriatic, and quite a significant feature in that part of Europe (fig 4).

Figure 4 – Courtesy of the Met Office

Yellow Warning for rain?

Even more interestingly, so far the Met Office haven’t issued any yellow warnings for heavy rain in southwestern parts during Saturday. I just wondered if the tropical origins of the air might even enhance the rainfall in theses parts.

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

Figure 1 – Courtesy of the Guardian

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“?

Tropical cyclones that form close to the Azores [1851-2017]

Figure 1 – HURDAT2 data courtesy of the NHC

I’ve spent sometime writing new code to allow me to rubber-band any area in a map, and plot the tracks of all the tropical cyclones that originated within this area. I did it to confirm what I thought was happening, and that is that most tropical cyclones in the central Atlantic would end up migrating northeastward towards the British Isle. I don’t know why I thought that, and once I got the program working I could see clearly how wrong I was (fig 1). As you can see from the results there is more of a Catherine-wheel effect going on, and if a tropical cyclone does form in that area of the central Atlantic, it seems that it can end up flying off in virtually any direction.

Ophelia is clearly visible as is ex-Hurricane Charley (1992), the other one I notice is ex-tropical storm Grace (2009) which I can’t remember at all, but apparently was at the time the northeastern-most forming Atlantic tropical cyclone on record.

Obviously I was motivated by the recent hurricane Ophelia to investigate where hurricanes that start their lives in the central Atlantic end up, especially where the SST are marginal, as was the case with Ophelia. It does make you appreciate just what an unusual hurricane Ophelia was, because although there have been tropical storms in past years, Ophelia is the first tropical cyclone to have formed in the central Atlantic and to make for the British Isles as a major hurricane.

The application is pretty flexible and as well as allowing you to rubber-band any area of the map with your mouse and find where all the tropical cyclones that originated in a selected area ended up, it also enables you to use in reverse, and what I mean by that is you can use it to find where all the tropical cyclones that terminated in a selected area started from. These are all the hurricanes that terminated over an area of southern Texas and northern Mexico since 1851, it’s a bit cluttered but it does seem to work (fig 2).

Figure 2 – HURDAT2 data courtesy of the NHC

I don’t know if there would be any call for this kind of functionality, but if there is I can now do it! I suppose the next query I should write is to find all tropical cyclones that reported a track point in a selected area. That would be an impossible task using 6 hour track points alone, and you would have to test if a track of a cyclone intersected with a selected area. I would have to be very desperate to take on a piece of coding as sophisticated as that.

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.

That’s torn it – a gust to 90 mph at Aberdaron

Figure 1

That’s torn it, there have been gusts higher than the 80 mph upper limit in the Met Office’s amber alert, but if we keep quiet and don’t mention it, they might just get away with it. The stations in question are Valley with a gust to 81 mph at 15 UTC, and Aberdaron with a gust of 90 mph, you just knew somehow that the upper limit of 80 mph was going to be exceeded, especially with a ferocious southwesterly 75 knot gradient (and I’m guessing here) running straight up the Irish Sea. I can’t see them upping their existing amber warning, although you never know.