BOOM.

Now then... there's quite a story unfolding just northeast of the Bahamas at the moment, as tropical storm Joaquin (probably a hurricane by now) has really got its act together over the past 36 hours and appears to have behaved in exactly the right way to maximise it's potential for future intensification.

This behaviour has been two-fold.

Firstly, the low level circulation of the storm made a dash south early in the period, toward its mid-level convective swirl, which pulled it away from some strong wind shear. Very few models saw that one coming... and although ECM did explore the idea, official NHC forecasts initially called for a weak tropical storm, upgrading to a moderate storm in the following outlook. The jump south then changed the game completely, and forecasts since have brought the storm up to hurricane strength by the end of Wednesday 30th.

Secondly, it has since maintained a southerly component to its motion rather than the due west motion that could have occurred, which has continued to take it into an increasingly low shear environment not just at present but also in terms of likely conditions over the coming 3 or 4 days. The models have responded by coming up with some increasingly dramatic - and dangerous - solutions.

Yet a very wide range of possible paths remains, as the models struggle severely with a weak steering environment over the coming two days followed by an uncertain trough in terms of timing, extent and orientation:

The main pack are curving the storm west, which is behaviour very reminiscent of Hurricane Sandy in 2012. This time around, it's caused by the trough being negatively tilted - the axis running more NW to SE than the usual SW to NE. Instead of the usual turn east, you get a turn west with nearby tropical cyclones.

Those that don't curve the storm west are either moving Joaquin along more slowly so that the trough ends up to its NE, or have the trough positively tilted (but note that the positive tilt solution has lost a lot of support over the past 24 hours).

The latest intensity guidance is... alarming:

This has been trending steadily upward with each of the last four sets of model runs. It's been a long time since I last saw such a tight clustering hitting category 4 intensity! Those ones which then climb toward category 5 beyond 72 hours are concerning... conditions are meant to be becoming less conducive for intensification by then presuming the storm is lifting north - but what if it doesn't? There is an outside chance that the storm is left meandering near the Bahamas over record-warm waters. Not sure that's what the cat 5 models are going with though - perhaps the trough takes longer to arrive in those solutions?

I'll wrap it up for now with this snapshot of the GFS 06z operational run. Yesterday, most of the op runs had hardly any development as the storm moved east toward the Azores... it's a very different story now! The 00z was more restrained but this 06z does represent the trend we're seeing in general this morning. 

Here's hoping that if Joaquin does achieve its true potential, it doesn't perform that hook west and slam into the U.S. 

Of course, without that, places such as Newfoundland then become at risk, and the storm could have major impacts in the extratropical Atlantic as well... there's little chance of a total let-off with this one unless, perhaps, dry air manages to invade the storm more than expected in the very near future.

Joaquin's now a hurricane officially. Last update had it with 75 mph max. sustained winds but based on the current satellite appearance some intensification since then has likely occurred. Indeed, the swirl of very cold cloud tops visible in this image betrays a developing eye wall, which if complete soon ought to allow for a more rapid intensification rate, perhaps to major 'cane status by late tomorrow (just my thoughts - for some reason the NHC only have a cat. 2 despite what the models keep putting out).

It seems odds on that this storm will prove to be the one that the 2015 Atlantic hurricane season is remembered for.

Also, I forgot to mention that in that GFS chart I posted, the low to the east is actually a system containing the remnants of Ida. It has development odds of around 40% for the next couple of days.

Stormchaser, do you think this is a medicane?

Even if Joaquin stays offshore, it's likely to be remembered for rainfall totals, with another 10" of rain being added to 10" from an existing stalled front in several areas south of Washington.

http://www.weather.com/forecast/national/news/soaking-weather-pattern-east-flooding

People, what about cyclone corbyn!? I recon we will see a full blown tropical storm in the mediteranian by 9am tommorow. If I'm wrong please correct, me. Look at the satellite imagery, this thing is amazing! 

It's finally starting to show some wrap-around tendencies which is... ominous.

Meanwhile, Joaquin has started to 'see':

Not literally of course! That would freak us all out!

We're still waiting for the storm to start making the turn, which should be in around 24 hours time. The Bahamas are in for an extended period of high winds, hurricane force for some.

Looking at the IR sat. loops, it really does give the impression that the storm is 'descending' onto the islands like a bat out of hell:

http://www.ssd.noaa.gov/PS/TROP/floaters/11L/imagery/avn_lalo-animated.gif

Convection remains very impressive thanks to those record (or near-record) warm SSTs and high oceanic heat content in the region. Plenty of room for a category 3 or 4 hurricane to be churning away by tomorrow evening.

Not only is this storm going to hammer the Bahamas, but if it then runs up the east coast, it's huge moisture field combined with the rain from a stalled out frontal boundary over the preceding days could lead to 7-day totals as high as 500 mm (20 inches) along those coastal regions, though that is the extreme upper end with 250 to 325 mm (10 to 15 inches) being expected more generally.

If the storm also hooks west and landfalls... the total damages have the potential to be exceptional. We can only hope that the storm stays well away from the coast (somehow...) and then shoots away northeast without landfall (or second landfall, depending on what happens in the Bahamas).

I'm amazed there hasn't been more press on this:

Eye wall seems to be forming on corbyn as wind sheer really starts to drop. Over the next few hours it seems like it could intensify to a category 1. It will hit Sardinia shortly after midday, with strong winds extending to corsica (my estimated track is given below)

As it moves over Sardinia it will transition to an extra-tropical storm though still maintain high wind speeds, after it leaves corsica unebelievabley models are indicating it could transition back into a 'hurricane' even a catogary 2 (top estimates?!). 

These potentially hurricane like systems must be rare even for medicanes.

Using Dvorak classification I think we are already at T4.0 which means this system could already be a catogary 1 hurricane. Amazing! 

Mahon in Minorca did get a bit gusty earlier, albeit a fair way short of hurricane strength at that location. Interesting system!

http://www.weatheronline.co.uk/

Joaquin has exceeded expectations and undergone rapid intensification overnight. A defined eyewall, tight signature and max sustained of 110kn takes the system to Cat3 and a major storm. Only EWRs and cooler patches of sst will prevent Joaquin from further intensification.

Track - the main issue. Only ECM of the blend recurves the storm out to see. The cluster, including UKMET, push it into the US between S Carolina and Rhode Island.

Something that will engage people in that area for sure.

I know Jocquain is taking the attention away from the medicane. Apologies if my posts seem a little insensitive, I just find the concept of a tropical system in the Mediterranean far more fascinating given that storms in the Atlantic are the status quo (its also why I posted about Ida - as a storm it was rather unusual).

This is the latest vis sat of the medicane. Dvorak classification puts it at about a T3.5 (strong tropical storm strength) though in reality systems away from the tropics tend to 'look healthier' due to (I think) stronger Coriolis forces. Its still tropical storm strength though with wind speeds at least 40Mph sustained on its NW flank. As it hits sardinia and corsica it will tend to become less symetric however rapid intensification is expected after pushing NW of corsica. 

The medicane after rapid re-intensification. 

The path the medicane takes looks about as bad as it gets for dumping biblical amounts of rain.

Thoughts are with two groups of people in very different places today, western Sicily and the central/western Bahamas!

Joaquin is starting to look like one of those infamous 'buzz-saw' hurricanes. You know, like Wilma...

http://www.ssd.noaa.gov/PS/TROP/floaters/11L/imagery/vis-animated.gif

On this next loop, you can see a frontal boundary approaching from the west. Eventually this will either send Joaquin packing or merge with it, but before then it may actually serve to increase the 'ventilation' of the storm - taking even more heat and moisture away at the upper levels to allow more to pile in at the surface, allowing the storm to intensify more readily than would otherwise be the case.

I believe that's when category 5 becomes a distinct possibility, but it may only be a short-lived window, after which vertical wind shear starts to rise and the cyclone may be starting to move over cooler waters, resulting in a steady winding-down... but potentially not fast enough to negate a serious U.S. landfall should the storm hook to the west as some model runs continue to show.

The odds for the storm heading northeast and avoiding such a landfall have risen since yesterday evening, which is encouraging.

It won't be an 'out to sea' storm regardless; it's making landfall on one of the smaller islands in the Bahamas as I type this sentence. It's largely uninhabited from what I've read, but it's a landfall nonetheless.

The medicane re intensified as expected, and an eye feature was quite nicely visible earlier:

I know people were focused on Joquain, but from looking at the French and Italian media, this system has done quite a lot of damage. There has been heavy flooding in Sardinia and Corsica, and I've seen pictures of uprooted trees e.c.t. 

Some quite high rainfall figures in the Med- around 2 inches of rain for Nice and Cannes so far today, while across Corsica rainfall total are anything between 3 and 5 inches over the last 24 hours.

Keraunos have been following Q's 'medicane' - he might be interested in the discussion.

I'll not link the Google translated version as the link tends to break but easy to see the story in the pictures.

http://www.keraunos.org/actualites/fil-infos/2015/octobre/fortes-pluies-orages-tempete-corse-alpes-maritimes-var-medicane-1-2-octobre-2015.html

I wonder if it'll move away NE'wards - and, if so, whether it'll deliver some serious snowfall to the highest Alps

I think the freezing level is quite high - near 3000m, and set to go higher in coming days. However it is currently snowing on Pian Rosa and Snow-Forecast is going for some hefty totals in the Zermatt area especially:

http://www.snow-forecast.com/maps/dynamic/switzerland?type=snow.next3days&&over=none&&symbols=snow

Since there is no official organisation watching medicanes. I have decided to start making my own archive. 

http://quantumoverlord.blogspot.co.uk/2015/10/medicane-season-2015-to-be-updated.html

I've started off with Alison (name picked at random beginning with a from generator). Any comments (can be left anonymously) about how to improve or what to include would be great. Itl be nice to be able to review the whole season come February - I've kinda decided to make September - January the official unofficial Mediterranean medicane season. 

I see that hurricane is still a powerful Cat 4 this evening with sustained winds of 150mph 

Serious flash flooding reported in South Carolina

Looks like the medicane left very severe damage in parts of the French Riviera - I assume this was due to the remnants of it anyway?

http://www.bbc.co.uk/news/world-europe-34437228

and some 72 hour rainfall totals go some way to explaining why:

http://www.weatheronline.co.uk/