Su Campu

I think instead of the UK, the focus will be shifting to Netherlands, Germany and Denmark, as it would appear this is where the real action will take place tomorrow. I'll be interested in observations from places like Helgoland, List/Sylt, etc. http://www.dwd.de/bvbw/appmanager/bvbw/dwdwwwDesktop?_nfpb=true&_windowLabel=dwdwww_main_book&T1400087811143553398307gsbDocumentPath=Navigation%2FOeffentlichkeit%2FWetter__Warnungen%2FRegionenwetter%2FRegion__morgen%2FNordwest__morgen__node.html%3F__nnn%3Dtrue&switchLang=en&_pageLabel=_dwdwww_wetter_warnungen_regionenwetter

The Rosenbloom Rule states that deep storms can go left of the model-forecast track.

Just a note for those using the meteocentre hourly analysis charts - the most accurate analyses are every 3 hours (1200, 1500, 1800, etc.) as these include 3-hourly synop, SHIP reports, etc., and therefore give a better picture. Hours outside of these only have some metars and buoy reports.

Gatwick's 1100Z TAF now backed down slightly to 35 gust 60 kt, from 40 gust 63 kt earlier. Heathrow still 35 gust 60. Amsterdam 45 gust 60 for a four-hour period from 1000Z tomorrow

A handy rule of thumb is that a low will travel parallel to the warm sector isobars until it starts to occlude, then it will run parallel to the isobars just ahead of the warm front thereafter

It's got nothing to do with pressure drops. Driving down the road you will get a more notable pressure change for every 8 metres drop or rise. More likely dehydration.

For me it's been an interesting few days from which we will all learn something. I'm really interested to see exactly how it works out. Gatwick TAF from 0500Z called for 40 gust 63 knots tomorrow morning, I think the 1100Z one will shave 5-10 knots off

The models haven't behaved badly, unless some malfunction can be diagnosed that has caused spurious output. They are all equally correct in that they all have slightly different attributes which yield slightly different outputs. Handling a the exact timing of a190-kt jet interacting with anomalous moisture and SSTs is prone to variations in interpretation. Lambasting one model over the other, or talking about the repercussions for the Met Office at this stage is pure rubbish. As always they have taken the information available to them and processed it to the best of their abilities. The fact that some people prefer to go to the Daily Express for their information is their problem.

EISN SIGMET 04 VALID 262107/270030 EINN- EISN SHANNON FIR/UIR EMBD TS FCST W OF A LINE N5100 W00800 - N5300 W00800 - N5425 W00810 TOP FL320 MOV E AT 20KT NC=

That looks like a very good book you already have. Goes into a lot of detail. Fica com isso e tudo irá bem!

Latest AMV shows 170-knot vectors atop the developing low in mid-Atlantic. From here

Incoming...

It's amazing how a system like this generates such a frenzy in southern England whereas it wouldn't cause a fuss elsewhere, in say Scotland or Ireland. It's not a criticism, just an observation.

Basically the global circulation's job is balancing out the large temperature difference between the equator and the Poles. Warm air flows poleward and cold air equatorward. Throw in the effect of the Earth's rotation (Coriolis force), and we get large wave patterns (Rossby waves) in the flow, with the jet stream forming due to the large thermal (and hence geopotential) difference where the two airmasses meet (the Polar Front). What is the book you are reading? I would recommend Tim Vasquez' books as good starting material, but if you already have a good grasp of physics then Roland Stuhl's "Meteorology for Scientists and Engineers" or James. R. Holton's "An Introduction to Dynamic Meteorology" (but you'd better be good at vector calculus for that one!).

I wish the misquoting of Michael Fish would stop. A hurricane didn't hit England, it was a storm. Just like Monday's.

As I said before, the Rosenbloom Rule hints that a storm like this will track to the left (north) of the model forecast tracks. This could mean places like the Isle of Wight could be wightly fooked! Still large scope for this to fall on the cold side of the polar front and hence not deepen as much. I think it'll be all to play for until t-24 hrs, and even then we could see a wide range of minimum pressur forecasts. I'm going for 965 hPa.

I reckon the low centre itself will be racing northeastwards at around 50 mph Sunday night. That foward speed will be added to the gradient winds on its southern flank, so it's looking dicey for the south coast and Channel!

This storm is nothing at the moment, and will only start appearing in the surface pressure field tomorrow afternoon.

Don't be at all surprised if it takes a track further north than the models are showing. The Rosenbloom Rule in effect.

Oi Eduardo The reason why troughs normally point to the equator (not always) is that they are areas of colder air, therefore they normally originate nearer to the Poles. Conversely, ridges are areas of warm air, therefore originate nearer to the equator. When I say cold or warm air I mean low or high geopotential, respectively. Geopotential (the height of a certain pressure level) is directly proportional to the virtual temperature (which in turn is proportional to the temperature and humidity) of an airmass. As cold air is denser than warmer air, the spacing between pressure levels is less in cold air. This means that all the pressure levels in cold airmasses are at a lower height than in warmer airmasses, therefore leading to the troughs and ridges. I wrote this article which might explain it a bit better. http://irishweatheronline.wordpress.com/how-weather-works/our-atmosphere-and-how-it-makes-weather/

I flew from Weston to Dundalk and back yesterday morning and shot some video along the way. The only snow remaining was on the Cooleys and Mournes and some far off Cavan hills. I reckon remains of that snow on the Mournes will still be there into May.

That low-mid level inversion that eroded to allow the Irish Sea to spring into action 48 hours ago is set to return later tonight and stamp out a lot of the activity by morning. I would expect a lot more in the way of scattered stratcumulus tomorrow with maybe just the odd snow grain. Amazing setup this week.

Snowed pretty much all day in Tallaght (100 m). Nothing stuck though

The actual Lyon soundings do seem to be missing from the usual sites at the moment, but this site gives excellent point forecast soundings in 1-hour steps out to 59 hours (WRF model). I find selecting "Petit émagramme" is visually better. http://www.meteociel.fr/modeles/sondage_wrf.php

Snow is a much less efficient reflector of radar energy than liquid drops therefore it won't show up well on radar. Yesterday's snow was very dry so although it looked like a whiteout to an observer on the ground it wasn't showing on the radar. The graupel was mostly what showed up as it is a snowflake with a layer of rime surrounding it.. If you look at actual liquid equivalent totals for what fell most places barely scraped 1 mm, with just 2 mm at Johnstown Castle where the bulk of the snow fell.