Ex-hurricanes & Their Effects On Uk's Weather

[Staffordshire]

Thought this would be a nice little thread to discuss ex-hurricanes that may reach our shores

Edited September 3, 2011 by Staffordshire

[summer blizzard]

May be better in the model outlook as they have little effect unless they are Cape Verde and approach from the Azores. Even Irene is delevering nothing more than a bog standard cold front today. The main action actually comes from a secondary low.

[kold weather]

Normally its not the ex-hurricane itself that comes here, as SB said we normally get a secondary low. what they do is allow for a higher thermal gradient then would normally be possible, hence allowing for stronger LP's to develop and this in turn really helps to get things going...

[Staffordshire]

Hehe sorry don't really know much about hurricanes, so Tuesday isn't irene it's a secondry LP that's formed of it?

Edited September 3, 2011 by Staffordshire

[Terminal Moraine]

Hehe sorry don't really know much about hurricanes, so Tuesday isn't irene it's a secondry LP that's formed of it?

Tuesday's low may have started life as 'Irene' but well before it reaches our shores it's no more than a standard Atlantic depression, and a primary not a secondary.

A secondary of sorts does develop to the south west by Thursday if GFS is to be believed, and gives a wet day over England and Wales as it moves slowly north east.

[Staffordshire]

Oh yes just seen that feature on Thursday looks like it could bring some fairly heavy PPN, Tuesday looks to have stronger winds however.

Tuesday's low may have started life as 'Irene' but well before it reaches our shores it's no more than a standard Atlantic depression, and a primary not a secondary.

A secondary of sorts does develop to the south west by Thursday if GFS is to be believed, and gives a wet day over England and Wales as it moves slowly north east.

[philglossop]

As someone who lived through the remains of Charley in 1986, it remains in my memory as one of the wettest foul August days ever. And if my memory is correct it was Bank Holiday Monday, we were taking my late Nan to Torquay for the day out. Well that was abandoned as road at Avonwick was flooded, so we went home instead!

Edited September 4, 2011 by philglossop

[summer blizzard]

the remmenants of hurricane irene are in the system which has the cold front over the uk today. modeling did originally show a secondary low senario however if tuesdays low is a primary then it bears no relation to ex irene although irene did likely enhance the thermal gradient, hence the gales. to get direct effects from ex hurricanes they need to approach from near the azores.

[Interitus]

Irene was not such a good example as the tropical characteristics were long since broken down after traversing the north east of the USA and Canada. A storm which recurves earlier without making landfall is more likely to have a direct influence on our weather and as it happens the current tropical storm Katia may possibly affect us next week if the GFS is to be believed though it is a long way off yet.

Of course another response to ex-hurricanes can possibly be the shifting of high pressure giving us a late taste of summer. If only!

Edit: make that hurricane Katia now.

Edited September 4, 2011 by Interitus

[Snowyowl9]

I`d have to august 2004 was by far the best EG of ex tropical storms coming on a S-ly tracking jet bringing the most humid thunderstorm august on record.

Tuesday looks wet and windy with gales in esposed west/hills.

[the storm fisherman]

there was an example last year i think where the eye which was embedded in the extratropical low was still visable as it started to cross Ireland

[TonyH]

Obviously not a hurricane but todays low looks impressive on the satellite spiralling over the west coast of Ireland (this is the former Irene I take it?):

[summer blizzard]

nope, irene brought the cold front which has cleared the east coast. that is just a secondary low.

[Interitus]

Irene was not such a good example as the tropical characteristics were long since broken down after traversing the north east of the USA and Canada. A storm which recurves earlier without making landfall is more likely to have a direct influence on our weather and as it happens the current tropical storm Katia may possibly affect us next week if the GFS is to be believed though it is a long way off yet.

Of course another response to ex-hurricanes can possibly be the shifting of high pressure giving us a late taste of summer. If only!

Edit: make that hurricane Katia now.

I see there is a thread dedicated to the possible effects of Katia next week, only 3 days after my heads-up

http://forum.netweather.tv/topic/70938-ex-ts-katia-to-hit-the-uk/

It will be worth keeping an eye out for the future Hurricane Maria also.

[Coast]

Equinoctial gales

Ex-hurricanes blow our way

by Philip Eden

Many Septembers bring settled late-summer weather during the first half of the month, giving way to much more disturbed conditions with rain and rough winds during the second half. If this changeover should happen within, say, a week of the autumnal equinox (on or around the 22nd) mariners will talk knowingly of "equinoctial gales". Both the spring and autumn equinoxes have long been associated with stormy winds, and over many centuries seafarers came to fear violent gales in British coastal waters during the latter parts of March and September.

Early in the present century these general observations became perverted into a belief by some that gales occurred more frequently at the equinoxes than at any other time of the year. The statistics do not support such an idea. What the records do show is that there is quite an abrupt increase in the frequency of high winds in British waters during the second half of September, and a more gradual decrease in late-March and early-April. Meteorologists suspected way back in the 19th century that some autumn windstorms were somehow linked to tropical hurricanes that had been reported several days earlier on the other side of the Atlantic. But they could not be certain because there was insufficient observational data over the ocean to enable the production of proper daily weather charts which would have allowed such a storm to be tracked from day to day.

We now know that a true hurricane can only maintain its power when it is located over the warmest parts of the planet's oceans - where surface waters are at 26C or more. It will dissipate rapidly after crossing a coastline and moving inland, and it will lose energy more gradually if it strays into a region of cooler water. However, even when such a hurricane has "died", there frequently remain extensive remnants of very warm and moist air in the upper atmosphere. If this warm and humid air is absorbed into the circulation of a travelling Atlantic temperate-latitude depression it may provide sufficient added energy to cause a dramatic intensificiation of that depression, and this is undoubtedly the cause of some (but by no means all) of the severe September gales that have swept northwest Europe over the years. This is why weather forecasters sometimes refer to "ex-hurricane A" or "the remnants of hurricane B". As we have seen, this is strictly speaking incorrect, but "the Atlantic depression containing the residual warmth and moisture of hurricane C" is an awful mouthful!

http://www.weatheron...low-our-way.htm

If you really want to read more:

Ex-hurricane Lili reintensified as an extratropical cyclone before travelling across the data-rich region of the British Isles on 28 October 1996. The cyclone centre passed close to a Mesosphere-Stratosphere-Troposphere (MST) radar, providing continuous profiles of wind etc. which were used to evaluate diagnostics from the mesoscale version of the operational UK Meteorological Office Unified Model. The paper presents a mesoanalysis of the mature extratropical cyclone using model output together with radar and satellite observations. The combined analysis reveals a vertically extensive warm core three-quarters surrounded by a low-level jet reaching over 40 m s⁻¹. There was an associated eye, relatively free of cloud and partly surrounded by a hook cloud producing extensive heavy rain, which was itself encircled by cooler dry-intrusion air. The stratospheric part of the dry intrusion (and its potential-vorticity (PV) anomaly) descended within a tropopause fold around the cloud hook generally to below 400 hPa, with small pockets penetrating significantly lower. The cyclone's reintensification as an extratropical cyclone was related to its interaction with the stratospheric PV anomaly. This interaction commenced immediately after the decay of the strong moist ascent and associated deep column of diabatically generated positive PV that had characterized the earlier tropical-cyclone phase. Following reintensification, the dry-intrusion air entered the eye region of the extratropical cyclone over a deep layer. The mesoscale model represented many aspects of the cyclone structure well but it underestimated the dryness of the dry-intrusion air entering the eye. The MST radar vividly depicted the region of moist boundary-layer air responsible for the hook cloud rising up into the region of the lowered tropopause.

http://onlinelibrary...455108/abstract

United Kingdom

On the October 28 and October 29, 1996, the United Kingdom was hammered by what The Times called "arrival from America of Hurricane Lili." Lili produced a 92 mph (148 km/h) gust at Swansea, South Wales, while bringing a four ft (1.20 m) storm surge that inundated the River Thames. In Somerset, 500 holiday cottages were severely damaged. A United States oil drilling platform, under tow in the North Sea, broke loose during the storm and nearly ran aground at Peterhead. On the Isle of Wight, a sailing boat was beached at Chale Bay; luckily all five occupants were rescued. The most damaging storm to have struck the United Kingdom, since the Great Storm of 1987, Lili killed two people and left £150 million. The storm also broke a four-month drought over southwest England.

http://en.wikipedia....ane_Lili_(1996)

[Snowyowl9]

Ex hurricane Katia to bring severe gales on monday,storm force wind in the NW very potent for early september.

http://www.wetterzentrale.de/pics/brack2.gif

The earlier fax showed the name written.

[Weather-history]

Here's a thread I posted on UKWeatherworld, 5 years ago on ex-hurricanes that affected the UK in the past

http://www.ukweatherworld.co.uk/forum/index.php?/topic/47929-ex-hurricanes-that-affected-the-british-isles/

[Snowyowl9]

Going by how much news this is making today,this must be unusual for it to swing so quickly across the atlantic and not hit the USA firstly.

http://www.voxy.co.nz/national/rare-tropical-storm-hit-uk/5/101010

Anyway the northern half will get the the worst of it.

[greybing]

What annoys me in scenarios similar to the forecast weather from the remnants of Katia is the purposeful bending of the truth by the media.The word 'Hurricane' is used in articles in substitution for 'remnants of -'.

Edited September 11, 2011 by greybing

[weatherguy]

Well there's bending of the truth like the above, then there's stuff like this:

http://www.dailymail.co.uk/news/article-2035394/Hurricane-Katia-hit-parts-Britain-Monday.html

That's right, they're claiming 50ft high waves

[Interitus]

Well there's bending of the truth like the above, then there's stuff like this:

http://www.dailymail...ain-Monday.html

That's right, they're claiming 50ft high waves

Very unlikely........but not impossible......

Forecasts are showing waves to around 35ft to the north of Northern Ireland and buoys and satellite altimetry estimates give a 16 metre i.e. over 50ft wave as having a 50 year return time for the outer Hebrides. But this is in open water - the wave height can be increased as they break over reefs. As an example, if you doubt a 50ft wave is possible round the British Isles, google +prowlers +Ireland

Edited September 11, 2011 by Interitus

[Snowyowl9]

Very unlikely........but not impossible......

Forecasts are showing waves to around 35ft to the north of Northern Ireland and buoys and satellite altimetry estimates give a 16 metre i.e. over 50ft wave as having a 50 year return time for the outer Hebrides. But this is in open water - the wave height can be increased as they break over reefs. As an example, if you doubt a 50ft wave is possible round the British Isles, google +prowlers +Ireland

Yep nothing`s impossible.

This is a very notable storm for early september,trees will be uprooted especially from north Wales northwards,always some who have to downplay these things.

It was very windy at the coast today,you could hardly stand up and large waves crashing. throwing form on the sea front.

[weatherguy]

@Interitus - Interesting, guess I dismissed it a bit too vigorously. I just used the logic that storm surges from "actual" hurricanes do not reach 50ft, therefore it seems highly implausible that a depression could cause waves of such size. Still, the "prowler" apparently is a one off wave, whereas the article I linked implies "waves" ie. plural.

@Snowyowl9 - I'm certainly not downplaying the storm, and don't deny it's power (why would I?), just the notion of predicting 50ft waves to hit seemed outrageous at first glance, particularly with the paper being, erm...well, the Daily Mail doesn't have the best rep around

[knightrider]

So with Katia out of the way, any prospect of any further ex-hurricane's or ex-tropical storms effecting the UK in the comming weeks? Maria or Naite perhaps?... If not then what about the prospect of any classic European Windstorms not related to Hurricane's?

[Lettucing Gutted]

In addition to extreme winds, waves and rainfall ex-hurricanes can also have contrasting effects on temperature over Britain. On the one hand on 21st September 2006 because he stalled to the immediate west of the UK ex-Hurricane Gordon drew up exceptionally warm and humid Continental Tropical air from the south with sunshine, humidity and warmth as high as 30C in the East-Midlands and a very high mean daily CET of 21.4C. In the already very warm September 2006 this hot spell secured September 2006 as the hottest September on record for the CET at least.

http://www.personal....006_weather.htm Thanks to Trevor Harley

http://www.wetterzen...00220060921.gif

http://www.wetterzen...00120060921.gif

http://www.metoffice...cetdl1772on.dat

On the other hand and in complete contrast on 25th August 1986 ex-Hurricane Charley combined with the southern boundary and Jetstream of a very large Polar Cell (for August) which extended all the way from the Arctic to over Britain. Ex-Hurricane Charley's powerful upper outflow strengthened the existing Polar Cell even more pulling down very cool and dry Continental Polar air from the North Pole. On 25th August 1986 were ex-Hurricane Charley's rainfall as high as 25 mm+ fell and evaporated into the the unseasonaly cool, dry air maximum temperatures failed to rise above 10C! In addition were skies cleared temperatures fell to a minimum as low as -3.4C at Kinbrace (Scottish Highlands) with a very cool mean daily CET of 11.5C again both of these on 25th August 1986. In the already cool August of 1986 this cold spell secured August 1986 as the one of the coldest Augusts on record for the CET and the coldest since 1956. The 25th August 1986 alone was the coldest and wettest August Bank Holiday on record.

http://www.personal....986_weather.htm Thanks again Trevor Harley

http://www.wetterzen...00219860825.gif

http://www.wetterzen...00119860825.gif

http://www.metoffice...cetdl1772on.dat

Edited September 16, 2011 by Craig Evans