Archives For December 2013

 

Should the UK start naming storms?

The number, frequency and rapid movement of recent UK storms has meant that, for many people and the media, one anonymous unnamed storm has merged into another. Identifying impacts and explaining the specific nature and different characteristics of each storm is often confusing.  The current procedure of UK storm nomenclature is by date, such as “the 2013 Dec23-24 storm” or, for more infamous specific high impact events, randomly adopted names are used, such as StJude.  Storm identification in the UK seems, therefore, to be rather an ad hoc, random, informal and possibly even disorganised process.  For a country that experiences a lot of storms and, seemingly, an increasing number of intense meteorological events, it would seem like a timely idea to START NAMING UK STORMS!

Naming storms that impact Germany and Central Europe has been a tradition at the Institute for Meteorology of the Free University (FU) Berlin since 1954. They run an interesting adopt-a-vortex scheme that allows users to (pay?) to adopt a LOW. more here…  http://www.met.fu-berlin.de/adopt-a-vortex/ Some forecasters in the UK use the Berlin vortex Euro-names already, especially on twitter.  Other professional forecasters fear that using such storm names will not help public understanding of meteorological events (not least because some of the worst UK storms are wave depressions that are spawned by rapid cyclogenesis from more persistent parent lows; this is more complex than a hurricane which tends to stay as one system).

Better known are the names given to hurricanes and typhoons in the Atlantic and Pacific since 1945.  Names like Hurricane Katrina, Superstorm Sandy, and Typhoon Haiyan are iconic in the public imagination and formally arranged by the World Meteorological Organisation using a formal alphabetical list.  http://www.wmo.int/pages/prog/www/tcp/Storm-naming.html. Whilst UK storms are not usually on the same scale as tropical hurricanes, they nervetheless have the potential for significant economic, environmental and social impacts.

http://en.wikipedia.org/wiki/Tropical_cyclone_naming

There are several benefits of naming storms, not least a heightened public awareness if storms have unique names.  With storm damage and intensity set to increase for the UK and considering Atlantic storms arrive here first in Europe, it seems like a good idea to start our own system of storm naming. The UKMO or http://www.rmets.org/ could run such a scheme and funds raised could be charitable or go towards funding the scheme.

A scheme similar to that of Adopt-A-Vortex where the public can pay to name a storm would help fund it.

Have your say below and, as a community we might be able to ask the UKMO to consider this as a proposal, you never know!

Quick interim storm summary graph with data from our Reigate weather station. Analysis and links to follow.  Below is a medley of images… analysis to be continued after festive season!  Meanwhile… hope you survived unscathed and Happy Christmas!

70mm total rainfall (manual rain gauge reading) now confirmed for Reigate during the storm 24hrs.

which was bigger, StJude or Caspar? (our name, not Dirk!) Caspar of course! Caspar goes on to Scotland today… 24 Dec

24-12-2013 05-07-51

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Dramatic VIIRS sat pic from 24 Dec midday: note boiling clouds along Atlantic front

http://www.getsurrey.co.uk/news/local-news/fallen-trees-floods-power-cuts-6444107

http://www.environment-agency.gov.uk/homeandleisure/floods/riverlevels/136484.aspx?stationId=7262

River Mole 3.45m above normal level: severe EA flood alert issued: the only one in the UK at the time.

Flanchford Bridge wall collapse

Severe weather warnings out: Gales and heavy rain across the South…

UKMO warnings page: http://www.metoffice.gov.uk/public/weather/warnings/#?tab=map&map=Warnings&zoom=5&lon=-3.50&lat=55.50&fcTime=1387756800

Flooding map: http://www.environment-agency.gov.uk/homeandleisure/floods/142151.aspx

Brief update on storm “Caspar” (our own name, middle one of Three Kings ): possibly worst in 130 years for UK (BBC source).

WIND: Reigate can expect possible gusts of 50-60mph, though the town itself is sheltered from southerly and SW winds by Priory Park hill and woodland so that we can shave off 20% from max wind gusts, usually.  The max quoted gust from UKMO is 66mph in small hours of Tues am as cold front goes through. StJude, the last big storm in October, had a max gust in town of 48mph during high winds that lasted only a few hours.  Caspar is set to be a longer duration, across a wider part of the country and is a bigger beast, the storm being centred off the NW of Scotland, rather than running through the Midlands like StJude.

Strongest ever jetstream? Chris Fawkes BBC weather

23-12-2013 05-20-02

Winds will spring up early tomorrow and by 11am could be gusting at 50mph.  They remain strong for the next 12 hours, peaking as the cold front arrives overnight/early morning Tuesday.

The emerging storm is now visible in the Atlantic as a familiar hook shape develops with cold and warm fronts.  The storm is set to explode over the next 24 hours in a process called cyclogenesis, caused by a very powerful 270mph jetstream “sucking” air off the ground as air diverges aloft.  This lowering of pressure by some 50mb in a few hours will cause air to “rush” into the “void” (converge) and this, in a simple way, is the cause of the maelstrom.  The spin of the Earth causes the winds to rotate into the centre of the Low pressure in a process called coriolis effect.

928mb

928mb

The surface pressure is expected to fall to somewhere around 926-928mb, one of the lowest pressures recorded near mainland UK (lowest land surface pressure 925.6mb, 1884, Perthshire). The BBC explains the development here:

http://www.bbc.co.uk/weather/features/25485532

RAIN: Reigate can expect almost continuous rain for 12 hours, starting early Monday morning, around 6am, through to around the same time on Tuesday. Heavy rain is caused as air rises, cools and condenses especially where warm air is forced to rise over cooler polar air.  This will happen especially at two moments as the storm passes…  first the warm front and then a cold front (overnight, probably Tuesday early am).  They have different characteristics.  Of most concern to us and the Environment Agency tomorrow, is that this storm will be causing more or less non-stop rain from 9am Monday through to about the same time Tuesday.  Rainfall totals 20-30mm can be expected during the course of the storm and, on saturated ground, this will cause flooding and plenty of surface water on roads.

22-12-2013 20-57-13

The “good thing” is that cold fronts pass pretty quickly and moderated wind conditions arrive soon thereafter, this means Tuesday is likely to see brightening ameliorating conditions arrive during the morning for any clear up. Flooding will be a problem by then and it’s likely that our River Mole will flood key back-routes and surface water on more major roads could be a problem.  Winds of more than 50mph can also causes trees to be knocked down and other damage is possible.

http://www.bbc.co.uk/news/uk-25484998

Finally, waves in the Atlantic are expected to reach near “phenomenal” heights with significant wave heights of 13m by Christmas Eve (which means waves double this height could occur once an hour).

After a quieter rest over Christmas things sadly don’t get a lot better… another storm is heading our way for Friday and the weekend.

23-12-2013 00-11-59

Three King storms?

December 21, 2013 — 1 Comment

Prepare for more stormy weather over the festive holiday… Reigate and Surrey is usually sheltered from the most extreme weather action but Mon/Tues could see significant weather even here, so watch forecasts if you are travelling. Check UKMO warnings for details. http://www.metoffice.gov.uk/public/weather/forecast/reigate-surrey#?tab=fiveDay&fcTime=1387584000

A powerful jetstream, blowing at up to 275mph across the Atlantic, is continuing to drag a train of storms to the UK through next week, though Christmas Day itself looks like a relatively quiet cool respite for us in Reigate.  Inland across the SE is usually sheltered from deep low pressure systems that track across the NW of Scotland: so far we have escaped the worst of these storms.  This week, there are 3 major storms that are due to arrive over the UK bringing gales and heavy rain to many parts.  Each storm brings progressively cool airmasses to the UK from an increasingly more polar origin.  So, let’s call these storms The Three Kings: Melchior, Caspar and Balthazar, the biggest of these is likely to be Caspar shown below in stark detail on the recent NOAA Atlantic forecast run. See if you can spot the UK under that mass of isobars and wind feathers (each feather = 10 knots).

hurricane force

hurricane force

First off, Melchior brings gold: heavy rain! Melchior has already arrived and is set to bring a windy and wet Saturday to the SE.  The notable feature of this storm is shown below as a fast moving cold front and remarkable clearance as polar maritime air sweeps in with showers.  Note how the wind direction is essentially from the Atlantic source, running over warm-ish sea surfaces to arrive here, hence our mild-ish temperatures. For the SE it is likely to be most windy around Saturday lunchtime, with gusts around 30-40mph and lots of rain adding up to 10-20mm during the course of the weekend. Local flooding possible.

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Reigate Priory Park 21 Dec around midday: wet!

Next up, Caspar: bearer of high winds and heavy rain! On Monday-Tuesday a LOW is set to rapidly intensify on the left-exit region of the jetstream.  A remarkably low central pressure of 928mb is forecast on current GFS and ECM runs, while the UKMO brings it down to 940mb (still v low). This storm exhibits all the hallmarks of rapid cyclogenesis and a “bomb” style depression: pressure falling very quickly (20mb in 3 hours) producing exceptionally high winds: knowing where these winds will occur is the tricky bit!  Caspar is set to track close to NW Scotland, with a jetstreak feature bringing unusually powerful winds across the SE on Monday night: so we may not escape the worst of this storm.  Model runs are currently bringing 70mph+ gusts to some parts of the SE.  So wind speeds could be higher than StJude for some locations: remember StJude was tightly located along the South Coast, Casper is a much bigger storm potentially covering the entire country in stormy weather at times.  These extreme wind forecasts may moderate (as the GFS usually does exaggerate things!) nearer the time but it is best to assume that Monday and Tuesday will be inclement weather for Reigate, the SE and the whole country: all models agree on this.  At 928mb, Caspar may not quite be a record breaker for low pressure but it is still a storm to watch, with a central pressure equivalent to a Cat4 hurricane!  (In 1884 a storm reputedly had a central pressure of 925.6mb, the lowest central pressure measured OVERLAND in UK; see below and strongest modern storm since 1993 Jan storm 914mb) Caspar unlikely to beat either of these records.  Caspar could bring snow to the north of the UK, especially to high ground.

Balthazar: the mysterious one as yet: after a quieter Christmas Day another storm is looking likely to emerge later next week that could drag down somewhat cooler air from the Poles.  This is way-off so details are sketchy but a gradual cooling with more direct influence of polar air might be a feature of late December. Throughout next week enjoy the festive period but if you are travelling it will be wise to check the UKMO forecast.

pics above from weatheronline, weatherweb.net and netweather

Reigate recorded a max gust of 36 mph last night as a vigorous ana-cold front produced a SQUALL LINE of extra heavy rain and gusty winds that rapidly crossed the country from west to east.  Needless to say, the squall line reduced in strength as it arrived in Reigate and the SE but we still experienced some gusty winds early on.  Nothing like as strong as the 80mph+ winds further west in Wales with associated hail.  An ana-front is where the warm sector air is forced to rise more vigorously than “usual”, in this case due to a strong jetstream encouraging uplift of air from the surface due to divergence and rapidly falling pressure aloft.  This literally “hoovers” air off the ground and produces lots of condensation, thick cumulonimbus clouds and plenty of heavy rain. Wind max during this storm for UK: S Uist 90mph; Plymouth 85mph. Other high winds include:

max gusts assoc with cold front

max gusts assoc with cold front

The culprit was the LOW pressure shown below in the UKMO analysis chart for 18 Dec.  A cause of this extra vigorous cold front was cold Polar air originating from Canada.  Spot the brisk W/NW winds following closely behind the front.

18-12-2013 20-24-36

The front produced 7.6mm of rain in a few hours. In total, since Saturday, Reigate has had 30mm of rain, so expect river levels to be high.  The River Mole has a flood warning in place from the Environment Agency. The Daily Express made a good call and got their prediction spot on a week ago with this article http://www.express.co.uk/news/nature/448402/Freak-storm-to-batter-Britain-100mph-winds-and-downpours-to-cause-chaos

What next?  There’s a calm period with a bright pleasant cool day coming up before more windy weather hits late Fri and heavy rain early this weekend.  A powerful jetstream is making for some stormy weather in the run up to Christmas.  There is the threat of a Channel storm around Christmas Day with possible heavy rain and gales for the south. Or the ECM if bringing in a very intense storm for the NW of the UK on Xmas Eve. Take your pick!

19-12-2013 07-05-43

19-12-2013 06-55-10

More technical details on ana fronts here http://www.zamg.ac.at/docu/Manual/SatManu/main.htm?/docu/Manual/SatManu/CMs/Cf/backgr.htm

and LEWP line echo wave pattern/squall lines http://www.estofex.org/guide/1_4_3.html

Reputedly, the first snow for over 100 years has fallen on the Sphinx but several photos on the web are actually of a model in Japan!  Anyhow, snow certainly fell across Cairo, N Egypt and even deeper snow has fallen over Israel, including Jerusalem and more widely across the Middle East and Turkey.  The upper air temperatures across Israel and Egypt are cold, of course, but only -2c or -3c at 850hPa which, in the UK is common and rarely produces snow for us… as a rule of thumb our 850hPa temps need to be at least -5c or lower to deliver much snow to the UK, especially the south away from hills.  So why did it snow on the Sphinx when the airmass was not really that cold?  BTW check this link for the sphinx in the snow pic http://urbanlegends.about.com/b/2013/12/14/sphinx-in-the-snow-photo.htm

13-12-2013 23-40-05

Cold, but not like the UK!

Well, it looks like the snow in Israel and Egypt is what meteorologists call “Lake or Sea Effect snow” and is quite common near the Great Lakes in the USA and across Japan but of course rather more unusual in the warmer Middle East. A deep LOW pressure (Winter Storm Alexa) swept across to the north of Israel dragging in bitterly cold strong N winds across Egypt and Israel and the Middle East as a whole.  The air originated from further north over continental Asia, where winter temperatures are extremely cold. The strong wind has crossed the Med (still fairly warm of course) in a wide arc across the warm sea surface which has allowed a good deal of moisture to evaporate, adding humidity and instability to the air mass.  A temperature difference of at least 13c is required to produce the greatest evaporation and moisture input required to produce plenty of “sea or lake effect snow”. SST across the Med off Israel is currently over 20c and this air mass had a temp of -3c at 850hPa and around freezing at sea level.

13-12-2013 23-47-19

On hitting land the strong wind experiences friction and literally “piles up” against the coast causing convergence and uplift.  The uplift, especially pushed up over the heights of Israel, causes cooling in the frigid polar air and, eventually, precipitation in the form of snow. Ingredients for sea effect snow were therefore all met in this case:

  • deep polar air mass
  • strong winds
  • temperature difference between the water and the air at 850hPa must be at least 13c for significant lake/sea effect snow
  • hills near the sea to encourage uplift

More pics here http://www.dailymail.co.uk/news/article-2523259/Historic-snow-fall-turns-Holy-Land-scenes-Christmas-cards.html

http://www.mirror.co.uk/news/world-news/cairo-snow-sphinx-picture-internet-2925810

Elsewhere in the region, winter storm Alexa has caused flooding in the Gaza strip http://www.bbc.co.uk/news/world-middle-east-25387020

The 2013 December 5-7 North Sea storm caused “the biggest UK storm surge for 60 years” (UK Environment Agency).  With associated gales across Scotland, coastal flooding in North Wales, Merseyside and the UK East coast, tidal river flooding in Hamburg, the closure of all major North Sea coastal surge barriers and disruptive snow further south in Europe, this storm system was arguably more powerful than StJude back in October.  Thankfully, this storm only killed 7 people across Northern Europe (http://www.bbc.co.uk/news/world-europe-25243460).

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09-12-2013 21-45-24

Essentially a storm surge is a higher-than-normal sea surface caused by low air pressure coinciding with high tides which, when thrown into shallow coastlines by winds, can produce exceptional coastal flooding.  A surge can also include associated lower-than-normal water levels with off-shore winds pushing water away from the coast at low tide.

15-12-2013 11-16-30

This post outlines the factors that makes the North Sea so vulnerable to storm surges and, further down, there is a summary of some impacts and a quick resume of the successful responses to this hazard event with some useful links.  Finally, before we get too smug and chill out entirely about future storm surge hazard…will development land lapped-up on exposed coasts, for example in the Thames Gateway, increase our future vulnerability in the face of sea level rise and climate change?  Is it sensible to build in these locations?

Animation shows storm surge rolling round the coast and into the North Sea.

http://www.bbc.co.uk/news/uk-25229885

Causes

The North Sea is particularly vulnerable to storm surges because of an unlucky combination of factors that come together to occasionally make the “perfect storm”.  Fortunately, not every North Sea storm produces a surge!  Remember that Tacloban in the Philippines was hit by an even bigger storm surge generated by Typhoon Haiyan due to similar forces and a funnel shaped bay.  Compare videos on this blog to see the difference between Tacloban and North Sea surges. So what comes together to produce the most significant storm surge hazards in the North Sea? There are at least 6 factors that combine to produce the biggest storm surges: here they are:

04-12-2013 23-01-02

1. Sea shape and low lying coastlines: The North Sea is particularly prone to dramatic storm surges because it is open to the North Atlantic and then tapers towards the south in a funnel shape. This funnel shape has the effect of allowing strong northerly winds to direct storm surges towards cities like London, Amsterdam and Hamburg and surrounding vulnerable low lying coastal areas including Norfolk, Lincolnshire, Essex, Kent and the Netherlands. Some of these areas are at or below sea level and require sea walls and dykes and barriers to protect them during storm surge events otherwise they will be flooded. The 1953 storm surge broke the rather primitive sea walls of the time and flooded large areas of Essex and even more of the Netherlands causing the worst European peace-time disaster since the war and killing 307 people in the UK and thousands in the Netherlands (see you tube documentaries below)

TechsmithWor6C52.png

2. Sea depth/ bathymetry: the North Sea gets shallower towards the bays and wetlands towards the south.  These shallows have the effect of increasing the height of tides and surges as they are forced up over submerged shelves into narrowing bays.  This is possibly why Boston, Lincs and Hamburg suffered some of the worst flooding because surges were forced up bays and rivers.

3. Intense low air pressure: A 1 millibar reduction in air pressure allows sea level to rise by 10mm.  This effect can be replicated by sucking water up through a straw. The storm that crossed to the north of Scotland on 5 December had a central pressure of 976mb that deepened to 968mb over the North Sea. This is a similar central pressure to the storm that caused the 1953 storm surge that killed 307 people in the UK and 1800 people in the Netherlands.

4. Storm track: the LOW pressure has to track east over north of Scotland, which will drive a surge of water into the North Sea that is then pushed south by vigorous onshore Northerly winds into the low lying east coast of UK.  Ideally, the storm should deepen on its’ track across the North Sea, thus allowing northerly winds to gain in strength driving the surge and associated wind waves south.

LOW track

LOW track

5. High tides: high spring tides are the final requirement for the biggest surges.  Tides migrate as a bulge of water around the coast and, for the worst impacts, any surge travelling south down the North Sea must match the dome of the highest tide to produce the highest water levels in any one place. Since high tides occur twice a day it is quite likely that high elements of the surge will match a high tide level somewhere down the east coast.

6. Wind driven waves: Finally, surge and tide heights can be increased yet further by strong on-shore winds producing locally high wind driven waves that can over-top sea walls.

Warnings and impacts

The impacts of the 2013 storm surge included flooding in coastal towns on the east coast of the UK with perhaps worst hit being Boston in Lincolnshire. Houses on some vulnerable stretches of coasts such as Hemsby were washed into the sea as waves eroded sand dunes.  There was also significant flooding in Rhyll, North Wales and along the Merseyside coast at New Brighton (note: not Brighton!) where a Morrisons supermarket was flooded. The worst impacts on major populations and cities were avoided by the raising of the Thames Barrier to defend London and the closure of the flood gates on the Delta Scheme in the Netherlands.

The storm was modeled over a week prior to impact.  Initially GFS and UKMO models were seeing a cold surge as the main factor bringing possible snow across the UK but from about 6-7 days out it became increasingly obvious that the exact track and orientation of the LOW meant that powerful northerly winds and a possible storm surge were the greatest risk.  The UK Met Office, with Environment Agency, then started preparations for warning those at risk from flooding.  Most news channels were airing significant coverage from 24 hours out.

http://www.hulldailymail.co.uk/Yorkshire-Wildlife-Trust-blamed-flock-sheep/story-20301801-detail/story.html

Responses

Significant flooding did occur along the East coast, notably in Scarborough in Yorks, Boston in Lincs and Hemsby in Norfolk. In Hemsby some vulnerable houses located on the sand dunes were washed into the sea. Bridges near the sea were shut for a time, like the Humber Bridge; and rail services in some eatern counties were disrupted for a time.  Power was cut to homes in Scotland due to high winds.  Hundreds of residents were evacuated prior to the floods in various locations but some claimed to have little warning.

The worst impacts were successfully controlled by the massively impressive engineering schemes built since the devastating 1953 floods.London has nearly 200 miles of flood walls and 8 barriers holding back the tidal Thames. The Thames Barrier was opened by the Queen in 1982.

The Eastern Scheldt storm barrier was closed for the first time since the 1970’s.  The Netherlands barriers are built to withstand a 1 in 10,000 year storm surge event so it is perhaps unsurprising that they easily saw off this event.  It is also noteworthy that the Dutch have great faith in their storm surge protection barriers.

These measures, along with warnings and on the ground assistance for places that were flooded, proved extremely effective.

http://www.bbc.co.uk/news/uk-25272050

http://www.bbc.co.uk/news/world-europe-25242991

Further useful links on 1953 and 2013 storm surges:

1953 storm surge: original newsreel and timewatch documentary

http://www.metoffice.gov.uk/news/in-depth/1953-east-coast-flood

The sting in the tale?

London is sinking into clay and, along with the rest of the SE, it is tilting into the sea partly due to an epeirogenic / isostatic adjustment taking place since the glaciation released the north of the country from the burden of millions of tonnes of glacial ice causing positive isostatic rebound in the north and related subsidence in the south.

Flood plains and reclaimed land exposed to storm surges are still being lapped up by hungry developers as places ripe for building, like the Thames Gateway in London.  But is it sensible to concentrate massive new urban development in low lying areas vulnerable to coastal flooding when we have sea level rise and climate change?

http://www.deeestuary.co.uk/news1.htm

November 2013 won’t be remembered for much weather drama in the UK, but it will certainly be remembered for brutal and destructive weather elsewhere in the world.  In particular, Typhoon Haiyan in the Philippines, which we recorded as it happened and during the aftermath here and here. It will also be remembered for some unusually powerful late-season tornadoes in Illinois, USA (see below).  For the UK, we had some autumn gales during early November mainly impacting coastal regions but, apart from these, it was a calm, relatively mild and dry month with only a few frosts in Reigate.  High pressure that did emerge later in the month yielded some anticyclonic gloom for Reigate as humid air spilled in from a cool North Sea and brought low stratocumulus to create days of “dreich”: anticyclonic gloom. Here are some pics of Reigate in the good bits when the sun shone. More data below.

November started unsettled with THREE “storms” (Lows) in three days which we named Mary, Mungo and Midge.  They were all associated with a zonal (westerly) jetstream and each low deepened, to a greater or lesser extent on their track across the UK.  Mary hardly ranked as a storm but Mungo yielded Force 10 gales in every sea around the UK.   Later in the month things cooled off when the jetstream became more loopy and brought air down from a more polar direction.  

November stats for Reigate, Surrey include:

Average temp in Reigate for November was 9.5c, which was exactly the same as Nov 2012.

Tmax 15.1c 

Tmin -2.4c

Total rainfall 51.2mm (78.8mm Nov 2012)

Thereafter. Typhoon Haiyan in the Philippines dominated the weather headlines and was recorded in detail on our blog.  There was also significant extreme weather in the USA and Canada, including tornadoes associated with severe early winter storm activity further north in Illinois, USA: a particularly powerful autumn tornado claimed lives in a town called Washington, Illinois.  The track of the Washington tornado is shown graphically in the picture below.  

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Below are two powerful videos on recent global weather extremes. First is an upsetting video of the Washington tornado hitting a house filmed as the occupants shelter for their lives, it unsurprisingly contains some bad language but is included here to illustrate the extreme impact that weather can have in the blink of an eye… and how some places a few metres away can be unscathed: this is not uncommon in many different weather hazards: surges, hurricanes, storms… discrete extremes (like sting jets) dependent on orientation, location and simply random meso-scale atmospheric chaos that cannot be predicted, can cause the most damage while other places remain unscathed relatively nearby. Tacloban in the Philippines was especially hard hit by the Typhoon Haiyan storm surge (eyewitness video below) because the bay shape acted as a funnel directing the most powerful storm surge carried by the hurricane eye.  Another example of how large scale weather phenomenon impacts are highly variable according to the unique exposure of certain locations (unlucky coastline) and the vulnerability of the population to the event.  Like other planetary systems, we should take care to understand the weather because it won’t necessarily take care of us.