Summer ready to arrive?

After much debate over whether we will have to endure another washout summer, and it did actually look like a bit of a damp squib until recently, it is now fairly certain that from the end of this week at least we shall experience some glorious summer weather.  All charts now seem to be in agreement that from around Friday temperatures will rise and blue skies and sunshine are on they way, and could actually stick around for a while.  Some say we could have the hottest July temperatures since 2006, which I have to say would be very welcome after last years washout.  The chart below gives a brilliant indication of what is to come:

A brilliant sight to see :)

 

That chart is for the 10th July, so you can see how well the UK is looking for this time.  Let’s just hope it continues until autumn, and is followed by a nice snowy winter!

The reason the weather is set to improve is again down to the position of the jet stream, which is set to head well north of the UK, allowing high pressure to build from the continent.  This picture is taken from Matt Hugo, and shows the position of the jet stream and how it allows the high pressure to reach us:

In summer, high pressure from the continent brings warmth and summery weather, whereas in winter it brings cold and snow.  Weather systems from the Atlantic (low pressure), regardless of season bring with them  wind and rain, and while we would expect these kind of weather systems to dominate through autumn or springtime, the position of the jet stream over the past few years has meant we have had Atlantic weather a lot more than usual, and this caused a lot of the flooding throughout last year.  In short, if everyone blows north we may be able to keep the jet stream well clear of us, and the summery weather will remain!

Jet Stream!!!

Soooo, I’m guessing most people have heard of the jet stream, but aren’t entirely sure of what it does.  As mentioned previously on this site the jet stream that we mention is the one that sits over the Atlantic and beyond.  There are actually 4 jet streams around the globe, 2 in the northern hemisphere, and 2 in the south.  They flow east to west, and as has been shown recently they can stray from their more “usual” path.  The jet stream affecting us would normally at this time of year be sitting above the UK, dragging the low pressure systems above our shores and allowing high pressure (warmer and sunnier in summer) to build over us.  As the jet stream has been sat to the south of the UK the low pressure systems, bringing with them rain, and basically doom and gloom, have been dragged right across the UK, with many of these slow-moving systems dumping massive, massive amounts of rainfall, hence this ridiculously wet weather we have been having.  The jet stream moving north means England will experience much better weather as of next week, with temperatures climbing and rainfall dropping significantly.  The North West of Scotland however can expect cooler temperatures and wet weather as the jet will bring low pressure over the top of the country.

It isn’t just the UK that has been unduly affected so far this year by the jet stream, North America are currently experiencing a drought, and have had record-breaking temperatures over the past few weeks, as the position of the jet stream has allowed high pressure to build over many states, bringing severe storms with it and extremely high temperatures. Russia has experienced devastating effects from flooding after large parts inundated with rain, with many deaths reported and devastating loss of infrastructure.

Back to us, and southern England will bask in better weather to begin with as the jet shifts, fingers crossed we won’t be too far behind and summer will finally kick in just in time for the summer holidays.  Watch this space!!

Info taken from Paul Hudson @bbc

More wet weather on the way – updated 19.17 (6/7/12)

As predicted the heaviest rain has headed further south and the midlands have recieved the brunt of the rain today, with many, many places reporting flooding, including Yorkshire and Durham, while the South West is expecting upto 100mm of rain tonight.  There is still heavy rain forecast in the region tonight and looking at the radar it looks like from around 8′o clock this evening could bring quite a bit of rain, and also into tomorrow but it shouldn’t cause as much disruption as originally expected.

Recent model runs have shown a slight shift in track, and the storm has shown to move slightly further south than first anticipated.  Therefore although Friday is still forecast to be very wet in the region, and it is now Saturday that looks to carry the most rainfall for us.  An Amber warning is in force for South Tyneside on Saturday, with flooding a possibility.  Tomorrow (Friday) is still forecast to be wet with some heavy downpours, and as the cold air meets warm there is a good chance of thunderstorms.  Advisories from my original post on this still stand, but attention is shifted slightly more towards Saturday now. 

With last Thursday’s events still very fresh in everybody’s minds I am sure the last thing people want to hear is that there is a lot of rain on the way, but unfortunately that is the case.  An area of low pressure sitting over the continent currently has our names right on it, and is expected to hit the UK, more specifically North East England, on Friday.  Accordingly the Met Office have weather warnings out relating to this weather system, and the North East currently has an Amber warning for some regions, and a Yellow warning for other areas.  These warnings are in response to the massive amounts of rainfall forecast.  Thursday is forecast to be wet/thundery with the potential for some locally heavy outbursts, especially in the afternoon, but it is Friday and Saturday that everyone has their eyes on.  Following recent heavy rainfall many areas are already saturated, and with the possibility for 60-100mm of rain on Friday that could cause problems with flooding, not only surface flooding, like we saw on the 28th June, but areas within the Amber warning area could also see some rivers overflow  Driving conditions could potentially be hazardous, and disruption to travel is likely, especially given that some services are still not running a normal route due to the recent flooding problems.    Looking ahead to Saturday, the area is still under an Amber alert from the Met Office, with further heavy and persistent rain forecast.  Again there is a likelihood of flooding from both surface water and rivers, and disruption to travel is likely.  With any weather event there is always uncertainty over where exactly will get the most rain, currently there is a high chance that the North East is in line for a very disruptive few days, and people should be aware that large amounts of rainfall are forecast and take appropriate action.  This page will be updated as more information becomes available, tomorrow’s 24 hour forecast will be more reliable than what is currently available and will shed more light on the exact track of this system.

For information on flooding and/or flood alerts please see the environment agency:

http://www.environment-agency.gov.uk/homeandleisure/floods/default.aspx

What is causing this unseasonal wet weather?

Many people are left scratching their heads at the rather extreme weather we have been experiencing of late, and as is often the case this is down to the jet stream.

The jet stream is a much talked about thing, but not many people actually know what it is, or what it does.  A jet stream forms high in the upper troposphere between two air masses of very different temperature. The greater the temperature difference between the air masses, the faster the wind blows in the jet stream.

This river of air has wind speeds which often exceed 100 mph, and sometimes peak over 200 mph. Jet streams usually form in the winter, when there is a greater contrast in temperature between cold continental air masses and warm oceanic air masses.  During the winter months, Arctic and tropical air masses create a stronger surface temperature contrast resulting in a strong jet stream. However, during the summer months, when the surface temperature variation is less dramatic, the winds of the jet are weaker. In summer, if the jet stream is to the north of us, we would generally have a warmer, drier summer, whereas if the jet stream is to the south of us, summers are usually wetter and cooler.In winter, a more southerly jet stream leaves us open to cold conditions to the north and east. Normally the jet stream in winter ensures generally mild, and at times wet and windy weather across our shores.

The jet stream is powered by temperature contrasts between the cold polar regions of the planet and the hot tropics. The heat wave that America is experiencing has pushed the jet stream further north than you would expect, and this has caused a large area of high pressure to form over Greenland, which has then pushed a part of the jet stream over the UK.

As it should be

For for the last three months, we have been under an accelerating part of the jet stream which has caused this horrendous wet weather we have had.  The jet stream is currently sitting to the south of the UK, which is drawing in these low pressure systems, which in turn are merging with the hot humid air from the Continent, and that is what is causing this torrential rain and thunderstorms we have been experiencing.

Current jet stream - this pic is from 2007 but we have a similar set up at present

The bad news is there is no change in forecast for at least 2 weeks, which means July has as much chance to be record breaking as June and April have been rainwise

Pictures courtesy of the BBC.

What a difference an hour makes…..

Elsewhere on this site I explain how varied our weather here in the UK can be.  A fantastic example of this is these 2 photos I took this morning, the first was taken at approximately 8.15, while the second was taken just over an hour later.  What a huge difference!

Summer – come out, come out wherever you are…..

Well yesterday was the first day of July, and the run of miserable autumnal weather continues.  Below average temperatures, higher than average rainfall and unseasonable winds are making summer so far feel more like October.  This entire year has been topsy-turvy weatherwise.  In fact you could say that about the past few years, the seasons aren’t particularly defined anymore.  Month on month records have been broken, most rainfall, highest temperatures…..As a nation we appear to have more of an interest in the weather than ever, and I think this must have a lot to do in which way the weather is portrayed in the media.  Week after week there seems to be some story about the weather.   “Arctic weather heads for Britain” erm yes its winter, it typically does get cold….”Snowmageddon” was a particular headline I liked after we had a few flurries.  Whether it be stories on the heat, the cold, the rain, wind etc etc, it always generates an interest when the media put their own brand of spin on it, and in turn this seems to whip us up into a frenzy.  So many so-called “experts” give their take on what the weather is going to do, and when it doesn’t turn out how they have said most people seem to say “hmm, the Met Office got it wrong” when in fact they were right, or had nothing to do with the forecast!

Anyway, back to the original point of our missing summer, I’m afraid there is no immediate signs of any let up in this miserable spell we are currently experiencing.  Several of the models are in agreement that for the next week at least the weather will be pretty samey, wet and a bit pants!  The weather will always do what it wants, especially here in Britain.  People think it always rains here and we have miserable weather, they aren’t far wrong at the moment!  The blame for this bad spell lies firmly at the feet of the jet stream, where it is currently positioned is doing NOTHING for sunshine, it is currently positioned well to the south of the Uk, meaning an area of low pressure will become almost stationary over us, bringing heavy rain and thunder to our shores.  Perhaps if we all blow hard enough we can push the jet stream into a better position??  Maybe not, but in the meantime we can all hope that it does shift position so that summer can begin.

Supercell hits South Tyneside!

June has continued the trend of record breaking weather, and again it is for rainfall.  While it has been extremely wet for most of the month, the 28th June will be one of those events that people remember for years.  At around 8am 2 storms formed in Wales, one headed north while the other crossed the Midlands.  The latter hit first, and spawned tornados, hail bigger than golf balls and torrential rain.  At around 4pm the other storm hit North east England.  The skies rolled in completely black, it was like something from Independence day!

After a bit of rain, and some thunder all went quiet, and many thought we had escaped the worst, myself included.  Then reports of immense rainfall came through from Newcastle and Gateshead, and the skies above South Tyneside opened again, accompanied by violent thunder and lightning.  In the hour upto 18.18 33.9mm of rain fell, as recorded by my weather station.  On average, June sees something along the lines of 40 mm of rain, so we had almost that amount in an hour, and yesterdays total rainfall was 46.2mm.  It has been said afterwards that we were hit with a supercell thunderstorm, which weather enthusiasts will be very excited about, as they are extremely rare in Britain, and make up less than 1% of our storms.

What sets this kind of storm apart from the others is the rotation in the cloud. A supercell is usually found in the warm part of a low pressure system, and can be one of the most dangerous types of storm. It is basically a huge rotating thunderstorm, the area of rotation withhin the storm is called a mesocyclone that can spawn a tornado. The storm itself can rotate when winds at different levels of the atmosphere come from different directions. If the winds are lined up just right, with just enough strength, the storm turns like a top. Air circulations within the storm combined with a strong updraft contribute to tornado formation.  There are reports that there were 3 supercell storms yesterday!!!  There was widespread flooding across the region, and as it hit at rush hour there was pandemonium on the roads.  The Tyne and Wear metro stopped all service due to water on the tracks and landslides, Newcastle’s Central Station flooded, as did the Quayside, aswell as many other areas, including the Metro Centre and Ikea in Gateshead, where part of the roof collapsed.  Heworth roundabout, one of the busiest roads during the commute was under over a foot of water.  More locally, Lindisfarne roundabout, Low Simonside and Tyne Dock were hit hard, as was Hedworth and Fellgate with many homes suffering with flood damage.  Some homes were struck by lighning, including 2 that subsequently caught fire.

So thats a quick report on yesterdays events, I will get back on and update more indepth and add pictured throughout the day

Record Breaking March/April 2012

Well we have had some pretty awesome weather over the past few months, March could easily have been mistaken for July, and April, well, I think some parts of the country were beginning to consider building an ark!  March was one of the driest and sunniest on record, and Aboyne, in Aberdeenshire recorded a temperature of  23.6C on Tuesday 27 March, beating the record of 23.2C set at Cromdale, near Grantown on Spey, the previous afternoon.  The month began fine and dry, and by the 20th most of the UK basked in glorious sunshine.  This all came to an abrupt end as cooler and cloudier conditions arrived by the end of the month.  A hosepipe ban in several counties in the south of England was declared and came into force on the 5th April. This is a result of the  2 very dry years we have had lately.  Typically though, no sooner was the drought declared than the heavens opened, and by the end of April many of the drought ridden areas were under water as several rivers burst their banks.  Some people have commented that this is the wettest drought ever, but 1 month of record breaking rainfall is not enough to lift the affected areas out of drought, although it has been a massive help.

Posted in UK

Extreme Weather – UK

While the United Kingdom is not particularly noted for extreme weather, it does occur, and conditions have been known to reach extreme levels on occasions.

In the winter of 1982, for a few days parts of central and southern England experienced temperatures lower than central europe and Moscow.  In contrast, the summers of 1975 and 1976 experienced temperatures as high as 35 °C (95 °F). It was so dry the country suffered drought and water shortages.  Extended periods of extreme weather, such as the drought of 1975–1976 and the very cold winters of 1946–1947, 1962–1963, 1978–79, 1981–1982, 2009–2010 and 2010–2011, are often caused by blocking anti-cyclones, which can persist for several days or even weeks. In winter they can bring long periods of cold dry weather and in summer long periods of hot dry weather.

There have also been occurrences of severe flash floods caused by intense rainfall, the most severe was the Lynmouth disaster of 1952 in which 34 people died and 38 houses and buildings were completely destroyed. In the summer of 2004, a severe flash flood devastated the town of Boscastle in cornwall.  Hoewever, the worst floods in the United Kingdom in modern times occurred in the North Sea flood of 1953. A powerful storm from the Atlantic moved around Scotland and down the east coast of England. As it moved south it produced a storm surge which was magnified as the North Sea became narrower further south. By the time the storm affected south-east England and the Netherlands, the surge had reached the height of 3.6 metres (12 ft). Over 300 people were killed by the floods in eastern England.

Thunderstorms are most common in southern and eastern England, and least common in the north and west.  As a result of this, inland areas in the south and east tend to have their wettest months in the summer while western, northern and eastern coasts are most likely to have their driest month in the spring and their wettest in late autumn. In London, thunderstorms occur on average 14–19 days a year, while in most of Northern Ireland and the west of Scotland thunderstorms occur on around 3 days a year.  Occasionally, thunderstorms can be severe and produce large hailstones as seen in ottery St Mary, Devon, in October 2008, where drifts reached 1.8 metres (5 ft 11 in).

Strong winds occur mainly in the autumn and winter months, associated with low pressure systems. The Great Storm of 1987 (23 fatalities) and the Burns’ Day Storm of 1990 (97 fatalities) are particularly severe examples. The United Kingdom has around 33 tornados per year, which is the second highest amount per land area in the world.

The most rain recorded to fall on a single day was 279 mm at Martinstown, Dorset on 18 July 1955, but also 243 mm fell at Bruton, Somerset on 28 June 1917.  Heavy rain also fell between 20 and 25 June in 2007; some areas experienced a months rainfall in one day. Four people died in the flooding and over £1.5 billion of damage to businesses and properties was caused.

Tropical Cyclones themselves do not affect the UK due to the seas being too cold, they need temperatures above 26.5 °C (79.7 °F) to remain active. The waters near the UK, the Atlantic Ocean, only have temperatures of 10 to 15 °C (50 to 59 °F), so any Tropical Cyclone that does come anywhere near the UK has said to have undergone a process called extratropical transition. This now means it is an extratropical cyclone, which the UK frequently experiences. The Great Storm of 1987 was a very deep depression which formed in the Bay of Biscay, which also contained the remnants of Hurricance Floyd.  Hurricane Lili of 1996 and Hurricane Gordon of 2006 both crossed the UK as strong extratropical cyclones with tropical storm-force winds, causing transport closures, power-cuts and flooding in large parts of the UK.

Facts and info from Wikipedia

 

British Cimate

British weather is divided into 4 seasons – Spring, Summer, Autumn and Winter.

SPRING

Climatologically The Met Office classes the first day of spring as the 1st day of March, but because of the variation in the days on which the equinox and solstice falls, it is more convenient to use whole months. The Met Office therefore classifies the spring months as being March, April and May.  Traditionally the first day of spring is Astronomically derived, and is March 20th.  At the time of the equinox the Sun will cross directly over the Earth’s equator. This moment is known as the vernal equinox in the Northern Hemisphere. For the Southern Hemisphere, this is the moment of the autumnal equinox.  Traditionally spring is thought to be about new beginnings, the weather gets warmer, the days get longer…..In spring, the axis of the Earth is increasing its tilt toward the Sun and the length of daylight rapidly increases for the relevant hemisphere. The hemisphere begins to warm significantly causing new plant growth to “spring forth,” giving the season its name.  Spring is generally a calm, cool and dry season, particularly because the Atlantic has lost much of its heat throughout the autumn and winter. However, as the sun rises higher in the sky and the days get longer, temperatures can rise relatively high, but often tend to drop off again at night due to the cool oceans and the warm weather dependent solely on the sun.  Thunderstorms and heavy showers can develop occasionally particularly towards the end of the season.

There is a fair chance of snow earlier in the season when temperatures are colder. Some of the country’s heaviest snowfalls of recent years have happened in the first half of March and snow showers can occur infrequently until mid-April.

Mean temperatures in Spring are markedly influenced by latitude. Most of Scotland and the mountains of Wales and northern England are the coolest areas of the UK, with average temperatures ranging from -0.6 to 5.8 °C (30.9 to 42.4 °F).  The southern half of England experiences the warmest spring temperatures of between 8.8 and 10.3 °C (47.8 and 50.5 °F)

 

SUMMER

Summer lasts from June to September and is the warmest season.  Rainfall totals can have a wide local variation due to localised thunderstorms. These thunderstorms mainly occur in southern, eastern, and central England and are less frequent and severe in the north and west. North Atlantic depressions are not as severe in summer but increase both in severity and frequency towards the end of the season. Summer can see high pressure systems from the Azores High.

Climatic differences at this time of year are more influenced by latitude and temperatures are highest in southern and central areas and lowest in the north. Generally, summer temperatures seldom go above 30 °C (86 °F), which happens more frequently in London and the South East than other parts of the country. Scotland and northern England have the coolest summers, while Wales and the south-west of England have warmer summers, and the south and south-east of England have the warmest summers.

Autumn

Autumn in the United Kingdom lasts from October to November. The season is notorious for being unsettled—as cool polar air moves southwards following the sun, it meets the warm air of the tropics and produces an area of great disturbance along which the country lies. This combined with the warm ocean due to heating throughout the spring and summer, produces the unsettled weather of autumn. In addition, when the air is particularly cold temperatures on land may be colder than the ocean, resulting in significant amounts of condensation and clouds which bring rain to the country.

Atlantic depressions during this time can become intense and winds of hurricane force (greater than 74 mph) can be recorded. Western areas, being closest to the Atlantic, experience these severe conditions to a significantly greater extent than eastern areas. As such, autumn, particularly the latter part, is often the stormiest time of the year. One particularly intense depression was the Great Storm of 1987.

However, the United Kingdom sometimes experiences an ‘Indian Summer’, where temperatures particularly by night can be very mild and rarely fall below 10 °C (50 °F). Such events are aided by the surrounding Atlantic Ocean and seas being at their warmest, keeping the country in warm air, despite the relatively weak sun.

Winter

Winter in the UK lasts from December to February. The season is generally cool, wet and windy.  Precipitation is plentiful throughout the season, though snow is relatively infrequent despite the country’s high latitude: The only areas with significant snowfall are the Scottish Highlands and the Pennines.  Towards the later part of the season the weather usually stabilises with less wind, less precipitation and lower temperatures. This change is particularly pronounced near the coasts mainly because the Atlantic Ocean is often at its coldest during this time after being cooled throughout the autumn and the winter. The early part of winter however is often unsettled and stormy; often the wettest and windiest time of the year.  Mean winter temperatures in the UK are most influenced by proximity to the sea. The coldest areas are the mountains of Wales and northern England, and inland areas of Scotland.  In the 1990s and 2000s, most of the winters were milder and usually wetter than average with daytime temperatures going below freezing a rare occurrence. In fact, the winter of 1995/1996 was the only one which was defined as below average in terms of the UK as a whole. The winters of 2008/09, 2009/10 and 2010/11 have however seen a different pattern with these three winters being defined as below or well below average with large snowfall amounts widespread and very low temperatures; this was the first time three consecutive cold winters in the UK have occurred since the 1960s.

The climate of the United Kingdom has not always been the way it is today. During some periods it was much warmer and in others it was much colder. The last glacial period was a period of extreme cold weather that lasted for tens of thousands of years and ended about 10,000 years ago. During this period the temperature was so low that much of the surrounding ocean froze and a great ice sheet extended over all of the United Kingdom except the south of England.  We think we are cold when temperatures reach 0, imagine being around back then!

The cold period from the 16th to the mid-19th centuries is known as the Little Ice Age.

Severe Weather – The Tornado

The United Kingdom has around 33 tornados per year, which is the second highest amount per land area in the world.

Although still made up of wind, a tornado is a completely different kettle of fish from a hurricane.  A tornado forms over land, it is a violent rotating column of air extending from a thunderstorm to the ground, and in some cases can destroy anything in its path.  Tornados can have windspeeds reaching 300mph, and can often form with very little warning.  Most tornadoes form from thunderstorms. You need warm, moist air  and cool, dry air. When these two air masses meet, they create instability in the atmosphere. A change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere. Rising air within the updraft tilts the rotating air from horizontal to vertical. An area of rotation, 2-6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation.  A funnel cloud is a rotating cone-shaped column of air extending downward from the base of a thunderstorm, but not touching the ground. When it reaches the ground it is called a tornado.

Twisters, as they are often known, are often accompanied by hail. Giant, persistent thunderstorms called supercells spawn the most destructive tornadoes.

These violent storms occur around the world, but the United States is a major hotspot with about a thousand tornadoes every year. “Tornado Alley,” a region that includes eastern South Dakota, Nebraska, Kansas, Oklahoma, northern Texas, and eastern Colorado, is home to the most powerful and destructive of these storms. U.S. tornadoes cause 80 deaths and more than 1,500 injuries per year.  The meteorological factors that drive tornadoes make them more likely at some times than at others. They occur more often in late afternoon, when thunderstorms are common, and are more prevalent in spring and summer. However, tornadoes can and do form at any time of the day and year.

Tornadoes’ distinctive funnel clouds are actually transparent. They become visible when water droplets pulled from a storm’s moist air condense or when dust and debris are taken up. Funnels typically grow about 660 feet (200 meters) wide.

Tornadoes move at speeds of about 10 to 20 miles (16 to 32 kilometers) per hour, although they’ve been clocked in bursts up to 70 miles (113 kilometers) per hour. Most don’t get very far though. They rarely travel more than about six miles (ten kilometers) in their short lifetimes.  Like hurricanes, tornados are classed by windspeed, as hurricanes have the saffir simpson scale, tornados haveThe Fujita Tornado Scale:

Category FO – Gale Tornado Category 40 – 72 mph
Light damage: some damage to chimneys, breaks branches off trees, pushes over shallow-rooted trees, and damages sign boards.

Category F1 –  Moderate Tornado Category 73 – 112 mph
Moderate damage: The lower limit Category 73 mph– is the beginning of hurricane wind speed, peels surfaces of roofs, mobile homes pushed off foundations or overturned, and moving autos pushed off roads.

Category F2 –  Significant Tornado Category 112 – 157 mph
Considerable damage: Roofs torn off the frames of houses, mobile homes demolished, boxcars pushed over, large trees snapped or uprooted, and heavy cars lifted off ground and thrown

Category F3 –  Severe Tornado Category 158 – 206 mph
Severe damage: Roofs and some walls torn off well-constructed houses, trains overturned, most trees in forest uprooted, and heavy cars lifted off ground and thrown.

Category F4 – Devastating Tornado Category 207 – 260 mph
Devastating damage: Well-constructed houses leveled, structures blown off weak foundations, and cars and other large objects thrown about.

Category F5 – Incredible Tornado Category 261 – 318 mph
Incredible damage: Strong frame houses are lifted off foundations and carried a considerable distance and disintegrated, automobile sized missiles fly through the air in excess of 100 meters, and trees debarked.

Category F6+ –  Inconceivable Tornado Category 319 – 379 mph
The maximum wind speed of tornadoes is not expected to reach the F6 wind speeds.

Tornadoes can be classified into one of three types:

Weak Tornadoes Category F0/F1
These tornadoes account for 74% of all tornadoes. They cause less than 5% of tornado deaths. Their lifetime is usually 1 – 10+ minutes with wind speeds less than 113 mph.

Strong Tornadoes Category F2/F3
These tornadoes account for 25% of all tornadoes. They cause nearly 30% of all tornado deaths and may last 20 minutes or longer. Their wind speeds are clocked between 113 and 206 mph.

Violent Tornadoes Category F4/F5
These rare tornadoes account for less than 2% of all tornadoes. However, they cause 67% of all tornado deaths nationwide. They may last for one hour or more with wind speeds greater than 206 mph.