Atlantic Hurricane Season

We take a look back at the North Atlantic Hurricane season (it is classed as being 1st June-30th November)


Or rather, MAY! This years season was kicked off early as Tropical Storm Alberto (min pressure of 995mb)formed on the 19th May off the coast of South Carolina, followed by Tropical Storm Beryl min pressure 992mb).  Beryl began life as a Sub Tropical Storm over the north-western Caribbean sea on May 26th, before reaching peak winds of 70mph the following day when she became a full Tropical Storm.  Beryl made landfall in Jacksonville, Florida where she weakened into a Tropical Depression as she headed towards Georgia and South Carolina.

Hurricane Chris (min pressure 987mb) was next, beginning life as a Tropical Storm on the 19th June, and becoming a Hurricane on the 21st.  As the storm hit colder waters 6 hours after becoming a hurricane it weakened back to a Tropical Storm and was absorbed by a larger non-tropical storm on the 22nd June.

Following quickly on Chris’s heels came Debby (min pressure 990mb), this Tropical Storm formed on the 23rd June in the Gulf of Mexico, and made landfall in Steinhatchee, Florida, on the evening of the 26th June.  The remnants of Debby dissipated on June 30th.


Hurricane Ernesto (min pressure 980mb) started life as a tropical wave off the west coast of Africa on the 26th of July, although did not gain Tropical status during this month.


Tropical Depression 5 was officially formed on the 1st August (this was the storm mentioned in July) and became Tropical Storm Ernesto the following day.  The storm moved over the Carribean, bringing with it high winds and heavy rain.  By the 7th August the storm was officially declared a Hurricane, and made landfall on the 8th August as a Catagory 1 Hurricane with winds of 85mph.   After weakening into a tropical storm and moving into the Bay Of Campeche, the storm made landfall again near Coatzacoalcos, Mexico where it dumped heavy rain before moving into the Eastern Pacific where it contributed to the formation of Tropical Storm Hector.

Tropical Storm Florence  (min pressure 1000mb) began life as a vigourous tropical wave off the coast of Africa on the 1st August, and by the 4th had became Tropical Depression 6.  By the next day it had strengthened to a Tropical Storm, although it soon weakened and the last advisory was issued that day by the NHC.

Tropical Storm Helene (min pressure 1004mb) began to form as a tropical wave near Cape Verde on August 6, and by the 9th had became organised enough to be named Tropical Depression 7.  The storm degenerated and on August 14th the storm moved inland.  By the 17th August the storm re-emerged into the Bay of Campeche and after rapid intensification it was immedietly named Tropical Storm Helen.  Helene moved northwest and made landfall near Tampico, Mexico on the following day.  Later that day, the storm was downgraded to a tropical depression, before dissipating early on August 19. The remnant tropical wave produced heavy rainfall in Trinidad and Tobago, and caused flooding and landslides on the Islands.

Another one that developed off the coast of Africa was Hurricane Gordan (min pressure 965mb), the low developed on the 10th August, and on the 15th August Tropical Depression 8 was born, and within 12 hours it intesified to become Tropical Storm Gordon.  After passing over the Azores Gordon developed more convection around its centre and was classed as a Hurricane on the 18th August.  Although passing directly over parts of the Azores damage was limited to power cuts and torrential rain caused some flooding.

The next storm yet again was born near the coast of Africa, a tropical wave developed over the 15/16th and headed west where it became Tropical Depression 9 on the 21st of the month.  Despite being quite disorganised, this storm was also named within 12 hours, just as Gordon was, and Tropical Storm Isaac (min pressure 968mb) was formed.  An eye formed on the 25th, and winds reached 70mph as the storm hit Haiti, causing flooding and damage to many places.  After moving back over water Isaac next made landfall in Cuba, although major damage was not expected.  Yet again Isaac was over open water, this time strenghtening into a Hurricane on the 28th August, and all eyes were suddenly focused on the Gulf of Mexico, moreso along the coasts of Louisiana and Mississippi as projected tracks had the storm making landfall in either state.  As it happened Isaac made landfall in Louisiana, near Port Fourchon on the 29th August, 7 years to the day since the much larger and more destructive Katrina hit the state.  Much was made of the dates, but thankfully although Isaac caused an awful lot of damage with flooding, it came nowhere near to what Katrina had done years before.

The next storm to form was Tropical Depression 10, this was a tropical wave that started producing disorganised showers between Africa and the Cape Verdi Islands on the 20th August.  2 days later it was classed as organised enough to be a Tropical Depression, and 10 was born.  On the 23rd August TD10 became Tropical Storm Joyce (min pressure 1006mb), although significant deelopment was neer a chance as the storm had such a strong wind shear to the south of the centre of circulation, and it soon dropped back to a depression, before the last advisory by the NHC was given out on the 24th August.

Hurricane Kirk was named as Tropical Depression 11 on the 28th August, and conditions at first appeared unfavourable for further development of this storm. However, the next advisory from the NHC upgraded the system to Tropical Storm Kirk, and after a further 2 days became a hurricane.  Hurricane Kirk (min pressure 970mb) reached catagory 2 status with winds of 105mph before hitting cooler waters and taking on Post Tropical status on the 2nd September.

The last storm to form during August was Hurricane Leslie (min pressure 968mb) which started as a tropical wave that moved off the west coast of Africa into the Atlantic on the 27th August, taking on a westerly track.  Deep convection began around the centre on the 30th and Tropical Depression 12 was born.  Due to the warm sea surface temperatures it very quickly intensified, and became Tropical Stomr Leslie the same day.  Despite being somewhat disorganised an eye like feature was noted on September 1st, and Leslie was upgraded to a Hurricane on September 5th.  After a journey up the east coast it made landfall in Canada on the 11th September, with 70mph winds where it became extra-tropical.


Hurricane Michael (min pressure 964mb) formed northwest of the Cape Verde Islands, and on the 3rd September it was deemed organised enough to become a Tropical Depression, before becoming a Tropical Storm the next day.  It didn’t really intensify much until the %th September when it was declared a Hurricane, and within 2 hours it reached category 2.  4 hours later it reached category 3, with peak winds of 115mph.  After maintaining its intensity the storm finally succumbed to high wind shear from nearby Tropical Storm Leslie and became a convection less vortex by September 11, when it was declared a post-tropical cyclone by the National Hurricane Center.

Hurricane Nadine (min pressure 978mb) was next up, the system was declared a Tropical Depression on the 10th September, and was upgraded to Tropical Storm status the following day.  and was then declared a hurricane on the 15th September.  After convection weakened, an upper-level low developed, and the wind field became larger than average, Nadine transitioned into a subtropical cyclone on September 21, and then declared a post-tropical cyclone the day after.  However, by the 23rd September the system became again a Tropical Cyclone, and held this intensity until the 28th at which time it was declared a Hurricane yet again.  Due to wind shear the following day, Nadine weakened back into a tropical storm, but briefly restrengthened into a hurricane for the third time hours later. It reached its peak intensity of 90 mph on September 30, holding on to its strength for 18 hours until it again started to weaken due to increasing wind shear and cooler waters. Nadine weakened to a minimal tropical storm on October 3, when it briefly reentered warm waters, thus dropping its pressure. On October 3, Nadine was picked up by the jet stream and eventually merged with a non-tropical system.


October 3rd saw the birth of Tropical Depression 15, and later that day this was upgraded to Tropical Storm Oscar (min pressure 994mb).  The storm reached peak intensity of 50mph winds on the 5th October, and early on the 6th the system was absorbed by a cold front.

Tropical Depression 16 originated North East of the Bahamas in early October, however it did not become organised enough to be declared a depression until the 11th of October, and later that same day was named Tropical Storm Patty (min pressure 994mb).  Wind shear inside the system soon weakened and the following day Patty was downgraded to  a depression, where soon after it fizzled out.

October 12th saw Tropical Storm Rafael (min pressure 969mb) organise enough to become the next named system of the year, and 3 days later was classed as a Hurricane.  By the 17th of October the system had become a strong extratropical cyclone with no threat.

The next storm to be named was the most talked about for years, Sandy (min pressure 940mb) was born on the 22nd October as Tropical Depression 18 about 320 miles south of Jamaica, and later that same day was upgraded and named Tropical Storm Sandy.  The NHC noted that “remaining nearly stationary over the warm waters of southwestern Caribbean Sea is never a good sign for this time of year.”  Sandy first made landfall in Jamaica on the 24th October as a Category 1 Hurricane, and as it continued its journey towards Cuba it was upgraded to a category 2 Hurricane with 110mph winds.  After striking Cuba the system weakened slightly before again becoming a Hurricane.  The convection organized further early on October 29,and around the same time, Sandy began transitioning into an extratropical storm early on October 29 after the western periphery of the circulation began interacting with a cold front.  Around this time much was made in the media of the “frankenstorm” that was going to hit mainland USA (the name as Halloween was right around the corner).  Sandy became post tropical and it began its journey towards the New Jersey area.  The intensity at landfall was estimated at 90 mph (150 km/h), although the strongest winds were located east and southeast of the center.  After moving ashore, Sandy continued to the west, weakening below hurricane force by the time it reached Pennsylvania. The hurricane caused widespread power outages and also dumped record snowfall on West Virginia. By 0900 UTC on October 31, the circulation degenerated into a trough of low pressure, with no discernible circulation.   Later that day, the remnants of Sandy spread into the Great Lakes, and the HPC issued its last advisory.

Tropical Storm Tony (min pressure 1000mb)  was the last of the 2012 Atlantic season, and began as a tropical wave on the 19th of October.  After meandering for a while it became a tropical Depression on the 20th, although it was expected to dissipate within days.  Tropical Depression Nineteen moved northward and became Tropical Storm Tony  October 24.  After a brief interlude as a named storm this was declared post tropical on the 25th October, when it was located south-west of the Azores.

Info from Wiki



Thunder and Lightning

Some people say that they can tell when a storm is coming.  The air “feels” different, animals quiten down, birds disappear until the storm has passed. 

There are actually several types of thunderstorm, although here in Britain we are most likely to experience one in the warmer months.  In summer months, the earths surface is heated by the sun, and with this warm air rising, and cooler air sinking it creates conditions for a storm.  The 3 more common storms are an Orographic storm, a frontal storm, and an Air mass thunderstorm.


These kind of storms are caused by the lifting of air over a mountain or a hillside.  These storms can be accompanied by large volumes of rainfall.


Frontal storms occur when different air masses meet, ie, when a cold front meets a warm front.  Cold air is denser than warm air, so as a cold front approaches warm air the warm air is lifted, which then creates unstable conditions in the troposphere (the lowest portion of earths atmosphere).  This unstable air can create massive thunderstorms, and can bring a lot of rain.  You can often see one of these storms developing, they appear as big, dark cumulonimbus clouds.  If there is enough cold air this kind of storm can appear day or night, although often a nightime storm can appear far more impressive as the lightning is more visible in the dark sky.


An air mass thunderstorm typically lasts less than an hour, and can be very localised.  It is caused when a large mass of warm, moist air interaacts with even a small pocket of cold air.  When these storms hit you can quickly find yourself drenched one minute, then drying out the next as the sky clears and the sun comes back out.


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.

Info from Wikipedia

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.


Hurricanes, cyclones, tropical storms, typhoons….these are all the same thing, but are named differently depending where on earth they are formed.

A storm that is created in the North Atlantic Ocean, the Northeast Pacific Ocean (east of the dateline) or the South Pacific Ocean (east of 160E) will be called a Hurricane.  The same kind of storm that forms in the Northwest Pacific Ocean, west of the dateline, will be called a Typhoon.  A Tropical Cyclone will form in the Southwest Indian Ocean.  These kind of storms can cause catastrophic damage if they reach land.

How do they form?

In the case of a hurricane, the storm begins life in tropical regions. They form there because they need warm water of at least 26°C, high humidity with moist air, light winds, and very warm surface temperatures. Summer and the early fall months are perfect for hurricanes to brew up in the oceans around us. Most of the Atlantic hurricanes brew up on the coast of Africa. For that the northern hemisphere hurricane season is considered through the months of June and November.  Continue reading