Hurricanes & Tornadoes

HURRICANES: These are some of the most destructive Storms on Earth!

These are known as ‘Hurricanes’, ‘Typhoons’ or ‘Cyclones’, depending upon where they occur, but essentially they are organised storm systems that form over warm waters and they then rotate (anticlockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere) and have sustained windspeeds of at least 74 M.P.H. (119 Km/Hr). These feed off of warm water, gaining strength all of the time, until they move into cooler waters (or over land) where they then lose their strength and then fill up as pressure rises steadily. In the U.S. the National Oceanic & Atmospheric Administration (NOAA) often fly reconnaissance and data gathering aircraft right into these Hurricanes, especially into the higher parts of the eye wall. The aircraft used are generally the very robust and strong Lockheed P.3 Orion which can easily withstand the turbulence, torque and hail that may be experienced. They are full of electronic tracking, radar and data collection consoles, as well as being able to drop ‘drop-sondes’ which monitor various parameters as they drop through the atmosphere. The information is continually passed back to the aircraft by telemetry. All of this information is then recorded for future hurricane research.

Some of the worst Hurricanes in living memory include Category 5 Hurricane ‘Andrew’ which hit South Florida on 24th August, 1992 (90 miles across with 165 M.P.H. winds), Hurricane ‘Katrina’ (28th-29th August, 2005), Hurricane ‘Rita’ (20th-23rd September, 2005) & Hurricane ‘Wilma’ which occurred around 18th October, 2005. Also, in October 2012, Hurricane ‘Sandy’ swept up the eastern and northeastern parts of the U.S.A. and this one was particularly potent in it’s eventual devastation! Three even more destructive Hurricanes than ‘Sandy’ occurred in 2017. These were Hurricane ‘Harvey’, Hurricane ‘Irma’ & Hurricane ‘Maria’. A full history and photos of Hurricane ‘Irma’ can be found on the following National Weather Service link: Hurricane ‘Irma’ 30 Aug 2017-17 Sep 2017.

As Global sea temperatures rise, so also does the frequency & destructive capability (winds & rains, as well as storm sea-surges) of so-called Super- Hurricanes, Super-Cyclones & Super-Typhoons. These are usually larger, stronger, and cover a bigger geographical area than a ‘standard’ Hurricane.

For more information about Hurricanes please refer to these links: National Hurricane Center, Miami, Florida and the Central Pacific Hurricane Center, Honolulu, Hawaii. This website is excellent for latest Hurricane information, advisories & warnings.

Hurricane Categories: Saffir-Simpson Hurricane Scale – (Worst to Least)

Category 5: Winds more than 252Km/hr (157 m.p.h.) – similar, or close to the speed of some high speed trains. (Worst)

Category 4: Winds 209-251Km/hr (130-156 m.p.h.) – faster than the world’s fastest roller coaster.

Category 3: Winds 178-208Km/hr (111-129 m.p.h) – similar, or close to the serving speed of many professional tennis players.

Category 2: Winds 154-177Km/hr (96-110 m.p.h) – as fast or faster than a baseball pitcher’s fastball

Category 1: Winds 119-153Km/hr: (74-95 m.p.h.) – faster than a cheetah (Least)

Typhoon Categories: (Worst to Least):

Category 5: 252Km/hr and higher (Worst)

Category 4: 209-251 Km/hr

Category 3: 178-208 Km/hr

Category 2: 154-177 Km/hr

Category 1: 119-154 Km/hr (Least)


Tornadoes are, for the most part, localised systems, often formed below Cumulonimbus clouds. (The U.S call these ‘thunderheads’.) These are most prevalent in the U.S.A., most often in the area which is known as ‘tornado alley’. Active cold fronts move southeastwards, forcing warm and moist air (from the southwest) upwards, therefore producing often slow moving and intense thunderstorms (these are known as ‘supercells’ and they are huge, – often slowly rotating in an anticlockwise manner). Under these ‘supercells’ often develop tornadoes (anything from F0-F5), heavy rain and large damaging hail, as well as very strong & gusty winds and they can be absolutely devastating, especially if they hit a populated area. The progress and intensity of these ‘supercells’ is often closely monitored by rainfall radar, high definition doppler radar, lightning detectors & satellite images. The largest hail tends to occur in Oklahoma.

The core of tornado alley extends from northern Texas, Louisiana, Oklahama, Kansas, Nebraska and South Dakota. The northern extent of tornado alley includes Minnesota, Wisconsin, Illinois & Indiana & also western Ohio. (most tornadoes occur between the Rocky Mountains & the Appalachian Mountains). The most active part of tornado alley tends to be around Wichita in Kansas. Tornadoes generally travel at between 30mph & 70mph. Tornado season usually starts in the Spring but given the right conditions, they can occur at any time of the year.

It is fairly well known in the U.K. that there are usually more ‘minor tornadoes’ per year than in the whole of the United States! Many of these are very small and therefore, go largely unnoticed and unreported. Usually, only a garden shed gets lifted up and destroyed, or a few roof tiles are lifted off and get spread around the street underneath! A small tree may get uprooted or a rubbish bin may well get thrown across the road! Under the right circumstances, a tornado can occur almost anywhere across the globe. Sometimes ‘funnel clouds’ are seen underneath a cumulonimbus cloud. These can only be called tornadoes if they actually touch the ground. Many of these do not reach the ground and they just disperse instead. If a tornado occurs over water, then it is called a waterspout. Small whirling columns can occur over land (usually caused by hot air rising). These are called dust devils and they can suck up dust, grass and hay or straw. They are not usually too violent and again, these often disperse over time.

This is the official Fujita Tornado Scale: (Worst to Least)

Force 5: 421-510 Km/hr – Damage to concrete buildings (Worst)

Force 4: 331-420 Km/hr – Houses destroyed, cars thrown about.

Force 3: 251-330 Km/hr – Houses flattened , forests blown down.

Force 2: 181-250 Km/hr – Whole roofs torn off & trees uprooted.

Force 1: 120-180 Km/hr – Roof tiles blown off, cars moved.

Force 0: 64-119 Km/hr – Light damage – tree branches break (Least)

Tornado Classifications: (TORRO) : founded by Terence Meaden (whom I was lucky enough to meet in around 1974!), originally called the Tornado Research Organisation, – it was expanded in 1982 following the inclusion of the Thunderstorm Census Organisation (after the death of it’s founder Morris Bower and his wife). The current head of TORRO is Paul Knightley, a professional meteorologist. The TORRO website can be found at:

(Tornado & Storm Research Organisation) : (Worst to Least)

T10 : Super Tornado : 121-134 m/sec (270-299 m.p.h) (Worst)

T9 : Intensely Devastating Tornado: 108-120 m/sec (241-269 m.p.h.)

T8: Severely Devastating Tornado: 96-107 m/sec (213-240 m.p.h.)

T7: Strongly Devastating Tornado: 84-95 m/sec (187-212 m.p.h.)

T6: Moderately Devastating Tornado: 73-83 m/sec (161-186 m.p.h.)

T5: Intense Tornado: 62-72 m/sec (137-160 m.p.h.)

T4: Severe Tornado: 52-61 m/sec (115-136 m.p.h.)

T3: Strong Tornado: 42-51 m/sec ( 93-114 m.p.h.)

T2: Moderate Tornado: 33-41 m/sec ( 73-92 m.p.h.)

T1: Mild Tornado: 25-37 m/sec (55-72 m.p.h.)

T0: Light Tornado: 17-24 m/sec (39-54 m.p.h.) (Least)

TORRO Tornado Classifications:

Weak Tornadoes: T0, T1, T2, T3

Strong Tornadoes: T4, T5, T6, T7,

Violent Tornadoes: T8, T9, T10, T11.