Tornadoes, waterspouts and funnel clouds are intense columnar vortices in the shape of funnels with very strong winds and very low pressure near the center. These features usually develop from intense thunderstorms and are severe localized phenomena which may be accompanied by heavy rain or severe squalls.
- The Origin of Tornadoes: Mesocyclones
- Funnel Clouds
- Other Strong-Wind Phenomena
Tornadoes are the least frequent of the three phenomena across Trinidad and Tobago, with one report of a confirmed tornado every 10-20 years, usually across Central and Western Trinidad. Waterspouts and funnel clouds are not uncommon across Trinidad and are usually seen off Trinidad’s Eastern and Western Coasts. These features are seen several times a year as severe thunderstorms approach Trinidad from the East, or intensifying thunderstorms moving into the Gulf of Paria. There are nearly no accounts of any tornado sightings from Tobago.
The Origin of a Tornado: Mesocyclones
Within showers and thundershowers (all convective showers), there is an updraft, where warm air rises into a thunderstorm.
However, when there is a change of wind speed or direction as the air rises (wind shear), this updraft begins to rotate. This rotating updraft is called a mesocyclone. As this mesocyclone, or rotating air, moves closer to the surface of the earth, this may cause a funnel cloud to form. If this funnel cloud/rotating updraft touches the surface of the earth (land), a tornado is formed. Alternatively, if this funnel cloud touches the surface of the ocean or a waterbody, it is considered a waterspout.
A funnel cloud is a funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind (mesocyclone) and extending from the base of a cloud (usually a cumulonimbus or towering cumulus cloud) but not reaching the ground or a water surface.
When this funnel cloud touches the ground, it either becomes a tornado (if it touches down on land) or a waterspout (if it touches down on water such as a lake, pond or ocean).
Funnel clouds have occurred in Trinidad, some of which have become tornadoes. These occurrences of funnel clouds over land in Trinidad are rare. The last confirmed event of a funnel cloud over land was the Charlieville Funnel Cloud of August 9th, 2009. This funnel cloud touched down near Warrenville and became a tornado.
A tornado is a rapidly rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as twisters, whirlwinds or cyclones.
Tornadoes form exactly like a funnel cloud, with the exception that the funnel cloud touches down on land and produces significant wind damage in a radial pattern.
The most recent confirmed tornadoes were the Caroni Tornadoes of September 29th, 2009 where two tornadoes touched down in the Caroni Plains.
Tornadoes do have a characteristic look on Doppler Radar Imagery where a feature called a “hook echo” can be seen.
Looking at the three Doppler Radar Scans from the Trinidad and Tobago Meteorological Service around the time of Sunday 2nd July 2017’s funnel cloud, we see the strengthening circulation forming a possible hook at 11:31 AM and a more defined hook at the 11:45 AM radar scan.
Waterspouts are perhaps the most familiar, and when conditions are right they can be quite common. As their name implies they occur over larger bodies of water – lakes or stretches of the sea – and have the typical funnel form of tornadoes.
In fact some of them, the tornadic waterspouts, are tornadoes which either move over water from the land or form over water. They are just as dangerous, form under a rotating storm or supercell, and like tornadoes are associated with a wall cloud.
The other, more common forms are fairweather waterspouts. They are less intense and tend to form over warm bodies of water in association with rapidly growing cumulus clouds.
While uncommon, they do occur off Trinidad and Tobago’s coast at times.
Other Strong-Wind Phenomena
Downbursts (or Microbursts) – A Common Occurrence
This is a more common feature in both Trinidad and Tobago that causes the usual gusty winds associated with heavy showers or thundershower activity. However, in severe cases, they can cause widespread damage and people mistakenly attribute them to tornado activity in Trinidad and Tobago based on the severity.
A downburst is an area of strong, downward moving air associated with a downdraft of a thunderstorm. As the downdraft impacts the ground, the air is forced outwards in all directions while it also curls backward. This results in incredible wind damage close to the surface of the ground, as well as horizontal rotation midway up between the ground and the base of the thundercloud.
Often, downbursts can produce straight-line wind damage over an area as small as 1 mile to as large as 250 miles from the center of the downdraft.
In fact, a downburst that spans a distance less than 2.5 miles in diameter is considered a microburst. Since thunderstorms and heavy shower activity are highly localized events in Trinidad and Tobago, we usually experience microbursts.
There are some similarities between a microburst/downburst and a tornado such as both are parented by severe thunderstorms, they can form rapidly and they both have the potential to produce very high wind speeds, and therefore significant wind damage. However, tornado damage tends to be localized and radial versus downburst/microburst winds cause damage along a straight line in one direction. (See below) Winds can reach up to 240 KM/H.
This is a rare feature for Trinidad and Tobago and occurs along the leading edge of straight-line winds associated with microbursts or downbursts. It is short-lived, on the order of seconds to a minute. We have rarely if never, seen this feature in recent records.
Dust devils form when hot air near the surface rises quickly through a small pocket of cooler, lower pressure air above it. If conditions are just right, the air may begin to rotate. As the air rises, this column of hot air is stretched vertically. As more hot surface air flow into this rotating wind column, replacing the air that is rising, the spinning effect becomes further intensified and self-sustaining. Typically, these fast current of surface winds whips up dust, to show the wind currents.
As available, extremely hot air near the surface is channeled up the dust devil, eventually surrounding cooler air will be sucked in. Once this occurs, the effect is dramatic, and the dust devil dissipates in seconds.
A dust devil needs:
- Flat conditions increase the likelihood of the hot-air “fuel” being a near constant. Dusty or sandy conditions will cause particles to become caught up in the vortex, making the dust devil easily visible.
- Clear skies or lightly cloudy conditions: The surface needs to absorb heat to create ideal dust devil conditions.
- Light or no wind and cool atmospheric temperature.
Most dust devils are very small and weak, often less than 3 feet (0.9 m) in diameter with maximum winds averaging about 45 miles per hour (70 km/h), and they often dissipate less than a minute after forming.