Funnel Clouds

A funnel cloud is a cone-shaped cloud, associated with a rotating column of wind, extending from the base of a cloud. Generally, funnel clouds extend from the base of a cumulonimbus (thunderstorm) or cumulus cloud. A funnel cloud does not reach the ground or water surface.

These types of clouds in Trinidad and Tobago are not unheard of, with a number of sightings reported and documented over the last few years. Funnel clouds, though for the most part, are harmless. However, it can become damaging and life-threatening if it touches down on land (becoming a tornado) or on water (becoming a waterspout.)

Content:
The Origin of Funnel Clouds
Funnel Cloud Formation

Classic
Cold-Air
Other

Forecasting and Detection
Occurrence and Frequency
Funnel Cloud Safety

The Origin of Funnel Clouds, Tornadoes and Waterspouts

Within showers and thundershowers (all convective showers), there is an updraft, where warm air rises.

Structure of a thunderstorm. (Credit: Encyclopedia Britannica, Inc.)

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 rotating updraft touches the surface of the earth (land), a tornado is formed. Alternatively, if the updraft touches the surface of the ocean or a waterbody, it is considered a waterspout.

A diagram showing how an updraft of a thunderstorm can become a rotating updraft. (Credit: Wikipedia)

A diagram showing how an updraft of a thunderstorm can become a rotating updraft. (Credit: Wikipedia)

Funnel Cloud Formation

Classic Funnel Clouds

Similar to the formation of a tornado or waterspout, a rotating column of air draws in water droplets – making a region of intense low-pressure visible. This rotating column of air can be found at the base of cumulonimbus clouds, where the updraft is located. Note that funnel clouds that are produced from cumulonimbus clouds are typically associated with supercell thunderstorms, a rare thunderstorm type in T&T.

A true funnel cloud rotates, but has no ground contact or debris, and does not produce damage.

There is some disagreement over the definition of a funnel cloud and a condensation funnel. According to the Glossary of Meteorology, a funnel cloud is any rotating cloud pendant from a cumulus or cumulonimbus, and thus most tornadoes are included under this definition.

Types of cumuliform clouds, or convective clouds. Small: cumulus humilis, also called "fair weather cumulus"; Medium: cumulus mediocris; Large: cumulus congestus, also known as towering cumulus; Extra large: cumulonimbus, also called thunderstorms (University of British Columbia/Roland Stull)
Types of cumuliform clouds, or convective clouds. Small: cumulus humilis, also called “fair weather cumulus”; Medium: cumulus mediocris; Large: cumulus congestus, also known as towering cumulus; Extra large: cumulonimbus, also called thunderstorms (University of British Columbia/Roland Stull)

Among many meteorologists, the ‘funnel cloud’ term is strictly defined as a rotating cloud that is not associated with strong winds at the surface, and condensation funnel is a broad term for any rotating cloud below a cumuliform (convective) cloud.

Note: The term condensation funnel may refer to either a tornadic cloud or a funnel cloud aloft, but the term funnel cloud exclusively refers to a rotating condensation funnel not reaching the surface. If strong cyclonic winds are occurring at the surface and are connected to a cloud base, regardless of condensation, then the feature is a tornado.

Cold-Air Funnel Clouds

Cold-air funnel clouds, and its associated vortex of wind, are generally much weaker than the vortex produced by supercells. Although cold-air funnels rarely make ground contact, surface-level vortices sometimes become strong enough for condensation cloud to “touch down” briefly, becoming visible as weak tornadoes or waterspouts.

Unlike the related phenomenon associated with severe thunderstorms, cold-air funnels are generally associated with partly cloudy skies in association with atmospheric boundaries such as sea breezes or outflow boundaries.

Sea breeze convergence mechanisms for the Gulf of Paria and the Atlantic Ocean across Trinidad which can produce thunderstorm activity.. Note that sea breeze convergence is possible across all coasts of both islands. Diagram: Trinidad and Tobago Weather Center
Sea breeze convergence mechanisms for the Gulf of Paria and the Atlantic Ocean across Trinidad which can produce thunderstorm activity.. Note that sea breeze convergence is possible across all coasts of both islands. Diagram: Trinidad and Tobago Weather Center

Sea breeze convergence is common along the Western coasts of both islands, particularly during days where overall easterly winds are light to non-existent. Funnel formation in this instance is usually due to cooler air aloft (higher in the atmosphere) over warmer air at the surface.

The funnels develop where atmospheric instability and moisture are sufficient to support towering cumulus clouds but typically limited to no or little precipitation. Cold-air funnels, although weak, may persist for several minutes, and areas of intermittently forming these types of clouds for tens of minutes. This is more common across Western areas of Trinidad during the Wet Season.

Multiple such areas of activity may form within the same region during afternoon heating, such as earlier in 2020 where multiple funnel clouds were spotted across Southwestern Trinidad.

Cold-air funnels weaken and eventually dissipate with loss of solar heating (heating from the sun). When precipitation does develop, the associated downdraft tends to cause the rapid demise of the cold-air funnels.

Other Funnel Clouds

Although not considered a separate kind of funnel cloud, some funnel clouds form with mesovortices associated with squall lines – the weather we experience with tropical cyclones and disturbances, which also can become tornadoes but are often not visible as funnel clouds or tornadoes because they usually occur within obscuring precipitation.

Forecasting & Detection

In the forecasting phase, we tend to look for light to near calm conditions, particularly along Western Trinidad where triggering mechanisms for shower and thunderstorm development are dominated by sea breeze convergence and daytime heating.

Looking at different heights in the atmosphere, we also look to see if there is a vertically stacked low-pressure, with a noted, decreasing temperature change as well as a clockwise turning of winds as you increase in height in the atmosphere.

However, all of these conditions can occur, but it does not guarantee the formation of a funnel cloud, much less a waterspout or tornado. This is where detection comes in, as these funnel cloud events tend to be brief.

In Trinidad and Tobago, we lack the advanced Doppler Radar that can show us how winds are moving near and inside showers. This is helpful in understanding what kinds of hazards the thunderstorm might have (tornado, microburst, gust fronts, etc.) associated with it. It also helps us understand how the thunderstorm is feeding itself.

However, even if we had an advanced Doppler Radar, there is difficulty in recognizing the small low-level circulations associated with cold core events on Doppler radar. The velocity signatures are minimal and usually blend in with background noise. Reflectivity is also usually very small (0-30 dBz), which makes cold core funnel or cold-core tornado detection using radar almost impossible.

This difficulty in forecasting such events results in short, if any, warning times for the public and, as mentioned earlier, these cold core funnels do occasionally touch down and cause damage and injuries.

Occurrence and Frequency

In recent years, there have been more sightings of funnel clouds across Trinidad (mainly) and Tobago – but this can largely be attributed to an increase in cameras across the country rather than an increase in frequency.

Here are a few instances of funnel cloud sightings across Trinidad and Tobago, dating back to late 2017 to early 2020:

Funnel Cloud Safety

If you spot a funnel cloud, head indoors to the lowest level of the nearest building, into a center room away from windows and doors. While some funnel clouds may never materialize into a tornado, gusty winds may still occur and can be hazardous.

Generally, these clouds dissipate without much impact to those on the ground. If you do spot one, and in a safe place, feel free to submit a report to us on our social media platforms!

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