Mirages are not a trap


Weather watch by Keith Banks

Exceptional atmospheric conditions on the night of April 14-15, 1912 facilitated the series of fateful decisions that caused the Titanic to collide with an iceberg, and the tragic loss of life that followed.

Images of distant objects are always displaced from their actual position, as light gradually bends as it passes through layers of air of different densities.

The physical process responsible for this is called refraction. Mirages are not hallucinations or illusions, they are optical manifestations of this physical process.

There are two types of candling, lower and higher. A lower mirage is seen under the actual object, when light enters a warm layer of low density air. Lower mirages are associated with hot deserts, but they can be seen frequently in the British Isles, on any extended flat surface that is warmer than the air above.

Beaches, roads and airfield runways are places where lower mirages are commonly seen in Caithness.

A top mirage is an image that is observed above the real object. These types occur on large flat lands or on sea surfaces much cooler than the air above and where a temperature inversion exists.

An inversion is a layer of air in the atmosphere where the temperature increases with altitude. When these conditions occur, light from an object near the horizon bends downward as it passes through layers of very cold, dense air, before reaching the eye.

These conditions can cause an object to appear above its actual position, and objects that are below the horizon can be highlighted and appear to be floating in the sky.

In historical context, research has revealed that on the night of April 14-15, 1912, unusually high atmospheric pressure associated with an intense high pressure area, where the warm waters of the Gulf Stream met the very cold waters of the Labrador Current, created a superior mirage.

An optical event, known as super refraction, obscured the view of many large icebergs and icicles present in a vast field of ice. It is reasonable to postulate that the very unusual weather conditions played a role in the fateful chain of events that culminated in the RMS Titanic disaster.

Closer to home, June 2021 was Wick’s hottest since that of 2017. A closer look at the city’s historic record for average air temperature for June has confirmed that it is currently the sixth hottest in a series dating back to 1910.

Wick’s precipitation record for June 2021 revealed that it was the driest since 2018 and is currently the 19th least humid in a series starting from 1910.

The average air temperature in Wick for June 2021 was 12.21 ° C (53.98 ° F). The long-term average, in terms of the 1981-2010 average period, is 10.95C (51.71F).

The average maximum daytime air temperature in Wick in June 2021 was 15.61 ° C (60.10 ° F). The long-term average for June, in terms of the value of this parameter, for the current average period of 30 years is 14.0C (57.2F). The highest maximum was 21.5C (70.7F), recorded on June 13. The highs of 20.0C (68.0F) and 21.1F (70.0F), seen on June 4 and 10, respectively, were also particularly warm temperatures for the city.

The lowest daytime high for the month was 11.7 ° C (53.1 ° F), noted on June 25.

The average minimum overnight air temperature for the city in June 2021 was 8.81 ° C (47.86 ° F). The long-term average for June is currently 7.90C (46.22F). The highest nighttime low was 13.2C (55.8F), recorded on June 11. The lowest ambient temperature for the month was 2.4C (36.3F), noted on June 22.

The lowest temperature noted at 5 cm above the grass was 0.6 C (33.1 F) on June 22.

Precipitation was measurable on 25 dates. The total for June 2021 was 24.4 mm (0.96 inch), or 45.7% of the long-term average for June. The wettest day was June 24. The amount recorded for the 24 hours starting at 9 a.m. (GMT) was 6.6 mm (0.26 inch).

There were no “galey days” during the month. Wind speeds reached or exceeded gale force 8 (39 mph / 33.9 knots) on two dates.

The strongest wind speed was observed during the hour ending at 10 a.m. (GMT) on June 14, when a force 6 west-southwest wind blew up to 40.3 mph / 35.0 knots, gale force 8 on the Beaufort scale.


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