Hurricanes like the one that hit Florida form in very specific conditions
Weather Watch by Keith Banks
Hurricanes are arguably the most spectacular phenomena occurring anywhere in the atmosphere, and the potential that these storms have to inflict catastrophic damage is enormous.
Hurricane genesis hinges upon specific conditions. If any of those are absent a hurricane will not develop.
Sea temperatures must be at least 26.5C, down to a depth of 150 feet. This causes the overlying atmosphere to become unstable, facilitating convection that generates thunderstorms.
Rapid cooling with altitude, coupled with a steep saturated lapse rate gradient in an unstable atmospheric environment allows the release of copious amounts of the latent heat of condensation that provides the energy that is necessary to fuel the hurricane.
High humidity in the lower and middle layers of the troposphere supplies the vast amounts of moisture that nourishes the storm.
Dry air weakens a hurricane because evaporation is a cooling process that inhibits convection.
One of the most important factors is limited vertical wind shear. Vertical wind shear are changes in wind direction and speed with altitude. Strong wind shear disrupts the hallmark symmetrical structure of a hurricane and has the potential to rip it apart.
Hurricanes form at latitudes that are more than 5 degrees from the Equator. The rotation of the Earth creates an apparent force called the Coriolis effect. The Coriolis effect is negligible at the Equator and strongest at the poles. The Coriolis effect deflects the air and is essential for creating the spinning motion of the hurricane.
Typically, an Atlantic hurricane – such as the one that hit Florida recently – begins life as a cluster of thunderstorms that have drifted off the coast of Africa. These features are also known as tropical disturbances or waves. If a disturbance encounters the conditions stated above, it will become a tropical storm and eventually evolve into a hurricane.
The Saffir-Simpson Hurricane wind scale classifies hurricane intensity on a scale of 1 to 5, with category 5 being the most destructive.
A review of Wick’s historic record for mean air temperature for September showed that September 2024 was the coolest since that of 2012, and is currently the 59th equal most cold in a series commencing from 1910.
The mean temperature was identical in September 1948.
In terms of precipitation, September 2024 was the least wet since that of 2022. However, a closer look at the town’s rainfall archive for a series of Septembers stretching back to 1910 revealed that it is presently the 14th wettest.
September 2024 experienced one ‘day of gale’.
Wick’s mean air temperature for September 2024 was 11.21C (52.18F). The long-term average in terms of the averaging period 1991-2020 is 11.79C (53.22F).
The town’s average daytime maximum air temperature for September 2024 was 13.75C (56.75F), 0.93C lower than the current long-term average for the month.
Highest maximum was 22.3C (72.1F), recorded on September 17. The lowest maximum was 10.2C (50.4F), observed on September 27.
Wick’s average overnight minimum air temperature for the month was 8.66C (47.59F). The long-term average in terms of the current 30-year averaging period is 8.89C (48.0F).
Highest minimum was 13.2C (55.8F), noted on September 2. Lowest minimum was 1.9C (35.4F), witnessed on September 25.
The lowest temperature recorded at 5cm over the grass was 0.5C (32.9F), on September 25.
Precipitation was measurable on 26 dates. The total for the month was 99.8mm (3.93 inches),or 150.7 per cent of the long-term average for September.
Wettest day was September 2. The quantity logged during the 24 hours commencing 9am (GMT), was 32.6mm (1.28 inches).
Wind velocities reached or surpassed gale force 8 (39.0mph/33.9knots), on two dates.
The windiest day was September 10 when a gale force 8 north-westerly wind gusted up to 52.9mph/46.0knots, severe gale force 9 on the Beaufort scale.