Near Record-Breaking Wet October for Antigua

The content originally appeared on: Antigua News Room

By Dale Destin

October 2023 will be etched into Antigua’s weather history as a month of near-record-breaking rainfall.

With an island-average total of 364.2 mm (14.34 in), it ranks as the second wettest October on record, coming close to the record set in 2008.

However, this month’s excessive rainfall wasn’t just significant for its timing; it was the sixth wettest of any month in Antigua’s recorded history, dating back to 1928. Let’s dig into the details of this significant climate anomaly.

The 364.2 mm of rain that drenched Antigua throughout October 2023 was just shy of the all-time October record of 384.3 mm (15.13 in) set in 2008. While it didn’t break the island-average record, some areas of Antigua likely had record-breaking rainfall for the month. Some locales had rainfall totals close to 400 mm (16 in).

October proved to be two-and-a-half times wetter than the norm, with the 364.2 mm (14.34 in) representing 246 percent of the typical monthly precipitation of 148.1 mm (5.83 in). Surprisingly, October exhibited more precipitation than the combined rainfall of the previous four months.

To put this into perspective, the rainfall on Antigua for October amounted to a volume of 22.4 billion imperial gallons (imp gal) or over 101.8 billion litres; this would fill 22.4 Potworks Dams, which holds a billion imp gal, when full. To illustrate further, a standard water bottle typically contains about 16.9 fluid ounces or 0.125 US gallons (0.110 imp gal). Therefore, 22.4 billion imp gal would equate to over 203.6 billion standard 16.9-ounce water bottles.

Remarkably, such heavy rainfall in October is a rarity for Antigua. The chance of such a soaking is a mere three percent. This frequency implies an occurrence rate of once every 33 years or approximately once per generation, on average. This is only the third time the month has had a foot or more of rainfall.

On an annual basis, experiencing such a wet month in Antigua is also uncommon. The chance of any month being this wet in a year is 10 percent, based on the climate pattern observed  from 1991 to 2020. Consequently, such a wet month typically reoccurs once every 10 years, on average. A named storm would quicker make landfall on Antigua before we see a month with this type of rainfall (knock on wood). It’s a statistical rarity, where only five other months in recorded history, spanning back to 1928, have been wetter among 1150 months. October 2023 stands as a one-percenter – a member of the top one percent of the rainfall population by wetness.

The drenching weather was caused mainly by two tropical cyclones – Tropical Storm Philippe and Hurricane Tammy, and a tropical disturbance. Philippe was the biggest rainmaker of the three, dowsing the country with over 200 mm or up to 8 inches of rain. Rainfall totals for Tammy max out at over 100 mm or about 4 inches for some areas. Additionally, the disturbance, which got spawned by Tammy, added up to a further four inches across parts of the island. Philippe alone accounted for over 50 percent of the rainfall.

The most impactful rainfall came from Philippe, and it was not all negative. Philippe positively impacted our rainfall catchments. Most catchments went from dry or low, to full or more than half. This was a welcome relief, as we were thirsting for rainfall. For nearly two years, virtually all of our potable water has been artificially produced from seawater. This supply hadn’t been sufficient, forcing many residents to endure prolonged periods (weeks) without public access to pipe-borne potable water.

However, alongside these positive effects, there were unwelcome consequences. Various areas experienced flooding to varying extents. Intense rainfall led to flash floods and overflowing gutters, causing damage to homes, roads, and bridges. Low-lying regions were particularly susceptible to inundation. Moreover, the excessive rainfall resulted in damage to crops, impacting agriculture and potentially leading to shortages or price hikes for certain produce as the Christmas season approached.