Weather tracker: ‘Pineapple express’ atmospheric river deluges California
During the first week of February two storms hit California in quick succession, both featuring intense precipitation thanks to the “pineapple express” atmospheric river.
Atmospheric rivers are long narrow channels of very moist air that flow through the atmosphere, transporting impressive amounts of water vapour that eventually fall as heavy rain or snow. The pineapple express is a famous recurring atmospheric river that forms near the Hawaiian Islands and flows north-east to the Pacific coast of North America.
After the initial storm during 31 January and 1 February, the second moved in between 4 and 6 February, both bringing persistent heavy rain across much of California and dumping snow on mountains.
The area between Santa Barbara and San Diego was particularly badly affected, with several places setting new rainfall records for the date or month. Downtown Los Angeles had received 10.57in of rainfall by 7 February, almost three times the February average, and 74% of the typical yearly rainfall.
A state of emergency was declared in several counties as widespread flash flooding occurred. In the hills of Los Angeles and San Francisco mudslides swept away buildings and cars, while coastal cliffs collapsed in Santa Barbara county and part of a major road was washed away in the Mojave desert. There were also strong winds, with gusts of more than 100mph recorded in some mountainous and coastal areas.
Nova Scotia also declared a state of emergency over the weekend, thanks to a strong storm between Friday and Monday that left at least a foot of snow across much of the province. Cape Breton Island was worst affected, with the town of Sydney recording 40.6in at its airport, while almost 60in was reported nearby.
Also this week, the EU’s Copernicus Climate Change Service reported that Earth’s average air temperature for the year between February 2023 and January 2024 was 1.52C above pre-industrial levels, marking the first time global heating has breached the 1.5C threshold over a full year.
In 2015, world leaders pledged to limit heating to 1.5C. This pledge refers to long-term changes, so a single 12-month period above 1.5C does not mean failure but it does bring the possibility of failure closer.
The Earth’s average sea surface temperature is also the highest it has ever been, having reached a new record of 21.05C on Saturday, surpassing 21.02C from August 2023.