Deepening low could threaten Iceland’s October pressure record

A rapidly deepening low-pressure system heading towards Iceland could threaten the country’s October record for low air pressure, mbl.is reports. The Icelandic Meteorological Office forecasts pressure could fall to about 936 hectopascals near the country’s southern and eastern coasts tomorrow.

The October record is 938.4 hectopascals, measured in 1963. Meteorologist Trausti Jónsson discussed the approaching low and the possibility of a record in a blog post.

Jónsson said pressure below 940 hectopascals was extremely rare in October, with just one previous reading that low in Iceland during the month. He said it was still uncertain how deep the low would become and how close to the country its lowest pressure would pass. When he wrote the post on Monday, he did not consider a new record the most likely outcome, though pressure could fall below other historical October lows.

Low is expected to deepen rapidly

When Jónsson wrote his post shortly after midday on Monday, the low was just off the northeastern coast of the United States, with pressure of about 1,003 hectopascals at its centre. Forecasts he cited showed it reaching a position about 1,000 kilometres east of Newfoundland by midday on Tuesday, with central pressure around 983 hectopascals.

A forecast from the European Centre for Medium-Range Weather Forecasts then placed the centre about 200 kilometres south of Reykjanes by midday on Wednesday, with pressure of about 936 hectopascals. The Icelandic Meteorological Office’s forecast on Tuesday said the centre was expected to move inland later on Wednesday.

The office has warned of storm-force winds and heavy precipitation, as well as blizzard conditions in the northwestern part of the country later in the day. High sea levels are also expected because of wind-driven water piling up along the coast.

October record dates to 1963

The lowest air pressure measured in Iceland in October was recorded at Stórhöfði in Vestmannaeyjar on 19 October 1963. The reading was 938.4 hectopascals. The next-lowest was 945.2 hectopascals at Sauðárkrókur on 23 October that year.

Three further October readings were below 946 hectopascals: 945.5 at Raufarhöfn on 26 October 1957, 945.7 at Stórhöfði on 1 October 1988, and 945.9 at Gjögur on 23 October 2008. Jónsson said the differences between those four readings were not statistically significant, so a sufficiently low reading tomorrow could stand out as a clear second-lowest October measurement even if the 1963 record remains intact.

Jónsson also recalled that the two storms in October 1963 had different effects. The first, on 19 October, brought a major coastal flood, while the second, four days later, caused damage mainly through wind.