Following up on Keith Grant's earlier post:

Shortly after 1900 today, the MSLP here rose above 1000 mbar for the
first time since just before 2100 on 15 February – a period of 310
consecutive hours below 1000 mbar. Since my hourly AWS records
commenced (March 1993), the three previous longest spells of the
barometer remaining below 1000 mbar have been:

• 179 hours, ended at 0500 UTC on 12 November 1997
• 140 h, ended at 1100 UTC on 24 October 2006, and
• 129 h, ended 1700 UTC on 7 February 2009

This spell of 310 consecutive hours is therefore the longest such
period of continuous low pressure (defined here as MSLP 1000 mbar)
within the last 17 years at this location, exceeding the previous
record by almost 75 per cent.

The mean monthly MSL pressure at 0900 UTC this month, 1003.6 mbar
here, is only the lowest since last November (1001.6 mbar) although it
is the lowest February mean since 1966 (1002.5 mbar). The mean for the
first half of the month of February 2010 was 1014.2 mbar but the
second half only 991.4 mbar (the 1971-2000 normal for February is
1016.7 mbar). The lowest of any month in the last 80 years has been
999.2 mbar in November 2000 (the only month on a long combined record
for west of London back to 1930 to have seen a mean 07/09z MSLP below
1000 mbar), but 19 months in the last 80 years have seen a mean lower
than that in February 2010.

My daily MSLP records only extend back to 1983, but I would not be
surprised if the mean for the second half of Feb 2010 is as low as, if
not lower, than any previous two-week period in the last 80 years. The
lowest 15 day mean in late Oct/early Nov 2000 was 993.9 mbar, and the
lowest since 1983 has been 993.5 mbar for the 15 days ended 26
December 1989.

--
Stephen Burt
Stratfield Mortimer, Berkshire