Monday, August 15, 2016

Strong Arctic Storm

A very strong low pressure system developed over the Arctic Ocean north of Siberia yesterday and intensified last night as it migrated eastward to the date line.  This morning the Canadian surface analysis estimated the minimum central pressure at 969mb, which is very low for the time of year.  The sequence of images below shows some analyses from the past 36 hours.

3am AKST yesterday:

3pm AKST yesterday:

9am AKST today:

The current position and intensity of the storm is quite reminiscent of the 2012 "Arctic hurricane" (documented here on this blog), although today's storm tracked from the west rather than the south, and it's not quite as strong as the 2012 storm.  The higher overall latitude of this storm may mean that the associated high winds do less damage to Arctic ice than the 2012 event; the 2012 storm is believed to have been one of the factors that led to that year's record low ice extent.  Today's chart of sea ice extent from the NSIDC conveniently shows the comparison of recent conditions to 2012 - see below, and note the dip in early August 2012.  This was probably at least partly caused by the storm, and so we may well see a similar sudden dip in sea ice extent in the next few days.

The current storm and that of August 2012 appear to be consistent with a long-term trend towards stronger storms during summer over the portion of the Arctic north of Alaska; see the chart below, created from the NCEP/NCAR global reanalysis.  One caveat here is that the reanalysis system ingests oceanic weather reports, so it's possible that the paucity of observations over the Arctic in earlier years prevented the reanalysis from fully capturing all the storms that actually occurred; however, the model is very capable of transporting information from data-rich to data-sparse areas, so this may not be a significant issue.  Here's an NSIDC article giving some additional perspective:

[Update August 16] Here's a chart of observed sea-level pressure at a buoy that happened to be located very close indeed to the track of the storm center.  If the measurement is accurate, then the storm was a little stronger than estimated by Environment Canada.

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