NOAA IR Satellite 1145Z 26 January 2013 showing 930 mb hurricane force storm.

NOAA IR Satellite 1145Z 26 January 2013 showing 930 mb hurricane force storm.

Last weekend saw an unusually intense hurricane force extratropical storm low over the North Atlantic.  An active weather pattern started showing up on computer models more than a week earlier and by the 21st, the official NOAA “96 hour North Atlantic surface forecast chart” showed a rapidly deepening 977mb storm low over the central North Atlantic for 12Z Friday January 25th moving northeastward with a forecasted central pressure dropping to 933mb by 12Z on Saturday the 26th!

NOAA OPC Surface Analysis 12Z 24 January 2013 showing fast moving low passing off the coast.

NOAA OPC Surface Analysis 12Z 24 January 2013 showing fast moving low passing off the coast.

This particular system began as a weak 1023 mb disturbance along an Arctic front that was moving south and east across the Central US on the afternoon of the 23rd.

By Thursday, the 24th the rapidly moving disturbance had passed off the Middle Atlantic coast and had deepened to 1013mb. By Thursday night it was becoming apparent that this storm could approach historic strength during the following 72 hours and the official NOAA forecasts predicted that this storm would deepen to near 977mb by 12Z Friday (Jan. 25th) and as low as 920 or 924 mb by 12Z Saturday with hurricane force winds up to 75-80 knots possible.

NOAA OPC Surface Forecast 12Z 25 January 2013 showing developing hurricane force storm

NOAA OPC Surface Forecast 12Z 25 January 2013 showing developing hurricane force storm

Once off the coast the developing disturbance moved very rapidly (at nearly 50kts) towards the east-northeast deepening quickly to 984mb by 12Z Friday.

NOAA OPC 500MB Analysis 12Z 25 January 2013 showing strong winds high above the sea surface.

NOAA OPC 500MB Analysis 12Z 25 January 2013 showing strong winds high above the sea surface.

The stage was set for very rapid (explosive) deepening and over the next 24 hours the central pressure of this now large hurricane force storm dropped 54 mb to 930mb!

weather bomb north atlantic

NOAA OPC Surface Analysis 12Z 26 January 2013 showing 930 mb hurricane force storm low.

NOAA OPC Surface Analysis 12Z 26 January 2013 showing 930 mb hurricane force storm low.

This generated huge waves of up to 18 meters (59 feet) as depicted on the NOAA OPC Sea State Analysis on the 26th.  Wave heights on the NOAA chart here are significant wave heights which are defined as the average of the 1/3 highest waves.  This means that there was a 1 in 10 chance for a wave of almost 23 meters (75 ft.) and a 1 in 100 chance that a wave could have been as high as 30 meters (98 ft.).

NOAA OPC Wave Analysis 12Z 26 January 2013 showing significant wave heights to 17 meters (59 ft.)

NOAA OPC Wave Analysis 12Z 26 January 2013 showing significant wave heights to 17 meters (59 ft.)

Although this was a very intense storm, it was not a record.  The all-time record for North Atlantic extratropical storms was the Braer Storm of January 1993 that reached a min pressure of 914 mb (26.99 in Hg) on January 10th. The 1993 storm caused blizzard conditions across much of Scotland and also led to the final breakup of the oil tanker MV Braer, which had been stranded in rocks off the Shetland Islands by a previous storm.

Wunderground meteorologist Jeff Masters listed 5 storms in his blog that reached central pressures between 920 and 926 mb since the late 1800s, as cataloged by British weather historian Stephen Burt.

 NOAA Verification

NOAA OPC has a web page where you can verify how good or bad their graphical forecasts were.  For this storm the NOAA OPC 48 hour forecast was  for 924mb min pressure at 12Z on the 26th which turned out to be a bit too aggressive as the actual storm verified at 930mb. Given that this was a system at the very deep end of the pool, the forecast was not too far off.

Verification NOAA OPC Jan 26th showing the 48 hour forecast chart and the actual analysis chart

Verification NOAA OPC Jan 26th showing the 48 hour forecast chart and the actual analysis chart

Via Ocean Weather Services Blog

north atlantic storm

Satellite view of storm, 26 Jan 2013 – UK Meterological Office

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