16 October 2017

UK and Ireland Smacked Hard By Ophelia

Posted by Dan Satterfield

My close friends in Wales report the “wheely bins” are all over the place. The obs at Dublin airport show winds have gusted to right at 60 mph during the afternoon and evening, and on Anglesey, in Wales the winds reach 65 mph!

Here is a view fo the storm from the Meteosat (ctsy Univ. of Dundee’s downlink station).

Click image for a very large version, suitable for framing (Yea, we meteorologists do that sort of thing).

Ophelia is no longer a hurricane. As it moved over the much colder waters of the North Atlantic it transitioned into what meteorologists call a hybrid warm core/cold core system. The term for this is an extratropical cyclone. Hurricanes have warmer air in the eye, while a typical mid-latitude low has colder air near the low-pressure center. A very good slide show explaining this courtesy of Professor Michael Leach is here. The differences are much more dramatic in the mid and upper levels of the storm, but this does not mean the winds have any less force. Met Eireann issued a red warning for the entire nation as Ophelia approached.

It’s a hurricane season for the record books and a real example of what warmer than normal ocean waters can do when the other conditions are favourable for tropical cyclones to develop. A warmer world may not have more hurricanes (the scientific jury is out on that question), but the fears that those that do develop will be much more powerful (and wetter) seem to be quite real. It’s very possible that the predictions of how tropical systems will behave as the world passes 1.5 or even 2.0 degrees C may be too conservative.

This is only one season, but it sure makes one wonder.