Rather surprisingly, Northern Scotland currently has the lowest annual rainfall anomalies for the whole of the UK, with an annual running accumulation to the end of September of just 90.9% of the 1981-2010 long-term average. The spell started with a very dry October and November in 2016, and the gap has only started to narrow in the last couple of months. It’s rather strange to think that somewhere can be seen as drier than average, when it’s seen rainfall totals of 1487.1 mm (58.5 inches) in the last year, but that’s the wonder of statistics for you.
The cold air ushered in by storm Xavier has certainly dropped the temperatures on the Zugspitze in the last 24 hours (fig 2). From a balmy max of 2.9°C yesterday, temperatures have quickly fallen away to around -9.1°C at 15 UTC this afternoon, but then again it is 9,718 feet up in the Wetterstein mountains in southern Germany close to the Austrian border. The strong northwesterly wind has died down a bit and they have had at least 20 cm of fresh snow during today, but how they manage to find any snow surface that’s not severely drifted to accurately measure a snow depth beats me.
Tropical Storm Nate is being reinvigorated by the warm waters of the Gulf of Honduras, after spending some time over land, Nate is now moving north by northwest at around 12 knots, and the next stop on her travels is the Yucatan peninsula, after which Nate is forecast to make landfall for the third time on the Gulf coast of America sometime on Sunday.
Irma was the most powerful hurricane of the 2017 season in the North Atlantic (fig 2) so far.
How did Irma compare with other hurricanes?
Irma had in fact the third highest ranking ACE index of any hurricane in the whole HURDAT2 data series which commenced in 1851 (fig 3), it trails hurricane Ivan, which lasted over three weeks back in 2014. If Irma hadn’t made landfall so quickly and turned northward rather than ploughing into Florida, it could well have lasted much longer and had an even higher ACE index.
If you gauge it on maximum wind speed rather than ACE, then Irma produced the joint second highest maximum wind speed of 160 knots, hurricane Allen of 1980 is still the strongest ranked on maximum wind speed (fig 4).
The only reason I have data for 2017 is because I’ve written some code to download all the 388 advisories issued from the NHC archives from the end of September. Once you have the advisories, you can them piece together into individual storm tracks. There is the proviso with collating statistics in this way, and that these provisional positions and intensities may differ a little with those in the definitive HURDAT2 series when it is updated next spring by the NHC.
At a number of places there was a touch of ground frost this Friday morning (fig 2), nothing very unusual in this for early October, and although its measured with what’s called a grass minimum thermometer, it was never called a grass frost even though it’s usually over grass where the lowest temperature occurs and where a frost is most clearly visible. In my days as an observer, we always laid a thermometer on a paving slab and measured the concrete minimum, which was usually, but not always a wee bit higher that the grass minimum. I wonder if that’s still being done?
Storm Xavier has certainly brought with it some lively old winds along with it today as she crossed the North Sea. Xavier is moving speedily east to join up with Wolfgang over eastern Poland, you remember the storm that looked like it might be named Brian? I should have worked out the speed, but roughly Xavier has travelled 850 km in 12 hours, which mean it must have been doing at least 35 knots. I can see maximum gusts as high as 76 mph at the rather spectacular Alte Weser Lighthouse, and one of 110 mph from the top of the Brocken in the Harz mountains both in Germany. Who say the UK doesn’t export anything to Germany these days?
Northwest severe gale force nine to storm ten along the Dutch Coast and soon across the German Bight. as storm Xavier rushes across northern Germany this morning and still deepening quite rapidly.