Hurricane Lorenzo: snow for the Alps?


Von meteomorris an 2 Oktober 2019 · 0

Hurricane Lorenzo appeared on the weather maps for the first time on September 21st. It then still was a meaningless low-pressure area above the equator. Little Lorenzo grew into a class 5 hurricane in 10 days and is on his way to Ireland via the Azores today. Waves of 20+ meters are generated with wind speeds around the core of more than 200 km/h. Waves that will shrink considerably over a long distance, but with an expected wave period of 20 seconds (sic), blazing-fast barrels are guaranteed along the shores of large parts of the Atlantic. (read more about Lorenzo's swell potential here).

(C) Windy
(C) Windy

Snow for the Alps?

It is for the first time ever that a class 5 hurricane is moving as far as the East Atlantic. Does that also mean snowfall and strong winds for the Alps? Lorenzo is expected to arrive in Ireland on Thursday, but a lot of his energy will be lost by then. Because although the warm gulf stream reaches Ireland through Svalbard, warm is relative. The water near Ireland is already considerably colder, which means that the hurricane will gradually lose its power (the temperature of the water is the most important energy source). Cooler or not, the expected wind speeds are still considerable for the west of Ireland.

But once Lorenzo travels by land, it loses even more of its energy and Lorenzo can't be called a hurricane anymore. Lorenzo will probably be above the UK and then move up the European mainland as a relatively weak storm depression during the night to Friday. It seems that it's not that powerful anymore.

(C) NOAA
(C) NOAA

Lorenzo will become part of the western current from Thursday and will head over the Alps via The Netherlands and Germany as a normal relatively weak storm depression. With this Lorenzo has temporarily pushed the jet stream north, with the emphasis on temporary.

Temporarily milder, then cooler again

It is snowing in the high alpine of the Alps with 10-30 cm of fresh snow above 2500 meters today (Wednesday), but on the approach of Lorenzo the cold air is pushed away again with a southwestern current. The snow that falls today will have a hard time due to the rise in air temperature in the higher air layers and the still strong and high sun.

(C) Hirlam
(C) Hirlam

Weekend and the days after: snowfall?

But if Lorenzo passes above the Alps, the current will eventually turn north again and cold air will find its way to the Alps. This results in snow at high altitude on Saturday and Sunday, with the snow line dropping the most in eastern Austria. But even more snow may follow after the weekend. The latest calculations assume that really cold air finds its way to the Alps on Monday and Tuesday. If that is the case, more cold air and snow will follow.

Jetstream
Jetstream

The most positive scenario
The most positive scenario

Conclusion:

  • Wednesday: snow at a high altitude
  • Thursday and Friday: mild again
  • Friday: some cooling and precipitation during the day
  • Saturday and Sunday: snow for high alpine with dropping snow line in the east
  • Monday and Tuesday: the most beautiful scenario is snowfall, but still a lot of noise in the models
  • Ultra long term: jetstream will be located north of the Alps: milder

In short, more and more dynamics that will bring snow to the Alps from time to time. It is time to start with getting stoked: our forecast maps have fresh runs ready every morning!

Stay stoked, Morris


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