Ex-hurricane Helene on her way to Europe. Next sign of the winter?


By meteomorris on 17 September 2018 · 3

We are in the middle of hurricane season. The United States are dealing with hurricane Florence and Europe will face the remnants of ex-hurricane Helene in the coming days. She will bring warm winds from the south at the beginning of the week, but the storms that follow in her slipstream may cause a second indication of winter getting closer at the end of this week. Below the forecast for the coming week with:

  • Helene on her way to the British Isles
  • Western jetstream on fire
  • Lots of dynamics in the models
  • Autum is always very dynamic
  • Next indication of winter for the Alps?

On the above video you can see how ex-hurricane Helene moves from the southwest towards the British Isles. She's expected there around Monday/Tuesday with wind and waves as a result. Because the wind is only modestly visible on the French coast because of a high pressure area, there's a good chance of great waves over there. Especially since two more storm depressions follow after Helene. NOAA (National Oceanic and Atmospheric Admininstration) monitors all tropical storms and hurricanes and Helene as well.

Western jetstream on fire

Although the real fireworks due to Helene are not happening, because the storm is mainly in the middel of the ocean, she makes sure the jetstream will be on fire. The jetstream will come straight from the west the coming week, and the wind speed at high altitude will reach 200 kilometers per hour or more. Two storms will follow for the British Isles next week. With a powerful high pressure area above Europe and low pressure above the ocean, the current remains southwest. That means wind and rain above the British Isles, but it's a nice Indian Summer in the Alps with a possible thunder storm on Tuesday.

Lots of dynamics in the models

There will be a lot of dynamics in the models from Thursday. For example, the calculation of yesterday (Sunday morning) indicated a lot of snow in the Alps for next weekend, but according to the calculations of last night and the runs after the storm depressions don't really succees to penetrate into Europe. In short there is a lot of dynamics in the models.

Autum is always very dynamic

Autumn marks the changing of the seasons. The sun loses its grip on the high north, allowing cold air to cluster there. At the same time, the arrival of storms starts from the southwest. If hot and cold air mixes, that will create a lot of dynamism. In particular, the position and strength of the jet stream then continuously changes the forecast. Long-term forecasts in autumn are therefore always very difficult and differences shift from day to day. You might say snow or no snow for the Alps, that is a big difference. That is true, but in terms of the weather, this sometimes means that the trajectory of the responsible storm is only 200 kilometers more to the north and the jet stream becomes WNW instead of NW. Areas that are therefore further away from a storm track often see dynamic expectations in autumn.

Next indication of winter for the Alps?

There was still a lot of snow on the maps yesterday (Sunday), but that chance is already a lot smaller today (Monday). But if there will be snow in the forecast, it will look like this according to the current calculations:

  • A storm moves to the British Isles from the southwest on Thursday. This comes with a lot of wind and rain. At the same time, high pressure dominates the weather above the Alps and the weather is pretty calm.
  • This storm is already above the North Sea with high pressure over the Azores and Russia on Friday. Between these high-pressure areas there is room for a breach towards the Alps. In the calculations of Sunday, the storm would find its way towards the Alps. In today's calculation (Monday) high-pressure from the Azores moves to the French mainland, keeping the real low temperatures and precipitation at a distance.
  • Instead of a current from the north-northwest current, you can expect a west-northwestern current above the northwest of Europe. The result is that cold air and some precipitation are expected to only gently hit the Alps with possibly some snow for the high alpine in Austria.

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Comments


  • Jeffrydejong
    Beginner
    Jeffrydejong op 17 September 2018 · 16:51
    We need Snow in November and not in September. Early drops are not always positive for a good winter. If it snows in November is mostly stays.

    De Visboer
  • meteomorris
    Expert
    meteomorris op 18 September 2018 · 08:48
    @Jeffrydejong, I agree but weather isn't something we can control. Which is also the beauty of it.
    May the powder be with you.
  • meteomorris
    Expert
    meteomorris op 18 September 2018 · 08:53
    New update. Still big differences between the models. Both models do expect some snow in the higher alpine the upcoming weekend. But for the start of next week the American GFS model is in favor of snow and cold air. The Euro model (ECMWF) does allow cold air to move in but high pressure may keep significant precipitation on a distance.

    Euro model: high pressure, chances on snow for the most eastern part of the Alps


    GFS model: NW flow and snow for the Northern Alps
    May the powder be with you.

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