2019 Autumn Discussion Thread (Northern Hemisphere)

We kicked off autumn with a night with low 18.4c

A bunch of twitter posts about hurricane Dorian.

Wet season blues setting in here. We've become locked in a pattern of overcast weather with little actual rainfall (and no thunder). Barely any change day-to-day. Very depressing.

A nice start to September here I feel the chill of autumn already.

Wednesday 4 September – Sunday 8 September

Rather unsettled with some chilly days

Overnight rain in the South will clear away early Wednesday morning, leaving things mostly dry and bright for the afternoon. However, a different story will play out further north were a low pressure system will drift into Scotland from the northwest, bringing heavy and thundery showers with some very strong wind gusts to the western coasts. As the low heads into the North Sea on Thursday, heavy showers will spread into South Scotland and North England. The Midlands and further south will likely escape any of the heavy or thundery showers, as well as the strongest winds.



Winds will ease Thursday as a weak front brings cloudy skies and patches of light rain or drizzle to most in the morning, although the driest conditions will be in the Southeast. A drier and brighter afternoon for all, but by Friday a cold front will move in from the northwest, bringing showers to most of the country, lingering the longest in the South. Further scattered showers are expected behind the front in West Scotland and Northern Ireland, and the odd rumble of thunder is possible here.



The weekend generally looks a bit more settled with high pressure building in behind the cold front, although a brisk north wind will keep things feeling rather cold on the east coast on Saturday. A few scattered light showers are likely through the weekend, mainly in the north, while mostly cloudy skies persist across the UK. However, things will trend a bit drier and warmer into Sunday afternoon, especially for England and Wales, with some longer sunny spells expected.


Monday 9 September – Sunday 15 September

Unsettled with some dry spells in the South

The brief settled spell from high pressure that is expected over the weekend may well come to a speedy end on Monday as the high weakens and shifts further south, allowing a frontal system to push in from the northwest. A cold front sweeping across the country will likely bring widespread wind, at times heavy, to most places, although the Southeast should at least see some drier weather for a time. The brisk northerly winds behind the front will make for a rather chilly night with lows widely in single figures.



This will then become the trend for the rest of the week with several fronts pushing in from the west keeping the weather unsettled and breezy for most. High pressure is expected to remain nearby, however, usually to the southwest or south, and this will mean that between fronts there will likely be some drier and calmer spells. These will occur more often in the southern half of the UK, which Scotland and Northern Ireland likely staying mostly cloudy and wet consistently.



Confidence is fairly high on the overall pattern, but there is a lot of potential variability on the day-to-day specifics. A frontal system expected mid-week is associated with the remains of Hurricane Dorian, and some major chances are likely if the storm makes landfall in the United States. There is a risk, about 30%, that high pressure will actually become more extensive, pushing fronts off to the north and bringing in some warmer and drier air from the south.

Monday 16 September – Sunday 29 September

Rain gradually clearing to the north

It currently looks like high pressure will gradually become more extensive across the country from the southwest after mid-September, although this will be a rather slow process. During the third week of September, low pressure areas are perhaps more likely to impact Scandinavia than the UK, although they could occasionally extend their influence westwards towards our shores. While confidence is rather low on the exact timing and extent of these episodes, they could bring some cooler, cloudier and wetter weather at times, with blustery showers or outbreaks of rain perhaps more likely to impact northern and eastern areas. However, the proximity of higher pressure means some lengthy drier, sunnier and warmer weather is in store as well, with these perhaps becoming more frequent later in the week.



By the final week of September, it looks like high pressure will have a lengthier stay across the UK, and this should encourage more widespread dry, warm and fine conditions as breezes more frequently come from the south-west. Areas of low pressure could quickly move east across the Atlantic, mainly close to Iceland, although some rather wet and breezy weather could linger across northern areas of Britain. However, much of the country should still experience a dry and rather warm end to the month.



Forecasting the British weather at this time of the year is made especially tricky by the development of hurricanes in the tropical Atlantic which can have a large impact on the weather pattern here. There is about a 40% chance that we will see a wetter, windier and cooler pattern lingering across the UK by the end of September.
www.bbc.co.uk/weather/outlook

Environment Canada tropical cyclone statement 🖕🏿Mörön🖕🏿


Most regions will see some tropical storm force winds, and south of the forecast track winds should reach hurricane force. As the storm moves into the Maritimes, there is the possibility of hurricane force northwesterlies behind the storm. Wind impacts may be enhanced by foliage on the trees, and may cause power outages.

Rainfall will be significant, especially north and west of Dorian's track. This suggests highest rainfall amounts are likely for the southern Maritimes and parts of Newfoundland, but some rain is likely over most regions. Amounts in excess of 50 mm are possible north and west of Dorian, and localised amounts near 100 mm are possible, especially for Nova Scotia.

There will also be some rough and pounding surf, especially for parts of Nova Scotia and Newfoundland. Waves will reach southwestern Nova Scotia on Saturday and build to near 10 metres over eastern Nova Scotia Saturday night. These waves will reach southern Newfoundland by Sunday morning. Waves near or higher than 5 metres will impact north facing coasts of the Gulf of St. Lawrence. Note that waves will break higher along the coast, and rip currents are likely. Please exercise extreme caution. Storm surge is possible, mainly for Nova Scotia and Newfoundland, but it is too early to be specific about impacts.

should be worth going to the beach to wave watch

Before and after

Very cold night today. -2.5'C in Latnivaara and 4.7'C at Umeå airport.